As confidentially submitted to the Securities and Exchange Commission on July 19, 2019 as
Amendment No. 1 to the confidential submission dated June 7, 2019.
This draft registration statement has not been filed publicly with the Securities and Exchange Commission and all information contained herein remains confidential.

Registration No. 333-      ​

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM S-1
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

SPRINGWORKS THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

100 Washington Blvd
Stamford, CT 06902
(203) 883-9490
(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Saqib Islam
Chief Executive Officer
100 Washington Blvd
Stamford, CT 06902
(203) 883-9490
(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies of all communications, including communications sent to agent for service, should be sent to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after this registration statement becomes effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, as amended, check the following box. ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of  “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided to Section 7(a)(2)(B) of the Securities Act. ☐

CALCULATION OF REGISTRATION FEE

(1) Estimated solely for the purpose of calculating the registration fee pursuant to Rule 457(o) under the Securities Act of 1933, as amended.

(2) Includes the offering price of shares that the underwriters may purchase pursuant to an option to purchase additional shares.

(3) Calculated pursuant to Rule 457(o) based on an estimate of the proposed maximum aggregate offering price.

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment that specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until this registration statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

The information in this preliminary prospectus is not complete and may be changed. These securities may not be sold until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities nor does it seek an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

Subject to completion, dated            , 2019

Preliminary prospectus

          shares

Common stock

This is an initial public offering of shares of common stock by SpringWorks Therapeutics, Inc. We are offering      shares of our common stock. The initial public offering price is expected to be between $     and $     per share.

Prior to this offering, there has been no public market for our common stock. We intend to apply to list our common stock on the Nasdaq Global Market under the symbol “SWTX.”

We are an “emerging growth company” as defined under U.S. federal securities laws and will be subject to reduced public company reporting requirements.

(1) See “Underwriting” for a description of compensation payable to the underwriters.

We have granted the underwriters an option for a period of up to 30 days to purchase up to         additional shares of our common stock.

Investing in our common stock involves risks. See “Risk factors” beginning on page 13 of this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the shares of common stock to purchasers on or about            , 2019.

Wedbush PacGrow

              , 2019

Table of contents

We and the underwriters have not authorized anyone to provide any information or to make any representations other than those contained in this prospectus or in any free writing prospectuses we have prepared. We and the underwriters take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may provide you. We are offering to sell, and seeking offers to buy, shares of common stock only in jurisdictions where offers and sales are permitted. The information contained in this prospectus is accurate only as of the date of this prospectus, regardless of the time of delivery of this prospectus or of any sale of the common stock.

Through and including            , 2019 (the 25th day after the date of this prospectus) all dealers that effect transactions in these securities, whether or not participating in this offering, may be required to deliver a prospectus. This is in addition to the dealers’ obligation to deliver a prospectus when acting as underwriters and with respect to their unsold allotments or subscriptions.

For investors outside of the United States: We have not, and the underwriters have not, done anything that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than the United States. Persons

i

outside of the United States who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of the shares of common stock and the distribution of this prospectus outside of the United States.

Presentation of Financial Information

Pursuant to the applicable provisions of the Fixing America’s Surface Transportation Act, we are omitting our condensed consolidated financial statements as of and for the three months ended March 31, 2018 and 2019. While the financial information for the three months ended March 31, 2018 and 2019 is otherwise required by Regulation S-X, we reasonably believe that it will not be required to be included in the Form S-1 filing at the time of the contemplated offering. We intend to amend the registration statement to include all financial information required by Regulation S-X at the date of such amendment before distributing a preliminary prospectus to investors.

ii

1

2

3

​

4

​

5

6

7

​

8

​

9

(in thousands, except share, unit, per share and per unit data)

​

​

Period from August 18, 2017 (inception) to December 31, 2017​

​

​

Year Ended December 31, 2018​

​

Consolidated statement of operations data:

​

​

​

​

​

​

​

​

​

​

​

​

​

Operating expenses:

​

​

​

​

​

​

​

​

​

​

​

​

​

Research and development

​

​

​

$

2,799

​

​

​

​

$

9,898

​

​

General and administrative

​

​

​

​

1,861

​

​

​

​

​

8,593

​

​

Total operating expenses

​

​

​

​

4,660

​

​

​

​

​

18,491

​

​

Loss from operations

​

​

​

​

(4,660)

​

​

​

​

​

(18,491)

​

​

Other income:

​

​

​

​

​

​

​

​

​

​

​

​

​

Interest income

​

​

​

​

21

​

​

​

​

​

678

​

​

Total Other Income

​

​

​

​

21

​

​

​

​

​

678

​

​

Net Loss

​

​

​

$

(4,639)

​

​

​

​

$

(17,813)

​

​

Net loss per common unit, basic and diluted(1)

​

​

​

$

—

​

​

​

​

$

(7.94)

​

​

Weighted average common units outstanding, basic and diluted(1)

​

​

​

​

—

​

​

​

​

​

2,244,215

​

​

Pro forma net loss per share, basic and diluted (unaudited)(2)

​

​

​

​

​

​

​

​

​

$

(0.30)

​

​

Pro forma weighted average common shares outstanding, basic and diluted (unaudited)(2)

​

​

​

​

​

​

​

​

​

​

58,749,660

​

​

10

​

​

​

As of December 31, 2018​

​

(in thousands)

​

​

Actual​

​

​

Pro Forma(1)​

​

​

Pro Forma As Adjusted(2)(3)​

​

Balance Sheet Data:

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

Cash and cash equivalents

​

​

​

$

45,648

​

​

​

​

$

45,648

​

​

​

​

$

​

​

Working capital(4)

​

​

​

​

43,353

​

​

​

​

​

43,353

​

​

​

​

​

​

​

​

Total assets

​

​

​

​

48,390

​

​

​

​

​

48,390

​

​

​

​

​

​

​

​

Convertible preferred units

​

​

​

​

62,930

​

​

​

​

​

—

​

​

​

​

​

​

​

​

Accumulated deficit

​

​

​

​

(22,452)

​

​

​

​

​

(22,452)

​

​

​

​

​

​

​

​

Members’ (deficit) equity

​

​

​

​

(19,369)

​

​

​

​

​

43,561

​

​

​

​

​

​

​

​

11

Reorganization

Prior to March 29, 2019, we conducted our business through SpringWorks Therapeutics, LLC, a Delaware limited liability company. On March 29, 2019, we completed a series of transactions pursuant to which SpringWorks MergerSub, LLC, a wholly owned subsidiary of SpringWorks Therapeutics, Inc., was merged with and into SpringWorks Therapeutics, LLC, or the Reorganization. Following such merger, SpringWorks Therapeutics, LLC survived as a wholly owned subsidiary of SpringWorks Therapeutics, Inc. In connection with the Reorganization:

•

Holders of SpringWorks Therapeutics, LLC Junior Series A convertible preferred units received one share of SpringWorks Therapeutics, Inc. Junior Series A convertible preferred stock for each outstanding Junior Series A convertible preferred unit held immediately prior to the Reorganization, with an aggregate of 6,437,500 shares of SpringWorks Therapeutics, Inc. Junior Series A convertible preferred stock issued in the Reorganization;

​

•

Holders of SpringWorks Therapeutics, LLC Series A convertible preferred units received one share of SpringWorks Therapeutics, Inc. Series A convertible preferred stock for each outstanding Series A convertible preferred unit held immediately prior to the Reorganization, with an aggregate of 103,000,000 shares of SpringWorks Therapeutics, Inc. Series A convertible preferred stock issued in the Reorganization;

​

•

Holders of SpringWorks Therapeutics, LLC common units received one share of SpringWorks Therapeutics, Inc. common stock for each outstanding common unit held immediately prior to the Reorganization, with an aggregate of 1,287,500 shares of common stock issued in the Reorganization; and

​

•

Holders of SpringWorks Therapeutics, LLC vested and unvested incentive units exchanged such incentive units for an equal number of shares of common stock or restricted common stock, respectively, given that the strike price for all incentive units that had been issued by SpringWorks Therapeutics, LLC was $0.00 per unit. The restricted common stock was issued with the same vesting terms as the unvested incentive units held immediately prior to the Reorganization. An aggregate of 19,038,927 shares of common stock and restricted common stock were issued to the prior holders of incentive units in the Reorganization.

​

Immediately following the Reorganization, we issued 86,639,279 shares of Series B convertible preferred stock on March 29, 2019.

All outstanding shares of our convertible preferred stock are convertible into shares of common stock at the then-effective conversion ratios.

In connection with the Reorganization, by operation of law, we acquired all assets of SpringWorks Therapeutics, LLC and assumed all of its liabilities and obligations, and we now operate our business through SpringWorks Therapeutics, Inc., which is the issuer in this offering. The purpose of the Reorganization was to reorganize our corporate structure so that SpringWorks Therapeutics, Inc. would continue as a corporation and so that our existing investors would own our capital stock rather than equity interests in a limited liability company. For the convenience of the reader, except as context otherwise requires, all information included in this prospectus is presented giving effect to the Reorganization; except that the consolidated financial statements and summary and selected historical consolidated financial data and other financial information included in this prospectus are those of SpringWorks Therapeutics, LLC prior to the Reorganization except as otherwise disclosed in this prospectus.

12

Risk Factors

Investing in our common stock involves a high degree of risk. You should carefully consider the risks described below, as well as the other information in this prospectus, including our consolidated financial statements and related notes appearing elsewhere in this prospectus and in the section entitled “Management’s discussion and analysis of financial condition and results of operations,” before deciding whether to invest in our common stock. The occurrence of any of the events or developments described below could harm our business, financial condition, results of operations and growth prospects. In such an event, the market price of our common stock could decline and you may lose all or part of your investment. Additional risks and uncertainties not presently known to us or that we currently deem immaterial also may impair our business operations.

Risks related to our financial position and need for additional capital

We have incurred significant net losses since our inception and anticipate that we will continue to incur net losses in the future.

We have incurred significant net losses in each reporting period since our inception. To date, we have not generated any revenue and we have financed our operations principally through equity financings. If our product candidates are not successfully developed and approved, we may never generate any revenue. We continue to incur significant research and development and other expenses related to our ongoing operations. As a result, we are not profitable and have incurred losses in each period since our inception. Our net losses were $4.6 million and $17.8 million for the period from August 18, 2017 (inception) to December 31, 2017 and the year ended December 31, 2018, respectively. As of December 31, 2018, we had an accumulated deficit of  $22.5 million. We expect to continue to incur significant losses for the foreseeable future, and we expect these losses to increase as we continue our research and development of, and seek regulatory approvals for, our product candidates, including our lead product candidates, nirogacestat and mirdametinib, and any future product candidates.

We anticipate that our expenses will increase substantially if, and as, we:

•

advance the development of our lead product candidates, nirogacestat and mirdametinib, through potentially registrational clinical trials and potentially for other indications;

​

•

advance our development programs for our other product candidates through clinical development and into later-stage clinical development;

​

•

seek marketing approvals for any product candidates that successfully complete clinical trials;

​

•

invest in or in-license other technologies or product candidates for further preclinical and clinical development;

​

•

hire additional personnel, including clinical, quality control, scientific, medical, business development and finance personnel, and continue to build our infrastructure;

​

•

expand our operational, financial and management systems and increase personnel, including personnel to support our clinical development, manufacturing and commercialization efforts and our operations as a public company;

​

•

maintain, expand and protect our intellectual property portfolio; and

​

•

establish a sales, marketing, medical affairs and distribution infrastructure to commercialize any products for which we may obtain marketing approval and intend to commercialize on our own or jointly with third parties.

​

13

To become and remain profitable, we or any potential future collaborators must develop and eventually commercialize products with significant market potential. This will require us to be successful in a range of challenging activities, including completing preclinical studies and clinical trials, obtaining marketing approval for product candidates, manufacturing, obtaining reimbursement approval, marketing and selling products for which we may obtain marketing approval and satisfying any post-marketing requirements. We may never succeed in any or all of these activities and, even if we do, we may never generate revenue that is significant or large enough to achieve profitability. If we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis. Our failure to become and remain profitable would decrease the value of our company and could impair our ability to raise capital, maintain our research and development efforts, expand our business or continue our operations. A decline in the value of our company also could cause you to lose all or part of your investment.

Even if we succeed in commercializing one or more of our product candidates, we will continue to incur substantial research and development and other expenditures to develop, register and market additional product candidates. We may encounter unforeseen expenses, difficulties, complications, delays and other unknown factors that may adversely affect our business. The size of our future net losses will depend, in part, on the rate of future growth of our expenses and our ability to generate revenue. Our prior losses and expected future losses have had and will continue to have an adverse effect on our stockholders’ equity and working capital.

We have a limited operating history, which may make it difficult to evaluate our prospects and likelihood of success.

We are a clinical-stage biopharmaceutical company with a limited operating history. We were formed in August 2017 and our operations to date have been focused on preparing and executing our clinical trials for our product candidates, building our infrastructure, raising capital and executing partnerships. Consequently, we have limited operations upon which to evaluate our business, and predictions about our future success or viability may not be as accurate as they could be if we had a longer operating history or a history of successfully developing and commercializing drug products. Investment in biopharmaceutical product development is highly speculative because it entails substantial upfront capital expenditures and significant risk that any potential product candidate will fail to demonstrate adequate activity or an acceptable safety profile, gain regulatory approval, secure market access and reimbursement and become commercially viable.

Although we announced the initiation of the DeFi trial, a potentially registrational Phase 3 clinical trial of nirogacestat, in May 2019, and expect to commence a potentially registrational Phase 2b clinical trial of mirdametinib, we have not yet demonstrated the ability to successfully enroll or complete clinical trials for any product candidate, we have no products approved for commercial sale and we have not generated any revenue from product sales to date. In addition, as a business with a limited operating history, we may encounter unforeseen expenses, difficulties, complications, delays and other known and unknown factors and risks frequently experienced by early-stage biopharmaceutical companies in rapidly evolving fields.

In addition, we will need to transition at some point from a company with a development focus to a company capable of supporting commercial activities, and may not be successful in such a transition.

Even if this offering is successful, we will require additional capital to fund our operations and if we fail to obtain necessary capital, we will not be able to complete the development and commercialization of our product candidates.

Our operations have consumed substantial amounts of cash since inception. We expect to continue to spend substantial amounts of cash to conduct further research and development and

14

clinical trials of our product candidates to seek regulatory approvals for our product candidates and to launch and commercialize any products for which we receive regulatory approval. As of December 31, 2018, we had $45.6 million in cash and cash equivalents. Subsequent to December 31, 2018, we have raised $164.4 million in gross proceeds from equity financings. Based on our current operating plan, we believe that the net proceeds from this offering, together with existing cash and cash equivalents, will be sufficient to fund our operating expenses and capital expenditure requirements through    . However, our future capital requirements and the period for which our existing resources will support our operations may vary significantly from what we expect, and we will in any event require additional capital in order to complete clinical development and obtain regulatory approval of our product candidates. Our monthly spending levels will vary based on new and ongoing development and corporate activities. Because the length of time and activities associated with development of our product candidates is highly uncertain, we are unable to estimate the actual funds we will require for development and any approved marketing and commercialization activities. Our future funding requirements will depend on many factors, including, but not limited to:

•

the initiation, progress, timing, costs and results of clinical trials for our product candidates;

​

•

the clinical and preclinical development and manufacturing plans we establish for these product candidates;

​

•

the number and characteristics of product candidates that we develop or in-license;

​

•

the cost of identifying and evaluating potential product candidates for acquisition or license, including the cost of preclinical activities or clinical activities;

​

•

the terms of any collaboration or licensing agreements we may choose to enter into;

​

•

the outcome, timing and cost of meeting regulatory requirements established by the U.S. Food and Drug Administration, or FDA, the European Medicines Agency, or EMA, and other comparable foreign regulatory authorities;

​

•

the cost of filing, prosecuting, defending and enforcing our patent claims and other intellectual property rights;

​

•

the cost of defending intellectual property disputes, including patent infringement actions brought by third parties against us or our product candidates;

​

•

the effect of competing technological and market developments;

​

•

the cost and timing of completion of commercial-scale manufacturing activities; and

​

•

the cost of establishing medical affairs and sales, marketing and distribution capabilities for any approved product candidates.

​

If we are unable to raise additional capital in sufficient amounts or on terms acceptable to us, we may have to significantly delay, scale back or discontinue the development or commercialization of one or more of our product candidates or one or more of our other research and development initiatives. Any of the above events could significantly harm our business, prospects, financial condition and results of operations and cause the price of our common stock to decline.

Raising additional capital may cause dilution to our existing stockholders, restrict our operations or require us to relinquish rights to our technologies or product candidates.

We do not have any committed external source of funds or other support for our development efforts and we cannot be certain that additional funding will be available on acceptable terms, or at all. Until we can generate sufficient product or royalty revenue to finance our cash requirements, which we may never do, we expect to finance our future cash needs through a

15

combination of public or private equity offerings, debt financings, collaborations, strategic alliances, licensing arrangements and other marketing or distribution arrangements. If we raise additional funds through public or private equity offerings, the terms of these securities may include liquidation or other preferences that adversely affect our stockholders’ rights. Further, to the extent that we raise additional capital through the sale of common stock or securities convertible or exchangeable into common stock, your ownership interest will be diluted. In addition, any debt financing may subject us to fixed payment obligations and covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we raise additional capital through marketing and distribution arrangements or other collaborations, strategic alliances or licensing arrangements with third parties, we may have to relinquish certain valuable rights to our product candidates, technologies, future revenue streams or research programs or grant licenses on terms that may not be favorable to us. We also could be required to seek commercial or development partners for our lead products or any future product candidate at an earlier stage than otherwise would be desirable or relinquish our rights to product candidates or technologies that we otherwise would seek to develop or commercialize ourselves.

The amount of our future losses is uncertain and our quarterly operating results may fluctuate significantly or may fall below the expectations of investors or securities analysts, each of which may cause our stock price to fluctuate or decline.

Our quarterly and annual operating results may fluctuate significantly in the future due to a variety of factors, many of which are outside of our control and may be difficult to predict, including the following:

•

the timing and success or failure of clinical trials for our product candidates or competing product candidates, or any other change in the competitive landscape of our industry, including consolidation among our competitors or partners;

​

•

our ability to successfully recruit and retain subjects for clinical trials, and any delays caused by difficulties in such efforts;

​

•

our ability to obtain marketing approval for our product candidates, and the timing and scope of any such approvals we may receive;

​

•

the timing and cost of, and level of investment in, research and development activities relating to our product candidates, which may change from time to time;

​

•

the cost of manufacturing our product candidates, which may vary depending on the quantity of production and the terms of our agreements with manufacturers;

​

•

our ability to attract, hire and retain qualified personnel;

​

•

expenditures that we will or may incur to develop additional product candidates;

​

•

the level of demand for our product candidates should they receive approval, which may vary significantly;

​

•

the risk/benefit profile, cost and reimbursement policies with respect to our product candidates, if approved, and existing and potential future therapeutics that compete with our product candidates;

​

•

the changing and volatile U.S. and global economic environments; and

​

•

future accounting pronouncements or changes in our accounting policies.

​

16

The cumulative effects of these factors could result in large fluctuations and unpredictability in our quarterly and annual operating results. As a result, comparing our operating results on a period-to-period basis may not be meaningful. This variability and unpredictability could also result in our failing to meet the expectations of industry or financial analysts or investors for any period. If our revenue or operating results fall below the expectations of analysts or investors or below any forecasts we may provide to the market, or if the forecasts we provide to the market are below the expectations of analysts or investors, the price of our common stock could decline substantially. Such a stock price decline could occur even when we have met any previously publicly stated guidance we may provide.

Risks related to research and development and the biopharmaceutical industry

Our business is highly dependent on the success of our lead product candidates, nirogacestat and mirdametinib, as well as other product candidates we may develop. If we are unable to successfully complete clinical development, obtain regulatory approval for or commercialize our product candidates, or if we experience delays in doing so, our business will be materially harmed.

To date, we have not yet completed any clinical trials or development of any product candidates. Our future success and ability to generate revenue from our product candidates, which we do not expect will occur for several years, if ever, is dependent on our ability to successfully develop, obtain regulatory approval for and commercialize one or more product candidates. We are currently enrolling patients in a potentially registrational Phase 3 clinical trial of nirogacestat and we expect to commence a potentially registrational Phase 2b clinical trial of mirdametinib in the third quarter of 2019. If either of our lead product candidates encounter safety or efficacy problems, development delays or regulatory issues or other problems, our development plans and business would be significantly harmed.

All of our other product candidates are in earlier stages of development and will require substantial additional investment for preclinical development, clinical development, regulatory review and approval in one or more jurisdictions.

We may not have the financial resources to continue development of, or to modify existing or enter into new collaborations for, a product candidate if we experience any issues that delay or prevent regulatory approval of, or our ability to commercialize, our product candidates, including:

•

our inability to demonstrate to the satisfaction of the FDA or comparable foreign regulatory authorities that our product candidates are safe and effective;

​

•

insufficiency of our financial and other resources to complete the necessary preclinical studies and clinical trials;

​

•

negative or inconclusive results from our preclinical studies, clinical trials or the clinical trials of others for product candidates similar to ours, leading to a decision or requirement to conduct additional preclinical studies or clinical trials or abandon a program;

​

•

product-related adverse events experienced by subjects in our clinical trials or by individuals using drugs or therapeutic biologics similar to our product candidates;

​

•

delays in submitting an Investigational New Drug application, or IND, or comparable foreign applications or delays or failure in obtaining the necessary approvals from regulators to commence a clinical trial or a suspension or termination of a clinical trial once commenced;

​

•

conditions imposed by the FDA, EMA or comparable foreign regulatory authorities regarding the scope or design of our clinical trials;

​

17

•

poor effectiveness of our product candidates during clinical trials;

​

•

better than expected performance of control arms, such as placebo groups, which could lead to negative or inconclusive results from our clinical trials;

​

•

delays in enrolling subjects in clinical trials;

​

•

high drop-out rates of subjects from clinical trials;

​

•

inadequate supply or quality of product candidates or other materials necessary for the conduct of our clinical trials;

​

•

greater than anticipated clinical trial or manufacturing costs;

​

•

unfavorable FDA, EMA or comparable regulatory authority inspection and review of a clinical trial site;

​

•

failure of our third-party contractors or investigators to comply with regulatory requirements or otherwise meet their contractual obligations in a timely manner, or at all;

​

•

delays and changes in regulatory requirements, policy and guidelines, including the imposition of additional regulatory oversight around clinical testing generally or with respect to our therapies in particular; or

​

•

varying interpretations of data by the FDA, EMA and comparable foreign regulatory authorities.

​

Clinical development involves a lengthy and expensive process, with an uncertain outcome. We may incur additional costs or experience delays in completing, or ultimately be unable to complete, the development and commercialization of our product candidates.

To obtain the requisite regulatory approvals to commercialize any product candidates, we must demonstrate through extensive preclinical studies and clinical trials that our product candidates are safe and effective in humans. Clinical testing is expensive and can take many years to complete, and its outcome is inherently uncertain. We may be unable to establish clinical endpoints that applicable regulatory authorities would consider clinically meaningful, and a clinical trial can fail at any stage of testing.

Differences in trial design between early-stage clinical trials and later-stage clinical trials make it difficult to extrapolate the results of earlier clinical trials to later clinical trials. Moreover, clinical data are often susceptible to varying interpretations and analyses, and many companies that have believed their product candidates performed satisfactorily in clinical trials have nonetheless failed to obtain marketing approval of their products. Additionally, we plan to conduct some open-label trials, where both the patient and investigator know whether the patient is receiving the investigational product candidate or either an existing approved drug or placebo. Open-label clinical trials are subject to various limitations that may exaggerate any therapeutic effect as patients in those trials are aware when they are receiving treatment. In addition, open-label clinical trials may be subject to an “investigator bias” where those assessing and reviewing the outcomes of the clinical trials are aware of which patients have received treatment and may interpret the information of the treated group more favorably given this knowledge. Where a randomized, placebo-controlled clinical trial is designed to allow enrolled subjects to cross-over from the placebo arm to the treatment arm, there may be a risk of inadvertent unblinding of subjects prior to cross-over, which may limit the clinical meaningfulness of those data and may require the conduct of additional clinical trials.

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Successful completion of clinical trials is a prerequisite to submitting a New Drug Application, or NDA, to the FDA, a Marketing Authorization Application, or MAA, to the EMA and similar marketing applications to comparable foreign regulatory authorities for each product candidate and, consequently, the ultimate approval and commercial marketing of any product candidates. Although we have initiated a potentially registrational clinical trial for nirogacestat and expect to initiate a potentially registrational clinical trial for mirdametinib in the third quarter of 2019, we do not know whether these trials or any of our clinical trials, including trials for our combination therapies using nirogacestat and mirdametinib, will be completed on schedule, if at all, or in some cases whether such clinical trials will begin.

We may experience delays in initiating or completing clinical trials and preparing for regulatory submissions. We also may experience numerous unforeseen events during, or as a result of, any future clinical trials that we could conduct that could delay or prevent our ability to receive marketing approval or commercialize our current product candidates or any future product candidates, including:

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regulators or institutional review boards, or IRBs, or ethics committees may not authorize us or our investigators to commence a clinical trial or conduct a clinical trial at a prospective trial site;

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we may experience delays in reaching, or fail to reach, agreement on acceptable terms with prospective clinical trial sites and prospective contract research organizations, or CROs, the terms of which can be subject to extensive negotiation and may vary significantly among different CROs and clinical trial sites;

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clinical trials of any product candidates may fail to show acceptable safety or efficacy, or produce negative or inconclusive results and we may decide, or regulators may require us, to conduct additional preclinical studies or clinical trials or we may decide to abandon product development programs;

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the number of subjects required for clinical trials of any product candidates may be larger than we anticipate, enrollment in these clinical trials may be slower than we anticipate or subjects may drop out of these clinical trials or fail to return for post-treatment follow-up at a higher rate than we anticipate;

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our third-party contractors may fail to comply with regulatory requirements or meet their contractual obligations to us in a timely manner, or at all, or may deviate from the clinical trial protocol or drop out of the trial, which may require that we add new clinical trial sites or investigators;

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we may elect to, or regulators, IRBs or ethics committees may require, that we or our investigators suspend or terminate clinical research or trials for various reasons, including noncompliance with regulatory requirements or a finding that the participants are being exposed to unacceptable health risks;

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the cost of clinical trials of any product candidates may be greater than we anticipate;

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the supply or quality of our product candidates or other materials necessary to conduct clinical trials of our product candidates may be inadequate to initiate or complete a given clinical trial;

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our product candidates may have undesirable side effects or other unexpected characteristics, causing us or our investigators, regulators, IRBs or ethics committees to suspend or terminate the clinical trials;

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reports from clinical testing of other therapies may raise safety or efficacy concerns about our product candidates; and

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the FDA, EMA or comparable regulatory authorities may require us to submit additional data, such as long-term toxicology studies, or impose other requirements before permitting us to initiate a clinical trial.

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We could also encounter delays if a clinical trial is suspended or terminated by us, the IRBs of the institutions in which such clinical trials are being conducted, or the FDA, EMA or comparable regulatory authorities, or recommended for suspension or termination by the Data Safety Monitoring Board, or DSMB, for such clinical trial. A suspension or termination may be imposed due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or clinical trial site by the FDA, EMA or comparable foreign regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a product or treatment, failure to establish or achieve clinically meaningful trial endpoints, changes in governmental regulations or administrative actions or lack of adequate funding to continue the clinical trial. Many of the factors that cause, or lead to, a delay in the commencement or completion of clinical trials may also ultimately lead to the denial of regulatory approval of our product candidates. Further, the FDA, EMA or comparable foreign regulatory authorities may disagree with our clinical trial design and our interpretation of data from clinical trials, or may change the requirements for approval even after they have reviewed and commented on the design for our clinical trials.

Our costs will increase if we experience delays in clinical testing or marketing approvals. We do not know whether any of our clinical trials will begin as planned, will need to be reassigned or will be completed on schedule, or at all. Significant clinical trial delays also could shorten any periods during which we may have the exclusive right to commercialize our product candidates and may allow our competitors to bring products to market before we do, potentially impairing our ability to successfully commercialize our product candidates and harming our business and results of operations. Any delays in our clinical development programs may harm our business, financial condition and results of operations significantly. The clinical trials sponsored by our partners with our product candidates in combination with our partners’ therapies pose the same development risks.

We were not involved in the early development of our lead product candidates or in the development of third-party agents used in combination with our product candidates; therefore, we are dependent on third parties having accurately generated, collected, interpreted and reported data from certain preclinical and clinical trials for our product candidates.

We had no involvement with or control over the preclinical and clinical development of any of our lead product candidates or third-party agents used in combination with our product candidates. We are dependent on third parties having conducted their research and development in accordance with the applicable protocols and legal, regulatory and scientific standards; having accurately reported the results of all preclinical studies and clinical trials conducted with respect to such product candidates; and having correctly collected and interpreted the data from these trials. If these activities were not compliant, accurate or correct, the clinical development, regulatory approval or commercialization of our product candidates will be adversely affected.

If our clinical trials fail to replicate positive results from earlier preclinical studies or clinical trials conducted by us or third parties, we may be unable to successfully develop, obtain regulatory approval for or commercialize our product candidates.

Our preclinical studies or early clinical trials of our product candidates, whether conducted by us or third parties, may not necessarily be predictive of the results of later clinical trials that we

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conduct. Similarly, even if we are able to complete our planned clinical trials of our product candidates, positive results from such clinical trials may not be replicated in our subsequent preclinical studies or clinical trials.

Many companies in the pharmaceutical and biotechnology industries have suffered significant setbacks in late-stage clinical trials after achieving positive results in early-stage development, and we cannot be certain that we will not face similar setbacks. These setbacks have been caused by, among other things, preclinical findings made while clinical trials were underway or safety or efficacy observations made in preclinical studies and clinical trials, including previously unreported adverse events. Moreover, preclinical and clinical data are often susceptible to varying interpretations and analyses and many companies that believed their product candidates performed satisfactorily in preclinical studies and clinical trials nonetheless failed to obtain FDA, EMA or comparable foreign regulatory authority approval. Furthermore, the approval policies or regulations of the FDA, EMA or comparable foreign regulatory authorities may significantly change in a manner rendering our clinical data insufficient for approval, which may lead to the FDA, EMA or comparable foreign regulatory authorities delaying, limiting or denying approval of our product candidates.

As an organization, we have never successfully completed any clinical trials, and we may be unable to do so for any product candidates we may develop.

We will need to successfully complete clinical trials in order to obtain the approval of the FDA, EMA or comparable foreign regulatory authorities to market any product candidates. Carrying out clinical trials, including later-stage registrational clinical trials, is a complicated process. As an organization, we have not previously completed any clinical trials. In order to do so, we will need to build and expand our clinical development and regulatory capabilities, and we may be unable to recruit and train qualified personnel. We also expect to continue to rely on third parties to conduct our clinical trials. See “—Risks related to our reliance on third parties—We rely on third parties to conduct certain aspects of our preclinical studies and clinical trials. If these third parties do not successfully carry out their contractual duties, meet expected deadlines or comply with regulatory requirements, we may not be able to obtain regulatory approval of or commercialize any potential product candidates.” Consequently, we may be unable to successfully and efficiently execute and complete necessary clinical trials in a way that leads to NDA submission and approval of our product candidates. We may require more time and incur greater costs than our competitors and may not succeed in obtaining regulatory approval of any product candidates that we develop. Failure to commence or complete, or delays in, our planned clinical trials, could prevent us from or delay us in commercializing our product candidates.

The successful development of biopharmaceuticals is highly uncertain.

Successful development of biopharmaceuticals is highly uncertain and is dependent on numerous factors, many of which are beyond our control. Product candidates that appear promising in the early phases of development may fail to reach the market for several reasons including:

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clinical trial results may show the product candidates to be less effective than expected (for example, a clinical trial could fail to meet its primary or key secondary endpoint(s)) or to have unacceptable side effects or toxicities;

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failure to receive the necessary regulatory approvals or a delay in receiving such approvals. Among other things, such delays may be caused by patients who fail the trial screening process, slow enrollment in clinical trials, patients dropping out of trials, patients lost to follow-up, length of time to achieve trial endpoints, additional time requirements for data analysis or NDA preparation, discussions with the FDA, an FDA request for additional preclinical or clinical data (such as long-term toxicology studies) or unexpected safety or manufacturing issues;

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preclinical study results may show the product candidate to be less effective than desired or to have harmful side effects;

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supply issues, manufacturing costs and formulation issues, including our inability to successfully combine our product candidates with other therapies;

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post-marketing approval requirements; and

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the proprietary rights of others and their competing products and technologies that may prevent our product candidates from being commercialized.

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The length of time necessary to complete clinical trials and to submit an application for marketing approval for a final decision by a regulatory authority varies significantly from one product candidate to the next and from one country to the next, and may be difficult to predict.

Even if we are successful in obtaining marketing approval, commercial success of any approved products will also depend in large part on the availability of coverage and adequate reimbursement from third-party payors, including government payors such as the Medicare and Medicaid programs and managed care organizations in the United States or country specific governmental organizations in foreign countries, which may be affected by existing and future healthcare reform measures designed to reduce the cost of healthcare. Third-party payors could require us to conduct additional studies, including post-marketing studies related to the cost effectiveness of a product, to qualify for reimbursement, which could be costly and divert our resources. If government and other healthcare payors were not to provide coverage and adequate reimbursement for our products once approved, market acceptance and commercial success would be reduced.

In addition, if any of our product candidates receive marketing approval, we will be subject to significant regulatory obligations regarding the submission of safety and other post-marketing information and reports and registration, and will need to continue to comply (or ensure that our third-party providers comply) with current good manufacturing practices, or cGMPs, and good clinical practices, or GCPs, for any clinical trials that we conduct post-approval. In addition, there is always the risk that we, a regulatory authority or a third party might identify previously unknown problems with a product post-approval, such as adverse events of unanticipated severity or frequency. Compliance with these requirements is costly, and any failure to comply or other issues with our product candidates post-approval could adversely affect our business, financial condition and results of operations.

We expect to develop nirogacestat and mirdametinib, and potentially future product candidates, in combination with other therapies, and safety or supply issues with combination use products may delay or prevent development and approval of such product candidates.

We intend to develop nirogacestat and mirdametinib, and likely other future product candidates, in combination with one or more other approved or unapproved rational therapies to treat cancer or other diseases. For example, we are currently evaluating mirdametinib in combination with lifirafenib, BeiGene’s RAF dimer inhibitor, and nirogacestat in combination with belantamab mafodotin, belantamab mafodotin, GSK's investigational antibody-drug conjugate, or ADC, targeted to B-cell maturation antigen, or BCMA.

Even if any product candidate we develop were to receive marketing approval or be commercialized for use in combination with other existing therapies, we would continue to be subject to the risks that the FDA, EMA or comparable foreign regulatory authorities outside of the United States could revoke approval of the therapy used in combination with our product or that safety, efficacy, manufacturing or supply issues could arise with any of those existing therapies. If the therapies we use in combination with our product candidates are replaced as the

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standard of care for the indications we choose for any of our product candidates, the FDA, EMA or comparable foreign regulatory authorities may require us to conduct additional clinical trials. The occurrence of any of these risks could result in our own products, if approved, being removed from the market or being less successful commercially.

We also may choose to evaluate nirogacestat or mirdametinib or any other future product candidates in combination with one or more cancer therapies that have not yet been approved for marketing by the FDA, EMA or comparable foreign regulatory authorities. We will not be able to market and sell nirogacestat, mirdametinib or any product candidate we develop in combination with an unapproved cancer therapy for a combination indication if that unapproved cancer therapy does not ultimately obtain marketing approval either alone or in combination with our product. In addition, unapproved cancer therapies face the same risks described with respect to our product candidates currently in development and clinical trials, including the potential for serious adverse effects, delay in their clinical trials and lack of FDA approval.

If the FDA, EMA or comparable foreign regulatory authorities do not approve these other drugs or revoke their approval of, or if safety, efficacy, quality, manufacturing or supply issues arise with, the drugs we choose to evaluate in combination with our product candidate we develop, we may be unable to obtain approval of or market such combination therapy.

Due to our limited resources and access to capital, we must prioritize development of certain programs and product candidates; these decisions may prove to be wrong and may adversely affect our business.

