Deciphera Pharmaceuticals (DCPH) 10-K9 Feb 212020 FY Annual reportFinancial data

Company Profile

Cover Page

Cover Page - USD ($)	12 Months Ended
Cover Page - USD ($)	Dec. 31, 2020	Jan. 31, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-38219
Entity Registrant Name	DECIPHERA PHARMACEUTICALS, INC.
Entity Address, State or Province	MA
City Area Code	781
Local Phone Number	209-6400
Title of 12(b) Security	Common Stock, $0.01 Par Value
Trading Symbol	DCPH
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Smaller Reporting Company	false
Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		57,625,943
Entity Public Float			$ 2,347,432,255
Documents Incorporated by Reference	Portions of the registrant's Proxy Statement for its 2021 Annual Meeting of Stockholders, which the registrant intends to file pursuant to Regulation 14A with the Securities and Exchange Commission not later than 120 days after the registrant's fiscal year ended December 31, 2020, are incorporated by reference into Part III of this Annual Report on Form 10-K.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0001654151
Current Fiscal Year End Date	--12-31
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	30-1003521
Entity Address, City or Town	Waltham
Entity Address, Address Line One	200 Smith Street
Entity Address, Postal Zip Code	02451

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 135,897	$ 120,320
Short-term marketable securities	416,033	459,256
Accounts receivable, net	13,896	0
Inventory	5,716	0
Prepaid expenses and other current assets	12,489	13,832
Total current assets	584,031	593,408
Long-term marketable securities	9,375	0
Long-term investments—restricted	3,102	1,510
Property and equipment, net	9,583	6,333
Operating lease assets	36,341	21,158
Total assets	642,432	622,409
Current liabilities:
Accounts payable	12,308	19,575
Accrued expenses and other current liabilities	55,227	38,716
Operating lease liabilities	2,457	1,747
Total current liabilities	69,992	60,038
Operating lease liabilities, net of current portion	28,764	15,904
Total liabilities	98,756	75,942
Commitments and contingencies (Note 14)
Stockholders' equity:
Common stock, $0.01 par value per share; 125,000,000 shares authorized; 57,596,144 shares and 51,617,639 shares issued and outstanding as of December 31, 2020 and 2019, respectively	576	516
Additional paid-in capital	1,297,557	1,033,819
Accumulated other comprehensive income (loss)	11	111
Accumulated deficit	(754,468)	(487,979)
Total stockholders' equity	543,676	546,467
Total liabilities and stockholders' equity	$ 642,432	$ 622,409

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	125,000,000	125,000,000
Common stock, shares issued (in shares)	57,596,144	51,617,639
Common stock, shares outstanding (in shares)	57,596,144	51,617,639

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Total revenues	$ 42,087	$ 25,000	$ 0
Cost and operating expenses:
Cost of sales	225	0	0
Research and development	198,970	157,610	82,887
Selling, General and Administrative Expense	114,082	68,116	21,212
Total cost and operating expenses	313,277	225,726	104,099
Loss from operations	(271,190)	(200,726)	(104,099)
Other income (expense):
Interest and other income, net	4,701	8,537	4,329
Interest expense	0	(67)	(84)
Total other income (expense), net	4,701	8,470	4,245
Net loss	$ (266,489)	$ (192,256)	$ (99,854)
Net loss per share—basic and diluted (in dollars per share)	$ (4.78)	$ (4.48)	$ (2.82)
Weighted average common shares outstanding—basic and diluted (in shares)	55,780,982	42,869,058	35,390,480
Comprehensive loss:
Net loss	$ (266,489)	$ (192,256)	$ (99,854)
Other comprehensive income (loss):
Unrealized gains (losses) on marketable securities	(100)	111	0
Total other comprehensive income (loss)	(100)	111	0
Total comprehensive loss	$ (266,589)	$ (192,145)	$ (99,854)

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Shares	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017		32,591,686
Beginning balance at Dec. 31, 2017	$ 183,973	$ 326	$ 379,516	$ 0	$ (195,869)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)		4,945,000
Issuance of common stock sold in public offering, net of underwriting discounts, commissions, and offering costs	185,259	$ 50	185,209
Issuance of common stock upon exercise of stock options (in shares)		140,074
Issuance of common stock under stock option and incentive and employee stock purchase plans	915	$ 1	914
Stock-based compensation expense	9,688		9,688
Net loss	(99,854)				(99,854)
Ending balance (in shares) at Dec. 31, 2018		37,676,760
Ending balance at Dec. 31, 2018	279,981	$ 377	575,327	0	(295,723)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)		12,432,431
Issuance of common stock sold in public offering, net of underwriting discounts, commissions, and offering costs	431,780	$ 124	431,656
Issuance of common stock upon exercise of stock options (in shares)		1,508,448
Issuance of common stock under stock option and incentive and employee stock purchase plans	6,441	$ 15	6,426
Stock-based compensation expense	20,410		20,410
Unrealized gains (losses) on marketable securities	111			111
Net loss	(192,256)				(192,256)
Ending balance (in shares) at Dec. 31, 2019		51,617,639
Ending balance at Dec. 31, 2019	546,467	$ 516	1,033,819	111	(487,979)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)		3,953,365
Issuance of common stock sold in public offering, net of underwriting discounts, commissions, and offering costs	206,276	$ 40	206,236
Issuance of common stock under stock option and incentive and employee stock purchase plans (in shares)		2,025,140
Issuance of common stock under stock option and incentive and employee stock purchase plans	$ 20,385	$ 20	20,365
Issuance of common stock upon exercise of stock options (in shares)	1,881,892
Stock-based compensation expense	$ 37,137		37,137
Unrealized gains (losses) on marketable securities	(100)			(100)
Net loss	(266,489)				(266,489)
Ending balance (in shares) at Dec. 31, 2020		57,596,144
Ending balance at Dec. 31, 2020	$ 543,676	$ 576	$ 1,297,557	$ 11	$ (754,468)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (266,489)	$ (192,256)	$ (99,854)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	37,137	20,410	9,688
Depreciation expense	2,305	830	317
Noncash lease expense	2,834	958	0
Gain on disposal of equipment	(7)	0	0
Net accretion of discounts on marketable securities	(1,611)	(3,999)	0
Changes in operating assets and liabilities:
Accounts receivable	(13,896)	0	0
Inventory	(3,241)	0	0
Prepaid expenses and other current assets	(1,772)	(10,321)	(5,770)
Accounts payable	(7,533)	10,862	3,991
Accrued expenses and other current liabilities	13,923	24,189	4,477
Operating lease liabilities	(1,333)	(319)	0
Other long-term liabilities	0	350	368
Net cash flows used in operating activities	(239,683)	(149,296)	(86,783)
Cash flows from investing activities:
Purchases of marketable securities	(1,096,769)	(817,142)	0
Maturities of marketable securities	627,913	261,216	0
Sales of marketable securities	504,216	100,780	0
Purchases of property and equipment	(5,316)	(4,935)	(1,125)
Proceeds from sale of equipment	7	0	0
Increase in restricted investments	(1,592)	(441)	(1,069)
Net cash flows provided by (used in) investing activities	28,459	(460,522)	(2,194)
Cash flows from financing activities:
Proceeds from public offerings, net of underwriting discounts and commissions	207,231	432,400	185,933
Repayment of notes payable to related party	0	(1,294)	(187)
Payments of public offering costs	(815)	(620)	(674)
Proceeds from stock option exercises and employee stock purchase plan	20,385	5,888	915
Net cash flows provided by financing activities	226,801	436,374	185,987
Net increase (decrease) in cash and cash equivalents	15,577	(173,444)	97,010
Cash and cash equivalents at beginning of period	120,320	293,764	196,754
Cash and cash equivalents at end of period	135,897	120,320	293,764
Supplemental disclosure of cash flow information:
Cash paid for interest	0	67	84
Addition of operating lease asset included in accrued expenses and other current liabilities	0	562	0
Supplemental disclosure of non-cash investing and financing activities:
Amounts capitalized under build-to-suit lease transaction	0	0	11,885
Purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities	239	661	0
Unsettled exercise of stock options	$ 0	$ 553	$ 0

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	12 Months Ended
Nature of the Business and Basis of Presentation	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	Nature of the Business and Basis of Presentation Deciphera Pharmaceuticals, Inc. (the Company) is a biopharmaceutical company focused on discovering, developing, and delivering important new medicines to patients for the treatment of cancer. The Company is leveraging its proprietary switch-control kinase inhibitor platform and deep expertise in kinase biology to develop a broad portfolio of innovative medicines. The Company has one approved drug, QINLOCK® (ripretinib), referred to as QINLOCK, which was developed through its proprietary platform. Beyond QINLOCK, the Company is developing three clinical stage drug candidates and advancing its research-stage programs. The Company wholly owns QINLOCK and all of its drug candidates with the exception of a development and commercialization out-license agreement for QINLOCK in the People's Republic of China, Hong Kong, Macau, and Taiwan, referred to as Greater China. The Company is preparing for a potential launch of QINLOCK in Europe and the Company has entered, and intends in the future to enter, into select distributor arrangements to offer QINLOCK in geographies where the Company does not intend to distribute QINLOCK on its own, such as Australia and Canada. On May 15, 2020, QINLOCK was approved by the United States (U.S.) Food and Drug Administration (FDA) for the treatment of adult patients with advanced gastrointestinal stromal tumor (GIST) who have received prior treatment with three or more kinase inhibitors, including imatinib. Following FDA approval of QINLOCK, in May 2020, the Company launched QINLOCK commercially in the U.S. In June 2020, QINLOCK was authorized for sale in Canada by Health Canada for the treatment of adult patients with advanced GIST who have received prior treatment with imatinib, sunitinib, and regorafenib. In July 2020, the Australian Therapeutic Goods Administration approved QINLOCK for the treatment of adult patients with advanced GIST who have received prior treatment with three or more kinase inhibitors, including imatinib. The Company is subject to risks and uncertainties common to companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, market acceptance and the successful commercialization of QINLOCK or any of the Company's current or future drug candidates for which it receives marketing approval, competition for QINLOCK or any of the Company's current or future drug candidates for which it receives marketing approval, protection of proprietary technology, ability to complete late-stage clinical trials, ability to obtain and maintain regulatory approvals, compliance with government regulations, the impact of the novel coronavirus (COVID-19) pandemic on its operations, and the ability to secure additional capital to fund operations. QINLOCK and the Company's drug candidates currently under development will require significant additional research and development efforts, including extensive preclinical and/or clinical testing and regulatory approval. In addition to supporting its research and development efforts, the Company will be required to invest in the Company's commercial capabilities and infrastructure, to support its launch and commercialization of QINLOCK, the Company's first and recently approved drug, and any current or future drug candidate for which the Company obtains marketing approval. These efforts require significant amounts of additional capital, adequate personnel and infrastructure, and extensive compliance-reporting capabilities. Even if the Company's drug development and commercialization efforts are successful, it is uncertain when, if ever, the Company will realize substantial revenue from product sales of QINLOCK or any current or future drug candidates for which it receives marketing approval. The full extent to which the COVID-19 pandemic, or the future outbreak of any other highly infectious or contagious diseases, may impact the Company's business, including its preclinical studies, clinical trial operations, or commercialization efforts will depend on continuously changing circumstances, which are highly uncertain and cannot be predicted at this time, such as the duration of such pandemic including future waves of infection, new strains of the virus that causes COVID-19, or the broad availability of effective vaccines, the actions taken to contain the pandemic or mitigate its impact, and the direct and indirect economic effects of the pandemic and containment measures, among others. The Company is continuing to monitor the long-term impact of COVID-19, if any, on its financial condition and results of operations. The ongoing fluidity of this situation precludes any prediction as to the full impact of the COVID-19 pandemic but it could have a material adverse effect on the Company's business, financial condition, and results of operations. The COVID-19 pandemic may also have the effect of heightening the risks to which the Company is subject, including various aspects of the Company's preclinical studies and ongoing clinical trials, the reliance on third parties in the Company's supply chain for materials and manufacturing of the Company's drug and drug candidates, disruptions in health regulatory agencies' operations globally, the volatility of the Company's common stock, and its ability to access capital markets, and the Company's ability to successfully launch, commercialize, and generate revenue from sales of QINLOCK. In June 2018, the Company issued and sold 4,945,000 shares of its common stock in a follow-on public offering at a public offering price of $40.00 per share, resulting in net proceeds of $185.3 million after deducting underwriting discounts and commissions and other offering expenses. In the third quarter of 2019, the Company issued and sold 12,432,431 shares of its common stock in a follow-on public offering at a public offering price of $37.00 per share, resulting in net proceeds of $431.8 million after deducting underwriting discounts and commissions and other offering expenses. In February 2020, the Company issued and sold 3,659,090 shares of its common stock in a follow-on public offering at a public offering price of $55.00 per share, resulting in net proceeds of $188.4 million after deducting underwriting discounts and commissions and other offering expenses. In August 2020, the Company entered into an Open Market Sale Agreement℠ (the Sales Agreement) with Jefferies LLC (Jefferies), pursuant to which the Company may issue and sell shares of its common stock having aggregate offering proceeds of up to $200.0 million (the Shares) from time to time through Jefferies as its sales agent. Upon delivery of a placement notice and subject to the terms and conditions of the Sales Agreement, Jefferies may sell the Shares by any method permitted by law deemed to be an "at the market offering" as defined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended. The Company may sell the Shares in amounts and at times to be determined by the Company from time to time subject to the terms and conditions of the Sales Agreement, but it has no obligation to sell any Shares under the Sales Agreement. The Company or Jefferies may suspend or terminate the offering of Shares upon notice to the other party and subject to other conditions. During the year ended December 31, 2020, the Company issued 294,275 shares resulting in net proceeds of $17.9 million after deducting underwriting discounts and commissions and other offering expenses under the Sales Agreement. As of December 31, 2020, there was up to $181.3 million available for future issuance under the Sales Agreement. The accompanying consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities, and commitments in the ordinary course of business. Since inception, the Company has incurred recurring losses including net losses of $266.5 million, $192.3 million, and $99.9 million for the years ended December 31, 2020, 2019, and 2018, respectively. As of December 31, 2020, the Company had an accumulated deficit of $754.5 million. The Company expects to continue to generate operating losses for the foreseeable future. The Company expects that its cash, cash equivalents, and marketable securities of $561.3 million as of December 31, 2020 will be sufficient to fund its operating expenses and capital expenditure requirements through at least 12 months from the issuance date of these consolidated financial statements. The future viability of the Company is dependent on its ability to raise additional capital to fund its operations. The Company will need to obtain substantial additional funding in connection with continuing operations. If the Company is unable to raise capital when needed, or on attractive terms, it could be forced to delay, reduce, or eliminate its research or drug development programs or certain commercialization efforts. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all. These consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated. Certain prior year amounts have been reclassified to conform to current year presentation. These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the U.S. (GAAP).

