View Filing Data

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2019	Mar. 09, 2020	Jun. 30, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	SPRINGWORKS THERAPEUTICS, INC.
Entity Central Index Key	0001773427
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Shell Company	false
Entity Ex Transition Period	false
Entity Public Float			$ 0
Entity Common Stock, Shares Outstanding		43,001,242
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 327,652	$ 45,648
Prepaid expenses and other current assets	3,709	1,382
Total current assets	331,361	47,030
Property and equipment, net	795	317
Equity investment	976
Restricted cash	540	540
Other assets	1,159	503
Total Assets	334,831	48,390
Current liabilities:
Accounts payable	2,654	774
Accrued expenses	8,953	2,568
Deferred rent	363	335
Total current liabilities	11,970	3,677
Long-term portion of deferred rent	789	1,152
Total liabilities	12,759	4,829
Commitments and contingencies
Convertible preferred units and stock:
Series A convertible preferred units, no par value, net of issuance costs; no units authorized, issued and outstanding at December 31, 2019; 103,000,000 units authorized; 63,600,000 units issued and outstanding at December 31, 2018.		62,930
Stockholders’ (deficit) equity:
Junior Series A convertible preferred units, no par value; no units authorized, issued or outstanding at December 31, 2019; 6,437,500 units authorized, issued and outstanding at December 31, 2018.		2,014
Common stock, $0.0001 par value, 150,000,000 shares authorized, 43,006,077 shares issued and outstanding, at December 31, 2019; no shares authorized, issued or outstanding at December 31, 2018.	4
Common units, no par value; no units authorized, issued or outstanding at December 31, 2019; 195,638 units authorized, issued and outstanding at December 31, 2018.
Additional paid-in capital	395,097	1,069
Accumulated deficit	(73,029)	(22,452)
Total stockholders’ equity (deficit)	322,072	(19,369)
Total liabilities, convertible preferred units, stock and stockholders’ equity (deficit)	$ 334,831	$ 48,390

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Common stock, Par value	$ 0.0001	$ 0.0001
Common stock, Shares authorized	150,000,000	0
Common stock, Shares issued	43,006,077	0
Common stock, Shares outstanding	43,006,077	0
Common units, Par value	$ 0	$ 0
Common units, Shares authorized	0	195,638
Common units, Shares issued	0	195,638
Common units, Shares outstanding	0	195,638
Series A convertible preferred unit
Temporary equity units, Par value	$ 0	$ 0
Temporary equity units, Shares authorized	0	103,000,000
Temporary equity units, Shares issued	0	63,600,000
Temporary equity units, Shares outstanding	0	63,600,000
Junior Series A convertible preferred unit
Preferred units, Par value	$ 0	$ 0
Preferred units, Shares authorized	0	6,437,500
Preferred units, Shares issued	0	6,437,500
Preferred units, Shares outstanding	0	6,437,500

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	4 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Operating expenses:
Research and development	$ 2,799	$ 42,545	$ 9,898
General and administrative	1,861	16,694	8,593
Total operating expenses	4,660	59,239	18,491
Loss from operations	(4,660)	(59,239)	(18,491)
Other income:
Interest income, net	21	3,547	678
Total other income	21	3,547	678
Equity investment loss		(2,614)
Net loss	(4,639)	(58,306)	(17,813)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss	(4,639)	(58,306)	(17,813)
Net gain attributable to extinguishment of Series A convertible preferred and Junior Series A convertible preferred units		7,729
Net loss attributable to common stockholders, basic and diluted	$ (4,639)	$ (50,577)	$ (17,813)
Net loss per unit, basic and diluted			$ (52.24)
Net loss per share, basic and diluted		$ (3.81)
Weighted average common units outstanding, basic and diluted			341,014
Weighted average common shares outstanding, basic and diluted		13,274,836

Consolidated Statement of Convertible Preferred Unit/Stock and Members’/Stockholders’ Equity/(Deficit) - USD ($) $ in Thousands	Junior Series A convertible preferred	Common stock options issued and outstanding	Additional Paid-in Capital	Accumulated Deficit	Total
Beginning balance at Aug. 18, 2017
Beginning balance (in shares) at Aug. 18, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of units, Value	$ 2,014				2,014
Issuance of units (in shares)	6,437,500
Net loss				(4,639)	(4,639)
Ending balance at Dec. 31, 2017	$ 2,014			(4,639)	(2,625)
Ending balance (in shares) at Dec. 31, 2017	6,437,500
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of units, Value			154		154
Issuance of units (in shares)		195,638
Issuance of incentive units, net of forfeitures			915		915
Issuance of incentive units, net of forfeitures (in shares)		2,905,568
Net loss				(17,813)	(17,813)
Ending balance at Dec. 31, 2018	$ 2,014		1,069	(22,452)	(19,369)
Ending balance (in shares) at Dec. 31, 2018	6,437,500	3,101,206
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of units, Value		$ 1	169,729		169,730
Issuance of units (in shares)		10,350,000
Convertible preferred extinguishment	$ 1,868			(1,868)
Stock compensation expense, net of forfeitures			3,109		3,109
Stock compensation expense, net of forfeitures (in shares)		(248,568)
Convertible preferred extinguishment				9,597	9,597
Conversion of convertible preferred stock into common stock	$ (3,882)	$ 3	221,169		217,290
Conversion of convertible preferred stock into common stock (in shares)	(6,437,500)	29,794,359
Exercise of stock options			21		21
Exercise of stock options (in shares)		9,080
Net loss				(58,306)	(58,306)
Ending balance at Dec. 31, 2019		$ 4	$ 395,097	$ (73,029)	$ 322,072
Ending balance (in shares) at Dec. 31, 2019		43,006,077

Consolidated Statement of Convertible Preferred Unit/Stock and Members’/Stockholders’ Equity/(Deficit) - Temporary Equity - USD ($) $ in Thousands	Series A convertible preferred unit	Series A convertible preferred stock	Series B convertible preferred stock	Series A and B Convertible Preferred Stock	Total
Beginning balance at Aug. 18, 2017
Beginning balance (in shares) at Aug. 18, 2017
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of convertible preferred units, net	$ 12,554
Issuance of convertible preferred units, net (in shares)	13,200,001
Ending balance at Dec. 31, 2017				$ 12,554
Ending balance (in shares) at Dec. 31, 2017				13,200,001
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of convertible preferred units, net	$ 50,376
Issuance of convertible preferred units, net (in shares)	50,399,999
Ending balance at Dec. 31, 2018				$ 62,930	$ 62,930
Ending balance (in shares) at Dec. 31, 2018				63,600,000
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of convertible preferred units, net		$ 39,367	$ 124,590
Issuance of convertible preferred units, net (in shares)		39,400,000	86,639,279
Convertible preferred extinguishment				$ (9,597)	9,597
Conversion of convertible preferred stock into common stock				$ (217,290)	$ 217,290
Conversion of convertible preferred stock into common stock (in shares)				(189,639,279)

Consolidated Statement of Convertible Preferred Unit/Stock and Members’/Stockholders’ Equity/(Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Issuance costs	$ 16,570
Series B convertible preferred stock
Legal Costs	$ 413,063

Consolidated Statements of Cash Flows - USD ($)	4 Months Ended	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net loss	$ (4,639,000)	$ (58,306,000)	$ (17,813,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	3,000	192,000	17,000
Stock compensation expense		3,109,000	1,069,000
Equity investment loss		2,614,000
Non-cash license expense	2,014,000
Changes in Operating Assets and Liabilities
Prepaid expenses and other current assets	(270,000)	(2,327,000)	(1,112,000)
Other assets		(656,000)	(503,000)
Accounts payable	283,000	1,880,000	491,000
Accrued expenses	370,000	6,385,000	2,198,000
Deferred rent		(335,000)	1,487,000
Net cash used in operating activities	(2,239,000)	(47,444,000)	(14,166,000)
Investing activities
Capital expenditures	(44,000)	(670,000)	(293,000)
Equity investments		(3,590,000)
Net cash used in investing activities	(44,000)	(4,260,000)	(293,000)
Financing Activities
Proceeds from issuance of common stock, net of issuance costs		169,730,000
Proceeds from issuance of Series A convertible preferred shares, net of issuance costs	12,554,000	39,367,000	50,376,000
Proceeds from issuance of Series B convertible preferred shares, net of issuance costs		124,590,000
Proceeds from stock option exercises		21,000
Net cash provided by financing activities	12,554,000	333,708,000	50,376,000
Net increase in cash and cash equivalents	10,271,000	282,004,000	35,917,000
Cash and cash equivalents including Restricted cash, beginning of period		46,188,000	10,271,000
Cash and cash equivalents including Restricted cash, end of period	$ 10,271,000	$ 328,192,000	$ 46,188,000