We may fail to identify and acquire, through purchase or license, viable new product candidates for clinical development for a number of reasons. If we fail to identify and acquire additional product candidates, our business could be materially harmed.

Efforts to identify and pursue new product candidates and disease targets require substantial technical, financial and human resources, regardless of whether they are ultimately successful. We currently rely on third parties, including current and future collaborators, to perform all of our research and preclinical activities. Programs may initially show promise in preclinical studies, yet fail to yield positive results during clinical development for a number of reasons, including:

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the methodology used may not be successful in identifying potential indications and/or product candidates; or

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product candidates may, after further study, be shown to have harmful adverse effects or other characteristics that indicate they are unlikely to be effective products.

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Because we have limited financial and human resources, we intend to initially focus on programs and product candidates for a limited set of indications. As a result, we may forego or delay pursuit of opportunities with other product candidates or for other indications with our existing product candidates that may later prove to have greater commercial potential or a greater likelihood of success. We may focus our efforts and resources on potential product candidates or other potential programs that ultimately prove to be unsuccessful.

Our future clinical trials or those of our future collaborators may reveal significant adverse events not seen in prior preclinical studies or clinical trials and may result in a safety profile that could inhibit regulatory approval or market acceptance of any of our product candidates.

If significant adverse events or other side effects are observed in any of our clinical trials, we may have difficulty recruiting patients to our clinical trials, patients may drop out of our trials or we may be required to abandon the trials or our development efforts of one or more product candidates altogether. For example, a prior Phase 2 clinical trial (A4581002) of mirdametinib was

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terminated and enrollment in the Phase 2 portion of a Phase 1/2 clinical trial (A4581001) was halted as a result of adverse events observed at doses of mirdametinib of 15 mg twice daily, or BID, or above using both intermittent and continuous dosing schedules. These adverse events included ocular disorders (visual disturbances, blurred vision and retinal vein occlusion), nervous system disorders (confusion, slowed ideation, slurred speech and hallucinations), musculoskeletal and connective tissue disorders (general weakness and neck muscle weakness associated with mild and moderate elevations in creatine phosphokinase) and cardiac disorders (decreased left ventricular ejection fraction and congestive heart failure). Although these doses were significantly higher than the maximum allowable dose of 4 mg BID in our planned Phase 2b clinical trial of mirdametinib in NF1-PN, we plan to treat patients in this upcoming trial for a period of up to 24 months, which would be longer than any subjects have been treated with mirdametinib in prior trials. In our planned Phase 2b clinical trial, we may observe adverse events similar to those that were seen at higher doses of mirdametinib in prior clinical trials owing to the potentially increased duration of treatment, or potentially other factors. In addition, the trial will enroll pediatric NF1-PN patients. Patients under 16 years of age have never before been exposed to mirdametinib treatment, and it is possible that there may be unanticipated adverse events observed in this patient population.

If we elect or are required to delay, suspend or terminate any clinical trial of any product candidates that we develop, the commercial prospects of such product candidates will be harmed and our ability to generate product revenues from any of these product candidates will be delayed or eliminated. Serious adverse events or other adverse events, as well as tolerability issues, observed in clinical trials could hinder or prevent market acceptance of the product candidate at issue.

We, the FDA, EMA or comparable foreign regulatory authorities or an IRB may suspend clinical trials of a product candidate at any time for various reasons, including a belief that subjects in such trials are being exposed to unacceptable health risks or adverse side effects. Some potential therapeutics developed in the biotechnology industry that initially showed therapeutic promise in early-stage trials have later been found to cause side effects that prevented their further development. Even if the side effects do not preclude the product candidate from obtaining or maintaining marketing approval, restrictions could be imposed on the approval or an approved product could be subject to a “black box” warning, and undesirable side effects may inhibit market acceptance of the approved product due to its tolerability versus other therapies.

If we encounter difficulties enrolling patients in any of our clinical trials, our clinical development activities could be delayed or otherwise adversely affected.

The timely completion of clinical trials in accordance with their protocols depends, among other things, on our ability to enroll a sufficient number of patients who remain in the trial until its conclusion. We may experience difficulties in patient enrollment in our clinical trials for a variety of reasons, including:

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the patient eligibility and exclusion criteria defined in the protocol;

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the size of the patient population required for analysis of the clinical trial’s primary endpoints;

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the proximity of patients to clinical trial sites;

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the design of the clinical trial;

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our ability to recruit clinical trial investigators with the appropriate competencies and experience, and the ability of these investigators to identify and enroll suitable patients;

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perception of the safety profile of our product candidates;

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our ability to obtain and maintain patient consents; and

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the risk that patients enrolled in clinical trials will drop out of the trials before completion.

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For example, we are developing nirogacestat for the treatment of desmoid tumors and mirdametinib for the treatment of NF1-PN, both of which are rare diseases with small patient populations. As a result, we may encounter difficulties enrolling subjects in our clinical trials for these product candidates due, in part, to the small size of these patient populations. In addition, our clinical trials will compete with other clinical trials for product candidates that are in the same therapeutic areas as our product candidates, and this competition will reduce the number and types of patients available to us, because some patients who might have opted to enroll in our trials may instead opt to enroll in a clinical trial being conducted by one of our competitors. Since the number of qualified clinical investigators is limited, we expect to conduct some of our clinical trials at the same clinical trial sites that some of our competitors use, which will reduce the number of patients who are available for our clinical trials in such clinical trial site. In addition, in the case of mirdametinib, we may face difficulty with enrollment due to physician or patient perception of an adverse tolerability profile.

Delays in patient enrollment may result in increased costs or may affect the timing or outcome of our clinical trials, which could prevent completion of these trials and adversely affect our ability to advance the development of our product candidates.

The target patient populations of nirogacestat for the treatment of desmoid tumors and mirdametinib for the treatment of NF1-PN are small and have not been definitively determined. We must be able to successfully commercialize our product candidates and achieve sufficient market share in order to achieve profitability and growth.

Desmoid tumors and NF1-PN are rare diseases with small patient populations that have not been definitively determined. Even if our product candidates obtain regulatory approval in the United States, the European Union or other major markets, our estimates of the number of treatable patients could be lower than expected, which would adversely affect our results of operations and our business.

We face significant competition from other biopharmaceutical companies, and our operating results will suffer if we fail to compete effectively.

The biopharmaceutical industry is characterized by intense competition and rapid innovation. Our competitors may be able to develop other compounds or drugs that are able to achieve similar or better results. Our potential competitors include major multinational pharmaceutical companies, established biotechnology companies, specialty pharmaceutical companies and universities and other research institutions. Many of our competitors have substantially greater financial, technical and other resources, such as larger research and development staff and experienced marketing and manufacturing organizations and well-established sales forces. Smaller or early-stage companies may also prove to be significant competitors, particularly as they develop novel approaches to treating disease indications that our product candidates are also focused on treating. Established pharmaceutical companies may also invest heavily to accelerate discovery and development of novel therapeutics or to in-license novel therapeutics that could make the product candidates that we develop obsolete. Mergers and acquisitions in the biotechnology and pharmaceutical industries may result in even more resources being concentrated in our competitors. Competition may increase further as a result of advances in the commercial applicability of technologies and greater availability of capital for investment in these industries. Our competitors, either alone or with collaboration partners, may succeed in developing, acquiring or licensing on an exclusive basis drug or biologic products that are more effective, safer, more easily commercialized or less costly than our product candidates or may

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develop proprietary technologies or secure patent protection that we may need for the development of our technologies and products. We believe the key competitive factors that will affect the development and commercial success of our product candidates are efficacy, safety, tolerability, reliability, convenience of use, price and reimbursement.

Even if we obtain regulatory approval of our product candidates, the availability and price of our competitors’ products could limit the demand and the price we are able to charge for our product candidates. We may not be able to implement our business plan if the acceptance of our product candidates is inhibited by price competition or the reluctance of physicians to switch from existing methods of treatment to our product candidates, or if physicians switch to other new drug or biologic products or choose to reserve our product candidates for use in limited circumstances. For additional information regarding our competition, see “Business—Competition.”

Even if any product candidate we develop receives marketing approval, it may fail to achieve the degree of market acceptance by physicians, patients, third-party payors and others in the medical community necessary for commercial success.

If any future product candidate we develop receives marketing approval, whether as a single agent or in combination with other therapies, it may nonetheless fail to gain sufficient market acceptance by physicians, patients, third-party payors and others in the medical community. If the product candidates we develop do not achieve an adequate level of acceptance, we may not generate significant product revenues and we may not become profitable. The degree of market acceptance of any product candidate, if approved for commercial sale, will depend on a number of factors, including:

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efficacy and potential advantages compared to other treatments;

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the ability to offer our products, if approved, for sale at competitive prices;

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convenience and ease of administration compared to other treatments;

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the willingness of the target patient population to try new therapies and of physicians to prescribe these therapies;

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the strength of marketing and distribution support;

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the ability to obtain sufficient third-party coverage, market access and adequate reimbursement; and

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the prevalence and severity of any side effects.

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Changes in methods of product candidate manufacturing or formulation may result in additional costs or delay.

As product candidates proceed through preclinical studies to late-stage clinical trials towards potential approval and commercialization, it is common that various aspects of the development program, such as manufacturing methods and formulation, are altered along the way in an effort to optimize processes and results. Such changes carry the risk that they will not achieve these intended objectives. Any of these changes could cause our product candidates to perform differently and affect the results of planned clinical trials or other future clinical trials conducted with the materials manufactured using altered processes. Such changes may also require additional testing, including bridging or comparability testing to demonstrate the validity of clinical data obtained in clinical trials following manufacturing changes, FDA notification or FDA approval.

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Because all prior clinical trials of nirogacestat and mirdametinib were conducted by third parties, we will need to perform analytical and other tests to demonstrate that any new drug product material is comparable in all respects, including potency, to the product used in such earlier clinical trials. There is no assurance that any such product will pass the required comparability testing, that any other future third-party manufacturer that we engage will be successful in producing our product candidates or that any materials produced by any third-party manufacturer that we engage will have the same effect in patients that we have observed to date with respect to materials used in prior clinical trials.

All of the above could delay completion of clinical trials, require the conduct of bridging clinical trials or the repetition of one or more clinical trials, increase clinical trial costs, delay approval of our product candidates and jeopardize our ability to commence sales and generate revenue.

Moreover, we have not yet manufactured or processed on a commercial scale and may not be able to do so for any of our product candidates if approved. We may make changes as we work to optimize our manufacturing processes, but we cannot be sure that even minor changes in our processes will result in therapies that are safe and effective and approved for commercial sale.

If product liability lawsuits are brought against us, we may incur substantial liabilities and may be required to limit commercialization of our product candidates.

We face an inherent risk of product liability as a result of testing our product candidates in clinical trials and will face an even greater risk if we commercialize any products. For example, we may be sued if our product candidates cause or are perceived to cause injury or are found to be otherwise unsuitable during clinical trials, manufacturing, marketing or sale. Any such product liability claims may include allegations of defects in manufacturing, defects in design, a failure to warn of dangers inherent in the product, negligence, strict liability or a breach of warranties. Claims could also be asserted under state consumer protection acts. If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be required to limit commercialization of our product candidates. Even successful defense would require significant financial and management resources. Regardless of the merits or eventual outcome, liability claims may result in:

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inability to bring a product candidate to the market;

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decreased demand for our products;

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harm to our reputation;

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withdrawal of clinical trial participants and inability to continue clinical trials;

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initiation of investigations by regulators;

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costs to defend the related litigation;

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diversion of management’s time and our resources;

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substantial monetary awards to clinical trial participants or patients who receive an approved product;

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product recalls, withdrawals or labeling, marketing or promotional restrictions;

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loss of revenue;

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exhaustion of any available insurance and of our capital resources;

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the inability to commercialize any product candidate, if approved; and

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a decline in our stock price.

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Our inability to obtain sufficient product liability insurance at an acceptable cost to protect against potential product liability claims could prevent or inhibit the commercialization of products we develop, alone or with collaborators. Even if our agreements with any current or future corporate collaborators entitle us to indemnification against losses, that indemnification may not be available or adequate should any claim arise. Although we currently carry $5.0 million in clinical trial insurance, that amount of insurance coverage may not be adequate, and, in the future, we may be unable to maintain this insurance coverage, or we may not be able to obtain additional or replacement insurance at a reasonable cost, if at all. Our insurance policies also have various exclusions, and we may be subject to a product liability claim for which we have no coverage. We may have to pay any amounts awarded by a court or negotiated in a settlement that exceed our coverage limitations or that are not covered by our insurance, and we may not have, or be able to obtain, sufficient capital to pay those amounts.

Risks related to government regulation

The regulatory approval process for our product candidates in the United States, the European Union and other jurisdictions is currently uncertain and will be lengthy, time-consuming and inherently unpredictable and we may experience significant delays in the clinical development and regulatory approval, if any, of our product candidates.

The research, testing, manufacturing, labeling, approval, selling, import, export, marketing and distribution of drug products are subject to extensive regulation by the FDA in the United States, the EMA in the European Union and comparable foreign regulatory authorities. We are not permitted to market any product in any jurisdiction until we receive marketing approval from the appropriate regulatory authority. We have not previously submitted an NDA to the FDA, an MAA to the EMA or similar marketing application to comparable foreign regulatory authorities. In the United States, an NDA must include extensive preclinical and clinical data and supporting information to establish that the product candidate is safe, pure and potent for each desired indication. An NDA must also include significant information regarding the chemistry, manufacturing and controls for the product, and the manufacturing facilities must complete a successful pre-approval inspection.

The FDA may also require a panel of experts, referred to as an Advisory Committee, to deliberate on the adequacy of the safety and efficacy data to support approval. The opinion of the Advisory Committee, although not binding, may have a significant impact on our ability to obtain approval of any product candidates that we develop based on the completed clinical trials.

In addition, clinical trials can be delayed or terminated for a variety of reasons, including delays or failures related to:

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obtaining regulatory authorization to begin a clinical trial, if applicable;

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the availability of financial resources to begin and complete the planned trials;

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reaching agreement on acceptable terms with prospective CROs and clinical trial sites, the terms of which can be subject to extensive negotiation and may vary significantly among different CROs and clinical trial sites;

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obtaining approval at each clinical trial site by an independent IRB or ethics committee;

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recruiting suitable patients to participate in a clinical trial in a timely manner;

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having patients complete a clinical trial or return for post-treatment follow-up;

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clinical trial sites deviating from clinical trial protocol, not complying with GCP requirements or dropping out of a trial;

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addressing any patient safety concerns that arise during the course of a clinical trial;

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addressing any conflicts with new or existing laws or regulations;

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adding new clinical trial sites; or

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manufacturing qualified materials under cGMP regulations for use in clinical trials.

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Patient enrollment is a significant factor in the timing of clinical trials and is affected by many factors. Further, a clinical trial may be suspended or terminated by us, the IRBs for the institutions in which such clinical trials are being conducted, or the FDA, EMA or comparable foreign regulatory authorities, or recommended for suspension or termination by the DSMB for such clinical trial, due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or clinical trial sites by the FDA, EMA or comparable foreign regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a product candidate, changes in governmental regulations or administrative actions or lack of adequate funding to continue the clinical trial. If we experience termination of, or delays in the completion of, any clinical trial of our product candidates, the commercial prospects for our product candidates will be harmed, and our ability to generate product revenue will be delayed. In addition, any delays in completing any clinical trials will increase our costs, slow down our product development and approval process and jeopardize our ability to commence product sales and generate revenue.

The FDA, EMA or comparable foreign regulatory authorities may disagree with our regulatory plan for our product candidates.

The general approach for FDA approval of a new drug is dispositive data from one or more well-controlled Phase 3 clinical trials of the product candidate in the relevant patient population. Phase 3 clinical trials typically involve a large number of patients, have significant costs and take years to complete.

Our clinical trial results may not support approval of our product candidates. In addition, our product candidates could fail to receive regulatory approval, or regulatory approval could be delayed, for many reasons, including the following:

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the FDA, EMA or comparable foreign regulatory authorities may disagree with the dosing regimen, design or implementation of our clinical trials;

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we may be unable to demonstrate to the satisfaction of the FDA, EMA or comparable foreign regulatory authorities that our product candidates are safe and effective for any of their proposed indications;

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the results of clinical trials may not meet the level of statistical significance required by the FDA, EMA or comparable foreign regulatory authorities for approval;

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we may be unable to demonstrate that our product candidates’ clinical and other benefits outweigh their safety risks;

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the FDA, EMA or comparable foreign regulatory authorities may disagree with our interpretation of data from preclinical studies or clinical trials;

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the data collected from clinical trials of our product candidates may not be sufficient to the satisfaction of the FDA, EMA or comparable foreign regulatory authorities to support the submission of an NDA or other comparable submission in foreign jurisdictions or to obtain regulatory approval in the United States or elsewhere;

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the FDA, EMA or comparable foreign regulatory authorities may fail to approve the manufacturing processes or facilities of third-party manufacturers with which we contract for clinical and commercial supplies; and

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the approval policies or regulations of the FDA, EMA or comparable foreign regulatory authorities may significantly change in a manner rendering our clinical data insufficient for approval.

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We may seek regulatory approval of our product candidates, including nirogacestat, based on an interim analysis conducted of a registrational trial, particularly if the interim analysis is statistically significant for the primary endpoint and the safety data demonstrate an acceptable safety and tolerability profile. The results of any such interim analysis would be discussed with FDA at a pre-NDA meeting to assess the adequacy of the data to support the submission of a NDA; however, if the FDA does not agree that the interim analysis provides a sufficient basis for regulatory approval, we would not submit an NDA until the conclusion of such registrational trial.

Interim “top-line” and preliminary results from our clinical trials that we announce or publish from time to time may change as more patient data become available and are subject to audit and verification procedures that could result in material changes in the final data.

From time to time, we may publish interim top-line or preliminary results from our clinical trials. Interim results from clinical trials that we may complete are subject to the risk that one or more of the clinical outcomes may materially change as patient enrollment continues and more patient data become available. Preliminary or top-line results also remain subject to audit and verification procedures that may result in the final data being materially different from the preliminary data we previously published. As a result, interim and preliminary data should be viewed with caution until the final data are available. Differences between preliminary or interim data and final data could significantly harm our business prospects and may cause the trading price of our common stock to fluctuate significantly.

We have been granted Orphan Drug Designation for nirogacestat and mirdametinib and may seek Orphan Drug Designation for other product candidates, and we may be unable to maintain the benefits associated with Orphan Drug Designation, including the potential for market exclusivity.

Regulatory authorities in some jurisdictions, including the United States and Europe, may designate drugs and therapeutic biologics for relatively small patient populations as orphan drugs. Under the Orphan Drug Act, the FDA may designate a drug or therapeutic biologic as an orphan drug if it is a drug or therapeutic biologic intended to treat a rare disease or condition, which is generally defined as a patient population of fewer than 200,000 individuals annually in the United States, or a patient population greater than 200,000 in the United States where there is no reasonable expectation that the cost of developing the drug or therapeutic biologic will be recovered from sales in the United States. In the United States, Orphan Drug Designation entitles a party to financial incentives such as opportunities for grant funding toward clinical trial costs, tax advantages and user-fee waivers. In addition, if a product that has Orphan Drug Designation subsequently receives the first FDA approval for the disease for which it has such designation, the product is entitled to orphan drug exclusivity, which means that the FDA may not approve any other applications, including a full NDA or Biologics License Application, or BLA, to market the same product for the same indication for seven years, except in limited circumstances, such as a showing of clinical superiority to the product with orphan drug exclusivity or where the manufacturer is unable to assure sufficient product quantity.

In June 2018, the FDA granted Orphan Drug Designation to nirogacestat for the treatment of desmoid tumors. In October 2018, the FDA granted Orphan Drug Designation to mirdametinib

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for the treatment of NF1. We may seek Orphan Drug Designations for nirogacestat and mirdametinib for other indications or for our other product candidates. There can be no assurances that we will be able to obtain such designations.

Even if we obtain Orphan Drug Designation for any of our future product candidates in specific indications, we may not be the first to obtain marketing approval of nirogacestat, mirdametinib or any other such product candidates for the orphan-designated indication due to the uncertainties associated with developing pharmaceutical products. In addition, exclusive marketing rights in the United States may be limited if we seek approval for an indication broader than the orphan-designated indication or may be lost if the FDA later determines that the request for designation was materially defective or if the manufacturer is unable to assure sufficient quantities of the product to meet the needs of patients with the rare disease or condition.

Further, even if we obtain orphan drug exclusivity in the United States for a product, that exclusivity may not effectively protect the product from competition because different drugs or therapeutic biologics with different active moieties can be approved for the same condition. Even after an orphan product is approved, the FDA can subsequently approve the same drug or therapeutic biologic with the same active moiety for the same condition if the FDA concludes that the later drug or therapeutic biologic is safer, more effective or makes a major contribution to patient care. In Europe, we could be prevented from marketing our products if a similar medicinal product is granted Orphan Drug Designation for the same indications that we are pursuing. Once authorized, with a limited number of exceptions, neither the competent authorities of the EU member states, the EMA or the European Commission are permitted to accept applications or grant marketing authorization for other similar medicinal products with the same therapeutic indication. Marketing authorization could also be granted to a similar medicinal product with the same orphan indication if the latter product is safer, more effective or otherwise clinically superior to the original orphan medicinal product. Further, the composition of matter patents for nirogacestat and mirdametinib expire in 2025 and 2021, respectively, and if orphan drug exclusivity does not protect these products from competition, our business and financial condition could be materially adversely affected. Orphan Drug Designation neither shortens the development time or regulatory review time of a drug or therapeutic biologic nor gives the drug or therapeutic biologic any advantage in the regulatory review or approval process. In addition, while we may seek Orphan Drug Designation for our future product candidates, we may never receive such designations.

Breakthrough Therapy Designation or Fast Track Designation from the FDA may not actually lead to a faster development or regulatory review or approval process.

The FDA has granted Fast Track Designation for nirogacestat for the treatment of adult patients with progressive, unresectable, recurrent or refractory desmoid tumors or deep fibromatosis, and has granted Fast Track Designation for mirdametinib for the treatment of patients at least two years of age with NF1-associated inoperable PN that are progressing or causing significant morbidity. We may seek Breakthrough Therapy Designation for our product candidates or Fast Track Designation for certain of our other product candidates.

If a product is intended for the treatment of a serious or life-threatening condition and the product demonstrates the potential to address unmet medical needs for this condition, the product sponsor may apply for Fast Track Designation. The FDA has broad discretion whether or not to grant this designation, so even if we believe one of our product candidates is eligible for this designation, we cannot assure you that the FDA would decide to grant it. Even if we do

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receive Fast Track Designation, we may not experience a faster development process, review or approval compared to conventional FDA procedures. The FDA may withdraw Fast Track Designation if it believes that the designation is no longer supported by data from our clinical development program.

A breakthrough therapy is defined as a product that is intended, alone or in combination with one or more other products, to treat a serious or life-threatening disease or condition, and preliminary clinical evidence indicates that the product may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. For products that have been designated as breakthrough therapies, interaction and communication between the FDA and the sponsor of the trial can help to identify the most efficient path for clinical development while minimizing the number of patients placed in ineffective control regimens.

Designation as a breakthrough therapy is within the discretion of the FDA. Accordingly, even if we believe one of our product candidates meets the criteria for designation as a breakthrough therapy, the FDA may disagree and instead determine not to make such designation. In any event, the receipt of a Breakthrough Therapy Designation may not result in a faster development process, review or approval compared to products considered for approval under conventional FDA procedures and does not assure ultimate approval by the FDA. In addition, even if a product candidate qualifies as a breakthrough therapy, the FDA may later decide that the product no longer meets the conditions for qualification and rescind the Breakthrough Therapy Designation.

The results of clinical trials conducted at clinical trial sites outside the United States might not be accepted by the FDA, and data developed outside of a foreign jurisdiction similarly might not be accepted by such foreign regulatory authority.

Some of the prior clinical trials for our product candidates were conducted outside the United States, and we intend to conduct additional clinical trials outside the United States. Although the FDA, EMA or comparable foreign regulatory authorities may accept data from clinical trials conducted outside the relevant jurisdiction, acceptance of these data is subject to certain conditions. For example, the FDA requires that the clinical trial must be well designed and conducted and performed by qualified investigators in accordance with ethical principles such as IRB or ethics committee approval and informed consent, the trial population must adequately represent the U.S. population, and the data must be applicable to the U.S. population and U.S. medical practice in ways that the FDA deems clinically meaningful. In addition, while these clinical trials are subject to the applicable local laws, acceptance of the data by the FDA will be dependent upon its determination that the trials were conducted consistent with all applicable U.S. laws and regulations. There can be no assurance that the FDA will accept data from trials conducted outside of the United States as adequate support of a marketing application. Similarly, we must also ensure that any data submitted to foreign regulatory authorities adheres to their standards and requirements for clinical trials and there can be no assurance a comparable foreign regulatory authority would accept data from trials conducted outside of its jurisdiction.

Our relationships with healthcare providers and physicians and third-party payors will be subject to applicable anti-kickback, fraud and abuse and other healthcare laws and regulations, which could expose us to criminal sanctions, civil penalties, contractual damages, reputational harm and diminished profits and future earnings.

Healthcare providers, physicians and third-party payors in the United States and elsewhere play a primary role in the recommendation and prescription of pharmaceutical products. Arrangements with third-party payors and customers can expose pharmaceutical manufacturers to broadly applicable fraud and abuse and other healthcare laws and regulations, including, without limitation, the federal Anti-Kickback Statute and the federal False Claims Act, or FCA, which may

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constrain the business or financial arrangements and relationships through which such companies sell, market and distribute pharmaceutical products. In particular, the research of our product candidates, as well as the promotion, sales and marketing of healthcare items and services, as well as certain business arrangements in the healthcare industry, are subject to extensive laws designed to prevent fraud, kickbacks, self-dealing and other abusive practices. These laws and regulations may restrict or prohibit a wide range of pricing, discounting, marketing and promotion, structuring and commission(s), certain customer incentive programs and other business arrangements generally. Activities subject to these laws also involve the improper use of information obtained in the course of patient recruitment for clinical trials. The applicable federal, state and foreign healthcare laws and regulations that may affect our ability to operate include, but are not limited to:

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the federal Anti-Kickback Statute, which prohibits, among other things, knowingly and willfully soliciting, receiving, offering or paying any remuneration (including any kickback, bribe or rebate), directly or indirectly, overtly or covertly, in cash or in kind, to induce, or in return for, either the referral of an individual, or the purchase, lease, order or recommendation of any good, facility, item or service for which payment may be made, in whole or in part, under a federal healthcare program, such as the Medicare and Medicaid programs. A person or entity can be found guilty of violating the statute without actual knowledge of the statute or specific intent to violate it. In addition, a claim including items or services resulting from a violation of the federal Anti-Kickback Statute constitutes a false or fraudulent claim for purposes of the FCA. The Anti-Kickback Statute has been interpreted to apply to arrangements between pharmaceutical manufacturers on the one hand and prescribers, purchasers, and formulary managers on the other. There are a number of statutory exceptions and regulatory safe harbors protecting some common activities from prosecution;

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the federal civil and criminal false claims laws and civil monetary penalty laws, including the FCA, which prohibit, among other things, individuals or entities from knowingly presenting, or causing to be presented, false or fraudulent claims for payment to, or approval by Medicare, Medicaid or other federal healthcare programs, knowingly making, using or causing to be made or used a false record or statement material to a false or fraudulent claim or an obligation to pay or transmit money to the federal government, or knowingly concealing or knowingly and improperly avoiding or decreasing or concealing an obligation to pay money to the federal government. Manufacturers can be held liable under the FCA even when they do not submit claims directly to government payors if they are deemed to “cause” the submission of false or fraudulent claims. The FCA also permits a private individual acting as a “whistleblower” to bring actions on behalf of the federal government alleging violations of the FCA and to share in any monetary recovery;

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the federal Health Insurance Portability and Accountability Act of 1996, or HIPAA, which created additional federal criminal statutes that prohibit knowingly and willfully executing, or attempting to execute, a scheme to defraud any healthcare benefit program or obtain, by means of false or fraudulent pretenses, representations or promises, any of the money or property owned by, or under the custody or control of, any healthcare benefit program, regardless of the payor (e.g., public or private) and knowingly and willfully falsifying, concealing or covering up by any trick or device a material fact or making any materially false statements in connection with the delivery of, or payment for, healthcare benefits, items or services relating to healthcare matters. Similar to the federal Anti-Kickback Statute, a person or entity can be found guilty of violating HIPAA without actual knowledge of the statute or specific intent to violate it;

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HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act of 2009, or HITECH, and their respective implementing regulations, which impose, among other

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things, requirements on certain healthcare providers, health plans and healthcare clearinghouses, known as covered entities, as well as their respective business associates, independent contractors that perform services for covered entities that involve the use, or disclosure of, individually identifiable health information, relating to the privacy, security and transmission of individually identifiable health information. HITECH also created new tiers of civil monetary penalties, amended HIPAA to make civil and criminal penalties directly applicable to business associates, and gave state attorneys general new authority to file civil actions for damages or injunctions in federal courts to enforce the federal HIPAA laws and seek attorneys’ fees and costs associated with pursuing federal civil actions;

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the federal Physician Payments Sunshine Act, created under the Patient Protection and Affordable Care Act, as amended, or ACA, and its implementing regulations, which require some manufacturers of drugs, devices, biologicals and medical supplies for which payment is available under Medicare, Medicaid or the Children’s Health Insurance Program (with certain exceptions) to report annually to the Centers for Medicare & Medicaid Services, or CMS, of the U.S. Department of Health and Human Services, or HHS, information related to payments or other transfers of value made to physicians (defined to include doctors, dentists, optometrists, podiatrists and chiropractors) and teaching hospitals, as well as ownership and investment interests held by physicians and their immediate family members; and

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analogous state and foreign laws and regulations, such as state anti-kickback and false claims laws, which may apply to sales or marketing arrangements and claims involving healthcare items or services reimbursed by non-governmental third-party payors, including private insurers, and may be broader in scope than their federal equivalents; state and foreign laws that require pharmaceutical companies to comply with the pharmaceutical industry’s voluntary compliance guidelines and the relevant compliance guidance promulgated by the federal government or otherwise restrict payments that may be made to healthcare providers; state and foreign laws that require drug manufacturers to report information related to payments and other transfers of value to physicians and other healthcare providers, marketing expenditures or drug pricing; state and local laws that require the registration of pharmaceutical sales representatives; and state and foreign laws governing the privacy and security of health information in certain circumstances, many of which differ from each other in significant ways and often are not preempted by HIPAA, thus complicating compliance efforts.

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The distribution of pharmaceutical products is subject to additional requirements and regulations, including extensive record-keeping, licensing, storage and security requirements intended to prevent the unauthorized sale of pharmaceutical products. Pharmaceutical companies may also be subject to federal consumer protection and unfair competition laws, which broadly regulate marketplace activities and activities that potentially harm consumers.

The scope and enforcement of each of these laws is uncertain and subject to rapid change in the current environment of healthcare reform, especially in light of the lack of applicable precedent and regulations. For example, on January 31, 2019, the HHS and HHS Office of Inspector General, or OIG, proposed an amendment to one of the existing federal Anti-Kickback Statute safe harbors (42 C.F.R. 1001.952(h)) which would prohibit certain biopharmaceutical manufacturers from offering rebates to pharmacy benefit managers, or PBMs, in the Medicare Part D and Medicaid managed care programs. The proposed amendment would remove protection for “discounts” from federal Anti-Kickback Statute enforcement action, and would include criminal and civil penalties for knowingly and willfully offering, paying, soliciting or receiving remuneration to induce or reward the referral of business reimbursable under federal healthcare programs. At the same time, HHS also proposed to create a new safe harbor to protect point-of-sale discounts that drug manufacturers provide directly to patients, and adds another safe harbor to protect certain administrative fees paid by manufacturers to PBMs. If this proposal

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is adopted, in whole or in part, it could affect the pricing and reimbursement for any products for which we receive approval in the future. Federal and state enforcement bodies have recently increased their scrutiny of interactions between healthcare companies and healthcare providers, which has led to a number of investigations, prosecutions, convictions and settlements in the healthcare industry. Ensuring business arrangements comply with applicable healthcare laws, as well as responding to possible investigations by government authorities, can be time and resource-consuming and can divert a company’s attention from the business.

It is possible that governmental and enforcement authorities will conclude that our business practices may not comply with current or future statutes, regulations or case law interpreting applicable fraud and abuse or other healthcare laws and regulations. If any such actions are instituted against us, and we are not successful in defending ourselves or asserting our rights, those actions could have a significant impact on our business, including the imposition of civil, criminal and administrative penalties, damages, fines, disgorgement, imprisonment, exclusion from participation in federal and state funded healthcare programs, contractual damages and the curtailment or restricting of our operations, as well as additional reporting obligations and oversight if we become subject to a corporate integrity agreement or other agreement to resolve allegations of non-compliance with these laws. Further, if any of the physicians or other healthcare providers or entities with whom we expect to do business is found to be not in compliance with applicable laws, they may be subject to significant criminal, civil or administrative sanctions, including exclusions from government funded healthcare programs. Any action for violation of these laws, even if successfully defended, could cause a biopharmaceutical manufacturer to incur significant legal expenses and divert management’s attention from the operation of the business. Prohibitions or restrictions on sales or withdrawal of future marketed products could materially affect business in an adverse way.

Obtaining and maintaining regulatory approval of our product candidates in one jurisdiction does not mean that we will be successful in obtaining regulatory approval of our product candidates in other jurisdictions.

Obtaining and maintaining regulatory approval of our product candidates in one jurisdiction does not guarantee that we will be able to obtain or maintain regulatory approval in any other jurisdiction, while a failure or delay in obtaining regulatory approval in one jurisdiction may have a negative effect on the regulatory approval process in others. For example, even if the FDA grants marketing approval of a product candidate, the EMA or comparable foreign regulatory authorities must also approve the manufacturing, marketing and promotion of the product candidate in those countries. Approval procedures vary among jurisdictions and can involve requirements and administrative review periods different from, and greater than, those in the United States, including additional preclinical studies or clinical trials, as clinical trials conducted in one jurisdiction may not be accepted by regulatory authorities in other jurisdictions. In many jurisdictions outside the United States, a product candidate must be approved for reimbursement before it can be approved for sale in that jurisdiction. In some cases, the price that we intend to charge for our products is also subject to approval.

We may also submit marketing applications in other countries. Regulatory authorities in jurisdictions outside of the United States have requirements for approval of product candidates with which we must comply prior to marketing in those jurisdictions. Obtaining foreign regulatory approvals and compliance with foreign regulatory requirements could result in significant delays, difficulties and costs for us and could delay or prevent the introduction of our products in certain countries. If we fail to comply with the regulatory requirements in international markets and/or receive applicable marketing approvals, our target market will be reduced and our ability to realize the full market potential of our product candidates will be harmed.

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Even if we receive regulatory approval of any product candidates, we will be subject to ongoing regulatory obligations and continued regulatory review, which may result in significant additional expense and we may be subject to penalties if we fail to comply with regulatory requirements or experience unanticipated problems with our product candidates.

If any of our product candidates are approved, they will be subject to ongoing regulatory requirements for manufacturing, labeling, packaging, storage, advertising, promotion, sampling, record-keeping, conduct of post-marketing studies and submission of safety, efficacy and other post-market information, including both federal and state requirements in the United States and requirements of comparable foreign regulatory authorities. In addition, we will be subject to continued compliance with cGMP and GCP requirements for any clinical trials that we conduct post-approval.

Manufacturers and manufacturers’ facilities are required to comply with extensive FDA, EMA and comparable foreign regulatory authority requirements, including ensuring that quality control and manufacturing procedures conform to cGMP regulations. As such, we and our contract manufacturers will be subject to continual review and inspections to assess compliance with cGMP and adherence to commitments made in any BLA, other marketing application and previous responses to inspection observations. Accordingly, we and others with whom we work must continue to expend time, money and effort in all areas of regulatory compliance, including manufacturing, production and quality control.