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, product revenue reserves, the accrual for research and development expenses, and the valuation of stock-based option awards. Estimates are periodically reviewed in light of changes in circumstances, facts, and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates. Segment Information The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company's singular focus is discovering, developing, and delivering important new medicines to patients for the treatment of cancer by tackling key mechanisms of drug resistance that limit the rate and/or durability of response to existing cancer therapies. Substantially all of the Company's tangible assets are held in the U.S. Revenues In accordance with Accounting Standards Codification (ASC) Topic 606, Revenue from Contracts with Customers (ASC 606), an entity recognizes revenue when its customer obtains control of promised goods or services in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. Product Revenues In May 2020, the Company began generating product revenue from sales of QINLOCK to specialty distributors and specialty pharmacies in the U.S. following the approval of QINLOCK by the FDA on May 15, 2020 for the treatment of adult patients with advanced GIST who have received prior treatment with three or more kinase inhibitors, including imatinib. The Company recognizes product revenues, net of variable consideration related to certain allowances and accruals, when the customer takes control of the product, which is typically upon delivery to the customer. Product revenue is recorded at the net sales price, or transaction price. The Company records product revenue reserves, which are classified as a reduction in product revenues, to account for the components of variable consideration. Variable consideration includes the following components: chargebacks, government rebates, trade discounts and allowances, product returns, and other incentives, which are described below. These reserves are based on estimates of the amounts earned or to be claimed on the related sales and are classified as reductions of accounts receivable (if the amount is payable to the Company's customer) or a liability (if the amount is payable to a party other than the Company's customer, other than product returns, which are recorded as liabilities). The Company's estimates of reserves established for variable consideration are calculated based upon a consistent application of the expected value method, which is the sum of probability-weighted amounts in a range of possible consideration amounts. These estimates reflect the Company's historical experience, current contractual and statutory requirements, specific known market events and trends, industry data, forecasted customer buying, and payment patterns. The amount of variable consideration that is included in the transaction price may be subject to constraint and is included in net product revenues only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration received may ultimately differ from the Company's estimates. If actual results vary, the Company adjusts these estimates, which could have an effect on earnings in the period of adjustment. Chargebacks and administrative fees: Chargebacks for discounts represent the Company's estimated obligations resulting from contractual commitments to sell product to qualified healthcare providers and government agencies at prices lower than the list prices charged to the customers who directly purchase the product from the Company. The customers charge the Company for the difference between what the customers pay the Company for the product and the customer's ultimate contractually committed or government required lower selling price to the qualified healthcare providers. As part of the Company's contractual commitments to sell product to qualified healthcare providers, the Company pays fees for administrative services, such as account management and data reporting. Government rebates: Government rebates consist of Medicare, Tricare, and Medicaid rebates. These reserves are recorded in the same period the related revenue is recognized. For Medicare, the Company also estimates the number of patients in the prescription drug coverage gap for whom it will owe a rebate under the Medicare Part D program. Trade discounts and allowances: The Company provides the customers with discounts that are explicitly stated in the contracts and recorded in the period the related product revenue is recognized. In addition, the Company also receives sales order management, inventory management, and data services from the customers in exchange for certain fees. Product returns: The Company estimates the amount of its product sales that may be returned by its customers and records this estimate in the period the related product revenue is recognized. The Company currently estimates product return liabilities based on available industry data and its visibility into the inventory remaining in the distribution channel. Other incentives: Other incentives include co-payment assistance provided to qualified patients, whereby the Company may provide financial assistance to patients with prescription drug co-payments required by the patient's insurance provider. Reserves for co-payment assistance are recorded in the same period the related revenue is recognized. Collaboration Revenues In June 2019, the Company entered into a License Agreement (the Zai License Agreement) with an affiliate of Zai Lab (Shanghai) Co., Ltd. (Zai), pursuant to which the Company granted Zai exclusive rights to develop and commercialize QINLOCK, including certain follow-on compounds (the Licensed Products), in Greater China (the Territory). In February 2020, the Company entered into a Supply Agreement (the Zai Supply Agreement), as required by terms in the Zai License Agreement, pursuant to which the Company will supply the Licensed Products to Zai for use in the Territory for clinical trials as well as commercial inventory, if QINLOCK obtains regulatory approval in the Territory. Subject to the Zai Supply Agreement, costs incurred by the Company for external manufacturing services are reimbursed by Zai. The Company accounts for its license and supply agreements with Zai under ASC 606. The Zai License Agreement includes development and regulatory milestone payments. Therefore, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant cumulative revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company's control or the licensee's control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. The Zai License Agreement also includes sales-based royalties for the license of intellectual property, including milestone payments based on the level of sales. As the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied. The Company recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied, either at a point in time or over time, and if over time, recognition is based on the use of an output or input method. For additional information on the Company's license and supply agreements, please read Note 3, Revenues , to these consolidated financial statements. Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of 90 days or less at the date of purchase to be cash equivalents. Marketable Securities Marketable securities consist of investments with original maturities greater than 90 days at the date of purchase. As of December 31, 2020 and 2019, the Company's marketable securities were comprised of debt securities and the Company considers its marketable securities portfolio to be available-for-sale. Available-for-sale marketable securities are classified as current or non-current based on each instrument's underlying effective maturity date and for which the Company has the intent and ability to hold the investment for a period of greater than 12 months. Marketable securities with maturities of less than 12 months from the balance sheet date are classified as current and are included in short-term marketable securities in the consolidated balance sheets. Marketable securities with maturities greater than 12 months from the balance sheet date for which we have the intent and ability to hold the investment for greater than 12 months are classified as non-current and are included in long-term marketable securities in the consolidated balance sheets. Available-for-sale marketable debt securities are recorded at fair market value and unrealized gains and losses are included in accumulated other comprehensive income (loss) in equity, net of related tax effects, except for the changes in allowance for expected credit losses, which are recorded in other income (expense), net, within the consolidated statements of operations and comprehensive loss. Realized gains and losses are reported in other income (expense), net, within the consolidated statements of operations and comprehensive loss on a specific identification basis. The Company conducts periodic reviews to identify and evaluate each investment in the Company's portfolio that has an unrealized loss to determine whether a credit loss exists. An unrealized loss exists when the current fair value of an individual security is less than its amortized cost basis. A credit loss is estimated by considering available information relevant to the collectability of the security and information about past events, current conditions, and reasonable and supportable forecasts. Any credit loss is recorded as a charge to other income (expense), net, not to exceed the amount of the unrealized loss. Unrealized losses other than the credit loss are recognized in accumulated other comprehensive income (loss). When determining whether a credit loss exists, the Company considers several factors, including whether the Company has the intent to sell the security or whether it is more likely than not that the Company will be required to sell the security prior to recovery of its amortized cost basis. If the Company has an intent to sell, or if it is more likely than not that the Company will be required to sell a debt security in an unrealized loss position before recovery of its amortized cost basis, the Company will write down the security to its fair value and record the corresponding charge as a component of other income (expense), net. No declines in value were deemed to be credit losses or other than temporary during the years ended December 31, 2020 or 2019, respectively. Concentrations of Credit Risk and of Significant Suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents, and marketable securities. The Company maintains all cash, cash equivalents, and marketable securities at accredited financial institutions, in amounts that exceed federally insured limits. The Company attempts to minimize the risks related to cash, cash equivalents, and marketable securities by investing in a range of financial instruments as defined by the Company. The Company has established guidelines related to credit ratings and maturities intended to safeguard principal balances and maintain liquidity. The marketable securities portfolio is maintained in accordance with the Company's investment policy, which defines allowable investments, specifies credit quality standards and limits the credit exposure of any single issuer. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company is dependent on third-party manufacturers to supply products for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs. Accounts Receivable Accounts receivable arise from product sales and amounts due from the Company's collaboration partners and have standard payment terms that generally require payment within 30 to 90 days. The amount from product sales represents amounts due from specialty distributors and specialty pharmacies in the U.S., which are recorded net of reserves for customer chargebacks, trade discounts and allowances, and other incentives to the extent such amounts are payable to the customer by the Company. The Company monitors economic conditions to identify facts or circumstances that may indicate that its receivables are at risk of collection. The Company provides reserves against accounts receivable for estimated losses, if any, that may result from a customer's inability to pay based on the composition of its accounts receivable, current economic conditions, and historical credit loss activity. Amounts determined to be uncollectible are charged or written-off against the reserve. During the year ended December 31, 2020, the Company did not record any expected credit losses related to outstanding accounts receivable. Inventory Inventories are stated at the lower of cost or estimated net realizable value with cost based on the first-in first-out method. Inventory that can be used in either the production of clinical or commercial products is expensed as research and development costs when identified for use in clinical trials. Prior to the regulatory approval of its drug candidates, the Company incurs expenses for the manufacture of drug product supplies to support clinical development that could potentially be available to support the commercial launch of those drugs. Until the date at which regulatory approval has been received or is otherwise considered probable, the Company records all such costs as research and development expenses. The Company performs an assessment of the recoverability of capitalized inventories during each reporting period and writes down any excess and obsolete inventory to its net realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded as a component of cost of sales in the Company's consolidated statements of operations and comprehensive loss. The determination of whether inventory costs will be realizable requires the use of estimates by management. If actual market conditions are less favorable than projected by management, additional write-downs of inventory may be required. Long-Term Investment — Restricted The Company's long-term investment—restricted balance is comprised of certificates of deposit. The certificates of deposit are held to secure letters of credit associated with the Company's lease for space at its headquarters location and to secure a credit card. The balances of such accounts are classified as non-current and are measured at carrying value in the consolidated balance sheets. Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows: Asset Category Estimated Useful Life Lab equipment 5 to 7 years Computer equipment 3 to 5 years Furniture and fixtures 7 years Leasehold improvements Shorter of life of lease Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in the consolidated statements of operations and comprehensive loss. The cost of normal, recurring, or periodic repairs and maintenance activities are expensed as incurred. Leases The Company adopted ASC Topic 842, Leases (ASC 842), using a modified retrospective approach, as of January 1, 2019, with no restatement of prior periods or cumulative adjustment to retained earnings. The Company elected the package of practical expedients, which permits the Company not to reassess under the new standards for prior conclusions about lease identification, lease classification and initial direct costs. The Company did not apply the hindsight practical expedient when determining the lease term for existing leases and assessing impairment of expired or existing leases. The Company elected the practical expedient for short-term leases and does not apply the recognition requirements to leases with a term of 12 months or less and recognizes those lease payments in the consolidated statements of operations and comprehensive loss on a straight-line basis over the lease term. The Company elected the practical expedient to not separate lease and non-lease components for real estate leases. The Company elected to utilize its incremental borrowing rate based on the remaining lease term as of the date of adoption. The Company accounts for a contract as a lease when it has the right to control the asset for a period of time while obtaining substantially all of the asset's economic benefits. The Company determines if an arrangement is a lease or contains an embedded lease at inception. For arrangements that meet the definition of a lease, the Company determines the initial classification and measurement of its operating right-of-use asset and operating lease liability at the lease commencement date and thereafter if modified. The lease term includes any renewal options that the Company is reasonably assured to exercise. The present value of lease payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its estimated secured incremental borrowing rate for that lease term. In addition to rent, the leases may require the Company to pay additional amounts for taxes, insurance, maintenance, and other expenses, which are generally referred to as non-lease components. The Company has elected to not separate lease and non-lease components. Only the fixed costs for lease components and their associated non-lease components are accounted for as a single lease component and recognized as part of a right-of-use asset and liability. Rent expense is recognized on a straight-line basis over the reasonably assured lease term based on the total lease payments and is included in operating expenses in the consolidated statements of operations and comprehensive loss. Impairment of Long-Lived Assets Long-lived assets consist of property, equipment, and operating lease assets. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets or asset group may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends, and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset group over its fair value, determined based on discounted cash flows. The Company did not record any impairment losses on long-lived assets during the years ended December 31, 2020, 2019, or 2018. Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies, and similar techniques. The Company's cash equivalents and marketable securities are carried at fair value, determined according to the fair value hierarchy described above. For additional information on the Company's fair value hierarchy, please read Note 4, Marketable Securities and Fair Value Measurements , to these consolidated financial statements. The carrying values of the Company's accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities. Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries, stock-based compensation and benefits, facilities costs, depreciation, manufacturing expenses, and external costs of outside vendors engaged to conduct preclinical development activities and trials. Prior to initial regulatory approval, the Company expenses costs relating to the production of inventory for the Company's drug and drug candidates as research and development expenses within the Company's consolidated statements of operations and comprehensive loss in the period incurred, unless the Company believes regulatory approval and subsequent commercialization of the drug candidate is probable and the Company expects the future economic benefit from sales of the drug to be realized. Advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses within the Company's consolidated balance sheets. The prepaid amounts are expensed as the related goods are delivered or the services are performed. Research Contract Costs and Accruals The Company has entered into various research and development contracts with research institutions and other companies both inside and outside of the U.S. These agreements are generally cancellable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or trials, including the phase or completion of events, invoices received, and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company's estimates. The Company's historical accrual estimates have not been materially different from the actual costs. Patent Costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as selling, general, and administrative expenses in the consolidated statements of operations and comprehensive loss. Stock-Based Compensation The Company measures all stock options and other stock-based awards granted to employees and directors based on the fair value on the date of the grant and recognizes compensation expense of those awards over the requisite service period, which is generally the vesting period of the respective award. The straight-line method of expense recognition is applied to all awards with service-only conditions while the graded-vesting method is applied to all awards with both service and performance conditions. The Company has granted performance-based awards under which the fair market value of the awards is expensed after assessing the probability that certain performance criteria will be met and the associated targeted payout level that is forecasted will be achieved. The Company accounts for forfeitures as they occur. The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive loss in the same manner in which the award recipient's payroll costs are classified or in which the award recipient's service payments are classified. Income Taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company's tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in its consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than- not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. Comprehensive Loss Comprehensive loss includes net loss as well as other changes in stockholders' equity (deficit) that result from transactions and economic events other than those with shareholders. For the years ended December 31, 2020 and 2019, the Company's other comprehensive income (loss) consisted of unrealized gains (losses) on marketable securities. For the year ended December 31, 2018, there was no difference between net loss and comprehensive loss. Net Loss per Share Basic net income (loss) per share is computed by dividing the net income (loss) by the weighted average number of common shares outstanding for the years ended December 31, 2020, 2019, and 2018. Diluted net income (loss) per share is computed by dividing the diluted net income (loss) by the weighted average number of common shares, including potential dilutive common shares assuming the dilutive effect of outstanding stock options and unvested restricted common stock, as determined using the treasury stock method. For periods in which the Company has reported net losses, diluted net loss per common share is the same as basic net loss per common share, since dilutive common shares are not assumed to have been issued if their effect is antidilutive. Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies that the Company adopts as of the specified effective date. Unless otherwise discussed below, the Company does not believe that the adoption of recently issued standards have or may have a material impact on its consolidated financial statements or disclosures. Credit Losses In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13). The FASB subsequently issued amendments to ASU 2016-13, which have the same effective date and transition date of January 1, 2020. This standard requires entities to estimate an expected lifetime credit loss on financial assets and report credit losses using an expected losses model rather than the incurred losses model that was previously used, and establishes additional disclosures related to credit risks. For available-for-sale debt securities with unrealized losses, the standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This standard limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and requires the reversal of previously recognized credit losses if fair value increases. This standard became effective for the Company on January 1, 2020, and adoption of this standard did not have a material impact on the consolidated financial statements and related disclosures.