Nature of Operations	12 Months Ended
Nature of Operations	Dec. 31, 2019
Nature of Operations
Nature of Operations	1. Nature of Operations SpringWorks Therapeutics, Inc. (“the Company”) was formed in Delaware on August 18, 2017 (“Inception”) and is a clinical-stage biopharmaceutical company focused on identifying, developing and commercializing therapies for underserved patient populations suffering from severe rare diseases and cancer. The Company has a pipeline of product candidates across various stages of development, currently focused on rare disease and oncology conditions. Two of the medicines are late stage clinical product candidates: nirogacestat and mirdametinib. Initial Public Offering On September 12, 2019, the Company completed an initial public offering (“IPO”) of its common stock. In connections with its IPO, the Company issued and sold 10,350,000 shares of its common stock at a price to the public of $18.00 per share. The net proceeds from the IPO were approximately $169.7 million after deducting underwriting discounts and commissions of $13.0 million and offering expenses of approximately $3.5 million. At the closing of the IPO, 196,076,779 shares of outstanding convertible preferred stock were automatically converted into 29,794,359 shares of common stock at a conversion rate of 6.5810-for-one. Following the IPO, there were no shares of preferred stock outstanding. Reverse Stock Split In August 2019, the Company’s Board of Directors and stockholders approved a one-for-6.5810 reverse stock split of the Company’s common stock. The reverse stock split became effective on August 30, 2019. Stockholders entitled to a fractional share as a result of the reverse stock split received a cash payment in lieu of the fractional shares at the initial public offering price. All common stock share and per share amounts in the consolidated financial statements and notes thereto have been retroactively adjusted, where applicable for all periods presented to give effect to the reverse stock split. The shares of common stock retained a par value of $0.0001 per share. Series B convertible preferred In March 2019, the Company authorized the sale and issuance of up to 86,639,279 shares of Series B convertible preferred stock. The Series B convertible preferred financing was closed in a single tranche at the original price of $1.4428 per share for gross proceeds of $125 million. Issuance costs totaled $0.4 million. The liquidation preference terms of each of the Series A convertible preferred stock and Junior Series A convertible preferred stock changed in connection with the issuance of Series B convertible preferred. Specifically, after receiving one times its original issue price, the Series A convertible preferred does not participate in the distribution with the Junior Series A convertible preferred prior to final distribution to all stockholders, and the Junior Series A convertible preferred does not participate with all other stockholders in the final distribution. The Company concluded that the changes in the Series A convertible preferred and Junior Series A convertible preferred liquidation preferences are a significant change in the economics of those instruments and therefore were accounted for as an extinguishment. Immediately following the extinguishment of Series A convertible preferred and Junior Series A convertible preferred, the same number of shares was reissued at fair value. As a result, the difference between (1) the fair value of the consideration transferred to the holders of the preferred stock and (2) the carrying amount of the extinguished instruments (net of issuance costs) was recorded to retained earnings. Reorganization Prior to March 29, 2019, the Company conducted its business through SpringWorks Therapeutics, LLC, a Delaware limited liability company. On March 29, 2019, the Company completed a series of transactions pursuant to which SpringWorks MergerSub LLC, a wholly owned subsidiary of SpringWorks Therapeutics, Inc., merged with SpringWorks Therapeutics, LLC, with SpringWorks Therapeutics, LLC surviving the merger as a wholly owned subsidiary of SpringWorks Therapeutics, Inc. (the “Reorganization”). Upon consummation of the Reorganization, the historical consolidated financial statements of SpringWorks Therapeutics, LLC became the historical consolidated financial statements of SpringWorks Therapeutics, Inc As part of the Reorganization: Holders of Series A convertible preferred Units of SpringWorks Therapeutics, LLC received one share of Series A convertible preferred stock of SpringWorks Therapeutics, Inc. for each Series A convertible preferred unit held immediately prior to the Reorganization; Holders of Junior Series A convertible preferred units of SpringWorks Therapeutics, LLC received one share of Junior Series A convertible preferred stock of Parent for each Junior Series A convertible preferred unit held immediately prior to the Reorganization; Holders of common units received one share of common stock of SpringWorks Therapeutics, Inc. for each common unit held immediately prior to the Reorganization; Each outstanding incentive unit converted into one share of common stock of SpringWorks Therapeutics, Inc. for each incentive unit held immediately prior to the Reorganization, and such common stock is subject to vesting in accordance with the vesting schedule applicable to such incentive units; and Holders of options exercisable to purchase common units (“unit options”) of SpringWorks Therapeutics, LLC received one stock option exercisable to purchase common stock of the Company for each unit option held immediately prior to the Reorganization, at the same exercise price of such unit option immediately prior to the Reorganization. Such stock options continue to be subject to vesting in accordance with the vesting schedule applicable to such unit options. Convertible Preferred Units and Members’ Deficit prior to Reorganization Series A convertible preferred In August 2017, the Company authorized the sale and issuance of up to 103,000,000 units of Series A convertible preferred units at $1.00 per unit for a total of $103 million of proceeds. The Series A convertible preferred financing was structured to close in three tranches. The first tranche closed in August 2017, resulting in the issuance of 13,200,001 units of Series A convertible preferred units for gross cash proceeds of $13.2 million. Issuance costs totaled $0.6 million. In April 2018, the second tranche of 50,399,999 units of Series A convertible preferred were issued at $1.00 per unit, or $50.4 million in gross proceeds. Issuance costs totaled $24,372. In March 2019, the third tranche of 39,400,000 units of Series A convertible preferred units were issued at $1.00 per unit, or $39.4 million in gross proceeds. Issuance costs totaled $32,694. Junior Series A convertible preferred In August 2017 and in conjunction with the formation of the Company and the License Agreements, the Company authorized and issued 6,437,500 units of Junior Series A convertible preferred units in exchange for four license agreements with Pfizer, Inc. (Pfizer) for the development and commercialization of products. No cash was received by the Company for these units. The Company determined the fair value of Junior Series A convertible preferred units in aggregate was $2.0 million based on the calculated enterprise value and the distribution preferences. The fair value of the Junior Series A convertible preferred units was then allocated across the four licenses relative to the present value of estimated discrete cash flows and recorded as research and development expense in the period from August 18, 2017 (inception) to December 31, 2017.

Risks and Liquidity	12 Months Ended
Risks and Liquidity	Dec. 31, 2019
Risks and Liquidity
Risks and Liquidity	2. Risks and Liquidity The Company has incurred losses and negative operating cash flows since inception and had an accumulated deficit of $73.0 million and $22.5 million and working capital of $319.4 million and $43.4 million at December 31, 2019 and 2018, respectively. The Company is subject to those risks associated with any biopharmaceutical company that has substantial expenditures for development. There can be no assurance that the Company’s development projects will be successful, that products developed will obtain necessary regulatory approval, or that any approved product will be commercially viable. In addition, the Company operates in an environment of rapid technological change and is largely dependent on the services of its employees, advisors, and consultants. The Company had cash and cash equivalents of $327.7 million and $45.6 million as of December 31, 2019 and 2018, respectively. This increase in the cash balance of approximately $282 million was primarily driven by net proceeds of $169.7 million from our initial public offering in September 2019, net proceeds of $124.6 million from the issuance of Series B convertible preferred stock in March 2019 and net proceeds of $39.4 million from the issuance of Series A convertible preferred units in March 2019, offset by a of loss from operations for the year ended December 31, 2019 of $58.3 million. Management estimates that its cash and cash equivalents will enable it to meet operational expenses through at least twelve months after the date that these financial statements were issued.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

3. Summary of Significant Accounting Policies

Basis of Presentation

These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP).

The Company does not have any components of other comprehensive income recorded within its consolidated financial statements, and, therefore, does not separately present a statement of comprehensive income in its consolidated financial statements.

Principles of Consolidation

The consolidated financial statements include the accounts of SpringWorks Therapeutics, Inc. and its subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Investments in business entities in which the Company lacks control but does have the ability to exercise significant influence over operating and financial policies are accounted for using the equity method of accounting.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, Research and Development expenses and the valuation of equity-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates as there may be changes in circumstances, facts and experience. Actual results may differ from those estimates or assumptions.

Segment Information

Operating segments are defined as components of an entity about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating segment operating exclusively in the United States.

Fair Value of Financial Instruments

The Company believes that the carrying amounts of the its financial instruments, including accounts payable and accrued expenses, approximate fair value due to the short-term nature of those instruments. The Company follows the provisions of Financial Accounting Standards Board (“FASB”) ASC Topic 820, “Fair Value Measurements and Disclosures” (ASC 820), for financial assets and liabilities measured on a recurring basis. This pronouncement defines fair value, establishes a framework for measuring fair value under GAAP and requires expanded disclosures about fair value measurements. The guidance requires that fair value measurements be classified in one of the following three categories:

Level 1 — Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets, or liabilities.

Level 2 — Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the instrument.

Level 3 — Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).

Cash and cash equivalents of $327.7 million and $45.6 million as of December 31, 2019 and 2018, respectively, consist of money market funds and are measured at fair value at the reporting date using quoted prices in active markets for identical assets (Level 1). The Company has no other financial assets or liabilities that are measured at fair value on a recurring basis.

Cash and Cash Equivalents

The Company considers all highly liquid instruments that have maturities of three months or less when acquired to be cash equivalents. The Company had cash and cash equivalents at December 31, 2019 and 2018 of $327.7 million and $45.6 million, respectively. The Company maintains its bank accounts at one major financial institution.

Concentration of Credit Risk

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains each of its cash and cash equivalent balances with high quality, financial institutions and, accordingly, such funds are not exposed to significant credit risk. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships.

Property and Equipment

Property and equipment consist of computer equipment, furniture and leasehold improvements and are recorded at cost. Property and equipment are depreciated on a straight-line basis over their estimated useful lives.

Research and Development

In accordance with FASB ASC Topic 730 10 55, “Research and Development”, expenditures for clinical development, including upfront licensing fees and milestone payments associated with products that have not yet been approved by the FDA, are charged to research and development expense as incurred. These expenses consist of expenses incurred in performing development activities, including salaries and benefits, unit-based compensation expenses, materials and supplies consumed, 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 the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of payment, and are reflected in the consolidated financial statements as prepaid or accrued development expenses. Nonrefundable advance payments for goods or services to be received in the future for use in development activities are deferred and capitalized. The capitalized amounts are expensed as the related goods are delivered or the services are performed. As of December 31, 2019 and 2018, the Company had made payments of $0.7 million and $0.5 million, respectively, for services to be received in the future. These payments are recorded as other assets in the Consolidated Balance Sheets.

General and Administrative

General and administrative expenses consist primarily of payroll and employee related costs, rent and utilities, infrastructure, corporate insurance, office expenses and professional fees.

Equity-based compensation expense

The Company accounts for employee equity-based compensation in accordance with Financial Accounting Standards Board Accounting Standards Codification Topic (“ASC”) 718, Compensation — Stock Compensation. ASC 718 requires all equity-based awards to employees and non-employee directors to be recognized as expense in the statement of operations based on the grant date fair value of the common and incentive unit, unit option, restricted stock and stock option awards. Equity-based awards vest over a four-year period. Generally, onboarding equity-based awards vest with the first 25% vesting following 12 months of employment or service and the remaining vesting in equal monthly installments over the following 36 months. Certain awards are subject to performance conditions and/or market conditions.