Any regulatory approvals that we receive for our product candidates may be subject to limitations on the approved indicated uses for which the product may be marketed or to the conditions of approval, or contain requirements for potentially costly post-marketing testing, including Phase 4 clinical trials and surveillance to monitor the safety and efficacy of the product candidate. Certain endpoint data we hope to include in any approved product labeling also may not make it into such labeling, including exploratory or secondary endpoint data such as patient-reported outcome measures. The FDA may also require a risk evaluation and mitigation strategies, or REMS, program as a condition of approval of our product candidates, which could entail requirements for long-term patient follow-up, a medication guide, physician communication plans or additional elements to ensure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. In addition, if the FDA, EMA or a comparable foreign regulatory authority approves our product candidates, we will have to comply with requirements including submissions of safety and other post-marketing information and reports and registration.

The FDA may impose consent decrees or withdraw approval if compliance with regulatory requirements and standards is not maintained or if problems occur after the product reaches the market. Later discovery of previously unknown problems with our product candidates, including adverse events of unanticipated severity or frequency, or with our third-party manufacturers or manufacturing processes, or failure to comply with regulatory requirements, may result in revisions to the approved labeling to add new safety information, imposition of post-market studies or clinical trials to assess new safety risks or imposition of distribution restrictions or other restrictions under a REMS program. Other potential consequences include, among other things:

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restrictions on the marketing or manufacturing of our products, withdrawal of the product from the market or voluntary or mandatory product recalls;

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fines, warning letters or holds on clinical trials;

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refusal by the FDA to approve pending applications or supplements to approved applications filed by us or suspension or revocation of license approvals;

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product seizure or detention or refusal to permit the import or export of our product candidates; and

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injunctions or the imposition of civil or criminal penalties.

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The FDA strictly regulates marketing, labeling, advertising and promotion of products that are placed on the market. Products may be promoted only for the approved indications and in accordance with the provisions of the approved label. The policies of the FDA, EMA and comparable foreign regulatory authorities may change and additional government regulations may be enacted that could prevent, limit or delay regulatory approval of our product candidates. We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative action, either in the United States or abroad. If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, we may lose any marketing approval that we may have obtained and we may not achieve or sustain profitability.

Coverage and reimbursement may be limited or unavailable in certain market segments for our product candidates, if approved, which could make it difficult for us to sell any product candidates profitably.

The success of our product candidates, if approved, depends on the availability of coverage and adequate reimbursement from third-party payors. We cannot be sure that coverage and reimbursement will be available for, or accurately estimate the potential revenue from, our product candidates or assure that coverage and reimbursement will be available for any product that we may develop.

Patients who are provided medical treatment for their conditions generally rely on third-party payors to reimburse all or part of the costs associated with their treatment. Coverage and adequate reimbursement from governmental healthcare programs, such as Medicare and Medicaid, and commercial payors is critical to new product acceptance.

Government authorities and third-party payors, such as private health insurers and health maintenance organizations, decide which drugs and treatments they will cover and the amount of reimbursement. Coverage and reimbursement by a third-party payor may depend upon a number of factors, including the third-party payor’s determination that use of a product is:

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safe, effective and medically necessary;

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appropriate for the specific patient;

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cost-effective; and

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neither experimental nor investigational.

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In the United States, no uniform policy of coverage and reimbursement for products exists among third-party payors. As a result, obtaining coverage and reimbursement approval of a product from a government or other third-party payor is a time-consuming and costly process that could require us to provide to each payor supporting scientific, clinical and cost-effectiveness data for the use of our products on a payor-by-payor basis, with no assurance that coverage and adequate reimbursement will be obtained. Even if we obtain coverage for a given product, the resulting reimbursement payment rates might not be adequate for us to achieve or sustain profitability or may require co-payments that patients find unacceptably high. Additionally, third-party payors may not cover, or provide adequate reimbursement for, long-term follow-up evaluations required following the use of product candidates, once approved. Patients are unlikely to use our product candidates, once approved, unless coverage is provided and reimbursement is adequate

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to cover a significant portion of their cost. There is significant uncertainty related to insurance coverage and reimbursement of newly approved products. It is difficult to predict at this time what third-party payors will decide with respect to the coverage and reimbursement for our product candidates.

Payment methodologies may be subject to changes in healthcare legislation and regulatory initiatives. For example, the Middle Class Tax Relief and Job Creation Act of 2012 required that CMS, the agency responsible for administering the Medicare program, reduce the Medicare clinical laboratory fee schedule by 2% in 2013, which served as a base for 2014 and subsequent years. In addition, effective January 1, 2014, CMS also began bundling the Medicare payments for certain laboratory tests ordered while a patient received services in a hospital outpatient setting. Additional state and federal healthcare reform measures are expected to be adopted in the future, any of which could limit the amounts that federal and state governments will pay for healthcare products and services, which could result in reduced demand for certain pharmaceutical products or additional pricing pressures.

Moreover, increasing efforts by governmental and third-party payors in the United States and abroad to cap or reduce healthcare costs may cause such organizations to limit both coverage and the level of reimbursement for newly approved products and, as a result, they may not cover or provide adequate payment for our product candidates. There has been increasing legislative and enforcement interest in the United States with respect to specialty drug pricing practices. Specifically, there have been several recent U.S. Congressional inquiries and proposed and enacted federal and state legislation designed to, among other things, bring more transparency to drug pricing, reduce the cost of prescription drugs under Medicare, review the relationship between pricing and manufacturer patient programs and reform government program reimbursement methodologies for drugs. We expect to experience pricing pressures in connection with the sale of any of our product candidates due to the trend toward managed healthcare, the increasing influence of health maintenance organizations, cost containment initiatives and additional legislative changes.

At the federal level, the Trump administration’s budget for fiscal year 2019 contains further drug price control measures that could be enacted during the 2019 legislative session or in other future legislation, including, for example, measures to permit Medicare Part D plans to negotiate the price of certain drugs under Medicare Part B, to allow some states to negotiate drug prices under Medicaid and to eliminate cost sharing for generic drugs for low-income patients. While any proposed measures will require authorization through additional legislation to become effective, Congress and the Trump administration have each indicated that it will continue to seek new legislative and/or administrative measures to control drug costs.

At the state level, legislatures are increasingly passing legislation and implementing regulations designed to control pharmaceutical and biological product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing.

On May 10, 2019, CMS announced a new pricing transparency rule, which goes into effect on July 9, 2019. This final rule requires direct-to-consumer television advertisements for prescription drugs and biological products for which reimbursement is available, directly or indirectly, through or under Medicare or Medicaid to include the list price of that product, except for a prescription drug or biological product that has a list price of less than $35 per month for a 30-day supply or typical course of treatment. Prescription drugs and biological products that are in violation of these requirements will be included on a public list. The pricing transparency rule could have a negative effect on our business.

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Ongoing healthcare legislative and regulatory reform measures may have a material adverse effect on our business and results of operations.

Changes in regulations, statutes or the interpretation of existing regulations could impact our business in the future by requiring, for example: (i) changes to our manufacturing arrangements; (ii) additions or modifications to product labeling; (iii) the recall or discontinuation of our products; or (iv) additional record-keeping requirements. If any such changes were to be imposed, they could adversely affect the operation of our business.

In the United States, there have been and continue to be a number of legislative initiatives to contain healthcare costs. For example, in March 2010, the ACA was passed, which substantially changed the way healthcare is financed by both governmental and private insurers, and significantly impacted the U.S. biopharmaceutical industry. The ACA, among other things, addressed a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for drugs that are inhaled, infused, instilled, implanted or injected, increased the minimum Medicaid rebates owed by manufacturers under the Medicaid Drug Rebate Program and extended the rebate program to individuals enrolled in Medicaid managed care organizations, established annual fees and taxes on manufacturers of certain branded prescription drugs and created a new Medicare Part D coverage gap discount program, in which manufacturers must agree to offer 70% point-of-sale discounts off negotiated prices of applicable brand drugs to eligible beneficiaries during their coverage gap period, as a condition for the manufacturer’s outpatient drugs to be covered under Medicare Part D.

Some of the provisions of the ACA have yet to be fully implemented, while certain provisions have been subject to judicial and Congressional challenges, as well as efforts by the Trump administration to repeal or replace certain aspects of the ACA. For example, Congress has considered legislation that would repeal or repeal and replace all or part of the ACA. While Congress has not passed repeal legislation, the Tax Reform Act includes a provision that repealed, effective January 1, 2019, the tax-based shared responsibility payment imposed by the ACA on certain individuals who fail to maintain qualifying health coverage for all or part of a year that is commonly referred to as the “individual mandate.” As a result of the individual mandate repeal, subsequent litigation challenged the validity of the ACA. On December 14, 2018, a U.S. District Court judge in the Northern District of Texas ruled that the individual mandate portion of the ACA is an essential and inseverable feature of the ACA, and therefore because the mandate was repealed as part of the Tax Cuts and Jobs Act, or TCJA, the remaining provisions of the ACA are invalid as well. The Trump administration and CMS have both stated that the ruling will have no immediate effect, and on December 30, 2018 the same judge issued an order staying the judgment pending appeal. It is unclear how this decision and any subsequent appeals and other efforts to repeal and replace the ACA will impact the ACA and our business.

Since January 2017, President Trump has signed two Executive Orders designed to delay the implementation of certain provisions of the ACA or otherwise circumvent some of the requirements for health insurance mandated by the ACA. Further, the Trump administration has concluded that cost-sharing reduction, or CSR, payments to insurance companies required under the ACA have not received necessary appropriations from Congress and announced that it will discontinue these payments immediately until those appropriations are made. The loss of the CSR payments is expected to increase premiums on certain policies issued by qualified health plans under the ACA. Bipartisan bills to appropriate funds for CSR payments were proposed in 2017 and 2018, but the proposals have not been enacted into law. Multiple state Attorneys General filed suit to stop the administration from terminating the subsidies, but their case was dismissed by a federal judge in California on July 18, 2018. Furthermore, on June 14, 2018, the U.S. Court of Appeals for the Federal Circuit ruled that the federal government was not required to pay more

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than $12 billion in ACA risk corridor payments to third-party payors who argued were owed to them. The effects of this gap in reimbursement on third-party payors, the viability of the ACA marketplace and providers, and the potential effect on our business, are not yet known.

Additionally, CMS has recently proposed regulations that would give states greater flexibility in setting benchmarks for insurers in the individual and small group marketplaces, which may have the effect of relaxing the essential health benefits required under the ACA for plans sold through such marketplaces. The Bipartisan Budget Act of 2018, or BBA, also amended the ACA, effective January 1, 2019, by increasing the point-of-sale discount that is owed by pharmaceutical manufacturers who participate in Medicare Part D and closing the coverage gap in most Medicare drug plans, commonly referred to as the “donut hole.” Moreover, in July 2018, CMS published a final rule permitting further collections and payments to and from certain ACA qualified health plans and health insurance issuers under the ACA risk adjustment program in response to the outcome of federal district court litigation regarding the method CMS uses to determine this risk adjustment. On May 23, 2019, CMS finalized a rule that amends the Medicare Advantage and Medicare Part D prescription drug benefit regulations to reduce out of pocket costs for plan enrollees and allows Medicare plans to negotiate lower rates for certain drugs. Among other things, the final rule allows Medicare Advantage plans to use pre authorization, or PA, and step therapy, or ST, for six protected classes of drugs, with certain exceptions (and modifications from the proposed rule) and permits plans to implement PA and ST in Medicare Part B drugs. The proposed rule proposed to change the definition of  “negotiated prices,” under which plan sponsors would be required to pass through all pharmacy price concessions at the point of sale; however, CMS is still reviewing comments from stakeholders on this issue. Litigation and legislative efforts to change or repeal the ACA are likely to continue, with unpredictable and uncertain results.

Other legislative changes have been proposed and adopted in the United States since the ACA was enacted. The Budget Control Act of 2011, among other things, created measures for spending reductions by Congress. A Joint Select Committee on Deficit Reduction, tasked with recommending a targeted deficit reduction of at least $1.2 trillion for the years 2013 through 2021, was unable to reach required goals, thereby triggering the legislation’s automatic reduction to several government programs, including aggregate reductions of Medicare payments to providers of 2% per fiscal year. These reductions went into effect on April 1, 2013 and, due to subsequent legislative amendments to the statute, including the BBA, will remain in effect through 2027, unless additional congressional action is taken. On January 2, 2013, the American Taxpayer Relief Act of 2012 was signed into law, which, among other things, further reduced Medicare payments to several types of providers.

These laws, and future state and federal healthcare reform measures may be adopted in the future, any of which may result in additional reductions in Medicare and other healthcare funding and otherwise affect the prices we may obtain for any of our product candidates for which we may obtain regulatory approval or the frequency with which any such product candidate is prescribed or used.

Off-label use or misuse of our products may harm our reputation in the marketplace or result in injuries that lead to costly product liability suits.

We are developing nirogacestat for the treatment of desmoid tumors and mirdametinib for the treatment of NF1-PN. If our product candidates are approved by the FDA, we may only promote or market our product candidates for their specifically approved indications. We will train our marketing and sales force against promoting our product candidates for uses outside of the approved indications for use, known as “off-label uses.” We cannot, however, prevent a physician from using our products off label, when in the physician’s independent professional

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medical judgment he or she deems it appropriate. Furthermore, the use of our products for indications other than those approved by the FDA may not effectively treat such conditions. Any such off-label use of our product candidates could harm our reputation in the marketplace among physicians and patients. There may also be increased risk of injury to patients if physicians attempt to use our products for these uses for which they are not approved, which could lead to product liability suits that that might require significant financial and management resources and that could harm our reputation.

Inadequate funding for the FDA, the SEC and other government agencies could hinder their ability to hire and retain key leadership and other personnel, prevent new products and services from being developed or commercialized in a timely manner or otherwise prevent those agencies from performing normal business functions on which the operation of our business may rely, which could negatively impact our business.

The ability of the FDA to review and approve new products can be affected by a variety of factors, including government budget and funding levels, ability to hire and retain key personnel and accept the payment of user fees, and statutory, regulatory, and policy changes. Average review times at the agency have fluctuated in recent years as a result. In addition, government funding of the SEC and other government agencies on which our operations may rely, including those that fund research and development activities, is subject to the political process, which is inherently fluid and unpredictable.

Disruptions at the FDA and other agencies may also slow the time necessary for new drugs to be reviewed and/or approved by necessary government agencies, which would adversely affect our business. For example, over the last several years, the U.S. government has shut down several times and certain regulatory agencies, such as the FDA and the SEC, have had to furlough critical employees and stop critical activities. If a prolonged government shutdown occurs, it could significantly impact the ability of the FDA to timely review and process our regulatory submissions, which could have a material adverse effect on our business. Further, upon completion of this offering and in our operations as a public company, future government shutdowns could impact our ability to access the public markets and obtain necessary capital in order to properly capitalize and continue our operations.

EU drug marketing and reimbursement regulations may materially affect our ability to market and receive coverage for our products in the European member states.

We intend to seek approval to market our product candidates in both the United States and in selected foreign jurisdictions. If we obtain approval in one or more foreign jurisdictions for our product candidates, we will be subject to rules and regulations in those jurisdictions. In some foreign countries, particularly those in the European Union, the pricing of drugs is subject to governmental control and other market regulations which could put pressure on the pricing and usage of our product candidates. In these countries, pricing negotiations with governmental authorities can take considerable time after obtaining marketing approval of a product candidate. In addition, market acceptance and sales of our product candidates will depend significantly on the availability of adequate coverage and reimbursement from third-party payors for our product candidates and may be affected by existing and future healthcare reform measures.

Much like the federal Anti-Kickback Statute prohibition in the United States, the provision of benefits or advantages to physicians to induce or encourage the prescription, recommendation, endorsement, purchase, supply, order or use of medicinal products is also prohibited in the European Union. The provision of benefits or advantages to physicians is governed by the national anti-bribery laws of EU Member States, such as the UK Bribery Act 2010. Infringement of these laws could result in substantial fines and imprisonment.

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Payments made to physicians in certain EU Member States must be publicly disclosed. Moreover, agreements with physicians often must be the subject of prior notification and approval by the physician’s employer, his or her competent professional organization and/or the regulatory authorities of the individual EU Member States. These requirements are provided in the national laws, industry codes or professional codes of conduct, applicable in the EU Member States. Failure to comply with these requirements could result in reputational risk, public reprimands, administrative penalties, fines or imprisonment.

In addition, in most foreign countries, including the European Economic Area, or EEA, the proposed pricing for a drug must be approved before it may be lawfully marketed. The requirements governing drug pricing and reimbursement vary widely from country to country. For example, the European Union provides options for its member states to restrict the range of medicinal products for which their national health insurance systems provide reimbursement and to control the prices of medicinal products for human use. Reference pricing used by various EU member states and parallel distribution, or arbitrage between low-priced and high-priced member states, can further reduce prices. A member state may approve a specific price for the medicinal product or it may instead adopt a system of direct or indirect controls on the profitability of the company placing the medicinal product on the market. In some countries, we may be required to conduct a clinical study or other studies that compare the cost-effectiveness of any of our product candidates to other available therapies in order to obtain or maintain reimbursement or pricing approval. There can be no assurance that any country that has price controls or reimbursement limitations for biopharmaceutical products will allow favorable reimbursement and pricing arrangements for any of our products. Historically, products launched in the European Union do not follow price structures of the United States and generally prices tend to be significantly lower. Publication of discounts by third-party payors or authorities may lead to further pressure on the prices or reimbursement levels within the country of publication and other countries. If pricing is set at unsatisfactory levels or if reimbursement of our products is unavailable or limited in scope or amount, our revenues from sales and the potential profitability of any of our product candidates in those countries would be negatively affected.

We may incur substantial costs in our efforts to comply with evolving global data protection laws and regulations, and any failure or perceived failure by us to comply with such laws and regulations may harm our business and operations.

The global data protection landscape is rapidly evolving, and we may be or become subject to or affected by numerous federal, state and foreign laws and regulations, as well as regulatory guidance, governing the collection, use, disclosure, transfer, security and processing of personal data, such as information that we collect about participants and healthcare providers in connection with clinical trials. Implementation standards and enforcement practices are likely to remain uncertain for the foreseeable future, which may create uncertainty in our business, affect our or our service providers’ ability to operate in certain jurisdictions or to collect, store, transfer use and share personal data, result in liability or impose additional compliance or other costs on us. Any failure or perceived failure by us to comply with federal, state, or foreign laws or self-regulatory standards could result in negative publicity, diversion of management time and effort and proceedings against us by governmental entities or others. For example, California recently passed the California Data Privacy Protection Act, which goes into effect in January 2020 and provides broad rights to California consumers with respect to the collection and use of their information by businesses. The new California law further expands the privacy and process enhancements and commitment of resources in support of compliance with California’s regulatory requirements and may lead to similar laws in other U.S. states or at a national level.

In addition to our operations in the United States, which may be subject to healthcare and other laws relating to the privacy and security of health information and other personal information,

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may seek to conduct clinical trials in EEA and may become subject to additional European data privacy laws, regulations and guidelines. The General Data Protection Regulation, (EU) 2016/679, or GDPR, became effective on May 25, 2018, and deals with the processing of personal data and on the free movement of such data. The GDPR imposes a broad range of strict requirements on companies subject to the GDPR, including requirements relating to having legal bases for processing personal information relating to identifiable individuals and transferring such information outside the EEA, including to the United States, providing details to those individuals regarding the processing of their personal information, keeping personal information secure, having data processing agreements with third parties who process personal information, responding to individuals’ requests to exercise their rights in respect of their personal information, reporting security breaches involving personal data to the competent national data protection authority and affected individuals, appointing data protection officers, conducting data protection impact assessments and record-keeping. The GDPR increases substantially the penalties to which we could be subject in the event of any non-compliance, including fines of up to 10,000,000 Euros or up to 2% of our total worldwide annual turnover for certain comparatively minor offenses, or up to 20,000,000 Euros or up to 4% of our total worldwide annual turnover for more serious offenses. Given the limited enforcement of the GDPR to date, we face uncertainty as to the exact interpretation of the new requirements on our trials and we may be unsuccessful in implementing all measures required by data protection authorities or courts in interpretation of the new law.

In particular, national laws of member states of the European Union are in the process of being adapted to the requirements under the GDPR, thereby implementing national laws which may partially deviate from the GDPR and impose different obligations from country to country, so that we do not expect to operate in a uniform legal landscape in the EEA. Also, as it relates to processing and transfer of genetic data, the GDPR specifically allows national laws to impose additional and more specific requirements or restrictions, and European laws have historically differed quite substantially in this field, leading to additional uncertainty. Further, the impact of the impending “Brexit”, whereby the United Kingdom is planning to leave the EEA in October of 2019, either with or without a “deal” is uncertain and cannot be predicted at this time.

In the event we commence clinical trials in the EEA, we must also ensure that we maintain adequate safeguards to enable the transfer of personal data outside of the EEA, in particular to the United States, in compliance with European data protection laws. We expect that we will continue to face uncertainty as to whether our efforts to comply with any obligations under European privacy laws will be sufficient. If we are investigated by a European data protection authority, we may face fines and other penalties. Any such investigation or charges by European data protection authorities could have a negative effect on our existing business and on our ability to attract and retain new clients or biopharmaceutical partners. We may also experience hesitancy, reluctance or refusal by European or multi-national clients or biopharmaceutical partners to continue to use our products and solutions due to the potential risk exposure as a result of the current (and, in particular, future) data protection obligations imposed on them by certain data protection authorities in interpretation of current law, including the GDPR. Such clients or biopharmaceutical partners may also view any alternative approaches to compliance as being too costly, too burdensome, too legally uncertain or otherwise objectionable and therefore decide not to do business with us. Any of the forgoing could materially harm our business, prospects, financial condition and results of operations.

Additional laws and regulations governing international operations could negatively impact or restrict our operations.

If we further expand our operations outside of the United States, we must dedicate additional resources to comply with numerous laws and regulations in each jurisdiction in which we plan to

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operate. The U.S. Foreign Corrupt Practices Act, or FCPA, prohibits any U.S. individual or business from paying, offering, authorizing payment or offering anything of value, directly or indirectly, to any foreign official, political party or candidate for the purpose of influencing any act or decision of the foreign entity in order to assist the individual or business in obtaining or retaining business. The FCPA also obligates companies whose securities are listed in the United States to comply with certain accounting provisions requiring the company to maintain books and records that accurately and fairly reflect all transactions of the corporation, including international subsidiaries, and to devise and maintain an adequate system of internal accounting controls for international operations.

Compliance with the FCPA is expensive and difficult, particularly in countries in which corruption is a recognized problem. In addition, the FCPA presents particular challenges in the pharmaceutical industry, because, in many countries, hospitals are operated by the government, and doctors and other hospital employees are considered foreign officials. Certain payments to hospitals in connection with clinical trials and other work have been deemed to be improper payments to government officials and have led to FCPA enforcement actions.

Various laws, regulations and executive orders also restrict the use and dissemination outside of the United States, or the sharing with certain non-U.S. nationals, of information classified for national security purposes, as well as certain products and technical data relating to those products. If we expand our presence outside of the United States, it will require us to dedicate additional resources to comply with these laws, and these laws may preclude us from developing, manufacturing or selling certain products and product candidates outside of the United States, which could limit our growth potential and increase our development costs.

The failure to comply with laws governing international business practices may result in substantial civil and criminal penalties and suspension or debarment from government contracting. The SEC also may suspend or bar issuers from trading securities on U.S. exchanges for violations of the FCPA’s accounting provisions.

We are subject to certain U.S. and foreign anti-corruption, anti-money laundering, export control, sanctions and other trade laws and regulations. We can face serious consequences for violations.

Among other matters, U.S. and foreign anti-corruption, anti-money laundering, export control, sanctions and other trade laws and regulations, which are collectively referred to as Trade Laws, prohibit companies and their employees, agents, clinical research organizations, legal counsel, accountants, consultants, contractors and other partners from authorizing, promising, offering, providing, soliciting or receiving, directly or indirectly, corrupt or improper payments or anything else of value to or from recipients in the public or private sector. Violations of Trade Laws can result in substantial criminal fines and civil penalties, imprisonment, the loss of trade privileges, debarment, tax reassessments, breach of contract and fraud litigation, reputational harm and other consequences. We have direct or indirect interactions with officials and employees of government agencies or government-affiliated hospitals, universities and other organizations. We also expect our non-U.S. activities to increase in time. We plan to engage third parties for clinical trials and/or to obtain necessary permits, licenses, patent registrations and other regulatory approvals and we can be held liable for the corrupt or other illegal activities of our personnel, agents or partners, even if we do not explicitly authorize or have prior knowledge of such activities.

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A portion of our manufacturing of our lead product candidates takes place in China through third-party manufacturers. A significant disruption in the operation of those manufacturers, a trade war or political unrest in China could materially adversely affect our business, financial condition and results of operations.

We currently contract manufacturing operations to third parties, and clinical quantities of our lead product candidates are manufactured by these third parties outside the United States, including in China, and we expect to continue to use such third-party manufacturers for such product candidates. Any disruption in production or inability of our manufacturers in China to produce adequate quantities to meet our needs, whether as a result of a natural disaster or other causes, could impair our ability to operate our business on a day-to-day basis and to continue our development of our product candidates. Furthermore, since these manufacturers are located in China, we are exposed to the possibility of product supply disruption and increased costs in the event of changes in the policies of the United States or Chinese governments, political unrest or unstable economic conditions in China. For example, a trade war could lead to tariffs on the chemical intermediates we use that are manufactured in China. Any of these matters could materially and adversely affect our business and results of operations. Any recall of the manufacturing lots or similar action regarding our product candidates used in clinical trials could delay the trials or detract from the integrity of the trial data and its potential use in future regulatory filings. In addition, manufacturing interruptions or failure to comply with regulatory requirements by any of these manufacturers could significantly delay clinical development of potential products and reduce third-party or clinical researcher interest and support of proposed trials. These interruptions or failures could also impede commercialization of our product candidates and impair our competitive position. Further, we may be exposed to fluctuations in the value of the local currency in China. Future appreciation of the local currency could increase our costs. In addition, our labor costs could continue to rise as wage rates increase due to increased demand for skilled laborers and the availability of skilled labor declines in China.

Risks related to our intellectual property

Our success depends in part on our ability to protect our intellectual property, and patent terms may be inadequate to protect our competitive position. It is difficult and costly to protect our proprietary rights and technology, and we may not be able to ensure their protection.

Our commercial success will depend in large part on obtaining and maintaining patent, trademark and trade secret protection of our proprietary technologies and our product candidates, their respective components, formulations, combination therapies, methods used to manufacture them and methods of treatment, as well as successfully defending these patents against third-party challenges. Our ability to stop unauthorized third parties from making, using, selling, offering to sell or importing our product candidates is affected by the extent to which we have rights under valid and enforceable patents that cover these activities. If our patents expire, or we are unable to secure and maintain patent protection for any product or technology we develop, or if the scope of the patent protection secured is not sufficiently broad, our competitors could develop and commercialize products and technology similar or identical to ours, and our ability to commercialize any product candidates we may develop may be adversely affected.

Patents have a limited lifespan. In the United States, if all maintenance fees are timely paid, the natural expiration of a patent is generally 20 years from its earliest U.S. non-provisional filing date. Various extensions such as patent term adjustments and/or extensions, may be available, but the life of a patent, and the protection it affords, is limited. Our current composition of matter patents covering nirogacestat and mirdametinib, which we licensed from Pfizer Inc., or Pfizer, in connection with the formation of our company, are expected to expire in 2025 and

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2021, respectively, not including any patent term extensions. Our earliest patents may expire before, or soon after, either product candidate achieves marketing approval in the United States or foreign jurisdictions. Upon the expiration of the current patents, we currently intend to rely on orphan drug exclusivity to market our lead products. Once the patent life has expired, we may be open to competition from competitive products, including generics. As a result, our patent portfolio may not provide us with sufficient rights to exclude others from commercializing products similar or identical to ours. The expiration of the patents covering our lead product candidates, and our inability to secure additional patent protection, could also have a material adverse effect on our business, results of operations, financial condition and prospects.

The patenting process is expensive and time-consuming, and we may not be able to file and prosecute all necessary or desirable patent applications at a reasonable cost or in a timely manner. In addition, we may not pursue or obtain patent protection in all relevant markets. It is also possible that we will fail to identify patentable aspects of our research and development output before it is too late to obtain patent protection. Moreover, in some circumstances, we may not have the right to control the preparation, filing and prosecution of patent applications, or to maintain the patents, covering technology that we license from or license to third parties and are reliant on our licensors or licensees.

The strength of patents in the biopharmaceutical field involves complex legal and scientific questions and can be uncertain. The patent applications that we own or in-license now or in the future may fail to result in issued patents with claims that cover our product candidates or uses thereof in the United States or in other foreign countries. Even if the patents do successfully issue, third parties may challenge the validity, enforceability or scope thereof, which may result in such patents being narrowed, invalidated or held unenforceable. Furthermore, even if they are unchallenged, the patents and patent applications covering our product candidates may not adequately protect our intellectual property or prevent others from designing around our claims. If the breadth or strength of protection provided by the patents we hold with respect to our product candidates is threatened, it could dissuade companies from collaborating with us to develop, and threaten our ability to commercialize, our product candidates. Further, if we encounter delays in our clinical trials, the period of time during which we could market our product candidates under patent protection would be reduced.

Since patent applications in the United States and most other countries are confidential for a period of time after filing, there is no certainty that any patent application related to a product candidate was the first to be filed. Furthermore, for United States applications in which at least one claim is entitled to a priority date before March 16, 2013, an interference proceeding can be provoked by a third party or instituted by the U.S. Patent and Trademark Office, or USPTO, to determine who was the first to invent any of the subject matter covered by the patent claims of an application.

We cannot be certain that we are the first to invent any inventions covered by a pending patent application and, if we are not, we could be subject to priority disputes. We may be required to disclaim part or all of the term of certain patents or all of the term of certain patent applications. There may be prior art of which we are not aware that may affect the validity or enforceability of a patent claim. There also may be prior art of which we are aware, but which we do not believe affects the validity or enforceability of a claim, which may, nonetheless, ultimately be found to affect the validity or enforceability of a claim. No assurance can be given that if challenged, our patents would be declared by a court to be valid or enforceable or that even if found valid and enforceable, a competitor’s technology or product would be found by a court to infringe our patents. We may analyze patents or patent applications of our competitors that we believe are relevant to our activities, and consider that we are free to operate in relation to our product

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candidates, but our competitors may achieve issued claims, including in patents we consider to be unrelated, which block our efforts or may potentially result in our product candidates or our activities infringing such claims. The possibility exists that others will develop products which have the same effect as our products on an independent basis which do not infringe our patents or other intellectual property rights, or will design around the claims of patents that we have had issued that cover our products.

Recent or future patent reform legislation could increase the uncertainties and costs surrounding the prosecution of our patent applications and the enforcement or defense of our issued patents. Under the enacted Leahy-Smith America Invents Act, or America Invents Act, enacted in 2013, the United States moved from a “first-to-invent” to a “first-to-file” system. Under a “first-to-file” system, assuming the other requirements for patentability are met, the first inventor to file a patent application generally will be entitled to a patent on the invention regardless of whether another inventor had made the invention earlier. The America Invents Act includes a number of other significant changes to U.S. patent law, including provisions that affect the way patent applications are prosecuted, redefine prior art and establish a new post-grant review system. The effects of these changes are currently unclear as the USPTO only recently developed new regulations and procedures in connection with the America Invents Act and many of the substantive changes to patent law, including the “first-to-file” provisions, only became effective in March 2013. In addition, the courts have yet to address many of these provisions and the applicability of the act and new regulations on specific patents discussed herein have not been determined and would need to be reviewed. However, the America Invents Act and its implementation could increase the uncertainties and costs surrounding the prosecution of any patent applications and the enforcement or defense of our issued patents, all of which could have a material adverse effect on our business and financial condition.

The degree of future protection for our proprietary rights is uncertain because legal means afford only limited protection and may not adequately protect our rights or permit us to gain or keep our competitive advantage. For example:

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others may be able to make or use compounds that are similar to the compositions of our product candidates but that are not covered by the claims of our patents;

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the active ingredients in our current product candidates will eventually become commercially available in generic drug products, and no patent protection may be available with regard to formulation or method of use;

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a company or its licensor, as the case may be, may fail to meet its obligations to the U.S. government in regard to any in-licensed patents and patent applications funded by U.S. government grants, leading to the loss of patent rights;

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such company or its licensors, as the case may be, might not have been the first to file patent applications for these inventions;

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others may independently develop similar or alternative technologies or duplicate any of our technologies;

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it is possible that a pending patent applications will not result in issued patents;

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it is possible that there are prior public disclosures that could invalidate our or our licensors’ patents, as the case may be, or parts of our or their patents;

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it is possible that others may circumvent our owned or in-licensed patents;

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it is possible that there are unpublished applications or patent applications maintained in secrecy that may later issue with claims covering our products or technology similar to ours;

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the laws of foreign countries may not protect our or our licensors’, as the case may be, proprietary rights to the same extent as the laws of the United States;

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the claims of our owned or in-licensed issued patents or patent applications, if and when issued, may not cover our product candidates;

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our owned or in-licensed issued patents may not provide us with any competitive advantages, may be narrowed in scope, or be held invalid or unenforceable as a result of legal challenges by third parties;

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the inventors of owned or in-licensed patents or patent applications may become involved with competitors, develop products or processes which design around our patents, or become hostile to us or the patents or patent applications on which they are named as inventors;

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it is possible that owned or in-licensed patents or patent applications omit individual(s) that should be listed as inventor(s) or include individual(s) that should not be listed as inventor(s), which may cause these patents or patents issuing from these patent applications to be held invalid or unenforceable;

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we have engaged in scientific collaborations in the past, and will continue to do so in the future. Such collaborators may develop adjacent or competing products to ours that are outside the scope of our patents;

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we may not develop additional proprietary technologies for which we can obtain patent protection;

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it is possible that product candidates we develop may be covered by third parties’ patents or other exclusive rights; or

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the patents of others may have an adverse effect on our business.

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We depend on intellectual property licensed from third parties, including from Pfizer for our lead product candidates, and termination of any of these licenses could result in the loss of significant rights, which would harm our business.

We are dependent on patents, know-how and proprietary technology, both our own and licensed from others. All patents covering nirogacestat and mirdametinib and any combination therapies using our product candidates are licensed from third parties. Any termination of a product license could result in the loss of significant rights and would cause material adverse harm to our ability to commercialize our product candidates. See “Business—License and collaboration agreements” for additional information regarding our license agreements.

Disputes may also arise between us and our licensors regarding intellectual property subject to a license agreement, including:

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the scope of rights granted under the license agreement and other interpretation-related issues;

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whether and the extent to which our technology and processes infringe on intellectual property of the licensor that is not subject to the licensing agreement;

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our right to sublicense patent and other rights to third parties under collaborative development relationships;

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our diligence obligations with respect to the use of licensed technology in relation to our development and commercialization of our product candidates and what activities satisfy those diligence obligations; and

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the ownership of inventions and know-how resulting from the joint creation or use of intellectual property by our licensors and us and our partners.

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If disputes over intellectual property that we have licensed prevent or impair our ability to maintain our current licensing arrangements on acceptable terms, we may be unable to successfully develop and commercialize the affected product candidates.

We are generally also subject to all of the same risks with respect to protection of intellectual property that we own, as we are for intellectual property that we license, which are described below. If we or our licensors fail to adequately protect this intellectual property, our ability to commercialize products could materially suffer.

If we fail to comply with our obligations under our patent licenses with third parties, we could lose license rights that are important to our business.

We are a party to license agreements pursuant to which we in-license key patents for our product candidates. At the time we began our operations in August 2017, we entered into four license agreements with Pfizer, including a license agreement for each of our lead product candidates, nirogacestat and mirdametinib. Each of our existing licenses imposes various diligence, milestone payment, royalty, insurance and other obligations on us. If we fail to comply with these obligations, our licensors may have the right to terminate the license, in which event we would not be able to develop or market the products covered by such licensed intellectual property.

We may have limited control over the maintenance and prosecution of these in-licensed rights, activities or any other intellectual property that may be related to our in-licensed intellectual property. For example, we cannot be certain that such activities by these licensors have been or will be conducted in compliance with applicable laws and regulations or will result in valid and enforceable patents and other intellectual property rights. We have limited control over the manner in which our licensors initiate an infringement proceeding against a third-party infringer of the intellectual property rights, or defend certain of the intellectual property that is licensed to us. It is possible that the licensors’ infringement proceeding or defense activities may be less vigorous than had we conducted them ourselves.