Revenues

Revenues	12 Months Ended
Revenues	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenues	Revenues Product Revenues To date, the Company's only source of product revenues has been from the sales of QINLOCK, which began in May 2020, following the approval of QINLOCK by the FDA on May 15, 2020 for the treatment of adult patients with advanced GIST who have received prior treatment with three or more kinase inhibitors, including imatinib. For the year ended December 31, 2020, product revenues were $39.5 million, which consisted of $38.0 million of revenues in the U.S. and $1.5 million of revenues outside of the U.S. The Company primarily sells QINLOCK through specialty distributors and specialty pharmacies. The Company recognized revenues from three customers accounting for 57%, 24%, and 10% of gross product revenues for the year ended December 31, 2020. As of December 31, 2020, two customers individually accounted for approximately 59% and 20% of accounts receivable associated with the Company's product sales. Activity in each of the product revenue allowance and reserve categories is summarized as follows: (in thousands) Trade discounts and allowances Chargebacks and administrative fees Government rebates and other incentives Returns Total Balance as of December 31, 2019 $ — $ — $ — $ — $ — Provision related to sales in the current year 556 1,663 2,923 856 5,998 Credits and payments made (404) (1,399) (490) (324) (2,617) Balance as of December 31, 2020 $ 152 $ 264 $ 2,433 $ 532 $ 3,381 The total reserves described above are summarized as components of the Company's consolidated balance sheets as follows: (in thousands) December 31, 2020 Reduction of accounts receivable, net $ 363 Component of accrued expenses and other current liabilities 3,018 Total revenue-related reserves $ 3,381 Collaboration Revenues In June 2019, the Company entered into the Zai License Agreement, pursuant to which the Company granted Zai exclusive rights to develop and commercialize the Licensed Products in the Territory. The Company retains exclusive rights to, among other things, develop, manufacture, and commercialize the Licensed Products outside the Territory. Pursuant to the terms of the Zai License Agreement, the Company received an upfront cash payment of $20.0 million and became eligible to receive up to $185.0 million in potential development and commercial milestone payments, consisting of up to $50.0 million of development milestones and up to $135.0 million of commercial milestones. In addition, during the term of the Zai License Agreement, Zai will be obligated to pay the Company tiered percentage royalties ranging from low to high teens on potential annual net sales of the Licensed Products in the Territory, subject to adjustments in specified circumstances. Under the Zai License Agreement, the Company recognized revenues of $2.3 million during the year ended December 31, 2020, which consisted of the achievement of a $2.0 million development milestone in the second quarter of 2020 and $0.3 million in reimbursable costs. Under the Zai License Agreement, the Company recognized revenue of $25.0 million during the year ended December 31, 2019, which consisted of the $20.0 million upfront payment and a $5.0 million INTRIGUE study-related development milestone payment, which the Company believed to be probable of achievement in the second quarter of 2019 and was achieved in July 2019. Subject to the terms and conditions of the Zai License Agreement, Zai will be responsible for conducting the development and commercialization activities in the Territory related to the Licensed Products. Subject to specified exceptions, during the term of the Zai License Agreement, each party has agreed that neither it nor its affiliates nor, with respect to Zai, its sublicensees, will conduct any development, manufacturing, and commercialization activities in the Territory that may be deemed competitive with the Licensed Products. In addition, under the Zai License Agreement, each party has granted the other party specified intellectual property licenses to enable the other party to perform its obligations and exercise its rights under the Zai License Agreement, including license grants to enable each party to conduct research, development and commercialization activities pursuant to the terms of the Zai License Agreement. The Zai License Agreement will continue on a Licensed Product-by-Licensed Product and region-by-region basis until the later of (i) the abandonment, expiry or final determination of invalidity of the last valid claim within the Company's patent rights that covers the Licensed Product in such region in the Territory; (ii) the expiry of the regulatory exclusivity for such Licensed Product in such region; or (iii) the close of business of the day that is exactly ten (10) years after the date of the first commercial sale of such Licensed Product in such region. Subject to the terms of the Zai License Agreement, Zai may terminate the Zai License Agreement for convenience by providing written notice to the Company, which termination will be effective following a prescribed notice period. In addition, the Company may terminate the Zai License Agreement under specified circumstances if Zai or certain other parties challenge our patent rights or if Zai or its affiliates do not conduct certain development activities with respect to one or more Licensed Products for a specified period of time, subject to specified exceptions. Either party may terminate the Zai License Agreement for the other party's uncured material breach of a material term of the Zai License Agreement, with a customary notice and cure period, or insolvency. After termination (but not natural expiration), the Company is entitled to retain a worldwide and perpetual license from Zai to exploit the Licensed Products. On a region-by-region and a Licensed Product-by-Licensed Product basis, upon the natural expiration of the Zai License Agreement as described above, the licenses granted by the Company to Zai under the Zai License Agreement in such region with respect to the Licensed Product become fully paid-up, perpetual and irrevocable. The Company identified the following promises under the Zai License Agreement: (1) the exclusive license, with the right to grant sublicenses, granted in the Territory for the Licensed Products; (2) initial and continuing know-how transfer for the Licensed Products; (3) clinical supply of the Licensed Products; (4) participation in the joint steering committee (JSC); and (5) regulatory and technical assistance responsibilities. The Company determined that the exclusive license is distinct and constitutes one performance obligation that is a right to use the Company's intellectual property. The Company determined that the promises under the Zai License Agreement related to the know-how transfer, clinical and commercial supply, participation in the JSC, and the assistance responsibilities are immaterial in the context of the Zai License Agreement and therefore are excluded from the assessment of performance obligations. The Company also evaluated certain options and contingent obligations contained within the Zai License Agreement to determine if they provide Zai with any material rights. The Company concluded that the options and contingent obligations were not issued at a significant and incremental discount, and therefore do not provide Zai with a material right. As such, these options and contingent obligations were excluded as performance obligations and will be accounted for if and when they occur or are exercised. The Company determined that the upfront payment of $20.0 million and the $5.0 million INTRIGUE study-related development milestone were probable of achievement and that a significant reversal of cumulative revenue would not occur upon resolution of the uncertainty, and constitutes the consideration to be included in the transaction price as of the commencement of the arrangement. The transaction price, totaling $25.0 million, was allocated to the one performance obligation, which was satisfied at a point in time upon delivery of the license in June 2019, and therefore the Company recognized license revenue in the full amount of the transaction price during the second quarter of 2019. Additionally, in the second quarter of 2020, the Company determined that the $2.0 million development milestone was probable of achievement and that a significant reversal of cumulative revenue would not occur upon resolution of the uncertainty, and constitutes consideration to be included in the transaction of the arrangement. The remaining potential milestone payments that the Company is eligible to receive were excluded from the transaction price and were fully constrained based on the probability of achievement. The Company will reevaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and if necessary, the Company will adjust its estimate of the transaction price. Because the performance obligation has been satisfied, any additions to the transaction price would be fully recognized in the period. The Company assessed the Zai License Agreement to determine whether a significant financing component exists and concluded that a significant financing component does not exist. In February 2020, the Company entered into the Zai Supply Agreement, as required by terms in the Zai License Agreement, pursuant to which the Company will supply the Licensed Products to Zai for use in the Territory for clinical trials as well as commercial inventory, if QINLOCK obtains regulatory approval in the Territory. Subject to the Zai Supply Agreement, costs incurred by the Company for external manufacturing services are reimbursed by Zai. Under the Zai Supply Agreement, the Company recognized revenues of $0.4 million for external manufacturing services provided during the year ended December 31, 2020.