Stock compensation expense is recognized using the straight-line method, based on the grant date fair value, over the requisite service period of the award, which is generally the vesting term.

For awards subject to performance conditions, as well as awards containing both market and performance conditions, the Company recognizes equity award compensation expense using an accelerated recognition method over the remaining service period when management determines that achievement of the milestone is probable. Management evaluates when the achievement of a performance-based milestone is probable based on the expected satisfaction of the performance conditions as of the reporting date.

The Company recognizes forfeitures at the time of the actual forfeiture event in accordance with the adoption of the guidance per Accounting Standard Update (“ASU”) No. 2016‑09.

The grant-date fair value of performance-based awards with market conditions is estimated using a Monte Carlo simulation method that incorporates the probability of the performance conditions being met as of the grant date.

For stock options issued, the Company estimates the grant date fair value and the resulting stock-based compensation expense using the Black-Scholes option-pricing model.

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:

Fair value of common stock.

Expected term — The expected term represents the period that the equity-based awards are expected to be outstanding. The expected term for our stock options was calculated using the simplified method.

Expected volatility — The Company lacks Company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until it has adequate historical data regarding the volatility of its own traded stock.

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.

Expected dividend — The Company has never paid dividends on its common units or stock and has no plans to pay dividends on its common stock. Therefore, the expected dividend yield is zero.

For equity-based compensation grants prior to the IPO, the Company estimated the fair value of equity awards granted using the special case of the market approach, including the guideline public company method and precedent transaction method which is known as a backsolve method. This option pricing model was utilized to solve for the implied total equity value that was consistent with the Company’s Series A convertible preferred units “backsolves” to a preferred share price. The backsolve method derives the implied equity value for one type of equity security from a contemporaneous transaction involving another type of security to calculate the equity value. The use of these valuation approaches required management to make assumptions with respect to the expected volatility of its units and stock, time until a liquidity event and risk-free interest rates. Equity value was allocated to the common, incentive and convertible preferred units, and common, restricted and convertible preferred stock using an option-pricing method. Under this method, the common and incentive units and common stock would have had value only if the funds available for distribution exceeded the value of the convertible preferred units’ liquidation preferences at the anticipated time of a liquidity event, such as a strategic sale, merger or IPO.

Net Loss per Unit and Share

Basic net loss per unit and per share is computed by dividing net loss by the weighted average number of common units and shares outstanding for the period. Diluted net loss per unit and share excludes the potential impact of convertible preferred units, unvested incentive units, convertible preferred stock, unvested restricted stock and stock options because their effect would be anti-dilutive due to the Company’s net loss. Since the Company had a net loss in each of the periods presented, basic and diluted net loss per common unit and share are the same.

Income Taxes

Income taxes are accounted for using the asset-and-liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized as income in the period that includes the enactment date. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes.

The Company recognizes deferred tax assets to the extent that it believes that these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies and results of recent operations. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.

The Company records uncertain tax positions in accordance with ASC 740 on the basis of a two-step process in which (1) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority.

The Company provides reserves for potential payments of tax to various tax authorities related to uncertain tax positions. These reserves are based on a determination of whether and how much of a tax benefit taken by the Company in its filings or positions is more likely than not to be realized following resolution of any potential contingencies related to the tax benefit. Potential interest related to the underpayment of income taxes will be classified as a component of income tax expense and any related penalties will be classified in income tax expenses in the statement of operations.

SpringWorks Therapeutics, LLC elected to be treated under the partnership provisions of the Internal Revenue Service Code prior to the reorganization on March 29, 2019. However, its five wholly owned subsidiaries, SpringWorks Operating Company, SpringWorks Subsidiary 1, SpringWorks Subsidiary 2, SpringWorks Subsidiary 3, and SpringWorks Subsidiary 4, are taxable corporations.

Subsequent to the Reorganization, SpringWorks Therapeutics, Inc. became the 100% owner of SpringWorks Therapeutics, LLC, creating a new ultimate parent company, and a consolidated group for income tax reporting. The Reorganization and change in tax status of the reporting entity did not have an impact on the consolidated tax provision.

Recently Adopted Accounting Pronouncements

In May 2014, the FASB issued ASU No. 2014‑09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014‑09”). ASU No. 2014‑09 eliminated transaction- and industry-specific revenue recognition guidance under FASB ASC Subtopic 605‑15, Revenue Recognition-Products and replaced it with a principle-based approach for determining revenue recognition. The new standard requires a company to recognize revenue upon transfer of goods or services to a customer at an amount that reflects the expected consideration to be received in exchange for those goods or services. ASU 2014‑09 defines a five-step approach for recognizing revenue, which may require a company to use more judgment and make more estimates than under the current guidance. In accordance with Topic 606, to determine revenue recognition for arrangements within the scope of ASC 606, the Company evaluated contracts to identify any contracts with a customer. After reviewing the contracts, management concluded the Company did not have any contracts with customers. The Company adopted ASU 2014-09 effective for the annual period ending December 31, 2019. The adoption of ASU 2014‑09 did not have a material impact on the Company’s financial statements.

In June 2018, the FASB issued ASU No. 2018-07, Improvements to Nonemployee Share-Based Payment Accounting (“ASU 2018-07”). ASU 2018-07 expands the scope of Topic 718, Compensation – Stock Compensation, to include share-based payments issued to non-employees for goods or services. Consequently, nonemployees and employees will be substantially aligned. ASU 2018-07 supersedes Subtopic 505-50, Equity – Equity-Based Payments to Non-Employees. The amendments are effective for fiscal years beginning after December 15, 2018. Early adoption is permitted, but not earlier than the adoption of Topic 606, Revenue from contracts with customers. The Company adopted ASU 2018-07 effective for annual period ending December 31, 2019. The adoption of ASU 2018‑07 did not have a material impact on the Company’s financial statements.

In August 2016, the FASB issued ASU 2016‑15 “Statement of Cash Flows (Topic 230) — Classification of Certain Cash Receipts and Cash Payments.” This standard requires entities that must present a statement of cash flows under Topic 230 to classify certain cash receipts and cash payments using a standardized method. The Company adopted ASU 2016-15 effective for annual period ending December 31, 2019. The adoption of ASU 2016‑15 did not have a material impact on the Company’s financial statements.

In November 2018, the FASB issued ASU 2016‑18 “Statement of Cash Flows (Topic 230) — Restricted Cash.” This standard requires entities that must present a statement of cash flows under Topic 230 to include in the cash and cash-equivalent balances in the statement of cash flows, those amounts that are deemed to be restricted cash and restricted cash equivalents. The adoption of ASU 2016 resulted in certain reclassifications in the Statement of Cash Flows for the year ended December 31, 2018 as follows:


		Fiscal year ended December 31, 2018
Statement of Cash Flows Caption		Presentation prior to adoption of ASU 2016-17		Presentation after adoption of ASU 2016-18
Changes in operating assets and liabilities- Other assets	$		(1,043)	$	(503)
Net cash used in operating activities			(14,706)		(14,166)
Net increase in Cash and Cas Equivalents			35,377		35,917
Cash and Cash Equivalents Ending Balance			45,648		46,188

Recently Issued Accounting Pronouncements

In February 2016, the FASB issued ASU 2016‑02 “Leases (Topic 842).” This standard requires entities that lease assets to recognize on the balance sheet the assets and liabilities of the rights and obligations created by those leases. The standard is effective for annual periods beginning after December 15, 2019 and interim periods within annual periods beginning after December 15, 2020. Early adoption is permitted. The Company is currently assessing the impact of the adoption of this authoritative guidance on its consolidated financial statements.

In August 2018, the FASB issued ASU No. 2018-15, Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). The FASB issued ASU 2018-15 to align the requirements for capitalizing implementation costs incurred in a cloud-based hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU 2018-15 is effective for annual and interim reporting periods beginning after December 15, 2019, and early adoption is permitted. The amendments under ASU 2018-15 may be applied either retrospectively or prospectively to all implementation costs incurred after adoption. The Company is evaluating the impact of ASU 2018-15 on its financial statements and the timing of adoption.

In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction Between Topic 808 and Topic 606. The ASU provides more comparability in the presentation of revenue for certain transactions between collaborative arrangement participants and only allows a company to present units of account in collaborative arrangements that are within the scope of the revenue recognition standard together with revenue accounted for under the revenue recognition standard. The parts of the collaborative arrangement that are not in the scope of the revenue recognition standard should be presented separately from revenue accounted for under the revenue recognition standard. The amendments in ASU No. 2018-18 are effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. The adoption of this guidance is not anticipated to have a material impact on the Company’s financial position and results of operations.

Property and Equipment

12 Months Ended

Dec. 31, 2019

Property and Equipment

Property and Equipment

4. Property and Equipment

Property and equipment, net consisted of the following:


	December 31,
(in thousands)	2019	2018	Useful Life
Leasehold improvements	855	293	Estimated life or lease term, whichever is shorter
Computer equipment	122	27	3 years
Furniture	31	18	5 years
	1,008	338
Less accumulated depreciation	(213)	(21)
	795	317

Depreciation expense was $192,000, $17,000 and $3,000 for the years ended December 31, 2019 and 2018 and for the period from August 18, 2017 (inception) through December 31, 2017, respectively.

Accrued Expenses

12 Months Ended

Dec. 31, 2019

Accrued Expenses

Accrued Expenses

5. Accrued Expenses

Accrued expenses consisted of the following:


	December 31,
(in thousands)	2019		2018
Accrued professional fees	$	793	$	1,040
Accrued compensation and benefits		3,147		1,178
Accrued research and development		4,447		—
Accrued other		566		350
	$	8,953	$	2,568

Equity-Based Compensation

12 Months Ended

Dec. 31, 2019

Equity-Based Compensation

Equity-Based Compensation

6. Equity Based Compensation

The Company recorded total equity-based compensation expense for the periods presented as follows:


	Year Ended	Year Ended
(in thousands)	December 31, 2019	December 31, 2018
Research and development	731	164
General and administrative	2,378	905
Total equity compensation expenses	3,109	1,069

2019 Equity Incentive Plan

In anticipation of the IPO, on August 30, 2019, the Company’s stockholders approved the 2019 Stock Option and Equity Incentive Plan (the “2019 Public Company Plan”), which became effective upon the effectiveness of the Company’s registration statement on September 12, 2019 in connection with the IPO. The 2019 Public Company Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock units, restricted stock awards, unrestricted stock awards and dividend equivalent rights to the Company’s officers, employees, directors and other key persons (including consultants). The number of shares initially reserved for issuance under the 2019 Public Company Plan is 3,537,225 shares, which shall be cumulatively increased each January 1, through and including January 1, 2030, by 5% of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or such lesser number of shares determined by the Company’s compensation committee.