If we are unable to protect the confidentiality of our trade secrets, our business and competitive position would be harmed.

In addition to patent protection, we rely heavily upon know-how and trade secret protection, as well as non-disclosure agreements and invention assignment agreements with our employees, consultants and third parties, to protect our confidential and proprietary information, especially where we do not believe patent protection is appropriate or obtainable. In addition to contractual measures, we try to protect the confidential nature of our proprietary information using physical and technological security measures. Such measures may not, for example, in the case of misappropriation of a trade secret by an employee or third party with authorized access, provide adequate protection for our proprietary information. Our security measures may not prevent an employee or consultant from misappropriating our trade secrets and providing them to a competitor, and recourse we take against such misconduct may not provide an adequate remedy to protect our interests fully. Enforcing a claim that a party illegally disclosed or misappropriated a trade secret can be difficult, expensive and time-consuming, and the outcome is unpredictable. In addition, trade secrets may be independently developed by others in a manner that could prevent legal recourse by us. If any of our confidential or proprietary information, such as our trade secrets, were to be disclosed or misappropriated, or if any such information was independently developed by a competitor, our competitive position could be harmed.

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In addition, courts outside the United States are sometimes less willing to protect trade secrets. If we choose to go to court to stop a third party from using any of our trade secrets, we may incur substantial costs. These lawsuits may consume our time and other resources even if we are successful. Although we take steps to protect our proprietary information and trade secrets, including through contractual means with our employees and consultants, third parties may independently develop substantially equivalent proprietary information and techniques or otherwise gain access to our trade secrets or disclose our technology.

Thus, we may not be able to meaningfully protect our trade secrets. It is our policy to require our employees, consultants, outside scientific collaborators, sponsored researchers and other advisors to execute confidentiality agreements upon the commencement of employment or consulting relationships with us. These agreements provide that all confidential information concerning our business or financial affairs developed or made known to the individual or entity during the course of the party’s relationship with us is to be kept confidential and not disclosed to third parties except in specific circumstances. In the case of employees, the agreements provide that all inventions conceived by the individual, and which are related to our current or planned business or research and development or made during normal working hours, on our premises or using our equipment or proprietary information, are our exclusive property. In addition, we take other appropriate precautions, such as physical and technological security measures, to guard against misappropriation of our proprietary technology by third parties.

Third-party claims of intellectual property infringement may prevent or delay our product discovery and development efforts.

Our commercial success depends in part on our ability to develop, manufacture, market and sell our product candidates and use our proprietary technologies without infringing the proprietary rights of third parties. There is a substantial amount of litigation involving patents and other intellectual property rights in the biotechnology and pharmaceutical industries, as well as administrative proceedings for challenging patents, including interference, derivation, inter partes review, post grant review, and reexamination proceedings before the USPTO or oppositions and other comparable proceedings in foreign jurisdictions. We may be exposed to, or threatened with, future litigation by third parties having patent or other intellectual property rights alleging that our product candidates and/or proprietary technologies infringe their intellectual property rights. Numerous U.S. and foreign issued patents and pending patent applications, which are owned by third parties, exist in the fields in which we are developing our product candidates. As the biotechnology and pharmaceutical industries expand and more patents are issued, the risk increases that our product candidates may give rise to claims of infringement of the patent rights of others. Moreover, it is not always clear to industry participants, including us, which patents cover various types of drugs, products or their methods of use or manufacture. Thus, because of the large number of patents issued and patent applications filed in our fields, there may be a risk that third parties may allege they have patent rights encompassing our product candidates, technologies or methods.

If a third party claims that we infringe its intellectual property rights, we may face a number of issues, including, but not limited to:

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infringement and other intellectual property claims which, regardless of merit, may be expensive and time-consuming to litigate and may divert our management’s attention from our core business;

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substantial damages for infringement, which we may have to pay if a court decides that the product candidate or technology at issue infringes on or violates the third party’s rights, and, if the court finds that the infringement was willful, we could be ordered to pay treble damages and the patent owner’s attorneys’ fees;

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a court prohibiting us from developing, manufacturing, marketing or selling our product candidates, or from using our proprietary technologies, unless the third party licenses its product rights to us, which it is not required to do;

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if a license is available from a third party, we may have to pay substantial royalties, upfront fees and other amounts, and/or grant cross-licenses to intellectual property rights for our products; and

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redesigning our product candidates or processes so they do not infringe, which may not be possible or may require substantial monetary expenditures and time.

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Some of our competitors may be able to sustain the costs of complex patent litigation more effectively than we can because they have substantially greater resources. In addition, any uncertainties resulting from the initiation and continuation of any litigation could have a material adverse effect on our ability to raise the funds necessary to continue our operations or could otherwise have a material adverse effect on our business, results of operations, financial condition and prospects.

Third parties may assert that we are employing their proprietary technology without authorization. Generally, conducting clinical trials and other development activities in the United States is protected under the Safe Harbor exemption as set forth in 35 U.S.C. §271. If and when any of our product candidates are approved by the FDA, that certain third-party may then seek to enforce its patent by filing a patent infringement lawsuit against us. While we do not believe that any claims of such patent that could otherwise materially adversely affect commercialization of our product candidates, if approved, are valid and enforceable, we may be incorrect in this belief, or we may not be able to prove it in a litigation. In this regard, patents issued in the U.S. by law enjoy a presumption of validity that can be rebutted only with evidence that is “clear and convincing,” a heightened standard of proof. There may be third-party patents of which we are currently unaware with claims to materials, formulations, methods of manufacture or methods for treatment related to the use or manufacture of our product candidates. Because patent applications can take many years to issue, there may be currently pending patent applications which may later result in issued patents that our product candidates may infringe. In addition, third parties may obtain patents in the future and claim that use of our technologies infringes upon these patents. If any third-party patents were held by a court of competent jurisdiction to cover the manufacturing process of our product candidates, constructs or molecules used in or formed during the manufacturing process, or any final product itself, the holders of any such patents may be able to block our ability to commercialize the product candidate unless we obtained a license under the applicable patents, or until such patents expire or they are finally determined to be held invalid or unenforceable. Similarly, if any third-party patent were held by a court of competent jurisdiction to cover aspects of our formulations, processes for manufacture or methods of use, the holders of any such patent may be able to block our ability to develop and commercialize the product candidate unless we obtained a license or until such patent expires or is finally determined to be held invalid or unenforceable. In either case, such a license may not be available on commercially reasonable terms or at all. If we are unable to obtain a necessary license to a third-party patent on commercially reasonable terms, or at all, our ability to commercialize our product candidates may be impaired or delayed, which could in turn significantly harm our business. Even if we obtain a license, it may be non-exclusive, thereby giving our competitors access to the same technologies licensed to us. In addition, if the breadth or strength of protection provided by our patents and any patent applications is threatened, it could dissuade companies from collaborating with us to license, develop or commercialize current or future product candidates.

Parties making claims against us may seek and obtain injunctive or other equitable relief, which could effectively block our ability to further develop and commercialize our product candidates.

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Defense of these claims, regardless of their merit, would involve substantial litigation expense and would be a substantial diversion of employee resources from our business. In the event of a successful claim of infringement against us, we or our licensors may have to pay substantial damages, including treble damages and attorneys’ fees for willful infringement, obtain one or more licenses from third parties, pay royalties or redesign our infringing products, which may be impossible or require substantial time and monetary expenditure. We cannot predict whether any such license would be available at all or whether it would be available on commercially reasonable terms. Furthermore, even in the absence of litigation, we may need to obtain licenses from third parties to advance our research or allow commercialization of our product candidates. We may fail to obtain any of these licenses at a reasonable cost or on reasonable terms, if at all. In that event, we would be unable to further develop and commercialize our product candidates, which could harm our business significantly.

Third parties may assert that our employees, consultants, collaborators or partners have wrongfully used or disclosed confidential information or misappropriated trade secrets.

As is common in the biotechnology and pharmaceutical industries, we employ individuals who were previously employed at universities or other biopharmaceutical or pharmaceutical companies, including our competitors or potential competitors. Although no claims against us are currently pending, and although we try to ensure that our employees and consultants do not use the proprietary information or know-how of others in their work for us, we may be subject to claims that we or our employees, consultants or independent contractors have inadvertently or otherwise used or disclosed intellectual property, including trade secrets or other proprietary information, of a former employer or other third parties. Litigation may be necessary to defend against these claims. If we fail in defending any such claims, in addition to paying monetary damages, we may lose valuable intellectual property rights or personnel. Even if we are successful in defending against such claims, litigation or other legal proceedings relating to intellectual property claims may cause us to incur significant expenses, and could distract our technical and management personnel from their normal responsibilities. In addition, there could be public announcements of the results of hearings, motions or other interim proceedings or developments, and, if securities analysts or investors perceive these results to be negative, it could have a substantial adverse effect on the price of our common stock. This type of litigation or proceeding could substantially increase our operating losses and reduce our resources available for development activities. We may not have sufficient financial or other resources to adequately conduct such litigation or proceedings. Some of our competitors may be able to sustain the costs of such litigation or proceedings more effectively than we can because of their substantially greater financial resources. Uncertainties resulting from the initiation and continuation of patent litigation or other intellectual property related proceedings could adversely affect our ability to compete in the marketplace.

We may not be successful in obtaining or maintaining necessary rights to develop any future product candidates on acceptable terms.

Because our programs may involve additional product candidates that may require the use of proprietary rights held by third parties, the growth of our business may depend in part on our ability to acquire, in-license or use these proprietary rights.

Our product candidates may also require specific formulations to work effectively and efficiently and these rights may be held by others. We may develop products containing our compounds and pre-existing pharmaceutical compounds. We may be unable to acquire or in-license any compositions, methods of use, processes or other third-party intellectual property rights from third parties that we identify as necessary or important to our business operations. We may fail to obtain any of these licenses at a reasonable cost or on reasonable terms, if at all, which would

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harm our business. We may need to cease use of the compositions or methods covered by such third-party intellectual property rights, and may need to seek to develop alternative approaches that do not infringe on such intellectual property rights which may entail additional costs and development delays, even if we were able to develop such alternatives, which may not be feasible. Even if we are able to obtain a license, it may be non-exclusive, thereby giving our competitors access to the same technologies licensed to us. In that event, we may be required to expend significant time and resources to develop or license replacement technology.

Additionally, we sometimes collaborate with academic institutions to accelerate our preclinical research or development under written agreements with these institutions. In certain cases, these institutions may provide us with an option to negotiate a license to any of the institution’s rights in technology resulting from the collaboration. Regardless of such option, we may be unable to negotiate a license within the specified timeframe or under terms that are acceptable to us. If we are unable to do so, the institution may offer the intellectual property rights to others, potentially blocking our ability to pursue our program. If we are unable to successfully obtain rights to required third-party intellectual property or to maintain the existing intellectual property rights we have, we may have to abandon development of such program and our business and financial condition could suffer.

The licensing and acquisition of third-party intellectual property rights is a competitive area, and companies, which may be more established, or have greater resources than we do, may also be pursuing strategies to license or acquire third-party intellectual property rights that we may consider necessary or attractive in order to commercialize our product candidates. More established companies may have a competitive advantage over us due to their size, cash resources and greater clinical development and commercialization capabilities. There can be no assurance that we will be able to successfully complete such negotiations and ultimately acquire the rights to the intellectual property surrounding the additional product candidates that we may seek to acquire.

We may be involved in lawsuits to protect or enforce our patents or the patents of our licensors, which could be expensive, time-consuming and unsuccessful.

Competitors may infringe our patents or the patents of our licensors. To counter infringement or unauthorized use, we may be required to file infringement claims, which can be expensive and time-consuming. In addition, in an infringement proceeding, a court may decide that one or more of our patents is not valid or is unenforceable, or may refuse to stop the other party from using the technology at issue on the grounds that our patents do not cover the technology in question. An adverse result in any litigation or defense proceedings could put one or more of our patents at risk of being invalidated, held unenforceable or interpreted narrowly and could put any patent applications at risk of not issuing. Defense of these claims, regardless of their merit, would involve substantial litigation expense and would be a substantial diversion of employee resources from our business.

We may choose to challenge the patentability of claims in a third party’s U.S. patent by requesting that the USPTO review the patent claims in an ex-parte re-exam, inter partes review or post-grant review proceedings. These proceedings are expensive and may consume our time or other resources. We may choose to challenge a third party’s patent in patent opposition proceedings in the European Patent Office, or EPO, or other foreign patent offices. The costs of these opposition proceedings could be substantial and may consume our time or other resources. If we fail to obtain a favorable result at the USPTO, EPO or other patent offices then we may be exposed to litigation by a third party alleging that the patent may be infringed by our product candidates or proprietary technologies.

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In addition, because some patent applications in the United States may be maintained in secrecy until the patents are issued, patent applications in the United States and many foreign jurisdictions are typically not published until 18 months after filing, and publications in the scientific literature often lag behind actual discoveries, we cannot be certain that others have not filed patent applications for technology covered by issued patents or any pending applications, or that we or, if applicable, a licensor were the first to invent the technology. Our competitors also may have filed, and may in the future file, patent applications covering our products or technology similar to ours. Any such patent application may have priority over our patents or any patent applications, which could require us to obtain rights to issued patents covering such technologies. If another party has filed a U.S. patent application on inventions similar to those owned by or in-licensed to us, we or, in the case of in-licensed technology, the licensor may have to participate in an interference proceeding declared by the USPTO to determine priority of invention in the United States. If we or one of our licensors is a party to an interference proceeding involving a U.S. patent application on inventions owned by or in-licensed to us, we may incur substantial costs, divert management’s time and expend other resources, even if we are successful.

Interference proceedings provoked by third parties or brought by the USPTO may be necessary to determine the priority of inventions with respect to our patents or any patent applications or those of our licensors. An unfavorable outcome could result in a loss of our current patent rights and could require us to cease using the related technology or to attempt to license rights to it from the prevailing party. Our business could be harmed if the prevailing party does not offer us a license on commercially reasonable terms. Litigation or interference proceedings may result in a decision adverse to our interests and, even if we are successful, may result in substantial costs and distract our management and other employees. We may not be able to prevent, alone or with our licensors, misappropriation of our trade secrets or confidential information, particularly in countries where the laws may not protect those rights as fully as in the United States.

Furthermore, because of the substantial amount of discovery required in connection with intellectual property litigation, there is a risk that some of our confidential information could be compromised by disclosure during such litigation. In addition, there could be public announcements of the results of hearings, motions or other interim proceedings or developments. If securities analysts or investors perceive these results to be negative, it could have a substantial adverse effect on the price of our common stock.

Obtaining and maintaining our patent protection depends on compliance with various procedural, document submission, fee payment and other requirements imposed by governmental patent agencies, and our patent protection could be reduced or eliminated for non-compliance with these requirements.

Periodic maintenance fees on any issued patent are due to be paid to the USPTO and foreign patent agencies in several stages over the lifetime of the patent. The USPTO and various foreign governmental patent agencies require compliance with a number of procedural, documentary, fee payment and other provisions during the patent application process and following the issuance of a patent. While an inadvertent lapse can in many cases be cured by payment of a late fee or by other means in accordance with the applicable rules, there are situations in which noncompliance can result in abandonment or lapse of the patent or patent application, resulting in partial or complete loss of patent rights in the relevant jurisdiction. Noncompliance events that could result in abandonment or lapse of a patent or patent application include, but are not limited to, failure to respond to official actions within prescribed time limits, non-payment of fees and failure to properly legalize and submit formal documents. In such an event, our competitors might be able to enter the market, which would have a material adverse effect on our business.

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Issued patents covering our product candidates could be found invalid or unenforceable if challenged in court or the USPTO.

If we or one of our licensing partners initiate legal proceedings against a third party to enforce a patent covering one of our product candidates, the defendant could counterclaim that the patent covering our product candidate, as applicable, is invalid and/or unenforceable. In patent litigation in the United States, defendant counterclaims alleging invalidity and/or unenforceability are commonplace, and there are numerous grounds upon which a third party can assert invalidity or unenforceability of a patent. Third parties may also raise similar claims before administrative bodies in the United States or abroad, even outside the context of litigation. Such mechanisms include re-examination, post grant review, and equivalent proceedings in foreign jurisdictions (e.g., opposition proceedings). Such proceedings could result in revocation or amendment to our patents in such a way that they no longer cover our product candidates. The outcome following legal assertions of invalidity and unenforceability is unpredictable. With respect to validity, for example, we cannot be certain that there is no invalidating prior art, of which we, our patent counsel and the patent examiner were unaware during prosecution. If a defendant were to prevail on a legal assertion of invalidity and/or unenforceability, or if we are otherwise unable to adequately protect our rights, we would lose at least part, and perhaps all, of the patent protection on our product candidates. Such a loss of patent protection could have a material adverse impact on our business and our ability to commercialize or license our technology and product candidates.

Changes in patent law in the United States and in ex-U.S. jurisdictions could diminish the value of patents in general, thereby impairing our ability to protect our products.

As is the case with other biopharmaceutical companies, our success is heavily dependent on intellectual property, particularly patents. Obtaining and enforcing patents in the biopharmaceutical industry involve both technological and legal complexity, and is therefore costly, time-consuming and inherently uncertain. In addition, the United States has recently enacted and is currently implementing wide-ranging patent reform legislation. Recent U.S. Supreme Court rulings have narrowed the scope of patent protection available in certain circumstances and weakened the rights of patent owners in certain situations. In addition to increasing uncertainty with regard to our ability to obtain patents in the future, this combination of events has created uncertainty with respect to the value of patents, once obtained. Depending on decisions by the U.S. Congress, the federal courts and the USPTO, the laws and regulations governing patents could change in unpredictable ways that would weaken our ability to obtain new patents or to enforce our existing patents and patents that we might obtain in the future. We cannot predict how these decisions or any future decisions by the courts, the U.S. Congress or the USPTO may impact the value of our patents. Similarly, any adverse changes in the patent laws of other jurisdictions could have a material adverse effect on our business and financial condition.

We may not be able to protect our intellectual property rights throughout the world.

Filing, prosecuting and defending patents on product candidates in all countries throughout the world is expensive. While our licensed patents, including the patents covering our lead product candidates, have been issued in major markets and other countries, our intellectual property rights in some countries outside the United States can be less extensive than those in the United States. In addition, the laws of some foreign countries do not protect intellectual property rights to the same extent as federal and state laws in the United States. Consequently, we may not be able to prevent third parties from practicing our inventions in all countries outside the United States, or from selling or importing products made using our inventions in and into the United States or other jurisdictions. Competitors may use our technologies in jurisdictions where

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we have not obtained patent protection to develop their own products and, further, may export otherwise infringing products to territories where we have patent protection but where enforcement is not as strong as that in the United States. These products may compete with our products in jurisdictions where we do not have any issued patents and our patent claims or other intellectual property rights may not be effective or sufficient to prevent them from competing.

Many companies have encountered significant problems in protecting and defending intellectual property rights in foreign jurisdictions. The legal systems of certain countries, particularly certain developing countries, do not favor the enforcement of patents, trade secrets and other intellectual property protection, particularly those relating to biopharmaceutical products, which could make it difficult for us or our licensors to stop the infringement of our patents or marketing of competing products against third parties in violation of our proprietary rights generally. The initiation of proceedings by third parties to challenge the scope or validity of our patent rights in foreign jurisdictions could result in substantial cost and divert our efforts and attention from other aspects of our business, could put our patents at risk of being invalidated or interpreted narrowly and any patent applications at risk of not issuing and could provoke third parties to assert claims against us or our licensors. We may not prevail in any lawsuits that we initiate and the damages or other remedies awarded, if any, may not be commercially meaningful. Accordingly, our efforts to enforce our intellectual property rights around the world may be inadequate to obtain a significant commercial advantage from the intellectual property that we develop or license.

If we do not obtain patent term extension and data exclusivity for any product candidates we may develop, our business may be materially harmed.

Depending upon the timing, duration and specifics of any FDA marketing approval of any product candidates we may develop, one or more of our U.S. patents may be eligible for limited patent term extension under the Drug Price Competition and Patent Term Restoration Action of 1984, or Hatch-Waxman Amendments. The Hatch-Waxman Amendments permit a patent extension term of up to five years as compensation for patent term lost during the FDA regulatory review process. A patent term extension cannot extend the remaining term of a patent beyond a total of 14 years from the date of product approval, only one patent may be extended and only those claims covering the approved drug, a method for using it or a method for manufacturing it may be extended. However, we may not be granted an extension because of, for example, failing to exercise due diligence during the testing phase or regulatory review process, failing to apply within applicable deadlines, failing to apply prior to expiration of relevant patents or otherwise failing to satisfy applicable requirements. Moreover, the applicable time period or the scope of patent protection afforded could be less than we request. If we are unable to obtain patent term extension or term of any such extension is less than we request, our competitors may obtain approval of competing products following our patent expiration, and our business, financial condition, results of operations and prospects could be materially harmed.

If our trademarks and trade names are not adequately protected, then we may not be able to build name recognition in our markets of interest and our business may be adversely affected.

Our trademarks or trade names may be challenged, infringed, circumvented or declared generic or determined to be infringing on other marks. We may not be able to protect our rights to these trademarks and trade names or may be forced to stop using these names, which we need for name recognition by potential partners or customers in our markets of interest. If we are unable to establish name recognition based on our trademarks and trade names, we may not be able to compete effectively and our business may be adversely affected.

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Risks related to our reliance on third parties

We rely on third parties to conduct certain aspects of our preclinical studies and clinical trials. If these third parties do not successfully carry out their contractual duties, meet expected deadlines or comply with regulatory requirements, we may not be able to obtain regulatory approval for, or commercialize, any potential product candidates.

We depend upon third parties to conduct certain aspects of our preclinical studies and depend on third parties, including independent investigators, to conduct our clinical trials, under agreements with universities, medical institutions, CROs, strategic partners and others. We expect to negotiate budgets and contracts with such third parties, which may result in delays to our development timelines and increased costs.

We commenced operations in August 2017 and we continue to build our infrastructure and hire personnel necessary to execute our operational plans. We will rely especially heavily on third parties over the course of our clinical trials, and, as a result, may have limited control over the clinical investigators and limited visibility into their day-to-day activities, including with respect to their compliance with the approved clinical protocol. Nevertheless, we are responsible for ensuring that each of our clinical trials is conducted in accordance with the applicable protocol, legal and regulatory requirements and scientific standards, and our reliance on third parties does not relieve us of our regulatory responsibilities. We and these third parties are required to comply with GCP requirements, which are regulations and guidelines enforced by the FDA and comparable foreign regulatory authorities for product candidates in clinical development. Regulatory authorities enforce these GCP requirements through periodic inspections of clinical trial sponsors, clinical investigators and clinical trial sites. If we or any of these third parties fail to comply with applicable GCP requirements, the clinical data generated in our clinical trials may be deemed unreliable and the FDA or comparable foreign regulatory authorities may require us to suspend or terminate these trials or perform additional preclinical studies or clinical trials before approving our marketing applications. We cannot be certain that, upon inspection, such regulatory authorities will determine that any of our clinical trials comply with GCP requirements. In addition, our clinical trials must be conducted with product produced under cGMP, requirements and may require a large number of patients.

Our failure or any failure by these third parties to comply with these regulations may require us to repeat clinical trials, which would delay the regulatory approval process. Moreover, our business may be adversely affected if any of these third parties violates federal or state fraud and abuse or false claims laws and regulations or healthcare privacy and security laws.

Any third parties conducting aspects of our preclinical studies or our clinical trials will not be our employees and, except for remedies that may be available to us under our agreements with such third parties, we cannot control whether or not they devote sufficient time and resources to our preclinical studies and clinical programs. These third parties may also have relationships with other commercial entities, including our competitors, for whom they may also be conducting clinical trials or other product development activities, which could affect their performance on our behalf. If these third parties do not successfully carry out their contractual duties or obligations or meet expected deadlines, if they need to be replaced or if the quality or accuracy of the preclinical or clinical data they obtain is compromised due to the failure to adhere to our protocols or regulatory requirements or for other reasons, our development timelines, including clinical development timelines, may be extended, delayed or terminated and we may not be able to complete development of, obtain regulatory approval of or successfully commercialize our product candidates. As a result, our financial results and the commercial prospects for our product candidates would be harmed, our costs could increase and our ability to generate revenue could be delayed or precluded entirely.

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If any of our relationships with these third-party CROs or others terminate, we may not be able to enter into arrangements with alternative CROs or other third parties or to do so on commercially reasonable terms.

Switching or adding additional CROs involves additional cost and requires management time and focus. In addition, there is a natural transition period when a new CRO begins work. As a result, delays may occur, which can materially impact our ability to meet our desired development timelines. Though we endeavor to carefully manage our relationships with our CROs and other third parties, there can be no assurance that we will not encounter similar challenges or delays in the future or that these delays or challenges will not have a material adverse impact on our business, financial condition and prospects.

Because we rely on third-party manufacturing and supply partners, our supply of preclinical and clinical development materials may become limited or interrupted or may not be of satisfactory quantity or quality.

We rely on third-party contract manufacturers to manufacture all of our preclinical and clinical trial product supplies. We do not own manufacturing facilities for producing any product supplies. There can be no assurance that our preclinical and clinical development product supplies will not be limited, interrupted, of satisfactory quality or continue to be available at acceptable prices. In particular, any replacement of our manufacturers could require significant effort and expertise because there may be a limited number of qualified replacements.

The manufacturing process for a product candidate is subject to FDA, EMA and comparable foreign regulatory authority review. Suppliers and manufacturers must meet applicable manufacturing requirements and undergo rigorous facility and process validation tests required by regulatory authorities in order to comply with regulatory standards, such as cGMPs. In the event that any of our manufacturers fails to comply with such requirements or to perform its obligations to us in relation to quality, timing or otherwise, or if our supply of components or other materials becomes limited or interrupted for other reasons, we may be forced to manufacture the materials ourselves, for which we currently do not have the capabilities or resources, or enter into an agreement with another third party, which we may not be able to do on reasonable terms, if at all. In some cases, the technical skills or technology required to manufacture our product candidates may be unique or proprietary to the original manufacturer and we may have difficulty transferring such skills or technology to another third party and a feasible alternative may not exist. These factors would increase our reliance on such manufacturer or require us to obtain a license from such manufacturer in order to have another third party manufacture our product candidates. If we are required to change manufacturers for any reason, we will be required to verify that the new manufacturer maintains facilities and procedures that comply with quality standards and with all applicable regulations and guidelines. The delays associated with the verification of a new manufacturer could negatively affect our ability to develop product candidates in a timely manner or within budget.

Our or a third party’s failure to execute on our manufacturing requirements and comply with cGMP could adversely affect our business in a number of ways, including:

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an inability to initiate or continue clinical trials of product candidates under development;

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delay in submitting regulatory applications, or receiving regulatory approvals, for product candidates;

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loss of the cooperation of an existing or future collaborator;

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subjecting third-party manufacturing facilities to additional inspections by regulatory authorities;

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requirements to cease distribution or to recall batches of our product candidates; and

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in the event of approval to market and commercialize a product candidate, an inability to meet commercial demands for our products.

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In addition, we contract with packaging providers with the appropriate expertise, facilities and scale to meet our needs. Failure to maintain cGMP can result in a contractor receiving FDA sanctions, which can impact our ability to operate or lead to delays in any clinical development programs. We believe that our current packaging contractors operate in accordance with cGMP, but we can give no assurance that FDA, EMA or comparable foreign regulatory authorities will not conclude that a lack of compliance exists. In addition, any delay in contracting for packaging services, or failure of the contract manufacturer to perform the services as needed, may delay any clinical trials, registration and launches, which could negatively affect our business.

Our product candidates and any drugs that we may develop may compete with other product candidates and drugs for access to manufacturing facilities. There are no assurances we would be able to enter into similar commercial arrangements with other manufacturers that operate under cGMP regulations and that might be capable of manufacturing for us. Any performance failure on the part of our existing or future manufacturers could delay clinical development or marketing approval.

We have not yet manufactured on a commercial scale and expect to rely on third parties to produce and process commercial quantities of our product candidates, if approved.

We expect to continue to rely on third-party manufacturers if we receive regulatory approval for our product candidates. We have not yet entered into any arrangement with a third party for the manufacture and supply of commercial quantities of our product candidates. To the extent that we enter into future manufacturing arrangements with third parties for commercial supply of our product candidates, if approved, we will depend on these third parties to perform their obligations in a timely manner consistent with contractual and regulatory requirements, including those related to quality control and assurance.

The facilities used by our contract manufacturers to manufacture our product candidates must be approved by the FDA, EMA or comparable foreign regulatory authorities following inspections that will be conducted after we submit an application to the FDA, EMA or comparable foreign regulatory authorities. We do not directly control the manufacturing process of, and will be completely dependent on, our contract manufacturing partners for compliance with cGMP requirements for the manufacture of our product candidates. If our contract manufacturers cannot successfully manufacture material that conforms to our specifications and the strict regulatory requirements of the FDA, EMA or comparable foreign regulatory authorities, they will not be able to secure and/or maintain regulatory approval for their manufacturing facilities. In addition, we have no direct control over the ability of our contract manufacturers to maintain adequate quality control, quality assurance and qualified personnel. If the FDA, EMA or a comparable foreign regulatory authority does not approve these facilities for the manufacture of our product candidates or if it withdraws any approval in the future, we may need to find alternative manufacturing facilities, which would significantly impact our ability to develop, obtain regulatory approval for or market our product candidates, if approved.

We are dependent on a small number of suppliers for some of the materials used to manufacture our product candidates, and on one company for the manufacture of the active pharmaceutical ingredient for each of our product candidates.

We currently depend on a small number of suppliers for some of the materials used in, and processes required to develop, our product candidates. We cannot ensure that these suppliers or service providers will remain in business or have sufficient capacity or supply to meet our needs,

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or that they will not be purchased by one of our competitors or another company that is not interested in continuing to work with us. Our use of a small number of suppliers exposes us to several risks, including disruptions in supply, price increases or late deliveries. There are, in general, relatively few alternative sources of supply for substitute materials. Our current vendors may be unable or unwilling to meet our future demands for our clinical trials or commercial sale. Finding suitable replacement suppliers, materials and processes could take a substantial amount of time and it may be difficult to establish replacement suppliers who meet regulatory requirements. Any disruption or delay in supply could compromise our ability to pursue development and eventual commercialization of our product candidates.

Our existing and future collaborations will be important to our business. If we are unable to maintain our existing collaborations or enter into new collaborations, or if these collaborations are not successful, our business could be adversely affected.

An important part of our strategy is to evaluate and, as deemed appropriate, extend our current or enter into additional partnerships in the future, including potentially with major biopharmaceutical companies. We have limited capabilities for product development and do not yet have any capability for commercialization. Accordingly, we have entered into collaborations with other companies to provide us with important technologies in order to more fully develop our product candidates, including mirdametinib, and we may enter into collaborations with other companies to provide us with important technologies or funding for our programs.

Any current or future collaborations we may extend or enter into may pose a number of risks, including the following:

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collaborators have significant discretion in determining the efforts and resources that they will apply;

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collaborators may not perform their obligations as expected;

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collaborators may not pursue development and commercialization of any product candidates that achieve regulatory approval or may elect not to continue or renew development or commercialization programs or license arrangements based on clinical trial results, changes in the collaborators’ strategic focus or available funding, or external factors, such as a strategic transaction that may divert resources or create competing priorities;

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collaborators may delay clinical trials, provide insufficient funding for a clinical trial program, stop a clinical trial or abandon a product candidate, repeat or conduct new clinical trials or require a new formulation of a product candidate for clinical testing;

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collaborators could independently develop, or develop with third parties, products that compete directly or indirectly with our products and product candidates if the collaborators believe that the competitive products are more likely to be successfully developed or can be commercialized under terms that are more economically attractive than ours;

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for collaborations involving combination therapies that have not yet been tested together, treatment emergent adverse events may be unforseen and may negatively impact the monotherapy development of our product candidates;

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product candidates discovered in collaboration with us may be viewed by our collaborators as competitive with their own product candidates or products, which may cause collaborators to cease to devote resources to the commercialization of our product candidates;

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collaborators may fail to comply with applicable regulatory requirements regarding the development, manufacture, distribution or marketing of a product candidate or product;

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collaborators with marketing and distribution rights to one or more of our product candidates that achieve regulatory approval may not commit sufficient resources to the marketing and distribution of such product or products;

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disagreements with collaborators, including disagreements over proprietary rights, contract interpretation or the preferred course of development, might cause delays or terminations of the research, development or commercialization of product candidates, might lead to additional responsibilities for us with respect to product candidates, or might result in litigation or arbitration, any of which would be time-consuming and expensive;

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collaborators may not properly maintain or defend our intellectual property rights or may use our proprietary information in such a way as to invite litigation that could jeopardize or invalidate our intellectual property or proprietary information or expose us to potential litigation;

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collaborators may infringe the intellectual property rights of third parties, which may expose us to litigation and potential liability; and

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collaborations may be terminated by the collaborator, and, if terminated, we could lose license rights to the applicable product candidates or could be required to raise additional capital to pursue further development or commercialization of the applicable product candidates.

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Under our collaboration agreement with BeiGene, the combination of mirdametinib and lifirafenib is being evaluated a Phase 1b clinical trial, and under our collaboration agreement with GSK, the combination of nirogacestat and belantamab mafodotin will be evaluated in a Phase 1b clinical trial that GSK plans to initiate. Under these existing collaboration arrangements, upon completion of the relevant clinical trials, we and our collaboration partner will negotiate in good faith to provide for the expansion of the respective clinical collaboration and the establishment of a commercial relationship. However, our partners have no obligation to continue development of the combination products, regardless of the applicable clinical trial results. We also jointly formed MapKure, LLC, or MapKure, with BeiGene for the development of BGB-3245, and although we will contribute to clinical development and other operational activities, we will not control the development process. MapKure may pursue a development plan that differs from our expectations, which may or may not be successful.

If our collaborations do not result in the successful discovery, development and commercialization of product candidates or if one of our collaborators elects not to enter into collaboration agreements to pursue future development, we may not receive any future funding or milestone or royalty payments under such collaborations. Risks relating to product development, regulatory approval and commercialization described in this prospectus may also apply to the activities of our collaborators.

Additionally, if one of our collaborators terminates its agreement with us, we may find it more difficult to attract new collaborators and our perception in the business and financial communities could be adversely affected.

Furthermore, we face significant competition in seeking appropriate partners for our product candidates and the negotiation process is time-consuming and complex. In order for us to successfully partner our product candidates, potential partners must view our product candidates as economically valuable in markets they determine to be attractive in light of the terms that we are seeking and other available products for licensing by other companies. In addition, there have been a significant number of recent business combinations among large biopharmaceutical companies that have resulted in a reduced number of potential future collaborators. Our ability to reach a definitive agreement for a collaboration will depend, among other things, upon our

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assessment of the collaborator’s resources and expertise, the terms and conditions of the proposed collaboration and the proposed collaborator’s evaluation of a number of factors. If we are unable to reach agreements with suitable collaborators on a timely basis, on acceptable terms, or at all, we may have to curtail the development of a product candidate, reduce or delay its development program or one or more of our other development programs, delay its potential commercialization or reduce the scope of any sales or marketing activities or planning, or increase our expenditures and undertake development or commercialization activities at our own expense. If we elect to increase our expenditures to fund development or commercialization activities on our own, we may need to obtain additional expertise or capital, which may not be available to us on acceptable terms, or at all. If we fail to enter into collaborations or do not have sufficient funds or expertise to undertake the necessary development and commercialization activities, we may not be able to further develop our product candidates, bring them to market and generate revenue from sales of drugs or continue to develop our technology, and our business may be materially and adversely affected. Even if we are successful in our efforts to establish new strategic partnerships, the terms that we agree upon may not be favorable to us, and we may not be able to maintain such strategic partnerships if, for example, development or approval of a product candidate is delayed or sales of an approved product are disappointing. Any delay in entering into new strategic partnership agreements related to our product candidates could delay the development and commercialization of our product candidates and reduce their competitiveness even if they reach the market.

Risks related to managing our business and operations

We will need to grow the size of our organization, and we may experience difficulties in managing this growth.