Marketable Securities and Fair

Marketable Securities and Fair Value Measurements	12 Months Ended
Marketable Securities and Fair Value Measurements	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Marketable Securities and Fair Value Measurements	Marketable Securities and Fair Value Measurements The following tables present marketable securities by contractual maturity and security type: As of December 31, 2020 (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Due within one year: U.S. government securities $ 298,335 $ 49 $ (1) $ 298,383 Commercial paper 62,037 9 (15) 62,031 Corporate debt securities 38,309 — (34) 38,275 Certificates of deposit 17,344 1 (1) 17,344 Due after one year through five years: U.S. government securities 9,370 5 — 9,375 Total $ 425,395 $ 64 $ (51) $ 425,408 As of December 31, 2019 (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Due within one year: Commercial paper $ 314,292 $ 74 $ (23) $ 314,343 U.S. government securities 78,612 48 (3) 78,657 Certificates of deposit 66,241 17 (2) 66,256 Total $ 459,145 $ 139 $ (28) $ 459,256 The following tables present information about the Company's financial assets measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values: As of December 31, 2020 (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 46,676 $ — $ 46,676 U.S. government securities — 30,000 — 30,000 Marketable securities: U.S. government securities — 307,758 — 307,758 Commercial paper — 62,031 — 62,031 Corporate debt securities — 38,275 — 38,275 Certificates of deposit — 17,344 — 17,344 Total $ — $ 502,084 $ — $ 502,084 As of December 31, 2019 (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 28,192 $ — $ 28,192 Certificates of deposit — 20,500 — 20,500 Marketable securities: Commercial paper — 314,343 — 314,343 U.S. government securities — 78,657 — 78,657 Certificates of deposit — 66,256 — 66,256 Total $ — $ 507,948 $ — $ 507,948 The tables above exclude certificates of deposit of $3.1 million and $1.5 million as of December 31, 2020 and December 31, 2019, respectively, that the Company held to secure a letter of credit associated with its leases and to secure a credit card account. The Company increased its credit card limit and corresponding certificate of deposit in the first quarter of 2020. The Company also increased its letter of credit and corresponding certificate of deposit associated with its leases in the fourth quarter of 2020. The certificates of deposit are Level 2 instruments and are measured at carrying value in the consolidated balance sheets in long-term investments—restricted and approximate fair value. For additional information on the letter of credit associated with the Company's leases, please read Note 7, Leases , to these consolidated financial statements. The fair value of Level 2 instruments classified as cash equivalents and marketable securities were determined through third-party pricing services. The pricing services use many observable market inputs to determine value, including reportable trades, benchmark yields, credit spreads, broker/dealer quotes, bids, offers, current spot rates, and other industry and economic events.

Inventory

Inventory	12 Months Ended
Inventory	Dec. 31, 2020
Inventory Disclosure [Abstract]
Inventory	Inventory The Company commenced the capitalization of QINLOCK inventory in May 2020 upon receiving FDA approval of QINLOCK. Capitalized inventory consisted of the following: (in thousands) December 31, 2020 Raw materials $ 1,352 Work in process 4,142 Finished goods 222 Total inventory $ 5,716 There were no inventory amounts written down as a result of excess, obsolescence, unmarketability, or other reasons charged to cost of sales during the year ended December 31, 2020.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
Property and Equipment, Net	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net consisted of the following: December 31, (in thousands) 2020 2019 Laboratory equipment $ 3,631 $ 2,195 Computer equipment 4,795 2,950 Furniture and fixtures 3,187 1,941 Leasehold improvements 1,895 908 Construction in progress 197 169 Total cost 13,705 8,163 Less: Accumulated depreciation (4,122) (1,830) Total property and equipment, net $ 9,583 $ 6,333 Depreciation expense was $2.3 million, $0.8 million, and $0.3 million for the years ended December 31, 2020, 2019, and 2018, respectively.

Leases

Leases	12 Months Ended
Leases	Dec. 31, 2020
Leases [Abstract]
Leases	Leases The Company leases real estate, including office and laboratory space. In May 2018, the Company entered into a lease for office space (the Initial Space) at 200 Smith Street in Waltham, Massachusetts (the Premises). The initial term of the lease expires in November 2029, unless terminated earlier in accordance with the terms of the lease. The Company is entitled to two five-year options to extend. The initial annual base rent is approximately $2.0 million and will increase annually for a total of $22.4 million over the lease term. In October 2019, the lease for the Initial Space commenced under ASC 842 and resulted in the addition of an operating lease asset of $21.2 million and corresponding lease liability of $17.0 million in the fourth quarter of 2019. The Premises became the Company's new headquarters in October 2019. Prior to the adoption of ASC 842, the Company was deemed to be the owner of the Initial Space during the construction period because of certain provisions within the lease agreement. As a result, as of December 31, 2018, the Company capitalized approximately $11.9 million (equal to the estimated cost of its leased portion of the Initial Space) as construction-in-progress within property and equipment, net and recorded a corresponding build-to-suit facility lease financing obligation. Under ASC 842, the Company was no longer considered the owner of the Initial Space and therefore the build-to suit asset and corresponding liabilities at December 31, 2018 were reversed as of the date of adoption of ASU 2016-02 on January 1, 2019 as the lease commencement date had not yet been met. In April 2019, the Company amended its lease for office space at the Premises to add an additional 38,003 square feet of space (the Additional Space) for a total of 82,346 square feet of space. The initial term of the lease for the Additional Space will expire in November 2029 unless terminated earlier in accordance with the terms of the lease and the Company is entitled to two five-year options to extend the lease. The initial annual base rent for the Additional Space is approximately $1.9 million and will increase annually for a total of $18.2 million over the lease term. In July 2020, the lease for the Additional Space commenced under ASC 842 and resulted in the addition of an operating lease asset of $16.5 million and a corresponding lease liability of $13.5 million in the third quarter of 2020. The Company is required to maintain a letter of credit associated with its leases at the Premises. The balances of the Company's certificate of deposit associated with the letter of credit for its leases at the Premises of $2.1 million and $1.1 million as of December 31, 2020 and 2019, respectively, were classified as long-term investment—restricted in the consolidated balance sheets. The Company increased the letter of credit and associated certificate of deposit by $1.0 million pursuant to the terms of the lease agreement for the Additional Space during the fourth quarter of 2020. In August 2020, the Company amended and restated its real estate leases primarily for office and laboratory space in Lawrence, Kansas (the 2020 Lawrence Lease Agreements). The initial term of the 2020 Lawrence Lease Agreements will expire on December 31, 2030 unless terminated earlier in accordance with the terms of the lease and the Company is entitled to two five-year options to extend the leases. The 2020 Lawrence Lease Agreements modified a previously existing operating lease which resulted in an additional operating lease asset of $1.4 million and a corresponding lease liability of $1.4 million during the third quarter of 2020. Additionally, as a result of the 2020 Lawrence Lease Agreements, some previously existing operating leases terminated as of December 31, 2020. The Company expects that additional new operating leases associated with additional lease space included in the 2020 Lawrence Lease Agreements will commence under ASC 842 in 2021. The Company's leases contain options to extend the lease terms; however, these extensions were not included in the operating lease assets and lease liabilities recorded on the consolidated balance sheets as they were not reasonably certain of being exercised. During the years ended December 31, 2020 and 2019, the Company was subject to certain lease agreements to accommodate short-term or temporary needs. The expenses related to the Company's short-term or temporary lease agreements are included in short-term lease costs for the years ended December 31, 2020 and 2019, as applicable. The Company's leases require the Company to pay for its share of certain operating expenses, taxes, and other expenses based on actual costs incurred and therefore, as the amounts are variable in nature, are expensed in the period incurred and included in variable lease costs for the years ended December 31, 2020 and 2019. Payment escalations specified in the leases are recognized on a straight-line basis over the lease terms. All of the Company's leases qualify as operating leases. The following table summarizes the presentation of the Company's operating leases in the consolidated balance sheet: December 31, (in thousands) 2020 2019 Operating lease assets $ 36,341 $ 21,158 Current operating lease liabilities $ 2,457 1,747 Operating lease liabilities, net of current portion 28,764 15,904 Total operating lease liabilities $ 31,221 $ 17,651 The components of lease expense were as follows: Year Ended December 31, (in thousands) 2020 2019 Operating lease cost $ 4,167 $ 1,223 Short-term lease cost 354 520 Variable lease cost 461 427 Total lease expense $ 4,982 $ 2,170 Additionally, as previously disclosed in the Company's 2018 Form 10-K and under the previous lease accounting standard, ASC 840, Leases, the Company recorded rent expense of $1.1 million during the year ended December 31, 2018. Future annual minimum lease payments under operating leases are as follows: (in thousands) As of December 31, 2020 2021 $ 4,143 2022 4,225 2023 4,308 2024 4,390 2025 4,472 Thereafter 18,520 Total future minimum lease payments 40,058 Less: imputed interest (8,837) Total operating lease liabilities $ 31,221 The weighted-average remaining lease term and weighted-average discount rate of the Company's operating leases are as follows: As of December 31, 2020 2019 Weighted-average remaining lease term in years 8.97 9.63 Weighted-average discount rate 5.60 % 5.36 % Supplemental disclosure of cash flow information related to the Company's operating leases included in cash flows used in operating activities in the consolidated statement of cash flows were as follows: Year Ended December 31, (in thousands) 2020 2019 Cash paid for amounts included in the measurement of operating lease liabilities $ 2,666 $ 532 Operating lease liabilities arising from obtaining operating lease assets $ 14,902 $ 17,144

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
Accrued Expenses and Other Current Liabilities	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following: December 31, (in thousands) 2020 2019 External research and development expenses $ 31,259 $ 20,462 Payroll and related expenses 17,255 12,902 Professional fees 3,306 3,810 Revenue-related reserves 3,018 — Other 389 1,542 Total accrued expenses and other current liabilities $ 55,227 $ 38,716

Common Stock

Common Stock	12 Months Ended
Common Stock	Dec. 31, 2020
Equity [Abstract]
Common Stock	Common Stock On June 11, 2018, the Company issued and sold 4,300,000 shares of its common stock in a follow-on public offering at a public offering price of $40.00 per share, resulting in net proceeds of $161.0 million after deducting underwriting discounts and commissions and other offering expenses. On June 20, 2018, the Company issued and sold an additional 645,000 shares of its common stock at the offering price of $40.00 per share, pursuant to the underwriters' full exercise of their option to purchase additional shares of common stock, resulting in additional net proceeds of $24.3 million after deducting underwriting discounts and commissions. On August 19, 2019, the Company issued and sold 10,810,810 shares of its common stock in a follow-on public offering at a public offering price of $37.00 per share, resulting in net proceeds of $375.4 million after deducting underwriting discounts and commissions and other offering expenses. On September 3, 2019, the Company issued and sold an additional 1,621,621 shares of its common stock at the offering price of $37.00 per share, pursuant to the underwriters' full exercise of their option to purchase additional shares of common stock, resulting in additional net proceeds of $56.4 million after deducting underwriting discounts and commissions. On February 19, 2020, the Company issued and sold 3,181,818 shares of its common stock in a follow-on public offering at a public offering price of $55.00 per share, resulting in net proceeds of $163.7 million after deducting underwriting discounts and commissions and other offering expenses. On February 25, 2020, the Company issued and sold an additional 477,272 shares of its common stock at the offering price of $55.00 per share, pursuant to the underwriters' full exercise of their option to purchase additional shares of common stock, resulting in additional net proceeds of $24.7 million after deducting underwriting discounts and commissions. In August 2020, the Company entered into the Sales Agreement with Jefferies, pursuant to which the Company may issue and sell shares of its common stock in "at-the-market" offerings having aggregate offering proceeds of up to $200.0 million from time to time through Jefferies as its sales agent. During the year ended December 31, 2020, the Company issued 294,275 shares resulting in net proceeds of $17.9 million under the Sales Agreement. As of December 31, 2020, there was up to $181.3 million available for future issuance under the Sales Agreement. For additional information on the Sales Agreement, please read Note 1, Nature of the Business and Basis of Presentation , to these consolidated financial statements.