The terms of stock options and restricted stock awards, including vesting requirements, are determined by the Board of Directors or its delegates, subject to the provisions of the 2019 Public Company Plan. Awards granted by the Company to employees and directors generally vest over four years.

As of December 31, 2019, there were 3,562,524 shares available for future issuance under the 2019 Public Company Plan.

2019 Equity Plan

On March 29, 2019, the Company adopted the 2019 Stock Option and Incentive Plan (“2019 Private Company Plan”) in connection with the Reorganization. The 2019 Private Company Plan originally had 5,292,355 shares available for issuance. In connection with the adoption of the 2019 Private Company Plan, all outstanding incentive units and unit options, granted under the 2018 Equity Plan, were exchanged for stock options and restricted stock under the 2019 Private Company Plan. The restricted common stock was issued with the same vesting terms as the unvested incentive units held immediately prior to the Reorganization. On June 4, 2019, the total shares available for issuance under the 2019 Private Company Plan was increased to 5,382,828 shares. On July 29, 2019, the total shares available for issuance was increased to 6,700,197.

In connection with the IPO no modification was triggered for the 2019 Private Company Plan and upon the effectiveness of the 2019 Public Company Plan no further grants will be made under the 2019 Private Company Plan. However, the shares of common stock underlying any awards that are forfeited, cancelled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without the issuance of stock, expire or are otherwise terminated (other than by exercise) under the 2019 Private Company Plan will be added back to the shares of common stock available for issuance under the 2019 Public Company Plan.

2018 Equity Plan

In January 2018, the Company adopted the 2018 Equity Incentive Plan (“2018 Equity Plan”). There were 2,738,929 incentive units (“incentive units”) initially available for issuance under the 2018 Equity Plan. The 2018 Plan was increased by 269,716 units for an aggregate of 3,008,645 as of December 31, 2018.

On March 19, 2019, the Company modified its operating agreement to allow for the award of unit options. In connection with the adoption of the 2019 Private Company Plan, as noted above, all outstanding awards were exchanged for identical awards under the 2019 Private Company Plan. No further grants can be made under the 2018 Equity Plan.

2019 Employee Stock Purchase Plan

On August 30, 2019, the Company’s stockholders approved the 2019 Employee Stock Purchase Plan (the “ESPP”), which became effective immediately preceding the effectiveness of the Company’s registration statement on September 12, 2019 in connection with the IPO. A total of 442,153 shares of common stock were reserved for issuance under the ESPP. In addition, the number of shares of common stock that may be issued under the ESPP will automatically increase each January 1, through and including January 1, 2028, by the lesser of (i) 663,229 shares of common stock, (ii) 1% of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or (iii) such lesser number of shares determined by the administrator of the Company’s ESPP. No offering periods under the ESPP had been initiated as of December 31, 2019.

Stock Options

A summary of the changes in the Company’s unit options through the Reorganization is as follows:


	Number	Weighted Average
	of Awards	Exercise Price
Outstanding at December 31, 2017 and December 31, 2018	—	$	—
Granted	148,415		1.65
Outstanding at March 29, 2019	148,415		1.65

A summary of the changes in the Company’s stock options during the period from the Reorganization through December 31, 2019 is as follows:


			Weighted
			Average
		Weighted	Remaining
		Average	Contractual	Aggregate
		Exercise	Life	Intrinsic
	Shares	Price	(Years)	Value
Outstanding at March 29, 2019	148,415	1.65	—	—
Granted	3,177,233	5.21	—	—
Exercised	(9,080)	2.30	—	—
Forfeited/cancelled	(90,843)	2.18	—	—
Outstanding at December 31, 2019	3,225,725	5.08	9.4	107,771,472
Exercisable at December 31, 2019	409,174	2.78	9.3	14,611,604

Aggregate intrinsic value is calculated by subtracting the exercise price of the option from the closing price of the Company’s common stock on closing date, multiplied by the number of shares per each option.

Assumptions used in determining the fair value of the stock options granted in 2019 include risk-free interest rate 1.45% – 2.47%, expected dividend yield of 0.00%, expected Life in years of 5.75 - 6.25 and expected volatility of 68.1% - 71.0%.

Expected term — The expected term represents the period that the equity-based awards are expected to be outstanding. The expected term for the Company’s stock options was calculated based on the weighted average vesting term of the awards and the contract period, or simplified method.

Expected dividend — The Company has never paid dividends on its common units or stock and has no plans to pay dividends on its common stock. Therefore, the expected dividend yield is zero.

Fair Value of Common Stock — Prior to the IPO, the fair value of the shares of common stock underlying the stock-based awards were determined by the Company’s Board of Directors with input from management. Since there was no public market for the common stock prior to September 12, 2019, the Company’s Board of Directors had determined the fair value of the common stock at the time of grant of the stock-based award by considering a number of objective and subjective factors, including having valuations of the common stock performed by a third-party valuation specialist. The fair value of the common stock is now determined by the public market.

At December 31, 2019, the total unrecognized compensation expense related to unvested stock options was $9.9 million, which the Company expects to recognize over a period of approximately 4 years. For the year ended December 31, 2019, total stock option compensation expense for outstanding stock options was $1.6 million.

2019 CEO Performance Award

In June 2019, the Company’s CEO received an award of 176,411 stock options (the “2019 CEO Performance Award”) at an exercise price of $7.50 per share. The 2019 CEO Performance Award can vest over 48 monthly installments based on four years of service, a performance condition (a liquidity event, such as an IPO) and market conditions, assuming continued employment and service through each vesting date. During the vesting period of four years, the 2019 CEO Performance Award is not earned unless the market condition is achieved on each vesting date. If the market condition is not achieved on a vesting date, but is achieved on a future vesting date, the award is earned for the entire period since the last date that such market condition was achieved. All or a portion of the award can be earned following the initial four-year service period if the market condition is next achieved after such four-year service period and Mr. Islam remains in continuous service. The market condition and performance condition are satisfied when the Company’s common stock is listed on a U.S. national securities exchange and achieves a 60-trading day average closing price of at least $28.49 per share (as adjusted for stock splits, recapitalizations, and similar events).

As a result of the IPO, the performance condition has been met; however, the market condition is not yet satisfied as of December 31, 2019.

The Company recorded $0.3 million stock compensation expense related to this award for the year ended December 31, 2019, which is included in stock option compensation expense. At December 31, 2019, the total unrecognized compensation expense related to the CEO Performance Award was $1.0 million, which the Company expects to recognize over a period of approximately 3.42 years.

Restricted Stock

A summary of the changes in the Company’s incentive units through the Reorganization is as follows:


	Number of	Weighted Average Grant
	Units	Date Fair Value
Outstanding at December 31, 2017	—	$	—
Granted	3,290,929		1.12
Vested	(401,824)		1.05
Forfeited	(385,361)		0.92
Unvested and outstanding at December 31, 2018	2,503,744		1.25
Vested	(228,209)		0.81
Forfeited	(12,570)		1.45
Unvested and outstanding at March 29, 2019	2,262,965		1.24

A summary of the changes in the Company’s restricted stock during the period from the Reorganization through December 31, 2019 is as follows:


		Weighted
		Average
	Number	Grant Date
	of Shares	Fair Value
Unvested and outstanding at March 29, 2019	2,262,965	1.24
Vested	(737,530)	1.26
Forfeited	(235,998)	1.36
Unvested and outstanding at December 31, 2019	1,289,437	1.21

At December 31, 2019, the total unrecognized compensation expense related to unvested restricted stock was $0.8 million, which the Company expects to recognize over a period of approximately 2.75 years. For the year ended December 31, 2019, total restricted stock compensation expense was $1.5 million.

License and Collaboration Agreements	12 Months Ended
License and Collaboration Agreements	Dec. 31, 2019
License and Collaboration Agreements
License and Collaboration Agreements	7. License and Collaboration Agreements Pfizer Inc. In August and October 2017, the Company entered into four license agreements with Pfizer for rights to certain technologies (the “License Agreements”). Under the License Agreements, the Company obtained from Pfizer the right to use research, develop, manufacture and commercialize certain products, including nirogacestat and mirdametinib. In connection with the License Agreements, the Company issued 6,437,500 units of Junior Series A convertible preferred units to Pfizer (see Note 1). No cash was received by the Company for these units. The Company is required to pay Pfizer milestones payments of up to an aggregate of $232.5 million for nirogacestat and up to an aggregate of $229.8 million for mirdametinib, each upon achievement of certain commercial milestone events. Royalties are also payable under each License Agreement based on a specified percentage of net sales ranging from mid-single digit percentages to the low 20s, Royalty payments under each License Agreement continue until the expiration of the last to expire licensed patent applicable to such product, but not less than ten years after the first commercial sale on a country-by-country basis. BeiGene, Ltd. (“BeiGene”) In August 2018, the Company entered into a clinical collaboration agreement with BeiGene to conduct a clinical study of the combination of mirdametinib and a BeiGene compound designated as lifirafenib. In accordance with the terms of the agreement, the Company and BeiGene share equally the costs associated with the clinical study. BeiGene is required to supply the BeiGene compound and the Company is required to supply mirdametinib to conduct the clinical study. The collaboration is guided by a joint steering committee. Specified areas of development require unanimous agreement among all members of the joint steering committee. The Company recorded $1.0 million and $0.4 million for the years ended December 31, 2019 and December 31, 2018, respectively, in connection with this collaboration agreement, which are classified as research and development expenses in the Company’s statement of operations. GSK clinical collaboration agreement (“GSK”) In June 2019, the Company entered into a clinical collaboration agreement with GlaxoSmithKline (“GSK”) (the “GSK Collaboration Agreement”), to evaluate the safety, tolerability and preliminary efficacy of nirogacestat and belantamab mafodotin. Under the terms of the GSK Collaboration Agreement, GSK will sponsor and conduct the adaptive Phase 1b study of nirogacestat, in combination with GSK’s BCMA antibody-drug conjugate, belantamab mafodotin, in patients with relapsed or refractory multiple myeloma. GSK will assume all development costs associated with the study. The Company agreed to manufacture and supply the Company compound for purposes of the study. Pursuant to the GSK Collaboration Agreement, GSK is responsible for administering the clinical trial and is responsible for all costs associated with the direct conduct of the clinical trial, other than the manufacture and supply of nirogacestat and certain expenses related to intellectual property rights. The collaboration is managed by a joint development committee of equal representation by the Company and GSK. Following completion of the clinical trial, within a specified period of time, either party may propose new agreements for the purpose of performing one or more additional clinical trials of the combination therapy for the treatment of relapsed and refractory multiple myeloma. If a party proposes to conduct an additional clinical trial, the parties will negotiate in good faith, without obligation, the details of a definitive agreement to provide for the expansion of the clinical collaboration. If the parties do not reach an agreement, and only one party wishes to proceed with an additional clinical trial, it may do so if the other party does not object to the protocol based on safety concerns.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies

Commitments and Contingencies

8. Commitments and Contingencies

Leases

In August 2018, the Company entered into a five-year operating lease in Durham, NC (the location of the Company’s clinical development operations), with two five-year renewal options. Rental payments under the renewal period will be at current market rates for the premises.

In October 2018, the Company entered into a lease for its corporate headquarters in Stamford, CT. The lease expires in November 2022. The Company received $1.5 million from the previous tenant in connection with the assumption of the lease. The Company recognizes rent expense for the office it currently occupies and records a deferred rent obligation representing the cumulative difference between actual rent payments, incentive received and rent expense recognized ratably over the lease period. The Company established a security deposit of $0.5 million in the form of a letter-of-credit.

The Company’s future minimum lease obligations as of December 31, 2019 are:


	Premises Operating
(in thousands)	Leases
2020		1,344
2021		1,372
2022		1,297
2023		135
Total Obligations	$	4,148

The Company recorded rent expense aggregating $1.6 million, $0.5 million and $42,000 for the years ended December 31, 2019 and December 31, 2018, and the period from August 18, 2017 (Inception) to December 31, 2017, respectively.

Contingencies

From time to time, the Company may be involved in disputes or regulatory inquiries that arise in the ordinary course of business. When the Company determines that a loss is both probable and reasonably estimable, a liability is recorded and disclosed if the amount is material to the financial statements taken as a whole. When a material loss contingency is only reasonably possible, the Company does not record a liability, but instead discloses the nature and the amount of the claim, and an estimate of the loss or range of loss, if such an estimate can reasonably be made.

As of December 31, 2019 and December 31, 2018, there was no litigation or contingency with at least a reasonable possibility of a material loss.

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Taxes

Income Taxes

9. Income Taxes

Prior to the Reorganization, SpringWorks Therapeutics, LLC elected to be treated under the partnership provisions of the Internal Revenue Service code. However, its five wholly owned subsidiaries, SpringWorks Operating Company,

SpringWorks Subsidiary 1, SpringWorks Subsidiary 2, SpringWorks Subsidiary 3, and SpringWorks Subsidiary 4, (“Combined Subsidiaries”) are taxable corporations.

For the years ended December 31, 2019 and December 31, 2018 and for the period from August 18, 2017 (inception) through December 31, 2017, the Company did not have a current or deferred income tax expense or benefit as the Company has incurred losses since inception.

As of December 31, 2019, the Company has federal, state and city net operating loss carryforwards of $75.7 million, $0.6 million and $3.8 million, respectively, which are available to reduce future taxable income. Federal net operating loss carryforwards of $55.4 million and $16.0 million reported in 2019 and 2018, will be available to offset 80% of taxable income for an indefinite period of time, until fully utilized. Federal net operating loss carryforwards of $4.3 million were reported in 2017 and the state and city net operating loss carryforwards expire at various dates through 2038. The Company also has federal tax credits of $0.8 million, which may be used to offset future tax liabilities. These tax credit carryforwards will expire in 2038.

The net operating loss and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions and other provisions within the Internal Revenue Code. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the Company immediately prior to an ownership change. Subsequent ownership changes may further affect the limitation in future years.

The Company has not recorded any reserves for uncertain tax positions as of December 31, 2019 or December 31, 2018. The Company has not conducted a study of research and development credit carryforwards. This study may result in an adjustment to the Company’s research and development credit carryforwards; however, until a study is completed, and any adjustment is known, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company’s research and development credits and, if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. Thus, there would be no impact to the balance sheets or statements of operations and comprehensive loss if an adjustment were required.

Interest and penalty charges, if any, related to unrecognized tax benefits will be classified as income tax expense in the accompanying statements of operations and comprehensive loss. As of December 31, 2019, the Company had no accrued interest or penalties related to uncertain tax positions.

Since the Company is in a loss carryforward position, it is generally subject to examination by the U.S. federal, state and local income tax authorities for all tax years in which a loss carryforward is available. The Company is not currently under examination by the Internal Revenue Service or any other jurisdictions for any tax years.

The principal components of the Subsidiaries deferred tax assets are as follows:


	As of December 31,
(in thousands)	2019		2018
Deferred tax assets:
Net operating loss carryforwards	$	16,252	$	3,342
Research and development credits		706		403
Orphan drug credit		71
Deferred rent		242		312
Accrued expenses		212		46
Depreciation		34		—
Stock compensation		496		—
Section 195 startup costs		—		1,270
Total deferred tax assets		18,013		5,373
Deferred tax liability		—		—
Valuation allowance		(18,013)		(5,373)
Net deferred tax assets	$	—	$	—

ASC 740 requires a valuation allowance to reduce the deferred tax assets reported if, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. After consideration of all the evidence, both positive and negative, the Company has recorded a full valuation allowance against its deferred tax assets at December 31, 2019 and December 31, 2018 because the Company’s management has determined that it is more likely than not that these assets will not be realized. The increase in the valuation allowance of $12.6 million in 2019 primarily relates to the net loss incurred by the Company.

In accordance with this guidance, the Company has adopted a policy under which, if required to be recognized in the future, interest related to the underpayment of income taxes will be classified as a component of income tax expense and any related penalties will be classified in operating expenses in the statements of operations.

The effective tax rate for the Company for the years ended December 31, 2019 and December 31, 2018 was zero percent. A reconciliation of the income tax expense at the federal statutory tax rate to the Company’s effective income tax rate follows:


	Year Ended December 31,
	2019		2018
Statutory tax rate	21.00	%	21.00	%
Federal and state return to provision adjustments	(0.01)		(1.08)
Research and development credit	0.57		2.02
Other	(0.03)		(0.04)
Change in valuation allowance	(21.53)		(21.90)
Effective tax rate	—	%	—	%

401(k) Plan	12 Months Ended
401(k) Plan	Dec. 31, 2019
Defined Contribution Plan [Abstract]
401(k) Plan	10. 401(k) Plan In 2017, the Company adopted a tax-qualified employee savings and retirement plan (the “401(k) Plan”) that covers all of its full-time employees who are at least 21 years of age. Pursuant to the 401(k) Plan, participants may elect to contribute up to the federally allowed maximum limits of their pretax earnings to the 401(k) Plan. As of December 31, 2019, the Company has not made any matching contributions.

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2019
Related Party Transactions
Related Party Transactions	11. Related Party Transactions Pfizer is a significant shareholder of the Company and a Pfizer employee is a member of the Board of Directors. See Note 7 for further details on transactions entered into with Pfizer Prior to the IPO, the Company regarded the Board of Directors (“BOD”) as related parties. The Company recorded consulting and BOD expenses totaling $0.2 million for the period January 1, 2019 through the date of the IPO. For the year ended December 31, 2018, the Company recorded consulting and BOD expenses totaling $0.3 million. For the period from August 18, 2017 (inception) to December 31, 2017, the Company recorded consulting and BOD expenses totaling $0.1 million.

Net Loss per Unit and Share and Unaudited Pro Forma Net Loss per Share

12 Months Ended

Dec. 31, 2019

Net Loss per Unit and Share and Unaudited Pro Forma Net Loss per Share

Net Loss per Unit and Share and Unaudited Pro Forma Net Loss per Share

12. Net Loss per Unit and Share and Unaudited Pro Forma Net Loss per Share

Basic and diluted net loss per unit and share is calculated as follows:


	Year Ended December 31,
(In thousands, except share, unit, per-share and per-unit data)	2019		2018
Numerator:
Net loss	$	(58,306)	$	(17,813)
Net gain attributable to extinguishment of Series A convertible preferred and Junior Series A convertible preferred units		7,729		—
Net loss attributable to common stockholders	$	(50,577)	$	(17,813)
Denominator:
Weighted average common units and shares outstanding, basic and diluted		13,274,836		341,014
Net loss per common unit and share, basic and diluted	$	(3.81)	$	(52.24)

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

Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:


	Year Ended December 31,
	2019	2018
Common stock options issued and outstanding	3,225,725	—
Restricted stock subject to future vesting	1,289,437	2,503,744
	4,515,162	2,503,744