As of June 1, 2019, we had 48 full-time employees. As our clinical development and commercialization plans and strategies develop, and as we transition into operating as a public company, we expect we will need additional managerial, clinical, manufacturing, medical, regulatory, sales, marketing, financial, legal and other personnel. Future growth would impose significant added responsibilities on members of management, including:

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recruiting, integrating, retaining and motivating additional employees;

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managing our development efforts effectively, including the clinical, manufacturing and quality review process for our product candidates, while complying with our contractual obligations to contractors, collaboration partners and other third parties; and

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improving our operational, financial and management controls, reporting systems and procedures.

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Our future financial performance and our ability to commercialize our product candidates, if approved, will depend, in part, on our ability to effectively manage any future growth, and our management may also have to divert a disproportionate amount of its attention away from day-to-day activities in order to devote a substantial amount of time to managing these growth activities.

We currently rely, and for the foreseeable future will continue to rely, in substantial part on third parties, including independent organizations, advisors and consultants, to provide certain services to support and perform our operations. There can be no assurance that the services of these third parties will continue to be available to us on a timely basis when needed, or that we can find qualified replacements. In addition, if we are unable to effectively manage our outsourced activities or if the quality, accuracy or quantity of the services provided is compromised for any reason, our clinical trials may be delayed or terminated, and we may not be able to obtain, or

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may be substantially delayed in obtaining, regulatory approval of our product candidates or otherwise advance our business. There can be no assurance that we will be able to manage our existing consultants or find other suitable outside contractors and consultants on economically reasonable terms, or at all.

If we are not able to effectively expand our organization by hiring new employees and expanding our groups of consultants and contractors, we may not be able to successfully execute the tasks necessary to further develop and commercialize our product candidates and, accordingly, may not achieve our development and commercialization goals.

We have no history of commercializing marketed products. Building our commercialization capabilities will require a significant investment of time and money. There can be no assurance that we will successfully set up our commercialization capabilities.

We are currently in the early stages of building our commercial capabilities to allow us to market our product candidates, if approved, either alone or in combination with others. Establishing commercialization capabilities will require substantial investment of time and money and may divert significant management focus and resources. In addition, we will be competing with larger biopharmaceutical and biotechnology companies with established commercialization and marketing capabilities as we seek to recruit suitable personnel. Accordingly, there can be no assurance that our efforts to set up commercialization capabilities will be successful.

If we lose key management personnel, or if we fail to recruit additional highly skilled personnel, our ability to pursue our business strategy will be impaired, could result in loss of markets or market share and could make us less competitive.

Our ability to compete in the highly competitive biopharmaceutical industries depends upon our ability to attract and retain highly qualified managerial, scientific and medical personnel. We are highly dependent on our management, scientific and medical personnel, including Saqib Islam, our Chief Executive Officer, Badreddin Edris, our Chief Business Officer, Jens Renstrup, our Chief Medical Officer and L. Mary Smith, our Senior Vice President, Clinical Research and Development. The loss of the services of any of our executive officers, other key employees, and other scientific and medical advisors, and our inability to find suitable replacements for these individuals could harm our business.

Competition for skilled personnel in our industry is intense and may limit our ability to hire and retain highly qualified personnel on acceptable terms, in a timely manner or at all. To induce valuable employees to remain at our company, in addition to salary and cash incentives, we have provided equity incentive awards that vest over time. The value to employees of restricted stock awards and stock options that vest over time may be significantly affected by movements in our stock price that are beyond our control, and may at any time be insufficient to counteract more lucrative offers from other companies. Despite our efforts to retain valuable employees, members of our management, scientific and development teams are at-will employees and may terminate their employment with us on short notice. We do not maintain “key man” insurance policies on the lives of these individuals or the lives of any of our other employees. Given the stage of our programs and our plans to expand operations, our success also depends on our ability to continue to attract, retain and motivate highly skilled junior, mid-level and senior personnel across our organization.

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We do not have the internal research capabilities required to independently discover new product candidates, and we plan to execute our growth strategy by identifying and in-licensing or acquiring additional product candidates that have been discovered and initially developed by others. We may not be successful in executing our growth strategy or such growth strategy may not deliver the anticipated results.

We do not have an internal discovery and preclinical research and development department to independently discover and initially develop new product candidates. We plan to source new product candidates, including those that may be complementary to our existing product candidates, by in-licensing or acquiring them from other companies, academic institutions or other asset originators. If we are unable to identify, in-license or acquire and integrate product candidates, our ability to pursue our growth strategy would be limited.

Research programs and business development efforts to identify new product candidates require substantial technical, financial and human resources, and we have no immediate plans to develop an internal discovery and preclinical research and development group. In-licensing and acquiring product candidates or development programs often requires significant payments and expenses and may consume valuable resources. We will need to devote a substantial amount of time and personnel to develop and commercialize any in-licensed or acquired technology or product candidate, in addition to doing so for our existing product candidates. Our business development efforts or acquisition or licensing attempts may fail to yield additional complementary or successful product candidates for clinical development and commercialization for a number of reasons, including the following:

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our identification or business development methodology or search criteria and process may be unsuccessful in identifying potential product candidates with a high probability of success for development progression;

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we may not be able or willing to assemble sufficient resources or expertise to identify and in-license or acquire additional product candidates;

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for product candidates we seek to in-license or acquire, we may not be able to agree to acceptable terms with the licensor or owner of those product candidates;

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any product candidates that we do in-license or acquire may not succeed in preclinical studies or clinical trials;

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we may not succeed in formulation or process development of such in-licensed or acquired product candidates;

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such in-licensed or acquired product candidates may be shown to have harmful side effects or may have other characteristics that may make the products unlikely to receive regulatory approval or be unmarketable if approved;

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competitors may develop alternatives that render such in-licensed product candidates obsolete or less attractive;

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in-licensed or acquired product candidates may be covered by third parties’ patents or other exclusive rights that we may not be able to access;

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in-licensed or acquired product candidates that we develop may not allow us to best make use of our expertise and our development and commercial infrastructure as currently expected;

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the market for a product candidate that we in-license or acquire may change during the course of our development of the product candidate so that such product candidate may become unreasonable to continue to develop;

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a product candidate that we in-license or acquire may not be capable of being produced in commercial quantities at an acceptable cost, or at all; and

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a product candidate that we in-license or acquire may not be accepted as safe and effective by patients, the medical community or third-party payors.

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If any of these events occur, we may not be successful in executing our growth strategy or our growth strategy may not deliver the anticipated results.

Our internal computer systems, or those used by our vendors, or other contractors or consultants, may fail or suffer security breaches.

Despite the implementation of security measures, our internal computer systems and those of our CROs and other third parties, including our contractors and consultants, are vulnerable to damage from computer viruses and unauthorized access. Like other companies of our size and in our industry, we have been the target of phishing attacks and attacks on our data and systems. While we have not experienced any material system failure or security breach to date, if such an event were to occur and cause interruptions in our operations, it could result in a material disruption of our development programs and our business operations. For example, the loss of preclinical or clinical data could result in delays in our regulatory approval efforts and significantly increase our costs to recover or reproduce the data. To the extent that any disruption or security breach were to result in a loss of, or damage to, our data or applications, or inappropriate disclosure of financial or confidential information, we could incur liability and the further development and commercialization of our product candidates could be delayed.

We could also be subject to risks caused by misappropriation, misuse, leakage, falsification or intentional or accidental release or loss of information maintained in the information systems and networks of our company and our contractors or consultants. In addition, outside parties may attempt to penetrate our systems or those of our contractors or consultants or fraudulently induce our personnel or the personnel of our contractors or consultants to disclose sensitive information in order to gain access to our data and/or systems. We may experience threats to our data and systems, including malicious codes and viruses, phishing and other cyber-attacks. The number and complexity of these threats continue to increase over time. If a material breach of our information technology systems or those of our contractors or consultants occurs, the market perception of the effectiveness of our security measures could be harmed and our reputation and credibility could be damaged. We could be required to expend significant amounts of money and other resources to repair or replace information systems or networks. In addition, we could be subject to regulatory actions and/or claims made by individuals and groups in private litigation involving privacy issues related to data collection and use practices and other data privacy laws and regulations, including claims for misuse or inappropriate disclosure of data, as well as unfair or deceptive practices. Although we develop and maintain systems and controls designed to prevent these events from occurring, and we have a process to identify and mitigate threats, the development and maintenance of these systems, controls and processes is costly and requires ongoing monitoring and updating as technologies change and efforts to overcome security measures become increasingly sophisticated. Moreover, despite our efforts, the possibility of these events occurring cannot be eliminated entirely. In addition, there can be no assurance that our internal information technology systems or those of our third-party contractors, or our consultants’ efforts to implement adequate security and control measures, will be sufficient to protect us against breakdowns, service disruption, data deterioration or loss in the event of a system malfunction, or prevent data from being stolen or corrupted in the event of a cyberattack, security breach, industrial espionage attacks or insider threat attacks which could result in financial, legal, business or reputational harm.

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Our employees, independent contractors, consultants, academic collaborators, partners and vendors may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements.

We are exposed to the risk of employee fraud or other illegal activity by our employees, independent contractors, consultants, academic collaborators, partners and vendors. Misconduct by these parties could include intentional, reckless and/or negligent conduct that fails to comply with the laws of the FDA, EMA and comparable foreign regulatory authorities, provide true, complete and accurate information to the FDA, EMA and comparable foreign regulatory authorities, comply with manufacturing standards we have established, comply with healthcare fraud and abuse laws in the United States and similar foreign fraudulent misconduct laws, or report financial information or data accurately or to disclose unauthorized activities to us. If we obtain FDA approval of any of our product candidates and begin commercializing those products in the United States, our potential exposure under such laws will increase significantly, and our costs associated with compliance with such laws are also likely to increase. These laws may impact, among other things, our current activities with principal investigators and research patients, as well as proposed and future sales, marketing and education programs. In connection with this offering, we will adopt a code of business conduct and ethics, but it is not always possible to identify and deter misconduct by our employees, independent contractors, consultants, academic collaborators, partners and vendors, and the precautions we take to detect and prevent such activities may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to comply with these laws or regulations. If any actions are instituted against us and we are not successful in defending ourselves or asserting our rights, those actions could result in the imposition of civil, criminal and administrative penalties, damages, monetary fines, imprisonment, disgorgement, possible exclusion from participation in government healthcare programs, additional reporting obligations and oversight if we become subject to a corporate integrity agreement or other agreement to resolve allegations of non-compliance with these laws, contractual damages, reputational harm, diminished profits and future earnings and the curtailment of our operations.

If we fail to comply with environmental, health and safety laws and regulations, we could become subject to fines or penalties or incur costs that could harm our business.

We are subject to numerous environmental, health and safety laws and regulations, including those governing the handling, use, storage, treatment and disposal of hazardous materials and wastes. Our development activities involve the use of biological and hazardous materials and can produce hazardous waste products. We cannot eliminate the risk of contamination or injury from these materials, which could cause an interruption of our commercialization efforts, research and development efforts and business operations, environmental damage resulting in costly clean-up and liabilities under applicable laws and regulations governing the use, storage, handling and disposal of these materials and specified waste products. Although we believe that the safety procedures utilized by our third-party manufacturers for handling and disposing of these materials generally comply with the standards prescribed by these laws and regulations, we cannot guarantee that this is the case or eliminate the risk of accidental contamination or injury from these materials. In such an event, we may be held liable for any resulting damages and such liability could exceed our resources and state or federal or other applicable authorities may curtail our use of certain materials and/or interrupt our business operations. Furthermore, environmental laws and regulations are complex, change frequently and have tended to become more stringent. We cannot predict the impact of such changes and cannot be certain of our future compliance. In addition, we may incur substantial costs in order to comply with current or

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future environmental, health and safety laws and regulations. These current or future laws and regulations may impair our research, development or production efforts. Failure to comply with these laws and regulations also may result in substantial fines, penalties or other sanctions.

Although we maintain workers’ compensation insurance to cover us for costs and expenses we may incur due to injuries resulting from the use of hazardous materials or other work-related injuries, this insurance may not provide adequate coverage against potential liabilities. We do not carry specific biological waste or hazardous waste insurance coverage, workers compensation or property and casualty and general liability insurance policies that include coverage for damages and fines arising from biological or hazardous waste exposure or contamination.

Our current operations are concentrated in two locations, and we or the third parties upon whom we depend may be adversely affected by earthquakes or other natural disasters and our business continuity and disaster recovery plans may not adequately protect us from a serious disaster.

Our current headquarters are located in Stamford, Connecticut. Our development operations are currently located in Durham, North Carolina. We currently outsource our manufacturing operations to third parties, and clinical quantities of our product candidates are manufactured by these third parties outside the United States, including in China and France. Any unplanned event, such as flood, fire, explosion, earthquake, extreme weather condition, medical epidemics, power shortage, telecommunication failure or other natural or manmade accidents or incidents that result in us being unable to fully utilize our facilities, or the manufacturing facilities of our third-party contract manufacturers, may have a material and adverse effect on our ability to operate our business, particularly on a daily basis, and have significant negative consequences on our financial and operating conditions. Loss of access to these facilities may result in increased costs, delays in the development of our product candidates or interruption of our business operations. Earthquakes or other natural disasters could further disrupt our operations and have a material and adverse effect on our business, financial condition, results of operations and prospects. If a natural disaster, power outage or other event occurred that prevented us from using all or a significant portion of our headquarters or our development operations, that damaged critical infrastructure, such as the manufacturing facilities of our third-party contract manufacturers, or that otherwise disrupted operations, it may be difficult or, in certain cases, impossible, for us to continue our business for a substantial period of time. Disaster recovery and business continuity plans may prove inadequate in the event of a serious disaster or similar event. We may incur substantial expenses as a result of the limited nature of our disaster recovery and business continuity plans, which could have a material adverse effect on our business. As part of our risk management approach, we maintain insurance coverage at levels that we believe are appropriate for our business. However, in the event of an accident or incident at these facilities, we cannot assure you that the amounts of insurance will be sufficient to satisfy any damages and losses. If our facilities, or the manufacturing facilities of our third-party contract manufacturers, are unable to operate because of an accident or incident or for any other reason, even for a short period of time, any or all of our research and development programs may be harmed. Any business interruption may have a material and adverse effect on our business, financial condition, results of operations and prospects.

Comprehensive tax reform legislation could adversely affect our business and financial condition.

On December 22, 2017, President Trump signed into law the TCJA that significantly reforms the Internal Revenue Code of 1986, as amended, or the Code. The TCJA, among other things, contains significant changes to corporate taxation, including reduction of the corporate tax rate from 34.0% to a flat rate of 21.0%, limitation of the tax deduction for interest expense to 30.0%

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of adjusted taxable income (except for certain small businesses), limitation of the deduction for net operating losses arising in taxable years beginning after December 31, 2017 to 80.0% of annual taxable income and elimination of net operating loss carrybacks applying to net operating losses arising in taxable years ending after December 31, 2017, and modifying or repealing many business deductions and credits (including reducing the business tax credit for certain clinical testing expenses incurred in the testing of certain drugs for rare diseases or conditions generally referred to as “orphan drugs”). The effect of the TCJA on our business, whether adverse or favorable, is uncertain and may not become evident for some period of time. We urge investors to consult with their legal and tax advisers regarding the implications of the TCJA on an investment in our common stock.

Our ability to use our net operating loss carryforwards and certain tax credit carryforwards may be subject to limitation.

As of December 31, 2018, we had net operating loss carryforwards for federal, state and city income tax purposes of  $14.2 million, $0.6 million and $3.8 million, respectively. Federal net operating loss carryforwards of  $4.3 million were recorded in 2017 and the state and city net operating loss carryforwards expire at various dates through 2038. Federal net operating loss carryforwards of  $9.9 million recorded in 2018 will be available to offset 80% of taxable income for an indefinite period of time, until fully utilized. As of December 31, 2018, we also had federal tax credits of  $0.4 million, which may be used to offset future tax liabilities. These tax credit carryforwards will expire in 2038. Under Section 382 of the Code, changes in our ownership may limit the amount of our net operating loss carryforwards and tax credit carryforwards that could be utilized annually to offset our future taxable income, if any. This limitation would generally apply in the event of a cumulative change in ownership of our company of more than 50% within a three-year period. Any such limitation may significantly reduce our ability to utilize our net operating loss carryforwards and tax credit carryforwards before they expire. Private placements and other transactions that have occurred since our inception, as well as this offering, may trigger such an ownership change pursuant to Section 382. Any such limitation, whether as the result of this offering, prior private placements, sales of our common stock by our existing stockholders or additional sales of our common stock by us, could have a material adverse effect on our results of operations in future years. The reduction of the corporate tax rate under TCJA may cause a reduction in the economic benefit of our net operating loss carryforwards and other deferred tax assets available to us. Under the TCJA, net operating losses generated in taxable years ending after December 31, 2017 will not be subject to expiration; however, under the TCJA, net operating losses generated in taxable years beginning after December 31, 2017 will be subject to limitation on deduction.

Unfavorable global economic conditions could adversely affect our business, financial condition or results of operations.

Our results of operations could be adversely affected by general conditions in the global economy and in the global financial markets. Portions of our future clinical trials may be conducted outside of the United States and unfavorable economic conditions resulting in the weakening of the U.S. dollar would make those clinical trials more costly to operate. Furthermore, the most recent global financial crisis caused extreme volatility and disruptions in the capital and credit markets. A severe or prolonged economic downturn could result in a variety of risks to our business, including a reduced ability to raise additional capital when needed on acceptable terms, if at all. A weak or declining economy or international trade disputes could also strain our suppliers, some of which are located outside of the United States, possibly resulting in supply disruption. Any of the foregoing could harm our business and we cannot anticipate all of the ways in which the current economic climate and financial market conditions could adversely impact our business.

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Risks related to our common stock and this offering

There has been no prior public market for our common stock, and we do not know whether an active, liquid and orderly trading market will develop for our common stock, or what the market price of our common stock will be, and as a result it may be difficult for you to sell your shares of our common stock.

Prior to this offering there has been no public market for shares of our common stock. Although we intend to apply to list our common stock on the Nasdaq Global Market, an active trading market for our shares may never develop or be sustained following this offering. You may not be able to sell your shares quickly or at the market price if trading in shares of our common stock is not active. The initial public offering price for our common stock will be determined through negotiations with the underwriters, and the negotiated price may not be indicative of the market price of the common stock after the offering. As a result of these and other factors, you may be unable to resell your shares of our common stock at or above the initial public offering price.

Further, an inactive market may also impair our ability to raise capital by selling shares of our common stock and may impair our ability to enter into strategic partnerships or acquire companies or products by using our shares of common stock as consideration.

The price of our stock may be volatile, and you could lose all or part of your investment.

The trading price of our common stock following this offering is likely to be highly volatile and could be subject to wide fluctuations in response to various factors, some of which are beyond our control, including limited trading volume. In addition to the factors discussed in this “Risk factors” section and elsewhere in this prospectus, these factors include:

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the commencement, enrollment or results of our ongoing and planned potentially registrational clinical trials for nirogacestat and mirdametinib;

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any delay in our regulatory filings for our product candidates and any adverse development or perceived adverse development with respect to the applicable regulatory authority’s review of such filings, including without limitation the FDA’s issuance of a “refusal to file” letter or a request for additional information;

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adverse results from or delays in future clinical trials;

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our decision to initiate a clinical trial, not to initiate a clinical trial or to terminate an existing clinical trial;

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adverse regulatory decisions, including failure to receive regulatory approval of our product candidates or any future product candidate;

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changes in laws or regulations applicable to our product candidates or any future product candidate, including but not limited to clinical trial requirements for approvals;

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changes in the structure of healthcare payment systems;

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adverse developments concerning our manufacturers;

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our inability to obtain adequate product supply for any approved product or inability to do so at acceptable prices;

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our inability to establish collaborations or partnerships, if needed;

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our failure to commercialize our product candidates, if approved;

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additions or departures of key medical, scientific or management personnel;

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unanticipated serious safety concerns related to the use of our product candidates;

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introduction of new products or services offered by us or our competitors;

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clinical trial results for other product candidates that could compete with our product candidates;

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announcements of significant acquisitions, strategic partnerships, joint ventures or capital commitments by us or our competitors;

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our ability to effectively manage our growth;

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actual or anticipated variations in quarterly operating results;

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our cash position;

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our failure to meet the estimates and projections of the investment community or that we may otherwise provide to the public;

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publication of research reports about us or our industry, or product candidates in particular, or positive or negative recommendations or withdrawal of research coverage by securities analysts;

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changes in the market valuations of similar companies;

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overall performance of the equity markets;

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sales of our common stock by us or our stockholders in the future;

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trading volume of our common stock;

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changes in accounting practices;

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ineffectiveness of our internal controls;

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disputes or other developments relating to proprietary rights, including patents, litigation matters and our ability to obtain patent protection for our technologies;

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significant lawsuits, including patent or stockholder litigation;

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general political and economic conditions; and

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other events or factors, many of which are beyond our control.

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In addition, the stock market in general, and the market for biopharmaceutical companies in particular, have experienced extreme price and volume fluctuations that have often been unrelated or disproportionate to the operating performance of these companies. Broad market and industry factors may negatively affect the market price of our common stock, regardless of our actual operating performance. If the market price of our common stock after this offering does not exceed the initial public offering price, you may not realize any return on your investment in us and may lose some or all of your investment. In the past, securities class action litigation has often been instituted against companies following periods of volatility in the market price of a company’s securities. This type of litigation, if instituted, could result in substantial costs and a diversion of management’s attention and resources, which would harm our business, operating results or financial condition.

We do not intend to pay dividends on our common stock so any returns will be limited to the value of our stock.

We currently anticipate that we will retain future earnings for the development, operation and expansion of our business and do not anticipate declaring or paying any cash dividends for the foreseeable future. Furthermore, future debt or other financing arrangements may contain terms prohibiting or limiting the amount of dividends that may be declared or paid on our common stock. Any return to stockholders will therefore be limited to the appreciation of their stock.

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Our principal stockholders and management own a significant percentage of our stock and will be able to exert significant control over matters subject to stockholder approval.

Immediately following the completion of this offering, our executive officers, directors and their affiliates and certain significant stockholders will beneficially hold, in the aggregate, approximately     % of our outstanding voting stock. Therefore, even after this offering, these stockholders will have the ability to influence us through this ownership position. These stockholders may be able to determine all matters requiring stockholder approval. For example, these stockholders may be able to control elections of directors, amendments of our organizational documents, or approval of any merger, sale of assets, or other major corporate transaction. This may prevent or discourage unsolicited acquisition proposals or offers for our common stock that you may feel are in your best interest as one of our stockholders.

If you purchase our common stock in this offering, you will incur immediate and substantial dilution in the book value of your shares.

The initial public offering price will be substantially higher than the pro forma as adjusted net tangible book value per share of our common stock after this offering. Investors purchasing common stock in this offering will pay a price per share that substantially exceeds the pro forma as adjusted net tangible book value per share after this offering. As a result, investors purchasing common stock in this offering will incur immediate dilution of  $     per share, based on an assumed initial public offering price of  $     per share, the midpoint of the price range set forth on the cover page of this prospectus, representing the difference between our pro forma as adjusted net tangible book value per share after giving effect to this offering and the assumed initial public offering price. Further, investors purchasing common stock in this offering will contribute approximately     % of the total amount invested by stockholders since our inception, but will own only approximately     % of the shares of common stock outstanding after this offering.

This dilution is due to our investors who purchased shares prior to this offering having paid substantially less when they purchased their shares than the price offered to the public in this offering. To the extent outstanding options are exercised, there will be further dilution to new investors. As a result of the dilution to investors purchasing shares in this offering, investors may receive significantly less than the purchase price paid in this offering, if anything, in the event of our liquidation. For a further description of the dilution that you will experience immediately after this offering, see “Dilution.”

We are an emerging growth company, and we cannot be certain if the reduced reporting requirements applicable to emerging growth companies will make our common stock less attractive to investors.

We are an emerging growth company, or EGC, as defined in the Jumpstart Our Business Startups Act, or the JOBS Act, enacted in April 2012. For as long as we continue to be an EGC, we may take advantage of exemptions from various reporting requirements that are applicable to other public companies that are not EGCs, including not being required to comply with the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act of 2002, as amended, or the Sarbanes-Oxley Act, reduced disclosure obligations regarding executive compensation in this prospectus and our periodic reports and proxy statements and exemptions from the requirements of holding nonbinding advisory votes on executive compensation and stockholder approval of any golden parachute payments not previously approved. We could be an EGC for up to five years following the year in which we complete this offering, although circumstances could cause us to lose that status earlier. We will remain an EGC until the earlier of  (i) the last day of the fiscal year (a) following the fifth anniversary of the completion of this offering, (b) in which we have total annual gross revenue of at least $1.07 billion or (c) in which we are deemed to be a large

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accelerated filer, which requires the market value of our common stock that is held by non-affiliates to exceed $700.0 million as of the prior June 30th and (ii) the date on which we have issued more than $1.0 billion in non-convertible debt during the prior three-year period.

We may choose to take advantage of some, but not all, of the available exemptions. We have taken advantage of reduced reporting burdens in this prospectus. In particular, we have not included all of the executive compensation information that would be required if we were not an EGC. We cannot predict whether investors will find our common stock less attractive if we rely on certain or all of these exemptions. If some investors find our common stock less attractive as a result, there may be a less active trading market for our common stock and our stock price may be more volatile.

Under the JOBS Act, EGCs can also delay adopting new or revised accounting standards until such time as those standards apply to private companies, which may make our financial statements less comparable to companies that comply with new or revised accounting pronouncements as of public company effective dates.

We will incur significant increased costs as a result of operating as a public company, and our management will be required to devote substantial time to new compliance initiatives.

As a public company, we will incur significant legal, accounting and other expenses that we did not incur as a private company. We will be subject to the reporting requirements of the Securities Exchange Act of 1934, as amended, or the Exchange Act, which will require, among other things, that we file with the SEC, annual, quarterly and current reports with respect to our business and financial condition. In addition, the Sarbanes-Oxley Act, as well as rules subsequently adopted by the SEC and                                               to implement provisions of the Sarbanes-Oxley Act, impose significant requirements on public companies, including requiring establishment and maintenance of effective disclosure and financial controls and changes in corporate governance practices. Further, in July 2010, the Dodd-Frank Wall Street Reform and Consumer Protection Act, or the Dodd-Frank Act, was enacted. There are significant corporate governance and executive compensation related provisions in the Dodd-Frank Act that require the SEC to adopt additional rules and regulations in these areas such as “say on pay” and proxy access. Recent legislation permits EGCs to implement many of these requirements over a longer period and up to five years from the pricing of this offering. Stockholder activism, the current political environment and the current high level of government intervention and regulatory reform may lead to substantial new regulations and disclosure obligations, which may lead to additional compliance costs and impact the manner in which we operate our business in ways we cannot currently anticipate.

We expect the rules and regulations applicable to public companies to substantially increase our legal and financial compliance costs and to make some activities more time-consuming and costly. If these requirements divert the attention of our management and personnel from other business concerns, they could have an adverse effect on our business. The increased costs will decrease our net income or increase our net loss, and may require us to reduce costs in other areas of our business. For example, we expect these rules and regulations to make it more difficult and more expensive for us to obtain director and officer liability insurance and we may be required to incur substantial costs to maintain the same or similar coverage. We cannot predict or estimate the amount or timing of additional costs we may incur to respond to these requirements. The impact of these requirements could also make it more difficult for us to attract and retain qualified persons to serve on our board of directors, our board committees or as executive officers.

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Sales of a substantial number of shares of our common stock by our existing stockholders in the public market could cause our stock price to fall.

If our existing stockholders sell, or indicate an intention to sell, substantial amounts of our common stock in the public market after the lock-up and other legal restrictions on resale discussed in this prospectus lapse, the trading price of our common stock could decline. Based on shares of common stock outstanding as of      , 2019, upon the completion of this offering we will have outstanding a total of       shares of common stock. Of these shares, only the shares of common stock sold in this offering by us, plus any shares sold upon exercise of the underwriters’ option to purchase additional shares, will be freely tradable without restriction in the public market immediately following this offering.

The lock-up agreements pertaining to this offering will expire 180 days from the date of this prospectus, subject to earlier release of all or a portion of the shares subject to such agreements by the representatives of the underwriters in their sole discretion. After the lock-up agreements expire, based upon the number of shares of common stock, on an as-converted basis, outstanding as of      , up to an additional      shares of common stock will be eligible for sale in the public market. Approximately     % of these additional shares are held by directors, executive officers and other affiliates and will be subject to certain limitations of Rule 144 under the Securities Act of 1933, as amended, or the Securities Act.

In addition, shares of common stock that are either subject to outstanding options or reserved for future issuance under our existing equity compensation plans will become eligible for sale in the public market to the extent permitted by the provisions of various vesting schedules, the lock-up agreements and Rule 144 and Rule 701 under the Securities Act. If these additional shares of common stock are sold, or if it is perceived that they will be sold, in the public market, the trading price of our common stock could decline. Additionally, the number of shares of our common stock reserved for issuance under the 2019 Stock Option and Equity Incentive Plan will automatically increase on January 1 of each year, beginning on January 1, 2020 and continuing through and including January 1, 2030, by     % of the total number of shares of our capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by our board of directors. Unless our board of directors elects not to increase the number of shares available for future grant each year, our stockholders may experience additional dilution.

After the completion of this offering, the holders of        shares of our common stock (including shares issuable upon conversion of our outstanding convertible preferred stock) will be entitled to rights with respect to the registration of their shares under the Securities Act, subject to the 180-day lock-up agreements described above. See “Description of capital stock—Registration rights.” Registration of these shares under the Securities Act would result in the shares becoming freely tradable without restriction under the Securities Act, except for shares held by affiliates, as defined in Rule 144 under the Securities Act. Any sales of securities by these stockholders could have a material adverse effect on the trading price of our common stock.

We have broad discretion in the use of our existing cash, cash equivalents and the net proceeds from this offering and may not use them effectively.

Our management will have broad discretion in the application of our existing cash, cash equivalents and the net proceeds from this offering, including for any of the purposes described in the section titled “Use of proceeds,” and you will not have the opportunity as part of your investment decision to assess whether such proceeds are being used appropriately. Because of the number and variability of factors that will determine our use of our existing cash and cash equivalents and the net proceeds from this offering, their ultimate use may vary substantially

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from their currently intended use. Our management might not apply our existing cash and cash equivalents and the net proceeds from this offering in ways that ultimately increase the value of your investment. The failure by our management to apply these funds effectively could harm our business. Pending their use, we may invest the net proceeds from this offering in short-term, investment-grade, interest-bearing securities. These investments may not yield a favorable return to our stockholders. If we do not invest or apply the net proceeds from this offering in ways that enhance stockholder value, we may fail to achieve expected financial results, which could cause our stock price to decline.

Anti-takeover provisions under our charter documents and Delaware law could delay or prevent a change of control which could limit the market price of our common stock and may prevent or frustrate attempts by our stockholders to replace or remove our current management.

Our amended and restated certificate of incorporation and amended and restated bylaws, which are to become effective immediately prior to the completion of this offering, contain provisions that could delay or prevent a change of control of our company or changes in our board of directors that our stockholders might consider favorable. Some of these provisions include:

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a board of directors divided into three classes serving staggered three-year terms, such that not all members of the board will be elected at one time;

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a prohibition on stockholder action through written consent, which requires that all stockholder actions be taken at a meeting of our stockholders;

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a requirement that special meetings of stockholders be called only by the chairman of the board of directors, the chief executive officer or by a majority of the total number of authorized directors;

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advance notice requirements for stockholder proposals and nominations for election to our board of directors;

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a requirement that no member of our board of directors may be removed from office by our stockholders except for cause and, in addition to any other vote required by law, upon the approval of not less than two-thirds of all outstanding shares of our voting stock then entitled to vote in the election of directors;

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a requirement of approval of not less than two-thirds of all outstanding shares of our voting stock to amend any bylaws by stockholder action or to amend specific provisions of our certificate of incorporation; and

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the authority of the board of directors to issue convertible preferred stock on terms determined by the board of directors without stockholder approval and which convertible preferred stock may include rights superior to the rights of the holders of common stock.

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In addition, because we are incorporated in Delaware, we are governed by the provisions of Section 203 of the Delaware General Corporation Law, which may prohibit certain business combinations with stockholders owning 15% or more of our outstanding voting stock. These anti-takeover provisions and other provisions in our amended and restated certificate of incorporation and amended and restated bylaws could make it more difficult for stockholders or potential acquirers to obtain control of our board of directors or initiate actions that are opposed by the then-current board of directors and could also delay or impede a merger, tender offer or proxy contest involving our company. These provisions could also discourage proxy contests and make it more difficult for you and other stockholders to elect directors of your choosing or cause us to take other corporate actions you desire. Any delay or prevention of a change of control transaction or changes in our board of directors could cause the market price of our common stock to decline.

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If securities or industry analysts do not publish research or publish inaccurate or unfavorable research about our business, our stock price and trading volume could decline.

The trading market for our common stock will depend in part on the research and reports that securities or industry analysts publish about us or our business. Securities and industry analysts do not currently, and may never, publish research on our company. If no securities or industry analysts commence coverage of our company, the trading price for our stock would likely be negatively impacted. In the event securities or industry analysts initiate coverage, if one or more of the analysts who covers us downgrades our stock or publishes inaccurate or unfavorable research about our business, our stock price may decline. If one or more of these analysts ceases coverage of our company or fails to publish reports on us regularly, demand for our stock could decrease, which might cause our stock price and trading volume to decline.

If we fail to maintain an effective system of internal control over financial reporting, we may not be able to accurately report our financial results or prevent fraud. As a result, stockholders could lose confidence in our financial and other public reporting, which would harm our business and the trading price of our common stock.

Effective internal controls over financial reporting are necessary for us to provide reliable financial reports and, together with adequate disclosure controls and procedures, are designed to prevent fraud. Any failure to implement required new or improved controls, or difficulties encountered in their implementation could cause us to fail to meet our reporting obligations. In addition, any testing by us conducted in connection with Section 404, or any subsequent testing by our independent registered public accounting firm, may reveal deficiencies in our internal controls over financial reporting that are deemed to be material weaknesses or that may require prospective or retroactive changes to our financial statements or identify other areas for further attention or improvement. Inferior internal controls could also cause investors to lose confidence in our reported financial information, which could have a negative effect on the trading price of our stock.

We will be required to disclose changes made in our internal controls and procedures on a quarterly basis and our management will be required to assess the effectiveness of these controls annually. However, for as long as we are an EGC, our independent registered public accounting firm will not be required to attest to the effectiveness of our internal controls over financial reporting pursuant to Section 404. We could be an EGC for up to five years. An independent assessment of the effectiveness of our internal controls over financial reporting could detect problems that our management’s assessment might not. Undetected material weaknesses in our internal controls over financial reporting could lead to restatements of our financial statements and require us to incur the expense of remediation.

Our disclosure controls and procedures may not prevent or detect all errors or acts of fraud.

Upon completion of this offering, we will become subject to certain reporting requirements of the Exchange Act. Our disclosure controls and procedures are designed to reasonably assure that information required to be disclosed by us in reports we file or submit under the Exchange Act is accumulated and communicated to management, recorded, processed, summarized and reported within the time periods specified in the rules and forms of the SEC. We believe that any disclosure controls and procedures or internal controls and procedures, no matter how well conceived and operated, can provide only reasonable, not absolute, assurance that the objectives of the control system are met. These inherent limitations include the realities that judgments in decision-making can be faulty, and that breakdowns can occur because of simple error or mistake. Additionally, controls can be circumvented by the individual acts of some persons, by

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collusion of two or more people or by an unauthorized override of the controls. Accordingly, because of the inherent limitations in our control system, misstatements or insufficient disclosures due to error or fraud may occur and not be detected.

Our amended and restated bylaws will designate the Court of Chancery of the State of Delaware as the exclusive forum for certain state law litigation that may be initiated by our stockholders, which could limit our stockholders’ ability to litigate disputes with us in a different judicial forum.