Stock-Based Awards

Stock-Based Awards	12 Months Ended
Stock-Based Awards	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Awards	Stock-Based Awards 2017 Equity Incentive Plan The Company's 2017 Stock Option and Incentive Plan (the 2017 Plan) provides for the grant of equity-based incentive awards. The number of shares initially reserved for issuance of awards under the 2017 Plan was 2,655,831 shares of common stock and may be increased by the number of shares under the 2015 Equity Incentive Plan (the 2015 Plan) and the 2017 Plan that are forfeited, cancelled, repurchased by the Company, or otherwise surrendered. The 2017 Plan provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning on January 1, 2018, by 4% of the outstanding number of shares of our common stock on the immediately preceding December 31, or such lesser number of shares as determined by the Compensation Committee of the Company's Board of Directors. As of December 31, 2020, 1,828,021 remained available for issuance under the 2017 Plan. The number of shares reserved for issuance under the 2017 Plan was increased by 2,303,845 shares effective January 1, 2021. 2015 Equity Incentive Plan Under the 2015 Plan the Company was authorized to sell or issue common shares or restricted common shares, or to grant options for the purchase of common shares, share appreciation rights, and other awards, to employees, members of the board of directors, consultants, and advisors of the Company. Upon effectiveness of the 2017 Plan no further awards were available to be issued under the 2015 Plan. Both the 2017 and 2015 Plans provide that they be administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. The exercise prices for stock options may not be less than 100% of the fair market value of the common stock on the date of grant and the term of awards may not be greater than ten years. The Company bases fair value of common stock on the quoted market price. Vesting periods are determined at the discretion of the board of directors. Awards granted to employees and directors typically vest over four years. 2017 Employee Stock Purchase Plan The 2017 Employee Stock Purchase Plan (the ESPP) initially reserved and authorized the issuance of up to 306,750 shares of common stock to participating employees. The ESPP provides that the number of shares reserved and available for issuance will automatically increase each January 1, beginning on January 1, 2018 and each January 1 thereafter through January 1, 2027, by the least of (i) 1% of the outstanding number of shares of common stock on the immediately preceding December 31; (ii) 400,000; shares or (iii) such number of shares as determined by the ESPP administrator. As of December 31, 2020, 1,372,135 remained available for issuance under the ESPP Plan. The number of shares reserved for issuance under the ESPP was increased by 400,000 shares effective January 1, 2021. The purchase price of common stock under the ESPP is equal to 85% of the lesser of (i) the fair market value per share of the common stock on the first business day of an offering period and (ii) the fair market value per share of the common stock on the purchase date. The fair value of the discounted purchases made under the ESPP is calculated using the Black-Scholes option-pricing model, which is described in further detail within the "Stock Option Valuation" section below, on the date of the first day of the offering period. The fair value of the look-back provision plus the 15% discount is recognized as stock-based compensation expense in the consolidated statements of operations and comprehensive loss over the 6-month purchase period. Employees began participating in the ESPP program during the first offering period of the ESPP program in the second quarter of 2020. There were 37,298 shares of common stock issued under the ESPP during the year ended December 31, 2020. Stock Option Valuation The fair value of each stock option award is estimated on the date of grant using the Black-Scholes option-pricing model, which uses as inputs the fair value of the Company's common stock and assumptions for the volatility of its common stock, the expected term of stock-based awards, the risk-free interest rate for a period that approximates the expected term of stock-based awards, and the expected dividend yield. Prior to October 2017, the Company was privately-held and lacked company-specific historical and implied volatility information. Therefore, it estimates its expected share volatility based on the historical volatility of a set of publicly traded peer companies as well as the limited historical volatility of its own traded stock price. The Company estimated the expected term of its options using the "simplified" method for awards that qualify as "plain-vanilla" options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends on common shares and does not expect to pay any cash dividends in the foreseeable future. The assumptions that the Company used to determine the fair value of options granted to employees and directors were as follows, presented on a weighted average basis: Year Ended December 31, 2020 2019 2018 Risk-free interest rate 1.2 % 2.2 % 2.8 % Expected term (in years) 6.1 6.2 6.1 Expected volatility 77.2 % 74.5 % 73.3 % Expected dividend yield 0 % 0 % 0 % The following table summarizes the Company's option activity from January 1, 2020 to December 31, 2020: Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding as of December 31, 2019 6,750,939 $ 19.36 Granted 1,331,148 $ 54.79 Exercised (1,881,892) $ 9.96 Forfeited/Expired (487,856) $ 33.27 Outstanding as of December 31, 2020 5,712,339 $ 29.53 7.8 $ 158,204 Options vested and expected to vest as of December 31, 2020 5,712,339 $ 29.53 7.8 $ 158,204 Options exercisable as of December 31, 2020 2,873,038 $ 20.60 7.1 $ 104,889 The aggregate intrinsic value of options is calculated as the difference between the exercise price of the options and the fair value of the Company's common shares for those options that had exercise prices lower than the fair value of the Company's common shares. The aggregate intrinsic value of options exercised during the years ended December 31, 2020, 2019, and 2018 was $86.0 million, $53.2 million, and $4.4 million, respectively. The weighted average grant-date fair value per share of options granted during the years ended December 31, 2020, 2019, and 2018 was $36.71, $19.22, and $19.68, respectively. Restricted Stock Units The 2017 Plan provides for the award of restricted stock units. During the years ended December 31, 2020, 2019, and 2018, the Company granted restricted stock units to employees that were subject to time-based vesting conditions that lapse between one year and four years from date of grant, assuming continued employment. During 2019, the Company granted 57,400 restricted stock units at a weighted average grant date fair value of $34.43 that were subject to performance-based vesting conditions. Vesting of the performance-based restricted stock units was contingent upon meeting a specific performance obligation and continued employment through the service period. The performance criteria associated with the performance-based restricted stock units became probable and was achieved during the second quarter of 2020. As a result, 55,200 performance-based restricted units at a weighted average grant date fair value of $34.43 vested during 2020 and the fair value of the performance-based restricted units that vested during 2020 was $3.6 million. 2,200 performance-based restricted units at a weighted average grant date fair value of $34.43 were forfeited during 2020. The Company granted no performance-based restricted units in 2020 or 2018. As of December 31, 2020, there were no unvested performance-based restricted units. All restricted stock units currently granted have been classified as equity instruments as their terms require settlement in shares. Restricted stock units with time-based and performance-based vesting conditions are valued on the grant date using the grant date market price of the underlying shares. The table below summarizes the Company's time-based restricted stock unit activity from January 1, 2020 to December 31, 2020: Number Weighted Unvested at December 31, 2019 99,500 $ 29.58 Granted 426,155 $ 51.74 Vested (50,750) $ 28.93 Forfeited (36,280) $ 52.66 Unvested at December 31, 2020 438,625 $ 49.28 The fair value of time-based restricted stock units that vested during the years ended December 31, 2020 and 2019 were $2.3 million and $0.5 million, respectively. No restricted stock units vested during the year ended December 31, 2018. Stock-Based Compensation Expense Stock-based compensation expense was classified in the statements of operations and comprehensive loss as follows: Year Ended December 31, (in thousands) 2020 2019 2018 Research and development $ 17,443 $ 7,934 $ 4,021 Selling, general, and administrative 19,694 12,476 5,667 Total stock-based compensation $ 37,137 $ 20,410 $ 9,688 The following table summarizes share-based compensation expense associated with each of our share-based compensation arrangements: Year Ended December 31, (in thousands) 2020 2019 2018 Stock options $ 29,925 $ 19,328 $ 9,578 Time-based restricted stock units 4,424 1,082 110 Performance-based restricted stock units 1,907 — — Employee stock purchase plan 881 — — Total stock-based compensation expense $ 37,137 $ 20,410 $ 9,688 As of December 31, 2020, total unrecognized compensation cost related to the unvested share-based awards was $85.0 million, which is expected to be recognized over a weighted average of 2.5 years. During the year ended December 31, 2019, the Company recorded $2.4 million of stock-based compensation expense related to the modification of stock options pursuant to the transition agreement with its former President and Chief Executive Officer, which was classified within selling, general, and administrative expenses in the statements of operations and comprehensive loss.

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
401(k) Savings Plan	Dec. 31, 2020
Retirement Benefits [Abstract]
401(k) Savings Plan	401(k) Savings Plan Effective January 1, 2018, the Company adopted the 2018 401(k) Plan, a defined contribution plan under Section 401(k) of the Internal Revenue Code, whereby the Company provides matching contributions of 100% of each employee's contribution up to a maximum matching contribution of 3% of the employee's eligible compensation and at a rate of 50% of each employee's contribution in excess of 3% up to a maximum of 5% of the employee's eligible compensation. Total employer matching contributions related to the 2018 401(k) Plan were $2.3 million, $0.9 million, and $0.4 million for the years ended December 31, 2020, 2019, and 2018, respectively.

Net Loss per Share

Net Loss per Share	12 Months Ended
Net Loss per Share	Dec. 31, 2020
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic net income (loss) per share is computed by dividing the net income (loss) by the weighted average number of common shares outstanding for the period. Diluted net income (loss) per share is computed by dividing the diluted net income (loss) by the weighted average number of common shares, including potential dilutive common shares assuming the dilutive effect as determined using the treasury stock method. For periods in which the Company has reported net losses, diluted net loss per common share is the same as basic net loss per common share, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss for during each of the periods presented. Basic and diluted net loss per share was calculated as follows: Year Ended December 31, (in thousands, except share and per share amounts) 2020 2019 2018 Numerator: Net loss $ (266,489) $ (192,256) $ (99,854) Denominator: Weighted average common shares outstanding—basic and diluted 55,780,982 42,869,058 35,390,480 Net loss per share—basic and diluted $ (4.78) $ (4.48) $ (2.82) Common Stock Equivalents The following potential dilutive securities, presented based on amounts outstanding at the end of each reporting period, have been excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive impact: As of December 31, 2020 2019 2018 Options to purchase common stock 5,712,339 6,750,939 5,787,151 Unvested restricted stock units 438,625 156,900 25,000 Unvested employee stock purchase plan shares 30,826 — — Total 6,181,790 6,907,839 5,812,151