Investments	12 Months Ended
Investments	Dec. 31, 2019
Investments
Investments	13. Investments MapKure In June 2019, the Company announced the formation of MapKure, an entity jointly owned by the Company and BeiGene. BeiGene licensed to MapKure exclusive rights to BGB‑3245, an oral, small molecule selective inhibitor of monomeric and dimeric forms of activating BRAF mutations, including V600 BRAF mutations, non-V600 BRAF mutations and RAF fusions. MapKure intends to advance BGB‑3245 through clinical development for solid tumor patients harboring BRAF driver mutations and BRAF fusions that were observed to be sensitive to the compound in preclinical studies. In addition to the Company’s equity ownership in MapKure, the Company has appointed a member to each of MapKure’s joint steering committee and board of directors. The Company will also contribute to clinical development and other operational activities for BGB‑3245 through a service agreement with MapKure. The Company purchased 3,500,000 Series A preferred units of MapKure, or a 25% ownership interest, of the outstanding units for $3.5 million, and BeiGene received 10,000,000 Series A preferred units as payment for its contributed intellectual property, or a 71.4% ownership interest. Two individuals each purchased 250,000 Series A preferred units, or 1.8% ownership interest each. Upon the first anniversary of the initial closing (the “Second Closing”), MapKure is obligated to sell another 4,000,000 Series A preferred units to the same two individuals and the Company. At the Second Closing, the Company is obligated to purchase 3,500,000 Series A preferred units, which will increase the Company’s ownership to 38.9%. The Company determined that MapKure is a variable interest entity. The Company is not the primary beneficiary as the Company does not have the power to direct the activities that most significantly impact the economic performance of MapKure. Accordingly, the Company does not consolidate the financial statements of MapKure and accounts for this investment using the Equity method of accounting. The Company reaffirmed its assessment as of December 31, 2019. In accordance with ASC 323-10-35-6, the Company records its portion of MapKure’s earnings or losses based on a one quarter lag. For the year ended December 31, 2019, the Company recognized a $2.6 million loss for its portion of MapKure’s losses. The Company’s investment in MapKure is included in “Equity method investments” in the Consolidated Balance Sheet as of December 31, 2019. The balance of the Company’s investment was $1.0 million at December 31, 2019, representing the maximum exposure to loss as a result of the Company’s involvement with MapKure.

Selected Quarterly Financial Data (unaudited)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Data (unaudited)

14. Selected Quarterly Financial Data (unaudited)

The following table provides the selected quarterly financial data for the years ended December 31, 2019 and December 31, 2018:


	Year Ended December 31, 2019
(in thousands except share and per share data)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
Loss from operations	$	(11,688)	$	(14,851)	$	(15,329)	$	(17,371)
Net loss attributable to common stockholders		(3,680)		(13,847)		(16,833)		(16,217)
Per common share:
Net loss per unit, basic and diluted		(5.41)		(15.75)
Net loss per share, basic and diluted						(1.77)		(0.39)


	Year Ended December 31, 2018
(in thousands except share and per share data)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
Loss from operations	$	(2,592)	$	(4,222)	$	(5,229)	$	(6,448)
Net loss attributable to common stockholders		(2,566)		(4,024)		(5,004)		(6,219)
Per common share:
Net loss per unit, basic and diluted		(19.35)		(18.50)		(11.55)		(10.82)

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Summary of Significant Accounting Policies

Basis of Presentation

These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP).

Principles of Consolidation

Use of Estimates

Segment Information

Fair Value of Financial Instruments

Level 1 — Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets, or liabilities.

Level 3 — Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).

Cash and Cash Equivalents

Concentration of Credit Risk

Property and Equipment

Research and Development

General and Administrative

General and administrative expenses consist primarily of payroll and employee related costs, rent and utilities, infrastructure, corporate insurance, office expenses and professional fees.

Equity-Based Compensation Expense

Equity-based compensation expense

Stock compensation expense is recognized using the straight-line method, based on the grant date fair value, over the requisite service period of the award, which is generally the vesting term.

The Company recognizes forfeitures at the time of the actual forfeiture event in accordance with the adoption of the guidance per Accounting Standard Update (“ASU”) No. 2016‑09.

For stock options issued, the Company estimates the grant date fair value and the resulting stock-based compensation expense using the Black-Scholes option-pricing model.

Fair value of common stock.

Expected dividend — The Company has never paid dividends on its common units or stock and has no plans to pay dividends on its common stock. Therefore, the expected dividend yield is zero.

Net Loss per Unit and Share

Income Taxes

Recently Adopted Accounting Pronouncements


		Fiscal year ended December 31, 2018
Statement of Cash Flows Caption		Presentation prior to adoption of ASU 2016-17		Presentation after adoption of ASU 2016-18
Changes in operating assets and liabilities- Other assets	$		(1,043)	$	(503)
Net cash used in operating activities			(14,706)		(14,166)
Net increase in Cash and Cas Equivalents			35,377		35,917
Cash and Cash Equivalents Ending Balance			45,648		46,188

Recently Issued Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Summary of Significant Accounting Policies

Reclassifications in the statement of cash flows


		Fiscal year ended December 31, 2018
Statement of Cash Flows Caption		Presentation prior to adoption of ASU 2016-17		Presentation after adoption of ASU 2016-18
Changes in operating assets and liabilities- Other assets	$		(1,043)	$	(503)
Net cash used in operating activities			(14,706)		(14,166)
Net increase in Cash and Cas Equivalents			35,377		35,917
Cash and Cash Equivalents Ending Balance			45,648		46,188

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2019

Property and Equipment

Property and equipment, net


	December 31,
(in thousands)	2019	2018	Useful Life
Leasehold improvements	855	293	Estimated life or lease term, whichever is shorter
Computer equipment	122	27	3 years
Furniture	31	18	5 years
	1,008	338
Less accumulated depreciation	(213)	(21)
	795	317

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2019

Accrued Expenses

Schedule of accrued expenses


	December 31,
(in thousands)	2019		2018
Accrued professional fees	$	793	$	1,040
Accrued compensation and benefits		3,147		1,178
Accrued research and development		4,447		—
Accrued other		566		350
	$	8,953	$	2,568

Equity-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of equity-based compensation expense related to restricted stock and stock options


	Year Ended	Year Ended
(in thousands)	December 31, 2019	December 31, 2018
Research and development	731	164
General and administrative	2,378	905
Total equity compensation expenses	3,109	1,069

Unit options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of the changes in the Company's options during the period


	Number	Weighted Average
	of Awards	Exercise Price
Outstanding at December 31, 2017 and December 31, 2018	—	$	—
Granted	148,415		1.65
Outstanding at March 29, 2019	148,415		1.65

Stock options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of the changes in the Company's options during the period


			Weighted
			Average
		Weighted	Remaining
		Average	Contractual	Aggregate
		Exercise	Life	Intrinsic
	Shares	Price	(Years)	Value
Outstanding at March 29, 2019	148,415	1.65	—	—
Granted	3,177,233	5.21	—	—
Exercised	(9,080)	2.30	—	—
Forfeited/cancelled	(90,843)	2.18	—	—
Outstanding at December 31, 2019	3,225,725	5.08	9.4	107,771,472
Exercisable at December 31, 2019	409,174	2.78	9.3	14,611,604

Incentive units

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of the changes in the Company's restricted stock


	Number of	Weighted Average Grant
	Units	Date Fair Value
Outstanding at December 31, 2017	—	$	—
Granted	3,290,929		1.12
Vested	(401,824)		1.05
Forfeited	(385,361)		0.92
Unvested and outstanding at December 31, 2018	2,503,744		1.25
Vested	(228,209)		0.81
Forfeited	(12,570)		1.45
Unvested and outstanding at March 29, 2019	2,262,965		1.24

Restricted stock

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of the changes in the Company's restricted stock


		Weighted
		Average
	Number	Grant Date
	of Shares	Fair Value
Unvested and outstanding at March 29, 2019	2,262,965	1.24
Vested	(737,530)	1.26
Forfeited	(235,998)	1.36
Unvested and outstanding at December 31, 2019	1,289,437	1.21

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies

Schedule of future minimum lease obligations


	Premises Operating
(in thousands)	Leases
2020		1,344
2021		1,372
2022		1,297
2023		135
Total Obligations	$	4,148

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Taxes

Schedule of principal components of the Subsidiaries deferred tax assets


	As of December 31,
(in thousands)	2019		2018
Deferred tax assets:
Net operating loss carryforwards	$	16,252	$	3,342
Research and development credits		706		403
Orphan drug credit		71
Deferred rent		242		312
Accrued expenses		212		46
Depreciation		34		—
Stock compensation		496		—
Section 195 startup costs		—		1,270
Total deferred tax assets		18,013		5,373
Deferred tax liability		—		—
Valuation allowance		(18,013)		(5,373)
Net deferred tax assets	$	—	$	—

Schedule of reconciliation of U.S. statutory income tax rate to effective tax rate


	Year Ended December 31,
	2019		2018
Statutory tax rate	21.00	%	21.00	%
Federal and state return to provision adjustments	(0.01)		(1.08)
Research and development credit	0.57		2.02
Other	(0.03)		(0.04)
Change in valuation allowance	(21.53)		(21.90)
Effective tax rate	—	%	—	%

Net Loss per Unit and Share and Unaudited Pro Forma Net Loss per Share - (Tables)

12 Months Ended

Dec. 31, 2019

Net Loss per Unit and Share and Unaudited Pro Forma Net Loss per Share

Schedule of Basic and diluted net loss per share


	Year Ended December 31,
(In thousands, except share, unit, per-share and per-unit data)	2019		2018
Numerator:
Net loss	$	(58,306)	$	(17,813)
Net gain attributable to extinguishment of Series A convertible preferred and Junior Series A convertible preferred units		7,729		—
Net loss attributable to common stockholders	$	(50,577)	$	(17,813)
Denominator:
Weighted average common units and shares outstanding, basic and diluted		13,274,836		341,014
Net loss per common unit and share, basic and diluted	$	(3.81)	$	(52.24)

Schedule of potential common units not included in the calculation of the diluted net loss per unit and share


	Year Ended December 31,
	2019	2018
Common stock options issued and outstanding	3,225,725	—
Restricted stock subject to future vesting	1,289,437	2,503,744
	4,515,162	2,503,744

Selected Quarterly Financial Data (unaudited) - (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Data (unaudited)