Pursuant to our amended and restated bylaws, as will become effective immediately prior to the completion of this offering, unless we consent in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware will be the sole and exclusive forum for the following types of actions or proceedings under Delaware statutory or common law: (i) any derivative action or proceeding brought on our behalf; (ii) any action asserting a claim of breach of a fiduciary duty or other wrongdoing by any of our directors, officers, employees or agents to us or our stockholders; (iii) any action asserting a claim against us arising pursuant to any provision of the General Corporation Law of the State of Delaware, our amended and restated certificate of incorporation or our amended and restated bylaws; (iv) any action to interpret, apply, enforce or determine the validity of our certificate of incorporation or bylaws; or (v) any action asserting a claim governed by the internal affairs doctrine, in each case subject to the Court of Chancery having personal jurisdiction over the indispensable parties named as defendants therein. This exclusive forum provision will not apply to any causes of action arising under the Securities Act or the Exchange Act or any other claim for which the federal courts have exclusive jurisdiction. The forum selection clause in our amended and restated bylaws may limit our stockholders’ ability to litigate disputes with us in a different judicial forum.

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Special Note Regarding Forward-looking Statements

This prospectus contains forward-looking statements that are based on management’s beliefs and assumptions and on information currently available to management. Some of the statements in the section captioned “Prospectus summary,” “Risk factors,” “Management’s discussion and analysis of financial condition and results of operations,” “Business” and elsewhere in this prospectus contain forward-looking statements. In some cases, you can identify forward-looking statements by the following words: “may,” “will,” “could,” “would,” “should,” “expect,” “intend,” “plan,” “anticipate,” “believe,” “estimate,” “predict,” “project,” “potential,” “continue,” “ongoing” or the negative of these terms or other comparable terminology, although not all forward-looking statements contain these words.

These statements involve risks, uncertainties and other factors that may cause actual results, levels of activity, performance or achievements to be materially different from the information expressed or implied by these forward-looking statements. Although we believe that we have a reasonable basis for each forward-looking statement contained in this prospectus, we caution you that these statements are based on a combination of facts and factors currently known by us and our projections of the future, about which we cannot be certain.

Forward-looking statements in this prospectus include, but are not limited to, statements about:

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the success, cost and timing of our product development activities and clinical trials, including statements regarding the timing of our ongoing Phase 3 clinical trial of nirogacestat, the initiation of our planned Phase 2b clinical trial of mirdametinib and the initiation and completion of any other clinical trials and related preparatory work, the expected timing of the availability of results of the clinical trials and the potentially registrational nature of the single Phase 3 clinical trial and the Phase 2b clinical trial;

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the potential attributes and benefits of our product candidates;

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our plans to commercialize any of our product candidates that achieve approval either alone or in partnership with others;

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our ability to obtain funding for our operations, including funding necessary to complete further development of our product candidates, and if approved, commercialization;

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the period over which we anticipate the proceeds of this offering, together with our existing cash and cash equivalents, will be sufficient to fund our operating expenses and capital expenditure requirements;

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the potential for our business development efforts to maximize the potential value of our portfolio;

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our ability to identify, in-license or acquire additional product candidates;

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the ability and willingness of our third-party collaborators to continue research and development activities relating to our product candidates that we are developing as combination therapies;

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our ability to obtain and maintain regulatory approval for our product candidates, and any related restrictions, limitations or warnings in the label of an approved product candidate;

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the potential benefit of Orphan Drug and Fast Track Designations for nirogacestat, mirdametinib and any other of our product candidates that may receive such designation;

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our ability to compete with companies currently marketing or engaged in the development of treatments for desmoid tumors or NF1-PN;

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our expectations regarding our ability to obtain and maintain intellectual property protection or market exclusivity for our product candidates and the direction of such protection;

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our ability and the potential to successfully manufacture our product candidates for preclinical studies, clinical trials and, if approved, for commercial use, the capacity of our current contract manufacturing organizations, or CMOs, to support clinical supply and commercial-scale production for product candidates and our potential election to pursue additional CMOs for manufacturing supplies of drug substance and finished drug product in the future;

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the size and growth potential of the markets for our product candidates, and our ability to serve those markets, either alone or in partnership with others;

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the rate and degree of market acceptance of our product candidates, if approved;

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regulatory developments in the United States and foreign countries;

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our ability to contract with third-party suppliers and manufacturers and their ability to perform adequately;

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the success of competing products that are or may become available;

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our ability to attract and retain key scientific, medical, commercial or management personnel;

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our estimates regarding expenses, future revenue, capital requirements and needs for additional financing; and

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our use of the proceeds from this offering.

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In addition, you should refer to the “Risk factors” section of this prospectus for a discussion of other important factors that may cause actual results to differ materially from those expressed or implied by the forward-looking statements. As a result of these factors, we cannot assure you that the forward-looking statements in this prospectus will prove to be accurate. Furthermore, if the forward-looking statements prove to be inaccurate, the inaccuracy may be material. In light of the significant uncertainties in these forward-looking statements, you should not regard these statements as a representation or warranty by us or any other person that we will achieve our objectives and plans in any specified time frame, or at all. The forward-looking statements in this prospectus represent our views as of the date of this prospectus. We anticipate that subsequent events and developments will cause our views to change. However, while we may elect to update these forward-looking statements at some point in the future, we have no current intention of doing so except to the extent required by applicable law. You should, therefore, not rely on these forward-looking statements as representing our views as of any date subsequent to the date of this prospectus.

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Market and Industry Data and Forecasts

We obtained the industry and market data used throughout this prospectus from our own internal estimates and research, as well as from independent market research, industry and general publications and surveys, governmental agencies and publicly available information in addition to research, surveys and studies conducted by third parties. Internal estimates are derived from publicly available information released by industry analysts and third-party sources, our internal research and our industry experience, and are based on assumptions made by us based on such data and our knowledge of our industry and market, which we believe to be reasonable. In some cases, we do not expressly refer to the sources from which this data is derived. In addition, while we believe the industry and market data included in this prospectus is reliable and based on reasonable assumptions, such data involve risks and uncertainties and are subject to change based on various factors, including those discussed in the section entitled “Risk factors.” These and other factors could cause results to differ materially from those expressed in the estimates made by the independent parties or by us.

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Use of Proceeds

We estimate that the net proceeds to us from the sale of the shares of our common stock in this offering will be approximately $     million, or approximately $     million if the underwriters exercise their option to purchase additional shares in full, based upon an assumed initial public offering price of  $     per share, the midpoint of the price range set forth on the cover page of this prospectus, after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us.

A $1.00 increase or decrease in the assumed initial public offering price of  $     per share, the midpoint of the price range set forth on the cover page of this prospectus, would increase or decrease the net proceeds to us from this offering by $     million, assuming the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same. Similarly, an increase or decrease of 1,000,000 in the number of shares offered by us would increase or decrease the net proceeds to us from this offering by $     million, assuming that the assumed initial public offering price remains the same. We do not expect that a change in the initial public offering price or the number of shares by these amounts would have a material effect on our uses of the proceeds from this offering, although it may accelerate the time at which we will need to seek additional capital.

We currently expect to use the net proceeds from this offering, together with our existing cash and cash equivalents, as follows:

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$     to fund                                     ;

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$     to fund                                     ;

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$     to further develop any additional product candidates that we elect to develop either alone or in combination with a partner;

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$     to expand our internal product development and clinical capabilities; and

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the remainder, if any, for working capital and other general corporate purposes.

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We may also use a portion of the net proceeds to in-license, acquire or invest in new businesses, technology or assets. Although we have no current agreements, commitments or understandings with respect to any such in-license or acquisition, we evaluate such opportunities and engage in related discussions with third parties from time to time.

Based on our current plans, we believe our existing cash and cash equivalents, together with the net proceeds from this offering, will be sufficient to fund our operating expenses and capital expenditure requirements through     . We have based this estimate on assumptions that may prove to be wrong, and we could use our available capital resources sooner than we expect.

The expected use of net proceeds from this offering represents our intentions based upon our present plans and business conditions. We cannot specify with certainty all of the particular uses for the net proceeds to be received upon the closing of this offering. Due to uncertainties inherent in the product development process, it is difficult to estimate the exact amounts of the net proceeds that will be used for any particular purpose. We may use our existing cash and cash equivalents and the future payments, if any, generated from any future collaboration agreements to fund our operations, either of which may alter the amount of net proceeds used for a particular purpose. In addition, the amount, allocation and timing of our actual expenditures will depend upon numerous factors, including the results of our research and development efforts, the timing and success of clinical trials and the timing of regulatory submissions. Accordingly, we will have broad discretion in using these proceeds.

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Pending the uses described above, we plan to invest the net proceeds of this offering in short- and immediate-term, interest-bearing obligations, investment-grade instruments, certificates of deposit or direct or guaranteed obligations of the U.S. government.

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Dividend Policy

We have never declared or paid any cash dividends on our capital stock. We do not anticipate paying any dividends on our capital stock in the foreseeable future. We currently intend to retain all available funds and any future earnings to fund the development and growth of our business. Investors should not purchase our common stock with the expectation of receiving cash dividends.

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Capitalization

The following table sets forth our cash and cash equivalents and our capitalization as of December 31, 2018:

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on an actual basis;

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on a pro forma basis to give effect to (i) the automatic conversion of all units outstanding as of December 31, 2018 into an aggregate of       shares of our common stock, as if such conversion had occurred on December 31, 2018, and (ii) the filing and effectiveness of our amended and restated certificate of incorporation immediately prior to the completion of this offering; and

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on a pro forma as adjusted basis to give further effect to the issuance and sale of       shares of our common stock in this offering at an assumed initial public offering price of  $     per share, the midpoint of the price range set forth on the cover page of this prospectus, after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us.

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You should read this information together with our consolidated financial statements and related notes appearing elsewhere in this prospectus and the information set forth in the sections entitled “Selected consolidated financial data” and “Management’s discussion and analysis of financial condition and results of operations.”

(1) The pro forma as adjusted information is illustrative only, and will depend on the actual initial public offering price and other terms of this offering determined at pricing. Each $1.00 increase or decrease in the assumed initial public offering price of  $     per share, the midpoint of the price range set forth on the cover page of this prospectus, would

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increase or decrease, as applicable, each of pro forma as adjusted cash and cash equivalents, additional paid-in capital, total members’ equity and total capitalization by $     million, assuming that the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same. We may also increase or decrease the number of shares we are offering. Each increase or decrease of 1,000,000 shares in the number of shares we are offering would increase or decrease, as applicable, each of pro forma as adjusted cash and cash equivalents, additional paid-in capital, total members’ equity and total capitalization by $     million, assuming the assumed initial public offering price per share remains the same.

The table above does not include:

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    shares of common stock issuable upon the exercise of stock options outstanding as of           , 2019 under our existing stock option and incentive plan, with a weighted average exercise price of  $    per share;

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    shares of common stock reserved for future issuance as of            , 2019 under our existing stock option and incentive plan, which will cease to be available for issuance at the time that our 2019 Equity Plan becomes effective;

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     shares of our common stock that will become available for future issuance under our 2019 Equity Plan, which will become effective upon the effectiveness of the registration statement of which this prospectus forms a part; and

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     shares of our common stock that will become available for future issuance under our ESPP which will become effective upon the effectiveness of the registration statement of which this prospectus forms a part.

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Dilution

If you invest in our common stock in this offering, your ownership interest will be diluted to the extent of the difference between the initial public offering price per share of our common stock and the pro forma as adjusted net tangible book value per share of our common stock immediately after this offering.

Our historical net tangible book value (deficit) was $(    ) million, or $(    ) per share, as of                , 2019. Our historical net tangible book (deficit) value is equal to our total tangible assets less our total liabilities and convertible preferred stock, and our historical net tangible book (deficit) per share is that number divided by the number of shares of common stock outstanding as of such date.

Our pro forma net tangible book value as of                 , 2019 was $     million, or $     per share. Our pro forma net tangible book value per share represents the amount of our total tangible assets reduced by the amount of our total liabilities and divided by the total number of shares of our common stock outstanding as of                 , 2019, assuming the automatic conversion of all outstanding shares of convertible preferred stock as of                 , 2019 into an aggregate of       shares of common stock, which conversion will occur immediately prior to the completion of this offering.

After giving effect to our sale of shares of common stock in this offering at an assumed initial public offering price of  $     per share, the midpoint of the price range set forth on the cover page of this prospectus, and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us, our pro forma as adjusted net tangible book value as of                 , 2019 would have been $     million, or $     per share. This represents an immediate increase in net tangible book value of  $     per share to existing stockholders and an immediate dilution in net tangible book value of  $     per share to purchasers of common stock in this offering. Dilution per share to new investors represents the difference between the amount per share paid by purchasers of shares of common stock in this offering and the pro forma as adjusted net tangible book value per share of common stock immediately after completion of this offering. The following table illustrates this dilution on a per share basis:

The pro forma as adjusted dilution information discussed above is illustrative only and will depend on the actual initial public offering price. Each $1.00 increase or decrease in the assumed public offering price of  $     per share, the midpoint of the price range set forth on the cover page of this prospectus, would increase or decrease, as applicable, our pro forma as adjusted net tangible book value by $     million, or $     per share, and dilution per share to investors in this offering by $     per share, assuming that the number of shares offered by us, as set forth

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on the cover of this prospectus, remains the same and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us. We may also increase or decrease the number of shares we are offering. Each increase or decrease of 1,000,000 in the number of shares we are offering would increase or decrease, as applicable, our pro forma as adjusted net tangible book value by $     million, or $     per share, and would increase or decrease, as applicable, dilution per share to investors in this offering by $     per share, assuming the assumed initial public offering price per share remains the same and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us.

If the underwriters’ option to purchase additional shares from us is exercised in full, the pro forma as adjusted net tangible book value per share after this offering would be $     per share, the increase in pro forma as adjusted net tangible book value per share to existing stockholders would be $     per share and the dilution to new investors purchasing shares in this offering would be $     per share, based on the assumed initial public offering price of  $     per share and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us.

The following table shows, as of                 , 2019, on the pro forma as adjusted basis described above (but before deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us), the differences between the existing stockholders and the purchasers of shares in this offering with respect to the number of shares purchased from us, the total consideration paid, which includes, in the case of existing stockholders, gross proceeds received from the issuance of common and redeemable convertible preferred stock, cash received from the exercise of stock options, and the value of any stock issued for services, and the average price paid per share (dollars in thousands, except per share amounts):

The tables and discussion above are based on the number of shares of our common stock outstanding as of            , 2019, and exclude:

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     shares of common stock issuable upon the exercise of stock options outstanding as of           , 2019 under our existing stock option and incentive plan with a weighted average exercise price of  $     per share;

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     shares of common stock reserved for future issuance as of            , 2019 under our existing stock option and incentive plan, which will cease to be available for issuance at the time that our 2019 Plan becomes effective;

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     shares of our common stock that will become available for future issuance under our 2019 Equity Plan, which will become effective upon the effectiveness of the registration statement of which this prospectus forms a part; and

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     shares of our common stock that will become available for future issuance under our ESPP, which will become effective upon the effectiveness of the registration statement of which this prospectus forms a part.

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To the extent that outstanding stock options are exercised, new stock options or warrants are issued, or we issue additional shares of common stock in the future, there will be further dilution

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to new investors. In addition, we may choose to raise additional capital because of market conditions or strategic considerations, even if we believe that we have sufficient funds for our current or future operating plans. If we raise additional capital through the sale of equity or convertible debt securities, the issuance of these securities could result in further dilution to our stockholders.

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Selected Consolidated Financial Data

You should read the following selected consolidated financial data together with our consolidated financial statements and the related notes appearing at the end of this prospectus and the “Management’s discussion and analysis of financial condition and results of operations” section of this prospectus. We have derived the selected statement of operations data for the period from August 18, 2017 (inception) to December 31, 2017 and the year ended December 31, 2018 and the summary balance sheet data as of December 31, 2017 and 2018 from our audited consolidated financial statements included elsewhere in this prospectus. Our historical results are not necessarily indicative of the results that may be expected in the future.

(1) As of December 31, 2017, there were no vested common units outstanding. Therefore, net loss per common unit, basic and diluted, is not presented for the period from August 18, 2017 (inception) through December 31, 2017.

(2) See Note 12 to the notes to our consolidated financial statements included in this prospectus for an explanation of the method used to calculate the pro forma net loss per share and pro forma weighted average number of common shares outstanding.

(1) We define working capital as current assets less current liabilities. See our consolidated financial statements and related notes appearing elsewhere in this prospectus for details regarding our current assets and current liabilities.

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Management’s Discussion and Analysis of Financial Conditions and Results of Operations

You should read the following discussion and analysis of our financial condition and results of operations together with the section titled “Selected consolidated financial data” and the consolidated financial statements and related notes included elsewhere in this prospectus. This discussion contains forward-looking statements based upon current expectations that involve risks and uncertainties. Our actual results may differ materially from those anticipated in these forward-looking statements as a result of various factors, including those identified below and those discussed in the section titled “Risk factors” and in other parts of this prospectus.

Overview

We are a clinical-stage biopharmaceutical company applying a precision medicine approach to acquiring, developing and commercializing life-changing medicines for underserved patient populations suffering from devastating rare diseases and cancer. We have a differentiated portfolio of small molecule targeted oncology product candidates and are advancing two potentially registrational clinical trials in rare tumor types, as well as several other programs addressing highly prevalent, genetically defined cancers. Our strategic approach and operational excellence in clinical development have enabled us to rapidly advance our two lead product candidates into late-stage clinical trials while simultaneously entering into multiple shared-value partnerships with industry leaders to expand our portfolio. From this foundation, we are continuing to build a differentiated, global biopharmaceutical company intensely focused on understanding patients and their diseases in order to develop transformative targeted medicines.

Our most advanced product candidate, nirogacestat, is an oral, small molecule gamma secretase inhibitor, or GSI, initially in development for the treatment of desmoid tumors, a rare and often debilitating and disfiguring soft tissue tumor for which there are currently no therapies approved by the U.S. Food and Drug Administration, or FDA. We believe nirogacestat may address the significant limitations associated with existing treatment options and has the potential to become the first therapy approved by the FDA for both newly diagnosed and previously treated desmoid tumors. Since we licensed nirogacestat from Pfizer Inc., or Pfizer, in August 2017, the FDA has granted us both Orphan Drug Designation and Fast Track Designation for this indication. In May 2019, we announced the initiation of the DeFi trial, a potentially registrational Phase 3 clinical trial of nirogacestat for patients with desmoid tumors. We expect to provide an update on the DeFi trial in 2020.

Our second product candidate is mirdametinib, an oral, small molecule MEK inhibitor initially in development for the treatment of NF1-PN, a rare tumor of the peripheral nerve sheath that causes significant pain and disfigurement, and that most often manifests in children. We believe that mirdametinib has the potential to offer a best-in-class profile in order to enable the long-term treatment required for this patient population, as compared to other MEK inhibitors. As with nirogacestat, we licensed mirdametinib from Pfizer in August 2017; since then, the FDA has granted us both Orphan Drug Designation and Fast Track Designation for NF1-PN. We expect to commence a potentially registrational Phase 2b clinical trial of mirdametinib for patients with NF1-PN in the third quarter of 2019.

In addition to our late-stage programs in rare oncology indications, we have expanded our portfolio to develop targeted therapies for the treatment of highly prevalent, genetically defined cancers. To advance this strategy, we are taking a precision medicine approach in collaboration with industry leaders, including BeiGene, Ltd., or BeiGene, and GlaxoSmithKline plc, or GSK, to develop combination approaches with nirogacestat and mirdametinib, as well as new standalone

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medicines. The first of these efforts is our ongoing collaboration with BeiGene, under which patients with advanced or refractory solid tumors harboring RAS mutations, RAF mutations or other MAPK pathway aberrations are being enrolled in a Phase 1b clinical trial evaluating the combination of mirdametinib and BeiGene’s RAF dimer inhibitor lifirafenib. The second of these efforts is our collaboration with GSK, under which patients with relapsed or refractory multiple myeloma will be enrolled in an adaptive Phase 1b clinical trial evaluating the combination of nirogacestat and belantamab mafodotin, GSK’s investigational antibody-drug conjugate, or ADC, targeted to B-cell maturation antigen, or BCMA.

Furthermore, we intend to continue to expand our portfolio by licensing additional programs with strong biological rationales and validated mechanisms of action. We also plan to continue using shared-value partnerships to maximize the potential of our therapies to serve patients. We believe that our clinical development capabilities and innovative partnership approach will continue to allow us to expand our shared-value relationships with innovators and maximize the potential of our existing and future portfolio.

We were originally formed as SpringWorks Therapeutics, LLC, a Delaware limited liability company in August 2017. Concurrent with our formation, we acquired exclusive worldwide licenses to nirogacestat and mirdametinib from Pfizer. In September 2018, we announced that we entered into a global clinical collaboration with BeiGene to evaluate the combination of mirdametinib with BeiGene’s RAF dimer inhibitor, lifirafenib. From our inception to March 29, 2019, we conducted our business through SpringWorks Therapeutics, LLC and were treated as a partnership for income tax purposes. Pursuant to the terms of a corporate reorganization that was completed on March 29, 2019, all of the equity interests in SpringWorks Therapeutics, LLC were exchanged for the same number and class of newly issued securities of SpringWorks Therapeutics, Inc., or the Reorganization, and, as a result, SpringWorks Therapeutics, LLC became a wholly owned subsidiary of SpringWorks Therapeutics, Inc. Following the Reorganization, we now conduct our business as SpringWorks Therapeutics, Inc. See the section entitled “Reorganization” for more information.

In June 2019, we announced the formation of MapKure, LLC, or MapKure, which is jointly owned by us and BeiGene. BeiGene licensed exclusive rights to MapKure to BGB-3245, and we will contribute to MapKure’s clinical development and other operational activities for BGB-3245.

Since our inception, our operations have been limited to organizing and staffing our company, business planning, raising capital and performing research and development of our product candidates, including nirogacestat for the treatment of desmoid tumors and mirdametinib for the treatment of NF1-PN.

We do not have any products approved for commercial sale and have not generated any revenues. As of December 31, 2018, we had cash and cash equivalents of  $45.6 million. Since inception and through December 31, 2018, we have funded our operations primarily by net proceeds of  $62.9 million from the sale of our Series A convertible preferred units prior to the Reorganization. In March 2019, we completed the final closing of  $39.4 million in gross proceeds from the sale of Series A convertible preferred units prior to our Reorganization, and raised $125 million in gross proceeds from the sale of our Series B convertible preferred stock. We believe that the net proceeds from this offering, together with our existing cash and cash equivalents, will enable us to fund our operating expenses and capital expenditure requirements into            .

Since inception, we have incurred significant operating losses. Our net losses were $4.6 million and $17.8 million for the period from August 18, 2017 (inception) to December 31, 2017 and the year ended December 31, 2018, respectively. As of December 31, 2018, we had an accumulated deficit of  $22.5 million. We expect to continue to incur significant expenses and operating losses

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for the foreseeable future. In addition, we anticipate that our expenses will increase significantly in connection with our ongoing activities, as we:

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advance our product candidates through clinical development, including our ongoing potentially registrational Phase 3 clinical trial for nirogacestat and planned potentially registrational Phase 2b clinical trial for mirdametinib;

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advance our other preclinical and clinical development programs, including our combination therapies, into and through clinical development;

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seek regulatory approvals for any product candidates that successfully complete clinical trials;

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increase the amount of research and development activities to identify, acquire and develop product candidates;

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hire additional clinical, quality control, medical, scientific and other technical personnel;

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expand our operational, financial and management systems and increase personnel, including personnel to support our clinical development, manufacturing, business development and commercialization efforts and our operations as a public company;

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maintain, expand and protect our intellectual property portfolio;

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complete commercial-scale outsourced manufacturing activities;

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establish sales, marketing and distribution capabilities for any product candidates for which we may receive regulatory approval in regions where we choose to commercialize our products on our own or jointly with third parties; and

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invest in or in-license other technologies or product candidates.

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We will not generate revenue from product sales unless and until we successfully complete clinical development and obtain regulatory approval for our product candidates. In addition, if we obtain regulatory approval for nirogacestat or mirdametinib, we expect to incur significant expenses related to developing our commercialization capabilities to support product sales, marketing and distribution activities, either alone or in collaboration with others.

As a result, we will need substantial additional funding to support our continuing operations and pursue our growth strategy. Until such time, if ever, as we can generate substantial product revenue, we expect to finance our operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements. To the extent that we raise additional capital through the sale of equity or convertible debt securities, your ownership interest will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect your rights as a common stockholder. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making acquisitions or capital expenditures or declaring dividends. If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or drug candidates, or grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt financings or other arrangements when needed, we may be required to delay, limit, reduce or terminate our research, product development or future commercialization efforts, or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

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Our license and collaboration agreements

Pfizer License Agreements

In August 2017, we entered into a license agreement, or the Nirogacestat License Agreement, with Pfizer pursuant to which we acquired exclusive worldwide rights to nirogacestat. Pursuant to the Nirogacestat License Agreement, we are required to pay Pfizer payments of up to an aggregate of  $232.5 million upon achievement of certain commercial milestone events. We will pay Pfizer tiered royalties on sales of nirogacestat ranging from mid-single digit to low second decile percentages, which may be subject to deductions for expiration of valid claims, amounts due under third-party licenses and generic competition.

In August 2017, we entered into a license agreement, or the mirdametinib License Agreement, with Pfizer pursuant to which we acquired exclusive worldwide rights to mirdametinib. Pursuant to the mirdametinib License Agreement, we are required to pay Pfizer up to an aggregate of $229.8 million upon achievement of certain commercial milestone events. We will pay Pfizer tiered royalties on sales of mirdametinib ranging from mid-single digit to low second decile percentages, which may be subject to deductions for expiration of valid claims, amounts due under third-party licenses and generic competition.

In connection with entering into the Pfizer license agreements, we issued an aggregate of 6,437,500 Junior Series A convertible preferred units to Pfizer, which units were converted into 6,437,500 shares of our Junior Series A convertible preferred stock pursuant to the Reorganization. As of December 31, 2018, we had not made any milestone or royalty payments under the Pfizer license agreements.

BeiGene Clinical Collaboration Agreement

In August 2018, we entered into a clinical collaboration agreement with BeiGene, or the BeiGene Collaboration Agreement, to evaluate the safety, tolerability and preliminary efficacy of combining lifirafenib and mirdametinib, in a Phase 1b clinical trial for patients with advanced or refractory solid tumors. Each party will be solely responsible for its costs associated with manufacturing and supply of its compound for the clinical trial. We and BeiGene will share equally the other costs associated with the clinical trial.

GlaxoSmithKline clinical collaboration agreement

In June 2019, we entered into a clinical trial collaboration and supply agreement with GSK, or the GSK Collaboration Agreement, to evaluate nirogacestat in combination with belantamab mafodotin, GSK's investigational BCMA ADC, in patients with relapsed or refractory multiple myeloma, in an adaptive Phase 1b clinical trial. We expect GSK to initiate the adaptive Phase 1b clinical trial evaluating the combination by the first quarter of 2020. GSK will be responsible for the conduct and expenses of the collaboration, which will be governed by a joint development committee with equal representation from each party.

See “Business—License and collaboration agreements” for more information on our license and collaboration agreements.

Components of our results of operations

Revenue

We have not generated any revenue since our inception and do not expect to generate any revenue from the sale of products in the near future, if at all. If our development efforts for our current product candidates or additional product candidates that we may develop in the future

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are successful and can be commercialized, we may generate revenue in the future from product sales. Additionally, we may enter into collaboration and license agreements from time to time that provide for certain payments due to us. Accordingly, we may generate revenue from payments from such collaboration or license agreements in the future.

Research and Development Expenses

Our research and development expenses consist of expenses incurred in connection with the development of our product candidates. These expenses include:

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employee-related expenses, which include salaries, benefits and stock-based compensation for our research and development personnel;

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fees paid to consultants for services directly related to our research and development programs;

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expenses incurred under agreements with third-party contract research organizations, investigative clinical trial sites and consultants that conduct research and development activities on our behalf;

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costs associated with preclinical studies and clinical trials;

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costs associated with the manufacture of drug substance and finished drug product for preclinical testing and clinical trials;

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costs associated with technology and intellectual property licenses; and

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an allocated portion of facilities and facility related costs, which include expenses for rent and other facility related costs and other supplies.

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Expenditures for clinical development, including upfront licensing fees and milestone payments associated with our product candidates, are charged to research and development expense as incurred. These expenses consist of expenses incurred in performing development activities, including salaries and benefits, materials and supplies, preclinical expenses, clinical trial and related clinical manufacturing expenses, depreciation of equipment, contract services and other outside expenses. Costs for certain development activities, such as manufacturing and clinical trials, are recognized based on an evaluation of the progress to completion of specific tasks using either time-based measures or data such as information provided to us by our vendors on their actual costs incurred.

We expect our research and development expenses to increase substantially for the foreseeable future as we continue to invest in activities related to developing our product candidates and our preclinical programs and as certain product candidates advance into later stages of development, including our ongoing potentially registrational Phase 3 clinical trial for nirogacestat and planned potentially registrational Phase 2b clinical trial for mirdametinib. The process of conducting the necessary clinical trials to obtain regulatory approval is costly and time-consuming, and the successful development of our product candidates is highly uncertain. As a result, we are unable to determine the duration and completion costs of our research and development projects or when and to what extent we will generate revenue from the commercialization and sale of any of our product candidates.

General and administrative expenses

General and administrative expenses consist primarily of salaries and related costs, including stock-based compensation, for personnel in executive, finance, corporate and business development and administrative functions. General and administrative expenses also include legal fees relating to patent and corporate matters; professional fees for accounting, auditing,

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tax and administrative consulting services; insurance costs; administrative travel expenses; and facility-related expenses, which include direct depreciation costs and allocated expenses for rent and maintenance of facilities and other operating costs.

We anticipate that our general and administrative expenses will increase in the future as we increase our headcount to support our continued development of our product candidates. We also anticipate that we will incur increased accounting, audit, legal, regulatory, compliance and director and officer insurance costs as well as investor and public relations expenses associated with being a public company.

Other Income (Expense)

Other income consists primarily of interest income. Interest income consists of interest earned on our cash equivalents, which consist of money market funds. We expect our interest income to increase due to our investment of cash received from the final closing of our last tranche of Series A convertible preferred units in March 2019 prior to the Reorganization and the sale of Series B convertible preferred stock in March 2019, as well as the net proceeds from this offering.

Income taxes

Since our inception, we have not recorded any income tax benefits for the net losses we have incurred in each year or for our research and development tax credits, as we believe, based upon the weight of available evidence, that it is more likely than not that all of our net operating loss carryforwards and tax credits will not be realized. As of December 31, 2018, we had U.S. federal, state and city net operating loss carryforwards of  $14.2 million, $0.6 million and $3.8 million, respectively, which may be available to offset future taxable income. Federal net operating loss carryforwards of  $4.3 million were recorded in 2017 and the state and city net operating loss carryforwards expire at various dates through 2038. Federal net operating loss carryforwards of $9.9 million recorded in 2018 will be available to offset 80% of taxable income for an indefinite period of time, until fully utilized. As of December 31, 2018, we also had federal tax credits of $0.4 million, which may be used to offset future tax liabilities. These tax credit carryforwards will expire in 2038. We have recorded a full valuation allowance against our net deferred tax assets at each balance sheet date.

Results of Operations

We commenced operations in August 2017. Accordingly, our consolidated financial statements and results of operations for the period from our inception through December 31, 2017 reflect only approximately three and a half months of operations. For that reason, there is limited comparability of our results of operations for the period from inception through December 31, 2017 with those for the full year 2018.

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Comparison of the period from August 18, 2017 (inception) to December 31, 2017 and the year ended December 31, 2018

The following table summarizes our results of operations for the period from August 18, 2017 (inception) to December 31, 2017 and the year ended December 31, 2018:

Research and development expenses

Research and development expenses were $2.8 million for the period from August 18, 2017 (inception) to December 31, 2017, compared to $9.9 million for the year ended December 31, 2018.

This increase was primarily related to additional direct costs of  $2.5 million; manufacturing and research costs of  $1.8 million to further progress the development activities for our product candidates, including preparations for clinical trials; personnel-related costs of  $2.5 million and professional and consulting fees of  $1.5 million, primarily due to increased headcount and consultant expenses. These increases were offset, in part, because of  $2.0 million of expenses we incurred in 2017 relating to the issuance of Junior Series A convertible preferred units in connection with the execution of the Pfizer license agreements.

We track outsourced development and manufacturing costs as well as personnel costs and other internal costs to specific development of product candidates. These external and internal research and development expenses are summarized by program in the table below:

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General and administrative expenses

General and administrative expenses for the period from August 18, 2017 (inception) to December 31, 2017 were $1.9 million, compared to $8.6 million for the year ended December 31, 2018. The increase in personnel-related costs of  $2.7 million was primarily due to the hiring of key executives in 2018, including the appointment of our Chief Executive Officer, Chief Business Officer, Chief Medical Officer and General Counsel, as well as additional personnel in our general and administrative functions as we continued to expand our operations to support the organization. The increase in equity-based compensation expense of  $0.9 million was primarily due to incentive units granted to certain executives in 2018. The increase in professional and consulting fees of  $2.3 million was primarily due to outsourcing various general and administrative activities to third parties.

Interest Income

Interest income for the year ended December 31, 2018 was $0.7 million due to interest earned on invested cash balances.

Liquidity and capital resources

Overview

Since inception through December 31, 2018, we funded our operations primarily by net proceeds of  $62.9 million from the sale of our Series A convertible preferred units prior to the Reorganization. At December 31, 2018, we had available cash and cash equivalents of $45.6 million.

In March 2019, we completed the final closing of  $39.4 million in gross proceeds from the sale of Series A convertible preferred units prior to our Reorganization, and raised $125 million in gross proceeds from the sale of our Series B convertible preferred stock.

We have incurred operating losses and experienced negative operating cash flows since our inception and anticipate that we will continue to incur losses for at least the foreseeable future. Our net loss was $17.8 million for the year ended December 31, 2018 and, as of December 31, 2018, we had an accumulated deficit of  $22.5 million.

Funding Requirements

Our primary use of cash is to fund operating expenses, primarily research and development expenditures. Cash used to fund operating expenses is impacted by the timing of when we pay these expenses, as reflected in the change in our outstanding accounts payable, accrued expenses and prepaid expenses.

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We believe that our net proceeds from this offering, together with our cash and cash equivalents as of December 31, 2018, and cash proceeds received in March 2019 from the sale of Series A convertible preferred units prior to our Reorganization and the sale of our Series B convertible preferred stock, will be sufficient to meet our projected operating requirements through         . We have based this estimate on assumptions that may prove to be wrong, and we could utilize our available capital resources sooner than we currently expect.

Our future funding requirements will depend on many factors, including the following:

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the initiation, progress, timing, costs and results of preclinical studies and clinical trials for our product candidates, including our ongoing potentially registrational Phase 3 clinical trial for nirogacestat and planned potentially registrational Phase 2b clinical trial for mirdametinib;

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the clinical development plans we establish for these product candidates;

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the number and characteristics of product candidates that we develop;

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the outcome, timing and cost of meeting regulatory requirements established by the FDA, EMA and other comparable foreign regulatory authorities;

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the terms of our existing and any future license or collaboration agreements we may choose to enter into, including the amount of upfront, milestone and royalty obligations;

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the other costs associated with in-licensing new technologies, such as any increased costs of research and development and personnel;

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the cost of filing, prosecuting, defending and enforcing our patent claims and other intellectual property rights;

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the cost of defending intellectual property disputes, including patent infringement actions brought by third parties against us or our product candidates;

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the effect of competing technological and market developments;

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the cost and timing of completion of commercial-scale outsourced manufacturing activities; and

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the cost of establishing sales, marketing and distribution capabilities for any product candidates for which we may receive regulatory approval in regions where we choose to commercialize our products on our own.

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We will need additional funds to meet operational needs and capital requirements for clinical trials, other research and development expenditures, and business development activities. Because of the numerous risks and uncertainties associated with the development and commercialization of our product candidates, we are unable to estimate the amounts of increased capital outlays and operating expenditures associated with our current and anticipated clinical studies.

Until such time, if ever, as we can generate substantial product revenue, we expect to finance our operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements. To the extent that we raise additional capital through the sale of equity or convertible debt securities, your ownership interest will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect your rights as a common stockholder. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making acquisitions or capital expenditures or declaring dividends. If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams,

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research programs or drug candidates, or grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt financings or other arrangements when needed, we may be required to delay, limit, reduce or terminate our research, product development or future commercialization efforts, or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

Cash flows

The following table summarizes our sources and uses of cash for each of the periods presented:

Cash Flows used in Operating Activities

Net cash used in operating activities was $14.7 million for the year ended December 31, 2018 and $2.2 million for the period from August 18, 2017 (inception) to December 31, 2017.