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes On October 2, 2017, immediately prior to the completion of its initial public offering (IPO), the Company engaged in a series of transactions whereby Deciphera Pharmaceuticals, LLC became a wholly owned subsidiary of Deciphera Pharmaceuticals, Inc., a Delaware corporation. As part of the transactions, shareholders of Deciphera Pharmaceuticals, LLC exchanged their shares of Deciphera Pharmaceuticals, LLC for shares of Deciphera Pharmaceuticals, Inc. on a one-for-5.65 basis (the Conversion). Prior to the Conversion on October 2, 2017, the Company had been treated as a partnership for tax purposes and had not been subject to U.S. federal or state income taxation. As a result, the Company had not recorded any U.S. federal or state income tax benefits for the net losses incurred prior to October 2, 2017 or for earned research and orphan drug credits as the operating losses incurred by the Company had been passed through to its members. Upon consummation of the Conversion on October 2, 2017, the Company became subject to Corporate U.S. federal and state income taxes. During the years ended December 31, 2020, 2019, and 2018, the Company reported net losses, and as a result, recorded no income tax benefits for the net operating losses (NOLs), due to its uncertainty of realizing a benefit from those items. A reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax rate is as follows: Year Ended December 31, 2020 2019 2018 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % State taxes, net of federal benefit 2.4 7.0 6.1 Research and orphan drug credit 2.1 5.4 9.6 Stock-based compensation 5.4 4.7 0.7 Permanent adjustments and other 0.5 (0.9) — Increase in deferred tax asset valuation allowance (31.4) (37.2) (37.4) Effective income tax rate — % — % — % During 2020, the Company completed a detailed study of its research and development and orphan drug credits. As a result, the Company adjusted its deferred tax asset balances and the impacts are included in the research and orphan drug credit line in the effective rate reconciliation above. The impacts of the decreases in the deferred tax asset balances have been completely offset by a decrease in the Company's valuation allowance which is included in the increase in deferred tax asset valuation allowance line in the reconciliation above. Net deferred tax assets consisted of the following: December 31, (in thousands) 2020 2019 Deferred tax assets (liabilities): Net operating loss carryforwards $ 159,192 $ 85,632 Research and orphan drug credit carryforwards 31,142 25,267 Stock-based compensation 8,928 5,535 Accrued expenses 3,779 2,951 Operating lease liabilities 9,321 5,841 Property and equipment (387) — Operating lease assets (8,811) (5,515) Other 16 (64) Total gross deferred tax assets 203,180 119,647 Valuation allowance (203,180) (119,647) Net deferred tax assets $ — $ — On December 22, 2017, the Tax Cuts and Jobs Act (TCJA) was signed into U.S. law. The TCJA includes a number of changes to existing tax law, including, among other things, a permanent reduction in the federal corporate income tax rate from a top marginal rate of 35% to a flat rate of 21%, effective as of January 1, 2018, as well as limitation of the deduction for net operating losses to 80% of annual taxable income and elimination of NOL carrybacks, in each case, for losses arising in taxable years beginning after December 31, 2017 (though any such net operating losses may be carried forward indefinitely). Further, on March 27, 2020, the previous U.S. President signed into law the Coronavirus Aid, Relief, and Economic Security Act (the CARES Act) in response to the U.S. COVID-19 pandemic, which, among other things, suspends the 80% limitation on the deduction for NOLs in taxable years beginning before January 1, 2021, permits a 5-year carryback of NOLs arising in taxable years beginning after December 31, 2017 and before January 1, 2021, and generally caps the limitation on the deduction for net interest expense at 50% of adjusted taxable income for taxable years beginning in 2019 and 2020. In addition, the CARES Act raises the corporate charitable deduction limit to 25% of taxable income and makes qualified improvement property generally eligible for 15-year cost-recovery and 100% bonus depreciation. The enactment of the CARES Act did not result in any material adjustments to the Company's income tax provision for the year ended December 31, 2020, or to its net deferred tax assets and related allowances as of December 31, 2020. The change in the valuation allowance was as follows: Year Ended December 31, (in thousands) 2020 2019 Valuation allowance as of beginning of year $ (119,647) $ (48,191) Net increases recorded to income tax provision (83,533) (71,456) Valuation allowance as of end of year $ (203,180) $ (119,647) As of December 31, 2020, the Company had NOL carryforwards for federal income tax purposes of $643.6 million, of which $16.6 million begin to expire in 2037 and $627.0 million may be carried forward indefinitely. As of December 31, 2020, the Company had NOL carryforwards for state income tax purposes of $479.2 million, which begin to expire in 2037. As of December 31, 2020, the Company also had available research and orphan drug credit carryforwards for federal and state income tax purposes of $28.8 million and $3.0 million, respectively, which begin to expire in 2037 and 2032, respectively. Utilization of the NOL carryforwards and research and orphan drug credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended (the Code), and similar state law due to ownership changes that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. If the Company experiences a change of control, as defined by Section 382 of the Code and similar state law, at any time since the IPO, utilization of the NOL carryforwards or research and orphan drug credit carryforwards may be subject to an annual limitation under Section 382 of the Code, which is determined by first multiplying the value of the Company's stock at the time of the ownership change by the applicable long-term tax-exempt rate, and then could be subject to additional adjustments, as required. Any limitation may result in expiration of a portion of the NOL carryforwards or research and orphan drug credit carryforwards before utilization. The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company's history of cumulative net losses incurred since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the deferred tax assets as of December 31, 2020. Management reevaluates the positive and negative evidence at each reporting period. The Company has not recorded any amounts for unrecognized tax benefits as of December 31, 2020. The Company will recognize interest and penalties related to uncertain tax positions in income tax expense when, if ever, it is in a taxable income position. As of December 31, 2020 and 2019, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company's statement of operations and comprehensive loss. The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending income tax examinations. The Company's tax years that are open under statute are from October 2, 2017 to the present. The Company's policy is to record interest and penalties related to income taxes as part of its income tax provision.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Purchase Commitments Associated with Commercial Supply Agreements The Company has entered into commercial supply agreements related to the supply of QINLOCK that require the Company to make binding forecasts for a certain amount of purchases. The related cancellation clauses would as a general matter require the Company to pay the full amount of these binding forecasts. As of December 31, 2020, the Company's contractual commitments for its commercial supply agreements were $8.8 million, of which $7.0 million is expected to be paid within one year and $1.8 million is expected to be paid between one Legal Proceedings The Company is not currently a party to any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses the costs related to its legal proceedings as they are incurred. Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners, and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and senior management that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
Selected Quarterly Financial Data (Unaudited)	Dec. 31, 2020
Quarterly Financial Data [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited) The following information has been derived from unaudited consolidated financial statements that, in the opinion of management, include all recurring adjustments necessary for a fair statement of such information: Three Months Ended (in thousands except per share data) Dec 31, Sep 30, Jun 30, Mar 31, Dec 31, Sep 30, Jun 30, Mar 31, Statements of Operations Data: Revenues $ 19,486 $ 15,449 $ 7,090 $ 62 $ — $ — $ 25,000 $ — Gross profit (1) 19,359 15,359 7,082 62 — — 25,000 — Loss from operations (62,999) (63,997) (68,932) (75,262) (70,373) (58,353) (22,975) (49,025) Net loss (62,740) (63,701) (67,241) (72,807) (67,216) (56,196) (21,460) (47,384) Net loss per share—basic and diluted $ (1.10) $ (1.13) $ (1.20) $ (1.36) $ (1.31) $ (1.28) $ (0.56) $ (1.25) (1) Gross profit is calculated as total revenues less cost of sales.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2020
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, product revenue reserves, the accrual for research and development expenses, and the valuation of stock-based option awards. Estimates are periodically reviewed in light of changes in circumstances, facts, and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.
Segment Information	Segment Information The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company's singular focus is discovering, developing, and delivering important new medicines to patients for the treatment of cancer by tackling key mechanisms of drug resistance that limit the rate and/or durability of response to existing cancer therapies. Substantially all of the Company's tangible assets are held in the U.S.
Revenues	Revenues In accordance with Accounting Standards Codification (ASC) Topic 606, Revenue from Contracts with Customers (ASC 606), an entity recognizes revenue when its customer obtains control of promised goods or services in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. Product Revenues In May 2020, the Company began generating product revenue from sales of QINLOCK to specialty distributors and specialty pharmacies in the U.S. following the approval of QINLOCK by the FDA on May 15, 2020 for the treatment of adult patients with advanced GIST who have received prior treatment with three or more kinase inhibitors, including imatinib. The Company recognizes product revenues, net of variable consideration related to certain allowances and accruals, when the customer takes control of the product, which is typically upon delivery to the customer. Product revenue is recorded at the net sales price, or transaction price. The Company records product revenue reserves, which are classified as a reduction in product revenues, to account for the components of variable consideration. Variable consideration includes the following components: chargebacks, government rebates, trade discounts and allowances, product returns, and other incentives, which are described below. These reserves are based on estimates of the amounts earned or to be claimed on the related sales and are classified as reductions of accounts receivable (if the amount is payable to the Company's customer) or a liability (if the amount is payable to a party other than the Company's customer, other than product returns, which are recorded as liabilities). The Company's estimates of reserves established for variable consideration are calculated based upon a consistent application of the expected value method, which is the sum of probability-weighted amounts in a range of possible consideration amounts. These estimates reflect the Company's historical experience, current contractual and statutory requirements, specific known market events and trends, industry data, forecasted customer buying, and payment patterns. The amount of variable consideration that is included in the transaction price may be subject to constraint and is included in net product revenues only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration received may ultimately differ from the Company's estimates. If actual results vary, the Company adjusts these estimates, which could have an effect on earnings in the period of adjustment. Chargebacks and administrative fees: Chargebacks for discounts represent the Company's estimated obligations resulting from contractual commitments to sell product to qualified healthcare providers and government agencies at prices lower than the list prices charged to the customers who directly purchase the product from the Company. The customers charge the Company for the difference between what the customers pay the Company for the product and the customer's ultimate contractually committed or government required lower selling price to the qualified healthcare providers. As part of the Company's contractual commitments to sell product to qualified healthcare providers, the Company pays fees for administrative services, such as account management and data reporting. Government rebates: Government rebates consist of Medicare, Tricare, and Medicaid rebates. These reserves are recorded in the same period the related revenue is recognized. For Medicare, the Company also estimates the number of patients in the prescription drug coverage gap for whom it will owe a rebate under the Medicare Part D program. Trade discounts and allowances: The Company provides the customers with discounts that are explicitly stated in the contracts and recorded in the period the related product revenue is recognized. In addition, the Company also receives sales order management, inventory management, and data services from the customers in exchange for certain fees. Product returns: The Company estimates the amount of its product sales that may be returned by its customers and records this estimate in the period the related product revenue is recognized. The Company currently estimates product return liabilities based on available industry data and its visibility into the inventory remaining in the distribution channel. Other incentives: Other incentives include co-payment assistance provided to qualified patients, whereby the Company may provide financial assistance to patients with prescription drug co-payments required by the patient's insurance provider. Reserves for co-payment assistance are recorded in the same period the related revenue is recognized. Collaboration Revenues In June 2019, the Company entered into a License Agreement (the Zai License Agreement) with an affiliate of Zai Lab (Shanghai) Co., Ltd. (Zai), pursuant to which the Company granted Zai exclusive rights to develop and commercialize QINLOCK, including certain follow-on compounds (the Licensed Products), in Greater China (the Territory). In February 2020, the Company entered into a Supply Agreement (the Zai Supply Agreement), as required by terms in the Zai License Agreement, pursuant to which the Company will supply the Licensed Products to Zai for use in the Territory for clinical trials as well as commercial inventory, if QINLOCK obtains regulatory approval in the Territory. Subject to the Zai Supply Agreement, costs incurred by the Company for external manufacturing services are reimbursed by Zai. The Company accounts for its license and supply agreements with Zai under ASC 606. The Zai License Agreement includes development and regulatory milestone payments. Therefore, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant cumulative revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company's control or the licensee's control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. The Zai License Agreement also includes sales-based royalties for the license of intellectual property, including milestone payments based on the level of sales. As the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied. The Company recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied, either at a point in time or over time, and if over time, recognition is based on the use of an output or input method. For additional information on the Company's license and supply agreements, please read Note 3, Revenues , to these consolidated financial statements.
Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of 90 days or less at the date of purchase to be cash equivalents.
Marketable Securities	Marketable Securities Marketable securities consist of investments with original maturities greater than 90 days at the date of purchase. As of December 31, 2020 and 2019, the Company's marketable securities were comprised of debt securities and the Company considers its marketable securities portfolio to be available-for-sale. Available-for-sale marketable securities are classified as current or non-current based on each instrument's underlying effective maturity date and for which the Company has the intent and ability to hold the investment for a period of greater than 12 months. Marketable securities with maturities of less than 12 months from the balance sheet date are classified as current and are included in short-term marketable securities in the consolidated balance sheets. Marketable securities with maturities greater than 12 months from the balance sheet date for which we have the intent and ability to hold the investment for greater than 12 months are classified as non-current and are included in long-term marketable securities in the consolidated balance sheets. Available-for-sale marketable debt securities are recorded at fair market value and unrealized gains and losses are included in accumulated other comprehensive income (loss) in equity, net of related tax effects, except for the changes in allowance for expected credit losses, which are recorded in other income (expense), net, within the consolidated statements of operations and comprehensive loss. Realized gains and losses are reported in other income (expense), net, within the consolidated statements of operations and comprehensive loss on a specific identification basis. The Company conducts periodic reviews to identify and evaluate each investment in the Company's portfolio that has an unrealized loss to determine whether a credit loss exists. An unrealized loss exists when the current fair value of an individual security is less than its amortized cost basis.
Concentrations of Credit Risk and of Significant Suppliers	Concentrations of Credit Risk and of Significant Suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents, and marketable securities. The Company maintains all cash, cash equivalents, and marketable securities at accredited financial institutions, in amounts that exceed federally insured limits. The Company attempts to minimize the risks related to cash, cash equivalents, and marketable securities by investing in a range of financial instruments as defined by the Company. The Company has established guidelines related to credit ratings and maturities intended to safeguard principal balances and maintain liquidity. The marketable securities portfolio is maintained in accordance with the Company's investment policy, which defines allowable investments, specifies credit quality standards and limits the credit exposure of any single issuer. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company is dependent on third-party manufacturers to supply products for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs.
Accounts Receivable	Accounts Receivable Accounts receivable arise from product sales and amounts due from the Company's collaboration partners and have standard payment terms that generally require payment within 30 to 90 days. The amount from product sales represents amounts due from specialty distributors and specialty pharmacies in the U.S., which are recorded net of reserves for customer chargebacks, trade discounts and allowances, and other incentives to the extent such amounts are payable to the customer by the Company. The Company monitors economic conditions to identify facts or circumstances that may indicate that its receivables are at risk of collection. The Company provides reserves against accounts receivable for estimated losses, if any, that may result from a customer's inability to pay based on the composition of its accounts receivable, current economic conditions, and historical credit loss activity. Amounts determined to be uncollectible are charged or written-off against the reserve. During the year ended December 31, 2020, the Company did not record any expected credit losses related to outstanding accounts receivable.
Inventory	Inventory Inventories are stated at the lower of cost or estimated net realizable value with cost based on the first-in first-out method. Inventory that can be used in either the production of clinical or commercial products is expensed as research and development costs when identified for use in clinical trials. Prior to the regulatory approval of its drug candidates, the Company incurs expenses for the manufacture of drug product supplies to support clinical development that could potentially be available to support the commercial launch of those drugs. Until the date at which regulatory approval has been received or is otherwise considered probable, the Company records all such costs as research and development expenses. The Company performs an assessment of the recoverability of capitalized inventories during each reporting period and writes down any excess and obsolete inventory to its net realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded as a component of cost of sales in the Company's consolidated statements of operations and comprehensive loss. The determination of whether inventory costs will be realizable requires the use of estimates by management. If actual market conditions are less favorable than projected by management, additional write-downs of inventory may be required.
Long-Term Investment-Restricted	Long-Term Investment — Restricted The Company's long-term investment—restricted balance is comprised of certificates of deposit. The certificates of deposit are held to secure letters of credit associated with the Company's lease for space at its headquarters location and to secure a credit card. The balances of such accounts are classified as non-current and are measured at carrying value in the consolidated balance sheets.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows: Asset Category Estimated Useful Life Lab equipment 5 to 7 years Computer equipment 3 to 5 years Furniture and fixtures 7 years Leasehold improvements Shorter of life of lease Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in the consolidated statements of operations and comprehensive loss. The cost of normal, recurring, or periodic repairs and maintenance activities are expensed as incurred.
Leases	Leases The Company adopted ASC Topic 842, Leases (ASC 842), using a modified retrospective approach, as of January 1, 2019, with no restatement of prior periods or cumulative adjustment to retained earnings. The Company elected the package of practical expedients, which permits the Company not to reassess under the new standards for prior conclusions about lease identification, lease classification and initial direct costs. The Company did not apply the hindsight practical expedient when determining the lease term for existing leases and assessing impairment of expired or existing leases. The Company elected the practical expedient for short-term leases and does not apply the recognition requirements to leases with a term of 12 months or less and recognizes those lease payments in the consolidated statements of operations and comprehensive loss on a straight-line basis over the lease term. The Company elected the practical expedient to not separate lease and non-lease components for real estate leases. The Company elected to utilize its incremental borrowing rate based on the remaining lease term as of the date of adoption. The Company accounts for a contract as a lease when it has the right to control the asset for a period of time while obtaining substantially all of the asset's economic benefits. The Company determines if an arrangement is a lease or contains an embedded lease at inception. For arrangements that meet the definition of a lease, the Company determines the initial classification and measurement of its operating right-of-use asset and operating lease liability at the lease commencement date and thereafter if modified. The lease term includes any renewal options that the Company is reasonably assured to exercise. The present value of lease payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its estimated secured incremental borrowing rate for that lease term. In addition to rent, the leases may require the Company to pay additional amounts for taxes, insurance, maintenance, and other expenses, which are generally referred to as non-lease components. The Company has elected to not separate lease and non-lease components. Only the fixed costs for lease components and their associated non-lease components are accounted for as a single lease component and recognized as part of a right-of-use asset and liability. Rent expense is recognized on a straight-line basis over the reasonably assured lease term based on the total lease payments and is included in operating expenses in the consolidated statements of operations and comprehensive loss.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets consist of property, equipment, and operating lease assets. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets or asset group may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends, and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. An impairment loss would be recognized when estimated
Fair Value Measurements	Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies, and similar techniques. The Company's cash equivalents and marketable securities are carried at fair value, determined according to the fair value hierarchy described above. For additional information on the Company's fair value hierarchy, please read Note 4, Marketable Securities and Fair Value Measurements , to these consolidated financial statements. The carrying values of the Company's accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries, stock-based compensation and benefits, facilities costs, depreciation, manufacturing expenses, and external costs of outside vendors engaged to conduct preclinical development activities and trials. Prior to initial regulatory approval, the Company expenses costs relating to the production of inventory for the Company's drug and drug candidates as research and development expenses within the Company's consolidated statements of operations and comprehensive loss in the period incurred, unless the Company believes regulatory approval and subsequent commercialization of the drug candidate is probable and the Company expects the future economic benefit from sales of the drug to be realized. Advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses within the Company's consolidated balance sheets. The prepaid amounts are expensed as the related goods are delivered or the services are performed.
Research Contract Costs and Accruals	Research Contract Costs and Accruals The Company has entered into various research and development contracts with research institutions and other companies both inside and outside of the U.S. These agreements are generally cancellable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or trials, including the phase or completion of events, invoices received, and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company's estimates. The Company's historical accrual estimates have not been materially different from the actual costs.
Patent Costs	Patent Costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as selling, general, and administrative expenses in the consolidated statements of operations and comprehensive loss.
Stock-Based Compensation	Stock-Based Compensation The Company measures all stock options and other stock-based awards granted to employees and directors based on the fair value on the date of the grant and recognizes compensation expense of those awards over the requisite service period, which is generally the vesting period of the respective award. The straight-line method of expense recognition is applied to all awards with service-only conditions while the graded-vesting method is applied to all awards with both service and performance conditions. The Company has granted performance-based awards under which the fair market value of the awards is expensed after assessing the probability that certain performance criteria will be met and the associated targeted payout level that is forecasted will be achieved. The Company accounts for forfeitures as they occur. The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive loss in the same manner in which the award recipient's payroll costs are classified or in which the award recipient's service payments are classified.
Income Taxes	Income Taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company's tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in its consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than- not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss as well as other changes in stockholders' equity (deficit) that result from transactions and economic events other than those with shareholders. For the years ended December 31, 2020 and 2019, the Company's other comprehensive income (loss) consisted of unrealized gains (losses) on marketable securities. For the year ended December 31, 2018, there was no difference between net loss and comprehensive loss.
Net Loss per Share	Net Loss per Share Basic net income (loss) per share is computed by dividing the net income (loss) by the weighted average number of common shares outstanding for the years ended December 31, 2020, 2019, and 2018. Diluted net income (loss) per share is computed by dividing the diluted net income (loss) by the weighted average number of common shares, including potential dilutive common shares assuming the dilutive effect of outstanding stock options and unvested restricted common stock, as determined using the treasury stock method. For periods in which the Company has reported net losses, diluted net loss per common share is the same as basic net loss per common share, since dilutive common shares are not assumed to have been issued if their effect is antidilutive.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies that the Company adopts as of the specified effective date. Unless otherwise discussed below, the Company does not believe that the adoption of recently issued standards have or may have a material impact on its consolidated financial statements or disclosures. Credit Losses In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13). The FASB subsequently issued amendments to ASU 2016-13, which have the same effective date and transition date of January 1, 2020. This standard requires entities to estimate an expected lifetime credit loss on financial assets and report credit losses using an expected losses model rather than the incurred losses model that was previously used, and establishes additional disclosures related to credit risks. For available-for-sale debt securities with unrealized losses, the standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This standard limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and requires the reversal of previously recognized credit losses if fair value increases. This standard became effective for the Company on January 1, 2020, and adoption of this standard did not have a material impact on the consolidated financial statements and related disclosures.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
Summary of Significant Accounting Policies (Tables)	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Estimated Useful life of Assets	Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows: Asset Category Estimated Useful Life Lab equipment 5 to 7 years Computer equipment 3 to 5 years Furniture and fixtures 7 years Leasehold improvements Shorter of life of lease