	Year Ended December 31, 2019
(in thousands except share and per share data)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
Loss from operations	$	(11,688)	$	(14,851)	$	(15,329)	$	(17,371)
Net loss attributable to common stockholders		(3,680)		(13,847)		(16,833)		(16,217)
Per common share:
Net loss per unit, basic and diluted		(5.41)		(15.75)
Net loss per share, basic and diluted						(1.77)		(0.39)


	Year Ended December 31, 2018
(in thousands except share and per share data)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
Loss from operations	$	(2,592)	$	(4,222)	$	(5,229)	$	(6,448)
Net loss attributable to common stockholders		(2,566)		(4,024)		(5,004)		(6,219)
Per common share:
Net loss per unit, basic and diluted		(19.35)		(18.50)		(11.55)		(10.82)

Nature of Operations (Details) $ / shares in Units, $ in Millions			1 Months Ended
	Sep. 12, 2019 $ / shares shares	Sep. 12, 2019 USD ($) $ / shares shares	Aug. 31, 2019 $ / shares	Dec. 31, 2019 $ / shares	Dec. 31, 2018 $ / shares
Subsidiary, Sale of Stock [Line Items]
Conversion rate	6.5810
Reverse stock split			0.1520
Common stock par value \| $ / shares			$ 0.0001	$ 0.0001	$ 0.0001
IPO
Subsidiary, Sale of Stock [Line Items]
Units issued to certain employees		10,350,000
Share Price \| $ / shares	$ 18.00	$ 18.00
Net proceeds from the IPO \| $		$ 169.7
Underwriting discounts and commissions \| $		13.0
Issuance costs \| $		$ 3.5
Number of shares converted		196,076,779
Number of shares issued upon conversion	29,794,359	29,794,359
Preferred stock outstanding	0	0

Nature of Operations - Series B convertible preferred (Details) - Series B convertible preferred stock $ / shares in Units, $ in Millions	1 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares
Class of Stock [Line Items]
Number of shares authorized to issue \| shares	86,639,279
Price per unit \| $ / shares	$ 1.4428
Proceeds from issuance of convertible stock	$ 125.0
Issuance costs	$ 0.4

Nature of Operations - Reorganization (Details)	Mar. 29, 2019 shares
Series A convertible preferred unit
Reorganizations [Line Items]
Number of stock per unit	1
Junior Series A convertible preferred unit
Reorganizations [Line Items]
Number of stock per unit	1
Common units
Reorganizations [Line Items]
Number of stock per unit	1
Incentive units
Reorganizations [Line Items]
Number of stock per unit	1
Unit options
Reorganizations [Line Items]
Number of stock per unit	1

Nature of Operations - Series A and Junior Series A convertible preferred Units (Details)	1 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares	Apr. 30, 2018 USD ($) $ / shares shares	Aug. 31, 2017 USD ($) tranche item $ / shares shares
Series A convertible preferred unit
Preferred Units, Preferred Partners' Capital Account [Abstract]
Number of preferred units authorized \| shares			103,000,000
Price per unit \| $ / shares			$ 1.00
Number of tranches \| tranche			3
Gross cash proceeds from issuance			$ 103,000,000
Junior Series A convertible preferred unit
Preferred Units, Preferred Partners' Capital Account [Abstract]
Number of preferred units authorized \| shares			6,437,500
Issuance of units (in shares) \| shares			6,437,500
Gross cash proceeds from issuance			$ 0
Number of license agreements for the development and commercialization of products received for issuance of preferred units \| item			4
Fair value of preferred units			$ 2,000,000
First tranche, August 2017 \| Series A convertible preferred unit
Preferred Units, Preferred Partners' Capital Account [Abstract]
Issuance of units (in shares) \| shares			13,200,001
Gross cash proceeds from issuance			$ 13,200,000
Issuance costs			$ 600,000
Second tranche, April 2018 \| Series A convertible preferred unit
Preferred Units, Preferred Partners' Capital Account [Abstract]
Price per unit \| $ / shares		$ 1.00
Issuance of units (in shares) \| shares		50,399,999
Gross cash proceeds from issuance		$ 50,400,000
Issuance costs		$ 24,372
Third tranche, March 2019 \| Series A convertible preferred unit
Preferred Units, Preferred Partners' Capital Account [Abstract]
Price per unit \| $ / shares	$ 1.00
Issuance of units (in shares) \| shares	39,400,000
Gross cash proceeds from issuance	$ 39,400,000
Issuance costs	$ 32,694

Risks and Liquidity (Details) - USD ($) $ in Thousands	1 Months Ended		4 Months Ended		12 Months Ended
Risks and Liquidity (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Risks and Liquidity
Accumulated deficit					$ (73,029)	$ (22,452)
Working Capital					319,400	43,400
Cash and cash equivalents					327,652	45,648
Net increase in cash and cash equivalents			$ 10,271		282,004	35,917
Proceeds from issuance of common stock, net of issuance costs					169,730
Proceeds from issuance of Series A convertible preferred shares, net of issuance costs		$ 39,400	12,554		39,367	50,376
Proceeds from issuance of Series B convertible preferred shares, net of issuance costs		$ 124,600			124,590
Net loss			$ (4,639)	$ (4,639)	$ (58,306)	$ (17,813)
IPO
Risks and Liquidity
Proceeds from issuance of common stock, net of issuance costs	$ 169,700

Summary of Significant Accounting Policies - Unaudited Pro Forma Information, Segment Information & Cash and Cash Equivalents (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)
Segment Information
Number of Operating Segments \| segment	1
Cash and Cash Equivalents
Cash and Cash Equivalents, at Carrying Value \| $	$ 327,652	$ 45,648

Summary of Significant Accounting Policies - Research and Development (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Research and Development Expense [Abstract]
Prepaid research and development expenses	$ 0.7	$ 0.5

Summary of Significant Accounting Policies - Equity-based compensation expense (Details)	12 Months Ended
	Dec. 31, 2019 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Vesting percentage	25.00%
Expected dividend yield	$ 0
First tranche, August 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	12 months
Second tranche, April 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	36 months

Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Details) $ in Thousands	4 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) subsidiary	Dec. 31, 2018 USD ($)
Statement of Cash Flows Caption
Number of wholly owned taxable subsidiaries \| subsidiary		5
Changes in operating assets and liabilities- Other assets		$ (656)	$ (503)
Net cash used in operating activities	$ (2,239)	(47,444)	(14,166)
Net increase in cash and cash equivalents	10,271	282,004	35,917
Cash and Cash Equivalents Ending Balance	$ 10,271	$ 328,192	46,188
Spring Works Therapeutics, LLC
Statement of Cash Flows Caption
Ownership percentage		100.00%
ASU 2016-18 \| Presentation prior to adoption
Statement of Cash Flows Caption
Changes in operating assets and liabilities- Other assets			(1,043)
Net cash used in operating activities			(14,706)
Net increase in cash and cash equivalents			35,377
Cash and Cash Equivalents Ending Balance			$ 45,648

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property and Equipment
Property, Plant and Equipment, Gross	$ 1,008	$ 338
Less accumulated depreciation	(213)	(21)
Property, Plant and Equipment, Net	795	317
Leasehold improvements
Property and Equipment
Property, Plant and Equipment, Gross	855	293
Computer equipment
Property and Equipment
Property, Plant and Equipment, Gross	$ 122	$ 27
Property, Plant and Equipment, Useful Life	3 years	3 years
Furniture
Property and Equipment
Property, Plant and Equipment, Gross	$ 31	$ 18
Property, Plant and Equipment, Useful Life	5 years	5 years

Property and Equipment – Additional Information (Details) - USD ($)	4 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Property and Equipment
Depreciation expense	$ 3,000	$ 192,000	$ 17,000

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Expenses
Accrued professional fees	$ 793	$ 1,040
Accrued compensation and benefits	3,147	1,178
Accrued research and development	4,447
Accrued other	566	350
Accrued expenses	$ 8,953	$ 2,568

Equity-Based Compensation - 2019 Equity Incentive Plan (Details) - shares		12 Months Ended
	Aug. 30, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years
Employee and Non employee \| Equity Incentive Plan 2019 \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive units available for issuance	3,537,225
Percentage of annual increase in the shares	5.00%
Vesting period	4 years
Shares available for future issuance		3,562,524

Equity-Based Compensation - 2019 Equity Plan (Details) - shares	Jul. 29, 2019	Jun. 04, 2019	Mar. 29, 2019
Stock options \| 2019 Stock Option and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units authorized	6,700,197	5,382,828	5,292,355

Equity-Based Compensation - Equity-based compensation expense related to restricted stock and stock options (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total equity compensation expenses	$ 3,109	$ 1,069
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total equity compensation expenses	731	164
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total equity compensation expenses	$ 2,378	$ 905

Equity-Based Compensation - 2018 Equity Plan (Details) - Incentive units - 2018 Equity Incentive Plan - shares	12 Months Ended
	Dec. 31, 2018	Jan. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units authorized	3,008,645	2,738,929
Increase in number of units	269,716

Equity-Based Compensation - 2019 Employee Stock Purchase Plan (Details) - 2019 Employee Stock Purchase Plan	Aug. 30, 2019 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance	442,153
Automatic increase in to shares authorized by the number of shares	663,229
Automatic increase in to shares authorized as percentage of outstanding stock	1.00%