Cash used in operating activities in the year ended December 31, 2018, was primarily due to our net loss for the year of  $17.8 million, adjusted by non-cash charges of  $1.1 million and a net change of  $2.0 million in our net operating assets and liabilities. The non-cash charges primarily consisted of  $1.1 million for equity-based compensation expense. The change in our net operating assets and liabilities was primarily due to an increase of  $2.7 million in accounts payable and accrued expenses and a $1.5 million increase in deferred rent, partially offset by a $2.2 million increase of other non-current assets.

Cash used in operating activities in the period from August 18, 2017 (inception) to December 31, 2017 was primarily due to our net loss for the year of  $4.6 million, adjusted by non-cash charges of  $2.0 million and net change of  $383,000 in our net operating assets and liabilities. The non-cash charges primarily consisted of  $2.0 million for expenses relating to the issuance of Junior Series A convertible preferred units in connection with the execution of the Pfizer licenses. The change in our net operating assets and liabilities was primarily due to an increase of $653,000 in accounts payable and accrued expenses and a $270,000 increase in other non-current assets.

Cash Flows from Investing Activities

During the period from August 18, 2017 (inception) to December 31, 2017 and the year ended December 31, 2018, cash used from investing activities was $44,000 and $293,000, respectively, primarily related to purchases of property and equipment.

Cash Flows provided by Financing Activities

During the period from August 18, 2017 (inception) to December 31, 2017, cash provided by financing activities was $12.6 million from the issuance of Series A convertible preferred units prior to the Reorganization.

During the year ended December 31, 2018, cash provided by financing activities was $50.4 million from the issuance of Series A convertible preferred units prior to the Reorganization.

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Contractual obligations and other commitments

The following table summarizes our contractual obligations as of December 31, 2018 and the effects that such obligations are expected to have on our liquidity and cash flows in future periods:

(1) Amounts in the table reflect payments due for our facility in Durham, North Carolina and our headquarters in Stamford, Connecticut under two operating lease agreements that expire in August 2023 and November 2022, respectively.

We enter into contracts in the normal course of business with third-party contract research organizations for clinical trials, preclinical studies, manufacturing and other services and products for operating purposes. These contracts generally provide for termination following a certain period after notice and therefore we believe that our non-cancelable obligations under these agreements are not material and they are not included in the table above.

We have not included milestone or royalty payments or other contractual payment obligations in the table above if the timing and amount of such obligations are unknown or uncertain.

We have not recorded any reserves for uncertain tax positions as of December 31, 2017 or 2018.

Off-Balance sheet arrangements

We have not entered into any off-balance sheet arrangements and do not have holdings in any variable interest entities.

Quantitative and qualitative disclosures about market risk

The primary objectives of our investment activities are to ensure liquidity and to preserve capital. We are exposed to market risks in the ordinary course of our business. These risks primarily include interest rate sensitivities. We had cash and cash equivalents of  $10.3 million and $45.6 million as of December 31, 2017 and 2018, respectively, which consisted of bank deposits and highly liquid money market funds. Historical fluctuations in interest rates have not been significant for us. We had no outstanding debt as of December 31, 2017 and 2018. Due to the short-term maturities of our cash equivalents, an immediate one percentage point change in interest rates would not have a material effect on the fair market value of our cash equivalents. To minimize the risk in the future, we intend to maintain our portfolio of cash equivalents in institutional market funds that are composed of U.S. Treasury and U.S. Treasury-backed repurchase agreements or short-term U.S. Treasury securities. We do not believe that inflation, interest rate changes or exchange rate fluctuations had a significant impact on our results of operations for any periods presented herein.

Critical accounting policies and estimates

This management’s discussion and analysis of our financial condition and results of operations is based on our consolidated financial statements, which have been prepared in accordance with U.S. generally accepted accounting principles. The preparation of these consolidated financial statements requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the

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consolidated financial statements, as well as the reported expenses incurred during the reporting periods. Our estimates are based on our historical experience and on various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions.

While our significant accounting policies are described in more detail in Note 3 to our consolidated financial statements appearing elsewhere in this prospectus, we believe that the following accounting policies are those most critical to the judgments and estimates used in the preparation of our consolidated financial statements.

Accrued Research and Development Costs

We record accrued expenses for estimated costs of our research and development activities conducted by third-party service providers, which include the conduct of clinical trials and preclinical studies. We record the estimated costs of research and development activities based upon the estimated amount of services provided but not yet invoiced and include these costs in accrued liabilities in the consolidated balance sheets and within research and development expense in the consolidated statement of operations. These costs are a significant component of our research and development expenses. We record accrued expenses for these costs based on factors such as estimates of the work completed and in accordance with agreements established with these third-party service providers. Any payments made in advance of services provided are recorded as prepaid assets, which are then expensed as the contracted services are performed.

We estimate the amount of work completed based on discussions with internal personnel and external service providers as to the progress or stage of completion of the services and the agreed-upon fee to be paid for such services. We make significant judgments and estimates in determining the accrued balance in each reporting period. As actual costs become known, we adjust our accrued estimates. Although we do not expect our estimates to be materially different from amounts actually incurred, our understanding of the status and timing of services performed, the number of patients enrolled and the rate of patient enrollment may vary from our estimates and could result in us reporting amounts that are too high or too low in any particular period. Our accrued expenses are dependent, in part, upon the receipt of timely and accurate reporting from clinical research organizations and other third-party service providers. For the periods presented, we have experienced no material differences between our accrued expenses and actual expenses.

Equity-Based Compensation

Prior to the Reorganization, our predecessor, SpringWorks Therapeutics, LLC, granted incentive units, which we accounted for as equity-classified awards. As part of the Reorganization, the incentive units were exchanged for shares of our common stock, in the case of vested incentive units, and restricted common stock, in the case of unvested incentive units.

Our predecessor entity measured employee equity-based compensation based on the grant date fair value of the equity-based awards and recognized equity-based compensation expense on a straight-line basis over the requisite service period of the awards, which generally vest over a four-year period with the first 25% vesting following 12 months of employment or service and the remaining incentive units vesting in equal quarterly installments over the following 36 months. For awards subject to performance conditions, we recognize equity-based compensation expense using an accelerated recognition method over the remaining period when we determine that achievement of the milestone is probable. In 2018, our predecessor made an accounting

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policy election to recognize forfeitures as they occur upon adoption of guidance per Accounting Standard Update, or ASU, No. 2016-09, Compensation—Stock Compensation, or ASU 2016-09. The adoption of ASU 2016-09 did not have a material impact on our consolidated financial statements. The term “forfeitures” is distinct from “cancellations” or “expirations” and represents only the unvested portion of the surrendered equity-based award. Following the Reorganization, we expect to employ the same approach towards equity-based compensation.

We recognize compensation expense for equity-based awards granted to non-employees over the related service period of the award.

We classify equity-based compensation expense in our consolidated statement of operations in the same manner in which the award recipient’s salary and related costs are classified or in which the award recipient’s service payments are classified.

For any incentive units or options that our predecessor entity issued and for any future stock options that we may issue, we estimate the grant date fair value and the resulting stock-based compensation expense, using the Black-Scholes option-pricing model. The grant date fair value of the stock-based awards is recognized on a straight-line basis over the requisite service periods, which are generally the vesting period of the respective awards. Forfeitures are accounted for as they occur.

The Black-Scholes option-pricing model requires the use of subjective assumptions which determine the fair value of stock-based awards, including the expected term and the price volatility of the underlying stock. These assumptions include:

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Fair value of common units—See “Determination of the fair value of equity-based awards” below.

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Expected term—The expected term represents the period that the equity-based awards are expected to be outstanding. The expected term for our unit options and stock options was calculated based on the weighted average vesting term of the awards and the contract period, or simplified method, as allowed by the SEC.

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Expected volatility—Since we are not yet a public company and do not have any trading history for our common stock, the expected volatility was estimated based on the average historical volatilities of common stock of comparable publicly traded entities over a period equal to the expected term of the unit options and stock option grants. The comparable companies were chosen based on their size, stage in the life cycle or area of specialty. We will continue to apply this process until enough historical information regarding the volatility of our own stock price becomes available.

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Risk-free interest rate—The risk-free interest rate is based on the U.S. Treasury yield in effect at the time of grant for zero-coupon U.S. Treasury notes with maturities approximately equal to the expected term of the awards.

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Expected dividend—We have never paid dividends on our common stock and have no plans to pay dividends on our common stock. Therefore, we used an expected dividend yield of zero.

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Determination of the Fair Value of Equity-Based Awards

As there has been no public market to date for the common units or incentive units of our predecessor entity which operated as a limited liability company, the estimated fair value of our common units and incentive units has been approved by our board of directors, with input from management, as of the date of each award grant, considering our most recently available independent third-party valuations of common units and incentive units and our board of directors assessment, with input from management, of additional objective and subjective factors

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that we believed were relevant and which may have changed from the date of the most recent valuation through the date of the grant. In addition, following the Reorganization there remains no public market for our common stock to date. The estimated fair value of our common stock has been determined by our board of directors as of the date of each award grant considering our most recently available independent third-party valuations of common stock and our board of directors’ assessment of additional objective and subjective factors that it believed were relevant and which may have changed from the date of the most recent valuation through the date of the grant. These independent third-party valuations were performed in accordance with the guidance outlined in the American Institute of Certified Public Accountants’ Accounting and Valuation Guide, Valuation of Privately-Held-Company Equity Securities Issued as Compensation. We estimated the value of our equity using the market approach, including the guideline public company method and a precedent transaction method which “backsolves” to a preferred price. We allocated equity value to our common units, incentive units and convertible preferred units or to our shares of common stock and shares of our convertible preferred stock, as the case may be, using an option-pricing method, or OPM. The OPM treats common securities and preferred securities as call options on the total equity value of a company, with exercise prices based on the value thresholds at which the allocation among the various holders of a company’s securities changes. Under this method, the common and incentive units have value only if the funds available for distribution exceed the value of the convertible preferred units’ liquidation preferences at the time of a liquidity event, such as a strategic sale, merger or initial public offering, or IPO.

As of January 31, 2018, our third-party valuation report estimated a valuation of our common and incentive units of  $0.12 per unit. As of April 17, 2018, our third-party valuation report estimated a valuation of our common and incentive units of  $0.22 per unit. As of February 28, 2019, our third-party valuation report estimated a valuation of our common and incentive units of  $0.25 per unit. As of March 31, 2019, our third-party valuation report estimated a value of our common and incentive units of  $0.35 per unit.

In addition to considering the results of these third-party valuations, management considered various objective and subjective factors to determine the fair value of our common units, incentive units and common stock as of each grant date, which may be a date later than the most recent third-party valuation date, including:

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the prices of our preferred securities sold to or exchanged between outside investors in arm’s length transactions, and the rights, preferences and privileges of our preferred securities as compared to those of our common units, incentive units or common stock, including the liquidation preferences of our preferred securities;

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the progress of our research and development efforts, including the status of preclinical studies and planned clinical trials for our product candidates;

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our financial position, including cash on hand, and our historical and forecasted performance and operating results;

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our stage of development and business strategy and the material risks related to our business and industry;

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the achievement of enterprise milestones, including entering into collaboration and license agreements;

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the valuation of publicly traded companies in the life sciences and biotechnology sectors, as well as recently completed mergers and acquisitions of peer companies;

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any external market conditions affecting the biotechnology industry, and trends within the biotechnology industry;

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the likelihood of achieving a liquidity event for the holders of our common units, incentive units and common stock, such as an IPO, or a sale of our company, given prevailing market conditions; and

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the analysis of IPOs and the market performance of similar companies in the biopharmaceutical industry.

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The assumptions underlying these valuations represent management’s best estimates, which involve inherent uncertainties and the application of management judgment. As a result, if factors or expected outcomes change and we use significantly different assumptions or estimates, our equity-based compensation expense could be materially different. Following the completion of this offering, the fair value of our common stock will be determined based on the quoted market price of our common stock.

Stock-based compensation expense was $0 and $1.1 million for the period from August 18, 2017 (inception) to December 31, 2017 and the year ended December 31, 2018, respectively.

Recent accounting pronouncements

See Note 3 to our consolidated financial statements “Summary of Significant Accounting Policies—Recently Issued Accounting Pronouncements” for more information.

Emerging growth company status and JOBS Act accounting election

We qualify as an “emerging growth company,” or EGC, as defined in the Jumpstart Our Business Startups Act of 2012, as amended, or the JOBS Act. As an EGC, we may take advantage of specified reduced disclosure and other requirements that are otherwise applicable generally to public companies. These provisions include, but are not limited to:

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being permitted to present only two years of audited financial statements in this prospectus and only two years of related “Management’s discussion and analysis of financial condition and results of operations” in our periodic reports and registration statements, including this prospectus;

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not being required to comply with the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act of 2002, as amended;

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reduced disclosure obligations regarding executive compensation in our periodic reports, proxy statements and registration statements, including in this prospectus; and

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exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and stockholder approval of any golden parachute payments not previously approved.

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We may take advantage of these exemptions until we are no longer an EGC. We will cease to be an EGC on the date that is the earliest of  (i) the last day of the fiscal year in which we have total annual gross revenues of  $1.07 billion or more; (ii) the last day of 2024; (iii) the date on which we have issued more than $1.0 billion in nonconvertible debt during the previous three years; or (iv) the last day of the fiscal year in which we are deemed to be a large accelerated filer under the rules of the Securities and Exchange Commission, or SEC, which means the market value of our common stock that is held by non-affiliates exceeds $700 million as of the prior June 30th. We may choose to take advantage of some but not all of these exemptions. We have taken advantage of reduced reporting requirements in this prospectus. Accordingly, the information

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contained herein may be different from the information you receive from other public companies in which you hold stock. In addition, the JOBS Act provides that an EGC can take advantage of an extended transition period for complying with new or revised accounting standards. This provision allows an EGC to delay the adoption of some accounting standards until those standards would otherwise apply to private companies. We have elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date we (i) are no longer an EGC or (ii) affirmatively and irrevocably opt out of the extended transition period provided in the JOBS Act. As a result, our financial statements may not be comparable to companies that comply with new or revised accounting pronouncements as of public company effective dates.

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Business

Overview

We are a clinical-stage biopharmaceutical company applying a precision medicine approach to acquiring, developing and commercializing life-changing medicines for underserved patient populations suffering from devastating rare diseases and cancer. We have a differentiated portfolio of small molecule targeted oncology product candidates and are advancing two potentially registrational clinical trials in rare tumor types, as well as several other programs addressing highly prevalent, genetically defined cancers. Our strategic approach and operational excellence in clinical development have enabled us to rapidly advance our two lead product candidates into late-stage clinical trials while simultaneously entering into multiple shared-value partnerships with industry leaders to expand our portfolio. From this foundation, we are continuing to build a differentiated, global biopharmaceutical company intensely focused on understanding patients and their diseases in order to develop transformative targeted medicines.

Our most advanced product candidate, nirogacestat, is an oral, small molecule gamma secretase inhibitor, or GSI, initially in development for the treatment of desmoid tumors, a rare and often debilitating and disfiguring soft tissue tumor for which there are currently no therapies approved by the U.S. Food and Drug Administration, or FDA. We believe nirogacestat may address the significant limitations associated with existing treatment options and has the potential to become the first therapy approved by the FDA for both newly diagnosed and previously treated desmoid tumors. Since we licensed nirogacestat from Pfizer Inc., or Pfizer, in August 2017, the FDA has granted us both Orphan Drug Designation and Fast Track Designation for this indication. In May 2019, we announced the initiation of the DeFi trial, a potentially registrational Phase 3 clinical trial of nirogacestat for patients with desmoid tumors. We expect to provide an update on the DeFi trial in 2020.

Our second product candidate is mirdametinib, an oral, small molecule MEK inhibitor initially in development for the treatment of neurofibromatosis type 1-associated plexiform neurofibromas, or NF1-PN, a rare tumor of the peripheral nerve sheath that causes significant pain and disfigurement, and that most often manifests in children. We believe that mirdametinib has the potential to offer a best-in-class profile in order to enable the long-term treatment required for this patient population, as compared to other MEK inhibitors. As with nirogacestat, we licensed mirdametinib from Pfizer in August 2017; since then, the FDA has granted us both Orphan Drug Designation and Fast Track Designation for NF1-PN. In the third quarter of 2019, we expect to commence the ReNeu trial, a potentially registrational Phase 2b clinical trial of mirdametinib for patients with NF1-PN.

In addition to our late-stage programs in rare oncology indications, we have expanded our portfolio to develop targeted therapies for the treatment of highly prevalent, genetically defined cancers. To advance this strategy, we are taking a precision medicine approach in collaboration with industry leaders, including BeiGene and GSK, to develop combination approaches with nirogacestat and mirdametinib, as well as new standalone medicines. The first of these efforts is our ongoing collaboration with BeiGene, under which patients with advanced or refractory solid tumors harboring RAS mutations, RAF mutations and other MAPK pathway aberrations are being enrolled in a Phase 1b clinical trial evaluating the combination of mirdametinib and BeiGene’s investigational RAF dimer inhibitor lifirafenib. The second of these efforts is our collaboration with GSK, under which patients with relapsed or refractory multiple myeloma will be enrolled in an adaptive Phase 1b clinical trial evaluating the combination of nirogacestat and belantamab mafodotin, GSK’s investigational antibody-drug conjugate, or ADC, targeted to B-cell maturation antigen, or BCMA. We expect GSK to initiate the adaptive Phase 1b clinical trial evaluating the combination by the first quarter of 2020.

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Furthermore, we intend to continue to expand our portfolio by licensing additional programs with strong biological rationales and validated mechanisms of action. We also plan to continue using shared-value partnerships to maximize the potential of our therapies to serve patients. We believe that our clinical development capabilities and innovative partnership approach will continue to allow us to expand our shared-value relationships with innovators and maximize the potential of our existing and future portfolio.

The following table summarizes our current portfolio of product candidates:

(1)

Being developed by MapKure, LLC, or MapKure, a newly formed entity jointly owned by us and BeiGene.

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For purposes of this prospectus, when we refer herein to a “potentially registrational trial,” we are referring to a clinical trial to evaluate efficacy and safety of a product candidate to potentially support submission of a marketing application for such product candidate with the applicable regulatory authorities. Such a trial is also sometimes referred to as a Phase 2/3 or Phase 3 clinical trial or a pivotal trial

Nirogacestat is currently in the potentially registrational Phase 3 DeFi clinical trial for the treatment of desmoid tumors, which are rare and often debilitating and disfiguring soft tissue tumors. Desmoid tumors can aggressively invade surrounding healthy tissues and cause significant morbidities, including severe pain, internal bleeding, incapacitating loss of range of motion and, in rare cases, death. There are currently no therapies approved by the FDA for the treatment of desmoid tumors. Nirogacestat has been generally well tolerated in over 200 subjects and clinical activity was observed in the desmoid tumor patients enrolled in two previous clinical trials, many of whom had been heavily pre-treated. Since then, the FDA has granted nirogacestat both Orphan Drug Designation and Fast Track Designation for the treatment of desmoid tumors. We are currently conducting the DeFi trial, a double-blind, randomized, placebo-controlled clinical trial in adults with progressing desmoid tumors. We believe that we have designed the DeFi trial such that, if nirogacestat demonstrates clinical activity consistent with that observed in desmoid tumor patients treated to date with nirogacestat, the primary endpoint of this clinical trial should be met. If the results are favorable, we plan to file for marketing approval for nirogacestat in the United States and select international markets.

Nirogacestat + belantamab mafodotin is being explored with GSK in patients with relapsed or refractory multiple myeloma, or RRMM. Belantamab mafodotin is the most clinically advanced BCMA ADC and clinical activity has been observed with belantamab mafodotin as a monotherapy

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in RRMM patients. We believe that the clinical activity of BCMA directed therapies, including belantamab mafodotin, may be enhanced with the addition of a GSI like nirogacestat. We expect GSK to initiate the adaptive Phase 1b clinical trial evaluating the combination by the first quarter of 2020. Other than expenses related to the manufacturing of nirogacestat and certain expenses related to intellectual property rights, GSK will be responsible for the conduct and expenses of the trial, which will be governed by a joint development committee with equal representation from each party.

Mirdametinib is expected to begin the potentially registrational Phase 2b ReNeu clinical trial for the treatment of NF1-PN in the third quarter of 2019. NF1-PN is a rare tumor of the peripheral nerve sheath that causes significant pain and disfigurement, and that most often manifests in children. There are currently no therapies approved by the FDA for the treatment of NF1-PN. In a previous Phase 2 clinical trial conducted in NF1-PN patients, mirdametinib was observed to be clinically active and generally well tolerated. Since then, the FDA has granted mirdametinib Orphan Drug Designation for the treatment of NF1 and Fast Track Designation for the treatment of NF1-PN. The upcoming ReNeu trial will be an open-label, single-arm trial that will enroll both pediatric and adult NF1-PN patients. Given the clinical activity and tolerability observed with mirdametinib in the previous NF1-PN clinical trial and informed by our discussions with the FDA, we designed the ReNeu trial in a manner that we believe has the potential to generate sufficient data to support approval in both pediatric and adult NF1-PN patients. If the results are favorable, we plan to file for marketing approval for mirdametinib in the United States and select international markets.

Mirdametinib + lifirafenib is a combination therapy that we are evaluating with BeiGene in patients with advanced or refractory solid tumors that harbor various oncogenic driver mutations in the mitogen activated protein kinase, or MAPK, pathway, a signaling pathway whose constitutive activation has been reported in approximately 25% of human cancers owing to mutations in genes such as RAS and RAF. Lifirafenib is a RAF dimer inhibitor that was observed to be clinically active in advanced solid tumor patients with RAS and RAF mutations. We believe that lifirafenib’s clinical activity should be enhanced with the addition of a potent and selective MEK inhibitor like mirdametinib, and provide a potentially promising combination therapy for cancers whose growth is reliant on MAPK pathway signaling, such as those with mutations in RAS or RAF. In May 2019, we announced the initiation of an adaptive Phase 1b clinical trial that is currently enrolling patients in Australia with advanced or refractory solid tumors harboring relevant genetic mutations in the MAPK pathway.

BGB-3245 is an investigational, oral, selective small molecule inhibitor of specific BRAF driver mutations and genetic fusions. BGB-3245 is being advanced via MapKure, a newly formed entity jointly owned by us and BeiGene. BGB-3245 was exclusively licensed to MapKure by BeiGene and is intended to be initially developed as a monotherapy. Preclinical activity has been observed with BGB-3245 in a range of tumor models with BRAF mutations and BRAF fusions that are presently unaddressed with approved BRAF-directed therapies. MapKure expects to initiate an adaptive Phase 1 dose escalation and expansion clinical trial evaluating BGB-3245 in genetically defined solid tumors by the first quarter of 2020.

Our history and team

We were founded in August 2017 and concurrently acquired rights to certain assets from Pfizer, including exclusive worldwide licenses to nirogacestat and mirdametinib. We have raised $228 million from leading strategic and institutional investors. Our strategic investors include Pfizer

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and GlaxoSmithKline, and our institutional investors include OrbiMed Advisors LLC, Bain Capital, LifeArc, Perceptive Advisors, Boxer Capital of the Tavistock Group, HBM Healthcare Investments, BVF Partners, Surveyor Capital (a Citadel company), Samsara BioCapital, ArrowMark Partners and other institutional investors.

We are led by biopharmaceutical experts with extensive experience in building and operating organizations that develop and deliver innovative medicines to patients. Our team has broad experience in clinical development, regulatory affairs, manufacturing and commercialization of novel medicines, particularly in rare diseases. Our Chief Executive Officer, Saqib Islam, has more than 25 years of experience in biopharmaceuticals and finance, and has led our key business operations and strategic corporate planning activities since our inception. Members of our management team have held leadership positions at companies that have successfully discovered, acquired, developed and commercialized therapies for a range of devastating rare diseases and cancers. These companies include Alexion Pharmaceuticals, Inc., AstraZeneca plc, Bamboo Therapeutics, Inc., Bristol-Myers Squibb Company, GlaxoSmithKline plc, Merck & Co., Inc., Moderna, Inc., Pfizer and United Therapeutics Corporation.

Our strategy

Our goal is to continue building a differentiated, global biopharmaceutical company by acquiring, developing and commercializing transformative medicines for underserved patient populations. We aim to be an industry leader in rare diseases and targeted oncology and are advancing a diversified portfolio of programs with the intention of efficiently delivering safe and effective medicines to patients.

The key elements of our strategy include:

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Efficiently advance our lead product candidates towards marketing approval. We believe that our leading drug development capabilities will enable us to continue efficiently advancing our product candidates towards marketing approval, and we will make use of accelerated regulatory pathways when possible. Since our inception in August 2017, we have made rapid progress advancing two product candidates towards marketing approval. Our first product candidate, nirogacestat, was granted Orphan Drug Designation and Fast Track Designation by the FDA for the treatment of desmoid tumors and is currently being evaluated in the potentially registrational DeFi trial; we expect to provide an update on this trial in 2020. Our second product candidate, mirdametinib, was granted Orphan Drug Designation by the FDA for the treatment of NF1 and Fast Track Designation for the treatment of NF1-PN, and we expect to commence enrollment in the potentially registrational ReNeu trial for the treatment of NF1-PN in the third quarter of 2019.

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Maximize the potential of our portfolio through strategic partnerships. We have entered into strategic partnerships to develop innovative combination therapies that leverage emerging insights into the fundamental mechanisms that drive cancer. Our strategy is to align incentives among parties by sharing development costs and downstream economics for selected partnered programs. By pursuing this strategy, we believe that we can access promising therapies being developed across the biopharmaceutical industry for which there is scientific and clinical rationale for combinations with our existing product candidates. We have announced collaborations with BeiGene and GSK and we intend to execute additional strategic partnerships in the future.

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Commercialize our product candidates, if approved, to bring new medicines to underserved patient populations. We intend to market and commercialize our product candidates, if approved, in the United States and select international markets, either alone or in partnership with others. We expect to build our medical affairs organization and commercial infrastructure

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using a focused and efficient approach, initially establishing market access, sales and marketing capabilities in a targeted manner that is appropriate for the relevant product opportunity. We believe that this approach will allow us to effectively reach the patients and physicians that our product candidates have been developed for and to maximize the commercial potential of our portfolio.

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Deploy our value-driven approach to identify, acquire and develop new medicines. We follow a scientifically rigorous approach to evaluating new opportunities to broaden our portfolio. When evaluating assets, we consider a variety of factors, including unmet medical need, biological rationale, feasibility of clinical development, potential for regulatory approval, intellectual property position, costs required to achieve both near- and long-term milestones, competitive landscape and commercial potential. Utilizing this strategy, we have continued to expand our reach in targeted oncology by collaborating with BeiGene to form MapKure, a new research-stage company that was recently created to develop precision medicines to treat patients with life-threatening diseases, with an initial focus on cancer. We intend to continue to work closely with our existing partners and other asset originators to further expand our portfolio in our current focus areas of rare diseases and targeted oncology.

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Continue to cultivate a tightly integrated network of patient advocacy groups, key opinion leaders, research institutions and healthcare providers. We believe that in order to develop our portfolio in an efficient and impactful manner, it is imperative to cultivate a network of key stakeholders. Integrating the experiences and insights from these stakeholders, which include the Desmoid Tumor Research Foundation, the Children’s Tumor Foundation and leading academic physicians and researchers, continues to inform our approach to developing therapies that can transform the lives of patients and their families suffering from devastating rare diseases and cancer.

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Our product candidates

Nirogacestat

Overview

Nirogacestat (PF-03084014), our most advanced product candidate, is an oral, selective GSI that we are developing for the treatment of certain oncology indications. Gamma secretase is a protease complex that cleaves numerous transmembrane proteins, including amyloid precursor protein, or APP, Notch, HER4, E-cadherin, N-cadherin, BCMA and CD44. Cleavage of these transmembrane proteins by gamma secretase leads to a variety of signaling events that result from the untethering of the cytoplasmic domains of these proteins. Several of gamma secretase’s substrates have been implicated in a variety of diseases, including APP in Alzheimer’s disease and Notch in cancer, forming the rationale for evaluating gamma secretase as a therapeutic target. We believe there is significant potential for nirogacestat to address both newly diagnosed and previously treated desmoid tumors and has the potential to be used more broadly in cancer, either alone or in combination with other therapies.

Desmoid tumors are rare, non-metastatic soft tissue tumors that can occur in both children and adults. Depending on tumor size and location, desmoid tumors can cause severe morbidities such as pain, disfigurement, internal bleeding and incapacitating loss of range of motion. We exclusively licensed worldwide rights to nirogacestat from Pfizer in August 2017. In June 2018, the FDA granted nirogacestat Orphan Drug Designation for the treatment of desmoid tumors and in November 2018 the FDA granted nirogacestat Fast Track Designation for the treatment of adult patients with progressive, unresectable, recurrent or refractory desmoid tumors or deep fibromatosis.

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Nirogacestat has been evaluated in eight clinical trials and over 200 subjects have been exposed to treatment. Nirogacestat’s clinical activity was observed in the two previous clinical trials that enrolled desmoid tumor patients, in which nirogacestat was generally well tolerated. Pfizer conducted a Phase 1 clinical trial of nirogacestat as a treatment for various types of solid tumors. Five of the seven evaluable desmoid tumor patients enrolled in this clinical trial experienced a partial response, or PR, as measured by Response Evaluation Criteria in Solid Tumors v1.0, or RECIST v1.0, a commonly used set of measures for evaluating the response of solid tumors to treatment, yielding a 71% objective response rate, or ORR. In these seven desmoid tumor patients, median progression free survival, or PFS, had not been reached at the time of publication owing to the lack of patients progressing on therapy.

The National Cancer Institute, or NCI, then conducted a Phase 2 clinical trial evaluating nirogacestat as a treatment for desmoid tumors. Of the 17 patients enrolled in this clinical trial, 16 were evaluable for a response, five of whom had a confirmed PR and 11 of whom had stable disease, or SD, yielding a disease control rate of 100%. Furthermore, due to the lack of patients progressing on therapy, at the time of publication median PFS had not been reached.

Nirogacestat has been generally well tolerated in desmoid tumor patients as evidenced by the duration of time on therapy. In the Phase 1 clinical trial, the mean time on therapy was approximately four years. In the Phase 2 clinical trial, 59% of patients remained on therapy for at least two years, and as of May 2019, six patients were continuing to receive nirogacestat.

Based on these encouraging results, in May 2019, we announced the initiation of the DeFi trial, a potentially registrational Phase 3, double-blind, randomized, placebo-controlled clinical trial. We believe that we have designed the DeFi trial such that if nirogacestat demonstrates clinical activity consistent with that observed in desmoid tumor patients treated to date with nirogacestat, the primary endpoint of this clinical trial, which is PFS, should be met. If the results are favorable, we plan to apply for marketing approval for nirogacestat in the United States and select international markets.

In addition to our monotherapy program in desmoid tumors, in June 2019 we announced that we entered into a clinical collaboration with GSK to explore the combination of nirogacestat with their BCMA targeted ADC, belantamab mafodotin (GSK2857916), in patients with RRMM. Belantamab mafodotin is the most clinically advanced BCMA targeted ADC and clinical activity has been observed with belantamab mafodotin as a monotherapy in heavily pretreated RRMM patients. We believe that the clinical activity of BCMA directed therapies, including belantamab mafodotin, may be enhanced with the addition of a GSI, like nirogacestat. We expect GSK to initiate the adaptive Phase 1b clinical trial evaluating the combination by the first quarter of 2020. GSK will be responsible for the conduct and expenses of the trial, which will be governed by a joint development committee with equal representation from each party.

Nirogacestat for Treatment of Desmoid Tumors

Disease Background

Desmoid tumors, also referred to as aggressive fibromatosis or desmoid-type fibromatosis, are rare and often debilitating and disfiguring soft tissue tumors characterized by a growth pattern that can invade surrounding healthy tissues, including joints, muscle and viscera. The morbidity of a desmoid tumor is driven by the location of the tumor and the aggressiveness of its growth pattern. Mesentery desmoid tumors, arising in the abdominal cavity, can cause potentially life-threatening abdominal vasculature and bowel obstructions. Similarly, if a desmoid tumor occurs in the head and neck region, it can result in potentially life-threatening impingement on

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vital structures. When desmoid tumors occur near joints, even small lesions can result in debilitating loss of range of motion, impaired mobility and severe pain. While variable in size, in rare cases, desmoid tumors have been documented to grow in excess of 30 cm in diameter.

Patients with desmoid tumors can experience severe impacts on their quality of life. The French desmoid tumor patient advocacy group, SOS Desmoïde, published a national survey of its members in 2015 to assess pain burden in desmoid tumor patients; out of 102 respondents, 63% noted the presence of pain associated with their disease, 38% of whom characterized their pain as permanent. During the prospective development of patient-reported outcome tools for desmoid tumors, Memorial Sloan Kettering and Quintiles evaluated the impacts of desmoid tumors in 31 patients and found that 81% reported disfigurement, 68% reported range-of-motion impairment and 65% reported a negative impact on their activities of daily living as a result of their tumors.

Desmoid tumors typically occur in patients between the ages of 15 to 60 years and are more commonly diagnosed in the second and third decades of life, with a two-to-three times higher prevalence in females. The yearly incidence is estimated to be two to five cases per million, and accordingly we estimate that there are approximately        new desmoid tumor patients diagnosed each year in the United States and Europe. We believe that there is also a large prevalent pool of desmoid tumor patients due to poor treatment options and the relatively low mortality of the disease. Most cases of desmoid tumor occur spontaneously and are associated with one of several mutations in the CTNNB1 gene, which encodes for the β-catenin protein. There is also a subset of desmoid tumor patients whose tumors are attributable to germline mutations in the APC gene, which encodes for a protein involved in the degradation of β-catenin. These patients have a syndrome known as familial adenomatous polyposis, or FAP, and the incidence of desmoid tumors is 800 to 1,000 times higher in FAP patients as compared to the general population. When APC or CTNNB1 mutations are present, tissue trauma, including surgery, pregnancy or soft tissue injury, can lead to the formation of desmoid tumors.

The clinical course of desmoid tumors varies across the patient population. Within any given patient, desmoid tumors can alternate between periods of rapid growth and stabilization, and spontaneous regressions have been reported in up to 20% of patients. Desmoid tumors can vary significantly in terms of their morphology and radiographic appearance but are generally routine to diagnose. Desmoid tumors are usually first noted upon physical examination or by using various imaging techniques, such as ultrasound, computed tomography, or CT, or magnetic resonance imaging, or MRI. Histologically, desmoid tumors appear with variable collagen deposition and are not clearly circumscribed. Definitive diagnosis relies upon immunohistochemical stains for nuclear localization of β-catenin. Diagnosis can also be confirmed by screening for mutations in the CTNNB1 and APC genes.

Current Treatment Landscape for Desmoid Tumors

There are currently no therapies approved by the FDA for the treatment of desmoid tumors. Historically, desmoid tumors were treated with surgical resection, but this approach has become less favored due to an emerging body of evidence showing a post-surgical tumor recurrence rate of up to 70%, which can potentially increase disease burden and require additional intervention. In addition to the high recurrence rates, surgery itself carries risk of complications and can also be highly morbid, occasionally requiring limb amputation. Given the potential morbidities of surgery and the uncertain magnitude and durability of its benefit, physicians now typically adopt a watchful waiting approach for patients who historically may have been candidates for surgery.

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Despite its limitations, surgery is still used when a desmoid tumor presents significant risk of morbidity or mortality, such as tumors arising in the head and neck. Radiation therapy may also be used alone or in conjunction with surgery but is generally not preferred given the reported risk of developing secondary neoplasms.

In addition to these local treatments, systemic therapies have been used off-label with varying degrees of activity and tolerability. These therapies include chemotherapeutic agents, such as liposomal doxorubicin and vinblastine/methotrexate, non-steroidal anti-inflammatory drugs, anti-hormonal therapies and tyrosine kinase inhibitors, such as sorafenib, imatinib and pazopanib. Of these agents, only sorafenib has been studied in a randomized, double-blind, placebo-controlled clinical trial in patients with desmoid tumors; this Phase 3 clinical trial was investigator-initiated and did not have a biopharmaceutical industry sponsor. Although sorafenib demonstrated a statistically significant improvement in PFS compared to placebo, tolerability was a substantial issue; 20% of treated patients discontinued due to adverse events and an additional 22% of treated patients withdrew consent. At a median follow-up time of 27 months, 61% of the patients receiving sorafenib had discontinued treatment. Overall, we believe that the available off-label systemic therapies are poorly suited for the treatment of desmoid tumors and have not demonstrated an acceptable balance of safety and activity in this population. Therefore, we believe a significant unmet medical need exists for the treatment of desmoid tumors.