Revenues (Tables)

Revenues (Tables)	12 Months Ended
Revenues (Tables)	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Analysis Of Amount Of And Change In Product Revenue Reserves	Activity in each of the product revenue allowance and reserve categories is summarized as follows: (in thousands) Trade discounts and allowances Chargebacks and administrative fees Government rebates and other incentives Returns Total Balance as of December 31, 2019 $ — $ — $ — $ — $ — Provision related to sales in the current year 556 1,663 2,923 856 5,998 Credits and payments made (404) (1,399) (490) (324) (2,617) Balance as of December 31, 2020 $ 152 $ 264 $ 2,433 $ 532 $ 3,381
Summary Of Total Product Revenue Reserves Included In The Consolidated Balance Sheets	The total reserves described above are summarized as components of the Company's consolidated balance sheets as follows: (in thousands) December 31, 2020 Reduction of accounts receivable, net $ 363 Component of accrued expenses and other current liabilities 3,018 Total revenue-related reserves $ 3,381

Marketable Securities and Fai_2

Marketable Securities and Fair Value Measurements (Tables)	12 Months Ended
Marketable Securities and Fair Value Measurements (Tables)	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Marketable Securities	The following tables present marketable securities by contractual maturity and security type: As of December 31, 2020 (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Due within one year: U.S. government securities $ 298,335 $ 49 $ (1) $ 298,383 Commercial paper 62,037 9 (15) 62,031 Corporate debt securities 38,309 — (34) 38,275 Certificates of deposit 17,344 1 (1) 17,344 Due after one year through five years: U.S. government securities 9,370 5 — 9,375 Total $ 425,395 $ 64 $ (51) $ 425,408 As of December 31, 2019 (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Due within one year: Commercial paper $ 314,292 $ 74 $ (23) $ 314,343 U.S. government securities 78,612 48 (3) 78,657 Certificates of deposit 66,241 17 (2) 66,256 Total $ 459,145 $ 139 $ (28) $ 459,256
Schedule of Financial Assets Measured at Fair Value on a Recurring Basis	The following tables present information about the Company's financial assets measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values: As of December 31, 2020 (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 46,676 $ — $ 46,676 U.S. government securities — 30,000 — 30,000 Marketable securities: U.S. government securities — 307,758 — 307,758 Commercial paper — 62,031 — 62,031 Corporate debt securities — 38,275 — 38,275 Certificates of deposit — 17,344 — 17,344 Total $ — $ 502,084 $ — $ 502,084 As of December 31, 2019 (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 28,192 $ — $ 28,192 Certificates of deposit — 20,500 — 20,500 Marketable securities: Commercial paper — 314,343 — 314,343 U.S. government securities — 78,657 — 78,657 Certificates of deposit — 66,256 — 66,256 Total $ — $ 507,948 $ — $ 507,948

Inventory (Tables)