Equity-Based Compensation - Stock options (Details) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Weighted Average Remaining Contractual Life and Aggregate Intrinsic Value
Stock compensation expense			$ 3,109,000	$ 1,069,000
Stock options
Number of Award
Outstanding at the beginning		148,415
Granted		3,177,233
Exercised		(9,080)
Forfeited/cancelled		(90,843)
Outstanding at the end		3,225,725	3,225,725
Exercisable		409,174	409,174
Weighted Average Exercise Price
Outstanding at the beginning (in dollars per share)		$ 1.65
Granted (in dollars per share)		5.21
Exercised (in dollars per share)		2.30
Forfeited/cancelled (in dollars per share)		2.18
Outstanding at the end (in dollars per share)		5.08	$ 5.08
Exercisable (in dollars per share)		$ 2.78	$ 2.78
Weighted Average Remaining Contractual Life and Aggregate Intrinsic Value
Outstanding at the end (in years)		9 years 4 months 24 days
Exercisable (in years)		9 years 3 months 18 days
Outstanding at the end (in dollars)		$ 107,771,472	$ 107,771,472
Exercisable (in dollars)		14,611,604	$ 14,611,604
Stock options \| 2019 Stock Option and Incentive Plan
Weighted Average Remaining Contractual Life and Aggregate Intrinsic Value
Minimum risk-free interest rate			1.45%
Maximum risk-free interest rate			2.47%
Expected dividend yield			0.00%
Unrecognized compensation expense, options		$ 9,900,000	$ 9,900,000
Share compensation recognition period			4 years
Stock compensation expense			$ 1,600,000
Stock options \| 2019 Stock Option and Incentive Plan \| Minimum
Weighted Average Remaining Contractual Life and Aggregate Intrinsic Value
Expected term			5 years 9 months
Expected volatility			68.10%
Stock options \| 2019 Stock Option and Incentive Plan \| Maximum
Weighted Average Remaining Contractual Life and Aggregate Intrinsic Value
Expected term			6 years 3 months
Expected volatility			71.00%
Unit options
Number of Award
Granted	148,415
Outstanding at the end	148,415
Weighted Average Exercise Price
Granted (in dollars per share)	$ 1.65
Outstanding at the end (in dollars per share)	$ 1.65

Equity-Based Compensation - CEO performance Award (Details) $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2019 installment $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Stock compensation expense \| $			$ 3,109	$ 1,069
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive units issued \| shares		3,177,233
Exercise price of option \| $ / shares		$ 5.21
Stock options \| CEO Performance Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive units issued \| shares	176,411
Exercise price of option \| $ / shares	$ 7.50
Service of CEO	4 years
Vesting period	4 years
Vesting period , number of monthly installments \| installment	48
Number of trading day on which average closing price is based	60 days
Average closing price \| $ / shares	$ 28.49
Unrecognized compensation expense, options \| $		$ 1,000	$ 1,000
Share compensation recognition period			3 years 5 months 1 day
Stock options \| CEO Performance Award \| Stock option compensation expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense \| $			$ 300

Equity-Based Compensation - Restricted stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Weighted Average Grant Date Fair Valued
Stock compensation expense			$ 3,109	$ 1,069
Restricted stock
Number of Units
Outstanding at the beginning		2,262,965
Vested		(737,530)
Forfeited		(235,998)
Unvested and outstanding at the end		1,289,437	1,289,437
Weighted Average Grant Date Fair Valued
Outstanding at the beginning (in dollars per share)		$ 1.24
Vested (in dollars per share)		1.26
Forfeited (in dollars per share)		1.36
Unvested and outstanding at the end (in dollars per share)		$ 1.21	$ 1.21
Unrecognized compensation expense, options		$ 800	$ 800
Share compensation recognition period			2 years 9 months
Stock compensation expense			$ 1,500
Incentive units
Number of Units
Outstanding at the beginning	2,503,744		2,503,744
Granted				3,290,929
Vested	(228,209)			(401,824)
Forfeited	(12,570)			(385,361)
Unvested and outstanding at the end	2,262,965			2,503,744
Weighted Average Grant Date Fair Valued
Outstanding at the beginning (in dollars per share)	$ 1.25		$ 1.25
Granted (in dollars per share)				$ 1.12
Vested (in dollars per share)	0.81			1.05
Forfeited (in dollars per share)	1.45			0.92
Unvested and outstanding at the end (in dollars per share)	$ 1.24			$ 1.25

License and Collaboration Agreements (Details) $ in Thousands	3 Months Ended	4 Months Ended	12 Months Ended
	Oct. 31, 2017 USD ($) item shares	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expenses		$ 2,799	$ 42,545	$ 9,898
Pfizer \| License agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of license agreements with rights to certain technologies \| item	4
Minimum period after first commercial sale on country-by-country basis	10 years
Pfizer \| License agreement \| Nirogacestat
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Maximum milestone payments under agreement	$ 232,500
Pfizer \| License agreement \| Mirdametinib
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Maximum milestone payments under agreement	$ 229,800
Pfizer \| License agreement \| Junior Series A convertible preferred unit
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Preferred Stock, Shares Issued \| shares	6,437,500
Gross cash proceeds from issuance	$ 0
BeiGene, Ltd \| clinical collaboration agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expenses			$ 1,000	$ 400

Commitments and Contingencies (Details)	1 Months Ended	4 Months Ended	12 Months Ended
Commitments and Contingencies (Details)	Oct. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Aug. 31, 2018 Option
Operating Leases
Rent expense		$ 42,000	$ 1,600,000	$ 500,000
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2020			1,344,000
2021			1,372,000
2022			1,297,000
2023			135,000
Total obligations			$ 4,148,000
Durham, NC
Operating Leases
Lease term					5 years
Number of renewal options \| Option					2
Renewal term					5 years
Stamford, CT
Operating Leases
Security Deposit	$ 500,000
Cash received from previous tenant	$ 1,500,000

Income Taxes - Deferred Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 16,252	$ 3,342
Research and development credits	706	403
Orphan drug credit	71
Deferred rent	242	312
Accrued expenses	212	46
Depreciation	34
Stock compensation	496
Section 195 startup costs		1,270
Total deferred tax assets	18,013	5,373
Valuation allowance	$ (18,013)	$ (5,373)

Income Taxes - Reconciliation of U.S. Statutory Income Tax Rate to Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of the U.S. statutory income tax rate to the Company's effective tax rate
Statutory tax rate	21.00%	21.00%
Federal and state return to provision adjustments	(0.01%)	(1.08%)
Research and development credit	0.57%	2.02%
Other	(0.03%)	(0.04%)
Change in valuation allowance	(21.53%)	(21.90%)
Effective tax rate	0.00%	0.00%

Income Taxes - Additional information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) subsidiary	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Income Taxes
Number of wholly owned taxable subsidiaries \| subsidiary	5
Corporate tax rate (as a percent)	21.00%	21.00%
Increase in valuation allowance	$ 12.6
Effective tax rate	0.00%	0.00%
Accrued interest or penalties	$ 0.0
Spring Works Therapeutics, LLC
Income Taxes
Ownership percentage	100.00%
Internal revenue service
Income Taxes
Net operating loss carryforwards	$ 75.7
Federal net operating loss carryforwards	$ 55.4	$ 16.0	$ 4.3
Available to offset	80.00%
Tax credit carryforwards	$ 0.8
State
Income Taxes
Net operating loss carryforwards	0.6
City
Income Taxes
Net operating loss carryforwards	$ 3.8

Related Party Transactions (Details) - USD ($) $ in Millions	4 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2019	Dec. 31, 2018
Director
Related Party Transaction [Line Items]
Consulting and BOD expenses	$ 0.1	$ 0.2	$ 0.3

Net Loss per Share and Unit - Basic and diluted net loss per Share (Details) - USD ($) $ in Thousands	3 Months Ended								4 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Net Loss per Unit and Share and Unaudited Pro Forma Net Loss per Share
Net loss attributable to common stockholders									$ (4,639)	$ (4,639)	$ (58,306)	$ (17,813)
Net gain attributable to extinguishment of Series A convertible preferred and Junior Series A convertible preferred units											7,729
Net loss attributable to common stockholders, basic and diluted	$ (16,217)	$ (16,833)	$ (13,847)	$ (3,680)	$ (6,219)	$ (5,004)	$ (4,024)	$ (2,566)	$ (4,639)		$ (50,577)	$ (17,813)
Weighted average common units and shares outstanding, basic and diluted											13,274,836	341,014
Net loss per common unit and share, basic and diluted											(3.81%)	(52.24%)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Loss per Share and Unit - Common Units (Details)	12 Months Ended
Net Loss per Share and Unit - Common Units (Details)	Dec. 31, 2017 shares
Net Loss per Unit and Share and Unaudited Pro Forma Net Loss per Share
Vested common units outstanding	0

Net Loss per Share and Unit - potential common units not included in the calculation of the diluted net loss per unit and share (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	4,515,162	2,503,744
Common stock options issued and outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	3,225,725
Restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	1,289,437	2,503,744

Investments (Details) - USD ($)	1 Months Ended	12 Months Ended
Investments (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2019
Investment in Mapkure			$ 976,000
Income (Loss) from Equity Method Investments			(2,614,000)
Individual One \| Series A Preferred Units
Shares purchased under the equity method investments	250,000
Ownership Interest	1.80%
Individual Two \| Series A Preferred Units
Shares purchased under the equity method investments	250,000
Ownership Interest	1.80%
BeiGene, Ltd \| Series A Preferred Units
Shares purchased under the equity method investments	10,000,000
Ownership Interest	71.40%
MapKure
Investment in Mapkure			1,000,000
Income (Loss) from Equity Method Investments			$ (2,600,000)
MapKure \| Series A Preferred Units
Investment in Mapkure	$ 3,500,000
Number of units obligated to sell	4,000,000
Preferred units purchased	3,500,000
Ownership Interest	25.00%
MapKure \| Series A Preferred Units \| Forecast
Shares purchased under the equity method investments		3,500,000
Ownership Interest		38.90%

Selected Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								4 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Loss from operations	$ (17,371)	$ (15,329)	$ (14,851)	$ (11,688)	$ (6,448)	$ (5,229)	$ (4,222)	$ (2,592)	$ (4,660)	$ (59,239)	$ (18,491)
Net loss attributable to common stockholders	$ (16,217)	$ (16,833)	$ (13,847)	$ (3,680)	$ (6,219)	$ (5,004)	$ (4,024)	$ (2,566)	$ (4,639)	$ (50,577)	$ (17,813)
Per common share:
Net loss per unit, basic and diluted			$ (15.75)	$ (5.41)	$ (10.82)	$ (11.55)	$ (18.50)	$ (19.35)			$ (52.24)
Net loss per share, basic and diluted	$ (0.39)	$ (1.77)
Vested common units outstanding												0