Our Solution—Nirogacestat for the Treatment of Desmoid Tumors

Nirogacestat is an oral, small molecule inhibitor of gamma secretase. We believe that nirogacestat can address the significant limitations associated with existing treatment options and has the potential to become the first therapy approved by the FDA for both newly diagnosed and previously treated desmoid tumors. In May 2019, we announced the initiation of our potentially registrational Phase 3 DeFi trial evaluating nirogacestat in patients with desmoid tumors.

Mechanism of Action

Nirogacestat is an oral, potent, selective, reversible, noncompetitive small molecule inhibitor of gamma secretase, an integral protease complex that cleaves numerous functionally important transmembrane proteins, including Notch. Gamma secretase’s cleavage of Notch causes the release of the Notch intracellular domain, or NICD, which shuttles into the nucleus and activates transcription of downstream target genes. Notch signaling is a regulator of cell proliferation and its dysregulation has been implicated in many forms of cancer. In desmoid tumor cell lines, nirogacestat has been observed to significantly decrease NICD release and reduce downstream activity of the Notch signaling pathway and decrease tumor cell migration, invasion and growth.

Clinical Experience with Nirogacestat

Over 200 subjects have been exposed to nirogacestat across eight clinical trials, not including our ongoing DeFi trial in desmoid tumor patients. Nirogacestat’s clinical activity was observed in the two previous clinical trials that enrolled desmoid tumor patients. Pfizer conducted a Phase 1 dose-escalation clinical trial in patients with solid tumors (A8641014), a subset of whom had a diagnosis of desmoid tumor. Given the activity of nirogacestat in the desmoid tumor patients treated in this Phase 1 clinical trial, the NCI conducted a Phase 2 clinical trial in desmoid tumor patients (WI180798), which evaluated nirogacestat at 150 mg twice daily, or BID, the same dose being used in our DeFi trial. Nirogacestat was initially intended to be developed as a potential treatment for Alzheimer’s disease, but early clinical trials evaluating its pharmacokinetics and biodistribution did not demonstrate adequate brain exposure to pursue this indication. Given Notch’s role in cancer, nirogacestat was subsequently investigated as a

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potential antitumor agent. We believe that the peripherally restricted exposure of nirogacestat, as well as the tolerability profile it has demonstrated across clinical trials to date, positions it as a potentially best-in-class GSI for oncology indications.

Nirogacestat was also investigated in three Phase 1 clinical trials conducted in healthy adult subjects to assess the pharmacokinetics and pharmacodynamics of single and multiple doses (A8641001, A8641002 and A8641008). Nirogacestat was further studied in clinical trials in patients with advanced cancers either as a monotherapy or in combination with other agents (A8641016, A8641019 and A8641020). Across all clinical trials, summarized in the table below, the dose range evaluated for nirogacestat was 1 mg once daily, or QD, to 330 mg BID.

Abbreviations: normal healthy volunteers (NHV), T-cell acute lymphoblastic leukemia (T-ALL), triple negative breast cancer (TNBC), lymphoblastic leukemia (LBL) and metastatic pancreatic ductal adenocarcinoma (mPDAC).

Phase 1 Dose-Escalation Clinical Trial (A8641014)

In June 2009, Pfizer commenced a Phase 1 dose-escalation clinical trial in patients with various solid tumors. This clinical trial was designed to determine the maximum tolerated dose, or MTD, ascertain the recommended Phase 2 dose and evaluate the safety and tolerability of nirogacestat. Sixty-four patients with solid tumors received doses of nirogacestat and the MTD was determined to be 220 mg BID. The recommended Phase 2 dose was determined to be 150 mg BID, given its comparable pharmacodynamic activity but more tolerable profile as compared to 220 mg BID.

Of the 64 solid tumor patients enrolled, 46 were evaluable for response, seven of whom had desmoid tumors. Of these desmoid tumor patients, five experienced a PR (defined as at least a 30% reduction in the target lesion as measured by RECIST v1.0), yielding a 71% ORR. In the evaluable desmoid tumor patients, median PFS had not been reached at the time of publication owing to the lack of patients progressing on therapy. Patients whose desmoid tumors arose from either germline mutations in APC or spontaneous mutations were enrolled in this clinical trial. Patients with both of these tumor mutational characteristics experienced an objective response. Of the 39 evaluable non-desmoid tumor patients in this clinical trial, whose diagnoses included colon, breast, thyroid, non-small cell lung and pancreatic cancer, only one patient experienced an objective response. The results of this clinical trial were reported in peer-reviewed medical journals in 2014 and 2017.

The following graph shows RECIST v1.0 responses for the seven evaluable desmoid tumor patients enrolled in this Phase 1 clinical trial:

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The following chart depicts the treatment course for each of the seven evaluable desmoid tumor patients in the Phase 1 clinical trial. Each bar shows the duration of clinical benefit for all therapies received since the time of diagnosis. Arrows on the right indicate patients who were still free of a new intervention, either on nirogacestat treatment (solid) or off nirogacestat treatment (striped), at the time of publication. As shown in the table below the chart, several of these patients were refractory to a number of previous interventions. The mean treatment duration for these patients was greater than four years, suggesting favorable, long-term tolerability of nirogacestat.

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The 64 patients enrolled in the Phase 1 clinical trial received nirogacestat doses ranging from 20 mg BID to 330 BID. The most common treatment-related adverse events (recorded in greater than 10% of patients) were diarrhea (55%), nausea (38%), fatigue (30%), hypophosphatemia (27%), vomiting (23%), rash (20%) and decreased appetite (17%). The majority of adverse events were Grade 1 through 3 and dose reductions due to treatment-related adverse events were infrequent. Treatment-related adverse events that led to temporary discontinuation or dose reduction included diarrhea, hypophosphatemia, rash, nausea, vomiting and fatigue, and most of these subsequently resolved. Seven patients (11%) permanently discontinued treatment due to adverse events. Of these, four patients (6%) discontinued due to a treatment-related adverse event (one for Grade 4 anaphylactic shock, one for Grade 1 visual impairment, one for a Grade 3 drug hypersensitivity reaction and one for Grade 3 rash). The Grade 4 anaphylactic shock adverse event was considered by the trial investigator to be related to intravenous treatment with morphine for pain control, as this adverse event started 25 minutes after morphine administration. However, treatment-related causality could not be excluded because the patient had received their first dose of nirogacestat before intravenous administration of morphine.

Long-term follow-up of the seven evaluable desmoid tumor patients in the Phase 1 clinical trial confirmed that all five patients who achieved a PR continued to maintain their responses between 48 and 73+ months. As of December 2016, four patients (patients 3, 4, 6 and 7) had stopped receiving nirogacestat but continued to be followed and remain free of progression between 11 and 53+ months after cessation of therapy. In all, the mean duration of clinical benefit observed was greater than 63 months. In addition, two patients continued to receive nirogacestat under a compassionate access protocol beyond the 2017 publication date, and as of November 2018, one of these patients remained on treatment, having received nirogacestat for over nine years. We believe the duration of clinical benefit and the tolerability profile observed in this Phase 1 clinical trial supported the rationale for the NCI’s subsequent clinical investigation of nirogacestat in desmoid tumor patients.

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Phase 2 Clinical Trial (WI180798)

The NCI commenced a Phase 2 clinical trial in desmoid tumor patients in November 2014. This clinical trial enrolled 17 desmoid tumor patients, who received nirogacestat every day in three-week cycles at the recommended Phase 2 dose of 150 mg BID. Patients were enrolled irrespective of their underlying mutation, which included germline and spontaneous APC mutations, as well as spontaneous CTNNB1 mutations (T41A and S45F). These patients were heavily pre-treated, having failed a median of four prior treatments (with a range of one to nine), which included various systemic therapies and local interventions, including surgery.

Sixteen patients were evaluable for a response using RECIST v1.1. Five patients had a confirmed PR and eleven patients had SD, yielding a disease control rate of 100% among the evaluable patients. Four of the five patients with a confirmed PR on nirogacestat had previously been treated with tyrosine kinase inhibitors, including sorafenib and imatinib, without a reported response. Median PFS had not been reached at the time of publication owing to the lack of patients progressing on therapy. Clinical benefit was observed independent of underlying mutation, number of previous treatments and type of previous treatments. As of May 2019, six of the patients enrolled in the Phase 2 clinical trial were still receiving nirogacestat.

Best responses in the Phase 2 clinical trial, as measured by RECIST v1.1, are shown in the following chart. Dotted lines represent cutoffs for PR (defined as a 30% reduction from baseline) and for progressive disease (defined as a 20% increase from baseline). SD is reflected between the dotted lines. Patient #01 was missing a baseline CT measurement and therefore MRI was used and, based on the publication, patient #14 was not evaluable for response per this trial protocol.

The following chart depicts treatment duration, clinical response and mutational status of desmoid tumor patients in the Phase 2 clinical trial. PR is denoted using black arrows, and the ten patients continuing on therapy at the time of publication are denoted using gray arrows.

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All patients in the Phase 2 clinical trial experienced at least one Grade 1 or Grade 2 adverse event. The most commonly reported adverse events regardless of grade and occurring in at least 30% of patients included diarrhea (76%), hypophosphatemia (76%), maculopapular rash (71%), aspartate aminotransferase increase (59%), nausea (53%), lymphocyte count decrease (53%), dry mouth (41%), alanine aminotransferase increase (35%) and anemia (35%). With the exception of hypophosphatemia, these adverse events were all reported as Grade 1 or Grade 2. The only Grade 3 adverse event occurring in at least 20% of patients was hypophosphatemia (47%), which is a known class effect of GSIs and was reversible with oral phosphate replacement therapy in the trial. Four patients required a dose reduction and one patient discontinued therapy due to Grade 2 urticaria that was not responsive to dose reduction. There were no Grade 4 adverse events reported.

DeFi Trial and Regulatory Pathway for Nirogacestat in Desmoid Tumors

Based upon the degree of clinical benefit for desmoid tumor patients observed in the Phase 1 and Phase 2 clinical trials, as well as our discussions with the FDA, in May 2019, we announced the initiation of our potentially registrational DeFi trial. The DeFi trial is being conducted under our open Investigational New Drug application, or IND, for nirogacestat.

The DeFi trial is a Phase 3, double-blind, randomized, placebo-controlled clinical trial being conducted at clinical sites in North America and Europe. The DeFi trial is designed to evaluate the efficacy, safety and tolerability of nirogacestat compared to placebo in patients with progressing desmoid tumors. This clinical trial will consist of two phases: a double-blind phase and an optional open-label extension, or OLE, phase. This clinical trial is enrolling desmoid tumor patients whose tumors have grown by at least 20% in the last 12 months as measured by RECIST v1.1 and will include both treatment-naïve and relapsed and refractory patients. Given the treatment effect observed in previous clinical trials, patients are eligible for enrollment irrespective of the number and type of previous treatments or the specific underlying mutations in APC or CTNNB1.

Patients are being randomized in a 1:1 ratio to receive 150 mg BID of nirogacestat or placebo every day for 28-day cycles. Eligible patients with confirmed disease progression on trial may enter the optional OLE phase to receive 150 mg BID of nirogacestat. We expect to enroll approximately 115 patients in this clinical trial. The primary PFS endpoint is defined as the time from randomization until the date of assessment of progression as determined using RECIST v1.1,

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or death by any cause. The documented date of radiographic progression will be determined by blinded independent central review. The FDA has stated that a PFS primary endpoint may support registration in an adequately designed trial with sufficient follow-up. In addition, the DeFi trial has been designed to enable a potential interim analysis.

The design of the DeFi trial is summarized in the schematic below:

Key secondary endpoints of the DeFi trial include safety and tolerability, ORR, duration of response and change in tumor volume. Patient-reported outcomes will also be key secondary endpoints in the DeFi trial and will be evaluated using several outcome instruments, including the Memorial Sloan Kettering/Desmoid Tumor Research Foundation Desmoid Tumor Impact and Desmoid Tumor Symptom scales, the Patient-Reported Outcomes Measurement Information System Physical Function scale, the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 and the Brief Pain Inventory. These instruments were selected to measure symptoms, impact of symptoms on daily living and outcomes that are most relevant to desmoid tumor patients.

In June 2018, the FDA granted nirogacestat Orphan Drug Designation for the treatment of desmoid tumors and in November 2018 the FDA granted nirogacestat Fast Track Designation for the treatment of adult patients with progressive, unresectable, recurrent or refractory desmoid tumors or deep fibromatosis. If the results from the DeFi trial are favorable, we plan to file for marketing approval for nirogacestat in the United States and select international markets.

Nirogacestat in combination with a BCMA-targeted ADC, belantamab mafodotin

BCMA is a cell surface protein universally expressed on MM cells, and the clinical activity of BCMA-targeted agents have been demonstrated in this indication. GSIs have been shown to increase BCMA expression on MM cells. Activity of this combination mechanism has been observed in multiple preclinical models of MM using BCMA-directed therapies in combination with GSIs, including with nirogacestat. We believe this combination, as compared to BCMA-directed therapies alone, may provide a meaningful clinical benefit to MM patients by improving response rates, prolonging the duration of clinical benefit or reducing the side effect profile by enabling administration at a lower dose.

In June 2019, we announced that we entered a clinical collaboration with GSK to explore the combination of nirogacestat with belantamab mafodotin, a BCMA targeted ADC, in patients with RRMM. Belantamab mafodotin is the most clinically advanced BCMA targeted ADC and clinical activity has been observed with belantamab mafodotin as a monotherapy in heavily pretreated RRMM patients. Other than expenses related to the manufacturing of nirogacestat and certain expenses related to intellectual property rights, GSK will be responsible for the conduct and expenses of the trial, which will be governed by a joint development committee with equal representation from each party. We expect GSK to initiate the adaptive Phase 1b clinical trial evaluating the combination by the first quarter of 2020 in combination with a BCMA-targeted antibody-drug conjugate, belantamab mafodotin.

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Disease Background – Multiple Myeloma

Multiple Myeloma, or MM, is a plasma cell neoplasm with substantial morbidity and mortality and is the second most common hematologic malignancy in the United States, accounting for approximately 10% of all hematologic cancers. The NCI surveillance, epidemiology and end results program estimated that in 2016 there were approximately 130,000 patients in the United States living with MM. Of these, approximately        have relapsed or are refractory to currently available therapies, representing a patient population with few therapeutic options, and a significant unmet medical need. It is estimated that approximately 13,000 individuals in the United States will die from MM in 2019.

MM is characterized by the expansion and abnormal accumulation of malignant plasma cells in the bone marrow, which disrupts normal bone marrow function and over time can lead to anemia, hypercalcemia, thrombocytopenia, bone pain, fatigue and weight loss. As the disease progresses, it destroys the surrounding bone marrow and can lead to renal failure, increased susceptibility to infection, skeletal deterioration and neurologic disease.

Current Treatment Landscape for MM

Treatment of MM has advanced significantly in the past decade driven by a deeper understanding of disease processes and a sequenced or polypharmacy approach. Newly diagnosed patients with MM are treated with either with stem cell transplants or with multiple classes of therapeutic agents, either alone or in combination, to attempt to control their disease progression. These agents include proteasome inhibitors such as bortezomib, immunomodulatory drugs such as lenalidomide, monoclonal antibodies such as daratumumab, histone deacetylase inhibitors such as panobinostat, alkylating agents such as melphalan, anti-inflammatories such as dexamethasone and chemotherapeutic agents such as doxorubicin. Despite these current options, the durability of clinical response and benefit is often brief. As there are no therapies that currently are considered curative, nearly all patients who survive initial treatments are eventually deemed resistant or refractory to available therapies and their disease continues to progress. By the time these heavily pretreated patients reach this advanced state, they are often directed to clinical trials for treatment with experimental agents. Due to the advanced condition of these patients, the refractory nature of their disease and the toll prior treatments have taken on their health, responses to treatment are generally poor.

BCMA-directed agents have emerged as a potentially promising approach for the treatment of RRMM patients due to the restriction of BCMA’s expression solely on the surface of plasmablasts and differentiated plasma cells. Though none are yet approved, we are aware of at least 20 distinct programs in preclinical and clinical development that target BCMA; these programs represent a variety of therapeutics modalities, including monoclonal antibodies, ADCs, autologous chimeric antigen receptor T-cells, or CAR-T cells, and allogeneic CAR-T cells.

We are also aware of at least two efforts to combine a GSI and a BCMA-directed agent to treat RRMM. Celgene Corporation is currently evaluating JCARH125, an autologous BCMA-directed CAR T-cell therapy, in combination with crenigacestat, a GSI licensed from Eli Lilly and Company in December 2017; this combination is currently in Phase 1/2 clinical testing. In December 2018, Novartis licensed the rights to another GSI, AL102, for use in combination with its autologous BCMA-directed CAR-T cell therapy; to our knowledge, this combination has not yet entered clinical testing. Each of crenigacestat and AL102 have been evaluated in Phase 1 clinical trials and a challenging tolerability profile was observed for both of these agents.

Our Solution – Combination of Nirogacestat and Belantamab Mafodotin

Belantamab mafodotin is the most clinically advanced BCMA ADC and was awarded Breakthrough Therapy Designation from the FDA in 2017. Belantamab mafodotin is delivered via

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a 60-minute intravenous infusion once every three weeks. Part 2 of GSK’s Phase 1 clinical trial of belantamab mafodotin, after dose-selection, enrolled 35 heavily pretreated RRMM patients, 40% of whom had received more than five previous lines of therapy. In Part 2 of this clinical trial 60% of patients achieved ORR, median time to first response was 1.2 months, median PFS was 12.0 months and median duration of response was 14.3 months.

At the recommended dose used in Part 2 of this clinical trial, 11% of patients discontinued due to adverse events. Grade 3 or 4 adverse events were reported in 83% of patients, with thrombocytopenia (35%) and anemia (17%) being the most common; there were no Grade 5 adverse events. Other Grade 3 or 4 adverse events that occurred in more than two patients, or in at least six percent of patients, included diarrhea (12%), hypokalemia (9%), lung infection (9%), pneumonia (9%), decreased neutrophil count (9%), back pain (6%), increased aspartate aminotransferase (6%), increased γ-glutamyl transferase (6%), keratitis (6%) and neutropenia (6%). In addition, four Grade 4 events (bacteremia, cholecystitis acute, cholecystitis infective and pericardial effusion) were reported.

The following chart shows the best responses to belantamab mafodotin for the 35 patients in Part 2 of this clinical trial. For patients with measurable serum M-protein, the percentage reduction in serum concentration is shown; for patients with urine-M-protein measurements, the percentage reduction in urine concentrations are shown; and for patients with no available serum or urine M-protein measurements, the percentage reduction in free light-chain concentrations are shown.

We believe that the planned Phase 1b clinical trial of our novel combination of nirogacestat and belantamab mafodotin will be the first clinical trial testing the combination of a GSI with a BCMA targeted ADC for patients with RRMM. We believe that nirogacestat, by maintaining a high level of surface expression of BCMA on MM cells and by reducing peripheral antigen sink resulting from shed BCMA extracellular domain, or ECD, can improve clinical outcomes over belantamab mafodotin alone. In particular, as compared to belantamab mafodotin alone, we believe this combination may improve response rates, prolong the duration of clinical benefit and reduce the side effect profile by enabling administration at a lower dose.

We believe BCMA-targeted therapies will occupy an important role in the future treatment paradigm of MM, with ADCs possessing particular advantages among the modalities being investigated to therapeutically target BCMA. In particular, ADCs possess several attractive features, including convenient infusion schedules and standard pharmaceutical manufacturing,

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storage and administration processes. In addition, dosing of ADCs can be readily modified throughout the course of treatment. ADCs also allow for the rapid commencement of therapy, which is potentially a key benefit, given how quickly RRMM can progress.

Given our clinical experience with nirogacestat as well as its tolerability profile at doses observed to be active in combination with belantamab mafodotin in preclinical models, we believe that nirogacestat could be a compelling and differentiated GSI for use in combination with a BCMA-directed therapy in MM.

Combination Mechanism of Action

Gamma secretase has been shown to directly cleave membrane-bound BCMA, resulting in the release of the BCMA ECD from the cell surface. By inhibiting gamma secretase, membrane-bound BCMA can be preserved, increasing target density while reducing levels of soluble BCMA ECD, which may serve as decoy receptors. Nirogacestat’s ability to enhance the activity of BCMA-directed therapies has been observed in multiple preclinical models of MM.

Belantamab mafodotin’s activity against BCMA-expressing MM cells is attributable to four potential mechanisms: (1) targeted delivery of its cytotoxic payload, (2) antibody-dependent cellular cytotoxicity, (3) BCMA receptor signaling inhibition due to blocking of ligand binding and (4) immunogenic cell death. Belantamab mafodotin is a humanized IgG1 monoclonal antibody targeting BCMA, which is conjugated to a monomethyl auristatin F, or MMAF, payload. Auristatin based cytotoxics have been employed in a variety of investigational ADCs, as well as in the approved agent brentuximab vedotin, a CD30 targeting molecule indicated in several hematologic malignancies.

The following graphic illustrates the effect of GSI on decreasing gamma secretase-mediated cleavage of BCMA, leading to increased density of target (BCMA) on malignant cells and reduced levels of decoy receptors (soluble BCMA ECD):

By increasing surface expression of BCMA, we believe belantamab mafodotin may be better able to target disease-causing MM cells and potentially improve activity and tolerability.

Planned Combination Therapy Future Clinical Trial

We and GSK have designed an adaptive Phase 1b trial evaluating the combination of nirogacestat and belantamab mafodotin in patients with RRMM. We expect GSK to initiate the

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adaptive Phase 1b clinical trial by the first quarter of 2020. The dose-escalation portion of this trial will test multiple doses of both nirogacestat and belantamab mafodotin to assess antitumor activity, safety and tolerability of the combination. Following the selection of a recommended dose for each agent, an additional expansion cohort of patients is intended to be treated with the combination therapy.

Mirdametinib

Overview

Mirdametinib (PD-0325901) is an oral, small molecule inhibitor of MEK1 and MEK2. MEK proteins occupy a pivotal position in the MAPK pathway, a key signaling network that regulates cell growth and survival, and that plays a central role in multiple oncology and rare disease indications.

We are initially investigating mirdametinib as a monotherapy for the treatment of patients with NF1-PN, a rare disorder characterized by mutations in the MAPK pathway that lead to the growth of peripheral nerve sheath tumors, which cause significant pain, disfigurement and morbidity. NF1-PN are most often diagnosed in the first two decades of life and are characterized by aggressive tumor growth, which is typically more rapid during childhood. In August 2017, we exclusively licensed worldwide rights to mirdametinib from Pfizer. In October 2018, the FDA granted mirdametinib Orphan Drug Designation for the treatment of NF1, and in May 2019, the FDA granted mirdametinib Fast Track Designation for the treatment of NF1-PN.

Mirdametinib has been evaluated in eight Phase 1 and 2 clinical trials, with over 200 subjects having been exposed to treatment. A Phase 2 clinical trial was conducted by the Neurofibromatosis Clinical Trial Consortium, which evaluated mirdametinib in 19 NF1-PN patients. In this clinical trial, 42% of patients experienced an objective response (defined as at least a 20% volumetric reduction in their target PN tumor) by 12 months of treatment. Based on the strength of these data and our interactions with the FDA, we expect to initiate our potentially registrational single-arm, open-label Phase 2b ReNeu clinical trial of mirdametinib in NF1-PN patients in the third quarter of 2019. The primary endpoint for the ReNeu trial will be ORR, with an objective response defined as at least a 20% reduction in tumor volume from baseline as determined by volumetric MRI assessment. If the results of this clinical trial are favorable, we plan to file for marketing approval for mirdametinib in the United States and select international markets.

In addition to our monotherapy program in NF1-PN, we believe that mirdametinib holds promise for use in multiple targeted combination therapies in oncology. Our first such effort is evaluating mirdametinib in combination with BeiGene’s RAF dimer inhibitor, lifirafenib (BGB-283). In May 2019, we announced the initiation of an adaptive Phase 1b clinical trial of this combination that is being conducted by BeiGene. This trial is currently enrolling patients in Australia with advanced or refractory solid tumors harboring relevant genetic mutations in the MAPK pathway.

Overview of the MAPK Pathway

The MAPK pathway, which relies upon the RAS-RAF-MEK-ERK signaling cascade, represents a central biological pathway in all human cells that is responsible for helping to regulate cellular transcription, proliferation and survival. The general structure of the pathway consists of RAS, a small GTPase, and three downstream protein kinases, RAF, MEK and ERK. In addition, at the level of RAS, the pathway is negatively regulated by several proteins, including neurofibromin, the protein encoded by the NF1 gene. Given its direct regulation of ERK, which directly controls

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downstream signaling through the MAPK pathway, MEK occupies a pivotal position in this signaling cascade and represents a rational therapeutic target for addressing indications where overactivation of the MAPK pathway contributes significantly to disease onset and/or progression.

Constitutive activation of the MAPK pathway has been reported in approximately 25% of human cancers, including colon, lung, breast, pancreatic, ovarian and renal tumors. The cause of pathway activation is varied and tissue-specific, but is driven by one or more of the following mechanisms, each of which is depicted in the illustration below: (i) upstream activation of one or more receptor tyrosine kinases, such as EGFR, (ii) mutations in a RAS isoform, such as KRAS and (iii) other mutations or aberrations within the pathway, such as in BRAF and NF1.

Mirdametinib for treatment of NF1-PN

Disease background

NF1 is a rare, autosomal dominant tumor predisposition disorder that arises from mutations in the NF1 gene, which encodes for neurofibromin, a key negative regulator of the MAPK pathway. NF1 is the most common form of neurofibromatosis, with an estimated global birth incidence of approximately 1 in 3,000 individuals. We estimate that there are approximately             patients living with NF1 in the United States and Europe. NF1 is clinically heterogeneous and manifests in

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a variety of symptoms across numerous organ systems, including abnormal pigmentation, skeletal deformities, tumor growth and neurological complications, such as cognitive impairment. Patients with NF1 have a 15-year mean reduction in their life expectancy compared to the general population.

NF1 patients have an approximately 30% to 50% lifetime risk of developing plexiform neurofibromas, or PN, which are tumors that grow in an infiltrative pattern along the peripheral nerve sheath and that can cause severe disfigurement, pain and functional impairment; in rare cases, NF1-PN may be fatal. NF1-PN are most often diagnosed in the first two decades of life and can be confirmed using routine imaging techniques. These tumors are characterized by aggressive growth, which is typically more rapid during childhood. NF1-PN typically do not spontaneously regress. In a study published in 2012 examining the natural growth dynamics of NF1-PN, 95 NF1-PN patients had the volumes of individual PN lesions monitored over time. Of these 95 patients, 69 were older than 16 years of age at the time of the initial assessment; these 69 patients had a total of 146 NF1-PN lesions monitored. At an average follow-up time of 2.4 years (range 1.05 to 4.10 years), six lesions (4.1%) were documented to have had a volumetric decrease of at least 20%.

While NF1-PN are benign, these tumors can undergo malignant transformation, leading to malignant peripheral nerve sheath tumors, or MPNST. NF1 patients have an 8% to 15% lifetime risk of developing MPNST, a diagnosis that carries with it a 12-month survival rate of under 50%. In addition to MPNST, NF1 patients are at an increased risk of developing other malignancies, including breast cancer and gliomas.

Current Treatment Landscape for NF1-PN

There are currently no therapies approved by the FDA for NF1-PN. The only definitive treatment for NF1-PN is surgical resection with wide margins, an outcome that can rarely be achieved in NF1-PN patients. This is because NF1-PN arise from nerve cells and grow in an infiltrative pattern, making it challenging to successfully resect tumors without severe comorbidities, such as permanent nerve damage and disfigurement. Patients that are ineligible for surgery or those who have had a recurrence post-surgery are often treated with a variety of off-label therapies. Among these off-label therapies are various systemic treatments, such as chemotherapy and immunotherapy, which have not been shown to consistently confer a clinical benefit.

The inadequacy of surgery and currently available off-label therapies highlights the need for improved systemic therapies. Given that NF1-PN is driven by overactivation of the MAPK pathway, MEK inhibitors have emerged as a class of therapies that hold significant promise for the treatment of NF1-PN, and we believe that MEK inhibitors have the potential to become the standard of care.

We are aware of at least three other MEK inhibitors in Phase 2 clinical trials for this indication, including a MEK inhibitor approved for other oncology indications that is sometimes used off-label in NF1-PN patients. Given the lifelong and devastating nature of NF1-PN, as well as the need to begin treating patients at a young age, we believe that the optimal MEK inhibitor is one that will have a tolerability profile suitable for long-term dosing while simultaneously arresting or reversing tumor growth.

Our Solution — Mirdametinib for the treatment of NF1-PN

Mirdametinib is an oral, small molecule inhibitor of MEK1 and MEK2, which we are developing as a monotherapy in NF1-PN. Based on results from prior clinical trials, we believe that mirdametinib, using the dose and schedule from the NF1-PN Phase 2 clinical trial, has the potential to offer a potentially best-in-class profile in order to enable the long-term treatment

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required for this patient population, as compared to other MEK inhibitors. Given the clinical activity and tolerability profile observed with mirdametinib in the previous NF1-PN clinical trial, and following our discussions with the FDA, we designed our potentially registrational Phase 2b clinical trial in a manner that we believe has the potential to generate sufficient data to support approval in both pediatric and adult NF1-PN patients. We intend to initiate this Phase 2b clinical trial in the third quarter of 2019. If the results are favorable, we plan to file for marketing approval for mirdametinib in the United States and select international markets.

Mechanism of Action

Neurofibromin is a critical repressor of RAS signaling and is impaired in patients with a mutated NF1 gene, resulting in constitutive activation of the MAPK pathway. MEK inhibitors can reduce MAPK pathway activity and therefore arrest or reverse NF1-PN growth, which has been observed clinically with several MEK inhibitors, including mirdametinib.

Clinical Experience with Mirdametinib

Over 200 subjects have been exposed to mirdametinib across eight clinical trials. Mirdametinib has shown clinical activity in a previous Phase 2 clinical trial conducted by the Neurofibromatosis Clinical Trial Consortium that enrolled adolescent and adult NF1-PN patients (WI176190). Given the activity and tolerability of mirdametinib in this clinical trial, we are utilizing the same dose and schedule in our potentially registrational Phase 2b ReNeu trial. Furthermore, based on discussions with the FDA, we will be enrolling pediatric NF1-PN patients, in addition to adolescent and adult patients.

Mirdametinib has been investigated in a Phase 1 clinical trial conducted in healthy adult subjects to assess the pharmacokinetics and pharmacodynamics of single and multiple doses (A4581004). Mirdametinib was further studied in additional clinical trials in patients with advanced cancers either as a monotherapy or in combination with other agents (A4581001, A4581002, B1271002, 13-506, M13DAP and MErCuRIC1). The table below summarizes these clinical trials.

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Abbreviations: normal healthy volunteer (NHV), non-small cell lung cancer (NSCLC), colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC).

In the monotherapy clinical trials, mirdametinib was tested across a broad dose range (from 1 mg QD to 30 mg BID), with the initial MTD determined to be 15 mg BID and the recommended Phase 2 dose determined to be 10 mg BID administered on a five days-on, two days-off schedule. Post-treatment biopsies taken in the A4581001 clinical trial showed a pharmacodynamic effect at doses as low as 1 mg QD, as measured by a greater than 90% decrease in levels of phosphorylated ERK from baseline, demonstrating inhibition of the MAPK pathway. Furthermore, in the Phase 2 clinical trial in NF1-PN patients, clinical activity was observed at doses of 4 mg BID and below. These pharmacodynamic and clinical activity data at doses below the MTD formed the rationale for continuing to advance mirdametinib in NF1-PN and in genetically defined solid tumors, either alone or in combination.

To date, the safety profile of monotherapy mirdametinib in patients with advanced cancers at doses lower than 10 mg BID using an intermittent schedule has been characterized by mostly manageable and reversible toxicities. The most frequently reported of these adverse events have been rash, nausea, vomiting, diarrhea and fatigue.

Other adverse events have been reported at a lower frequency, though these adverse events primarily occurred in patients who received doses above 10 mg and up to 30 mg BID. These adverse events included ocular disorders (visual disturbances, blurred vision and retinal vein occlusion), nervous system disorders (confusion, slowed ideation, slurred speech and hallucinations), musculoskeletal and connective tissue disorders (general weakness and neck muscle weakness associated with mild and moderate elevations in creatine kinase) and cardiac disorders (decreased left ventricular ejection fraction and congestive heart failure). Due to the adverse events observed, a prior Phase 2 clinical trial (A4581002) was terminated and enrollment in the Phase 2 portion of a Phase 1/2 clinical trial (A4581001) was halted. In each of these trials, mirdametinib at doses of 15 mg BID or above was being evaluated using both intermittent and continuous dosing schedules. These doses were significantly higher than the maximum allowable dose of 4 mg BID in the Phase 2 NF1-PN trial described below, in which mirdametinib was observed to be generally well tolerated. Our potentially registrational Phase 2b ReNeu trial in NF1-PN will have this same maximum allowable dose of 4 mg BID.

Phase 2 Clinical Trial in NF1-PN (WI176190)

The Phase 2 clinical trial evaluating mirdametinib in adolescents and adults with NF1-PN enrolled 19 patients between 16 and 39 years of age. This clinical trial commenced in June 2014 and preliminary results were presented in 2017 at a conference organized by the Children’s Tumor Foundation. Patients received an oral dose of 2 mg/m2 BID with a maximum dose of 4 mg BID on a four-week cycle of three weeks-on, one week-off. Eight patients (42%) achieved an objective response by cycle 12, prospectively defined as a volumetric reduction in their target PN of at least 20%.

The protocol specified that patients were to be removed from the clinical trial if they did not achieve at least a 15% volumetric reduction in their target PN by cycle eight of treatment, corresponding to approximately eight months on therapy. Patients achieving at least a 15% reduction in their target PN by cycle eight of treatment, but who did not achieve at least a 20% reduction in their target PN by cycle 12 of treatment, were also removed from the trial.

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Importantly, it has been observed in subsequent clinical trials of other MEK inhibitors that some NF1-PN patients achieved their first objective response to therapy 12 months or more following the start of treatment. Therefore, we believe that the design of this clinical trial was not optimized to demonstrate the full potential of mirdametinib’s antitumor activity in the NF1-PN patients that were enrolled, a consideration that we have aimed to address in our upcoming potentially registrational Phase 2b ReNeu trial by allowing patients to remain on treatment for up to 24 months.

Mirdametinib was generally well tolerated in this trial. There were no Grade 4 adverse events reported. Related treatment-emergent Grade 2 and Grade 3 adverse events occurring in at least 20% of patients included acneiform rash (53%), fatigue (26%) and nausea (21%). The only Grade 3 treatment-related adverse event reported was pain. Five patients (26%) had dose reductions due to adverse events, including two patients for Grade 2 rash, one patient for Grade 2 nausea, one patient for Grade 2 fatigue and one patient for Grade 2 pain. Two patients permanently discontinued mirdametinib in this trial, both at cycle four; one of these discontinuations was due to noncompliance with the trial protocol and other was due to a Grade 2 rash.

Mirdametinib Planned Future Clinical Trial in NF1-PN and Regulatory Pathway

Given the degree of clinical benefit observed in patients with NF1-PN in the previous Phase 2 clinical trial of mirdametinib, and informed by our discussions with the FDA, we expect to initiate the potentially registrational ReNeu clinical trial in the third quarter of 2019. The ReNeu trial will be conducted under our IND for mirdametinib that became effective in April 2019, and will be a Phase 2b, longitudinal, open-label clinical trial designed to evaluate the efficacy, safety and tolerability of mirdametinib in patients at least two years of age with an inoperable NF1-PN that is causing significant morbidity or major deformity. The ReNeu trial will be conducted at clinical sites in North America. As in the previous Phase 2 clinical trial in NF1-PN patients, mirdametinib

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will be administered orally at a 2 mg/m