Inventory (Tables)	12 Months Ended
Inventory (Tables)	Dec. 31, 2020
Inventory Disclosure [Abstract]
Schedule of Inventory, Current	Capitalized inventory consisted of the following: (in thousands) December 31, 2020 Raw materials $ 1,352 Work in process 4,142 Finished goods 222 Total inventory $ 5,716

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
Property and Equipment, Net (Tables)	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Summary of Property and Equipment, Net	Property and equipment, net consisted of the following: December 31, (in thousands) 2020 2019 Laboratory equipment $ 3,631 $ 2,195 Computer equipment 4,795 2,950 Furniture and fixtures 3,187 1,941 Leasehold improvements 1,895 908 Construction in progress 197 169 Total cost 13,705 8,163 Less: Accumulated depreciation (4,122) (1,830) Total property and equipment, net $ 9,583 $ 6,333

Leases (Tables)

Leases (Tables)	12 Months Ended
Leases (Tables)	Dec. 31, 2020
Leases [Abstract]
Operating Leases in the Consolidated Balance Sheet	All of the Company's leases qualify as operating leases. The following table summarizes the presentation of the Company's operating leases in the consolidated balance sheet: December 31, (in thousands) 2020 2019 Operating lease assets $ 36,341 $ 21,158 Current operating lease liabilities $ 2,457 1,747 Operating lease liabilities, net of current portion 28,764 15,904 Total operating lease liabilities $ 31,221 $ 17,651
Components of Lease Expense	The components of lease expense were as follows: Year Ended December 31, (in thousands) 2020 2019 Operating lease cost $ 4,167 $ 1,223 Short-term lease cost 354 520 Variable lease cost 461 427 Total lease expense $ 4,982 $ 2,170
Summary of Future Annual Minimum Lease Payments Under Operating Leases	Future annual minimum lease payments under operating leases are as follows: (in thousands) As of December 31, 2020 2021 $ 4,143 2022 4,225 2023 4,308 2024 4,390 2025 4,472 Thereafter 18,520 Total future minimum lease payments 40,058 Less: imputed interest (8,837) Total operating lease liabilities $ 31,221
Operating Lease Weighted Average Remaining Term and Discount Rate	The weighted-average remaining lease term and weighted-average discount rate of the Company's operating leases are as follows: As of December 31, 2020 2019 Weighted-average remaining lease term in years 8.97 9.63 Weighted-average discount rate 5.60 % 5.36 %
Schedule of Cash Flow, Supplemental Disclosures, Leases, Lessee	Supplemental disclosure of cash flow information related to the Company's operating leases included in cash flows used in operating activities in the consolidated statement of cash flows were as follows: Year Ended December 31, (in thousands) 2020 2019 Cash paid for amounts included in the measurement of operating lease liabilities $ 2,666 $ 532 Operating lease liabilities arising from obtaining operating lease assets $ 14,902 $ 17,144

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
Accrued Expenses and Other Current Liabilities (Tables)	Dec. 31, 2020
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	December 31, (in thousands) 2020 2019 External research and development expenses $ 31,259 $ 20,462 Payroll and related expenses 17,255 12,902 Professional fees 3,306 3,810 Revenue-related reserves 3,018 — Other 389 1,542 Total accrued expenses and other current liabilities $ 55,227 $ 38,716

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
Stock-Based Compensation (Tables)	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Summary of Assumptions used to Determine the Fair Value of Options Granted to Employees and Directors	The assumptions that the Company used to determine the fair value of options granted to employees and directors were as follows, presented on a weighted average basis: Year Ended December 31, 2020 2019 2018 Risk-free interest rate 1.2 % 2.2 % 2.8 % Expected term (in years) 6.1 6.2 6.1 Expected volatility 77.2 % 74.5 % 73.3 % Expected dividend yield 0 % 0 % 0 %
Summary of Option Activity	The following table summarizes the Company's option activity from January 1, 2020 to December 31, 2020: Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding as of December 31, 2019 6,750,939 $ 19.36 Granted 1,331,148 $ 54.79 Exercised (1,881,892) $ 9.96 Forfeited/Expired (487,856) $ 33.27 Outstanding as of December 31, 2020 5,712,339 $ 29.53 7.8 $ 158,204 Options vested and expected to vest as of December 31, 2020 5,712,339 $ 29.53 7.8 $ 158,204 Options exercisable as of December 31, 2020 2,873,038 $ 20.60 7.1 $ 104,889
Summary of RSU Activity	The table below summarizes the Company's time-based restricted stock unit activity from January 1, 2020 to December 31, 2020: Number Weighted Unvested at December 31, 2019 99,500 $ 29.58 Granted 426,155 $ 51.74 Vested (50,750) $ 28.93 Forfeited (36,280) $ 52.66 Unvested at December 31, 2020 438,625 $ 49.28
Classification of Stock-Based Compensation Expense	Stock-based compensation expense was classified in the statements of operations and comprehensive loss as follows: Year Ended December 31, (in thousands) 2020 2019 2018 Research and development $ 17,443 $ 7,934 $ 4,021 Selling, general, and administrative 19,694 12,476 5,667 Total stock-based compensation $ 37,137 $ 20,410 $ 9,688 The following table summarizes share-based compensation expense associated with each of our share-based compensation arrangements: Year Ended December 31, (in thousands) 2020 2019 2018 Stock options $ 29,925 $ 19,328 $ 9,578 Time-based restricted stock units 4,424 1,082 110 Performance-based restricted stock units 1,907 — — Employee stock purchase plan 881 — — Total stock-based compensation expense $ 37,137 $ 20,410 $ 9,688

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
Net Loss per Share (Tables)	Dec. 31, 2020
Earnings Per Share [Abstract]
Summary of Basic and Diluted Net Loss per Share	Basic and diluted net loss per share was calculated as follows: Year Ended December 31, (in thousands, except share and per share amounts) 2020 2019 2018 Numerator: Net loss $ (266,489) $ (192,256) $ (99,854) Denominator: Weighted average common shares outstanding—basic and diluted 55,780,982 42,869,058 35,390,480 Net loss per share—basic and diluted $ (4.78) $ (4.48) $ (2.82)
Summary of Potential Dilutive Securities	The following potential dilutive securities, presented based on amounts outstanding at the end of each reporting period, have been excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive impact: As of December 31, 2020 2019 2018 Options to purchase common stock 5,712,339 6,750,939 5,787,151 Unvested restricted stock units 438,625 156,900 25,000 Unvested employee stock purchase plan shares 30,826 — — Total 6,181,790 6,907,839 5,812,151

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate	A reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax rate is as follows: Year Ended December 31, 2020 2019 2018 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % State taxes, net of federal benefit 2.4 7.0 6.1 Research and orphan drug credit 2.1 5.4 9.6 Stock-based compensation 5.4 4.7 0.7 Permanent adjustments and other 0.5 (0.9) — Increase in deferred tax asset valuation allowance (31.4) (37.2) (37.4) Effective income tax rate — % — % — %
Schedule of Net Deferred Tax Assets	Net deferred tax assets consisted of the following: December 31, (in thousands) 2020 2019 Deferred tax assets (liabilities): Net operating loss carryforwards $ 159,192 $ 85,632 Research and orphan drug credit carryforwards 31,142 25,267 Stock-based compensation 8,928 5,535 Accrued expenses 3,779 2,951 Operating lease liabilities 9,321 5,841 Property and equipment (387) — Operating lease assets (8,811) (5,515) Other 16 (64) Total gross deferred tax assets 203,180 119,647 Valuation allowance (203,180) (119,647) Net deferred tax assets $ — $ —
Schedule of Changes in Valuation Allowance for Deferred Tax Assets	The change in the valuation allowance was as follows: Year Ended December 31, (in thousands) 2020 2019 Valuation allowance as of beginning of year $ (119,647) $ (48,191) Net increases recorded to income tax provision (83,533) (71,456) Valuation allowance as of end of year $ (203,180) $ (119,647)

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
Selected Quarterly Financial Data (Unaudited) (Tables)	Dec. 31, 2020
Quarterly Financial Data [Abstract]
Schedule of Selected Quarterly Financial Data	The following information has been derived from unaudited consolidated financial statements that, in the opinion of management, include all recurring adjustments necessary for a fair statement of such information: Three Months Ended (in thousands except per share data) Dec 31, Sep 30, Jun 30, Mar 31, Dec 31, Sep 30, Jun 30, Mar 31, Statements of Operations Data: Revenues $ 19,486 $ 15,449 $ 7,090 $ 62 $ — $ — $ 25,000 $ — Gross profit (1) 19,359 15,359 7,082 62 — — 25,000 — Loss from operations (62,999) (63,997) (68,932) (75,262) (70,373) (58,353) (22,975) (49,025) Net loss (62,740) (63,701) (67,241) (72,807) (67,216) (56,196) (21,460) (47,384) Net loss per share—basic and diluted $ (1.10) $ (1.13) $ (1.20) $ (1.36) $ (1.31) $ (1.28) $ (0.56) $ (1.25) (1) Gross profit is calculated as total revenues less cost of sales.

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 25, 2020	Feb. 19, 2020	Sep. 03, 2019	Aug. 19, 2019	Jun. 20, 2018	Jun. 11, 2018	Aug. 31, 2020	Feb. 29, 2020	Jun. 30, 2018	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Nature Of Business And Basis Of Presentation [Line Items]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions, and offering costs																		$ 206,276	$ 431,780	$ 185,259
Net loss										$ (62,740)	$ (63,701)	$ (67,241)	$ (72,807)	$ (67,216)	$ (56,196)	$ (21,460)	$ (47,384)	(266,489)	(192,256)	$ (99,854)
Accumulated deficit										(754,468)				$ (487,979)				(754,468)	$ (487,979)
Cash, cash equivalents and marketable securities										561,300								$ 561,300
Common Shares
Nature Of Business And Basis Of Presentation [Line Items]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)																		3,953,365	12,432,431	4,945,000
Issuance of common stock sold in public offering, net of underwriting discounts, commissions, and offering costs																		$ 40	$ 124	$ 50
Follow On Offering \| Common Shares
Nature Of Business And Basis Of Presentation [Line Items]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)	477,272	3,181,818	1,621,621	10,810,810	645,000	4,300,000		3,659,090	4,945,000						12,432,431
Additional offering price of common stock (in dollars per share)	$ 55	$ 55	$ 37	$ 37	$ 40	$ 40		$ 55	$ 40						$ 37
Issuance of common stock sold in public offering, net of underwriting discounts, commissions, and offering costs	$ 24,700	$ 163,700	$ 56,400	$ 375,400	$ 24,300	$ 161,000		$ 188,400	$ 185,300						$ 431,800
Open Market Sale Agreement
Nature Of Business And Basis Of Presentation [Line Items]
Authorized aggregate offering proceeds							$ 200,000
Available for future issuance										$ 181,300								$ 181,300
Open Market Sale Agreement \| Common Shares
Nature Of Business And Basis Of Presentation [Line Items]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)																		294,275
Issuance of common stock sold in public offering, net of underwriting discounts, commissions, and offering costs																		$ 17,900

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Summary of Estimated Useful life of Assets (Details)	12 Months Ended
	Dec. 31, 2020
Lab equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	5 years
Lab equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	7 years
Computer equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	3 years
Computer equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	5 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	7 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	Shorter of life of lease or 15 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Significant Accounting Policies [Line Items]
Credit losses	$ 0
Impairment losses on long-lived assets		$ 0
Accounts receivable, credit losses	0
Impairment losses on long-lived assets	$ 0	$ 0	$ 0
Common stock, shares outstanding (in shares)	57,596,144	51,617,639
Minimum
Significant Accounting Policies [Line Items]
Income tax examination, likelihood percentage	50.00%

Revenues - Product Revenue Allo

Revenues - Product Revenue Allowance and Reserve Categories (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 0
Provision related to sales in the current year	5,998
Credits and payments made	(2,617)
Ending balance	3,381
Trade discounts and allowances
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	0
Provision related to sales in the current year	556
Credits and payments made	(404)
Ending balance	152
Chargebacks and administrative fees
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	0
Provision related to sales in the current year	1,663
Credits and payments made	(1,399)
Ending balance	264
Government rebates and other incentives
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	0
Provision related to sales in the current year	2,923
Credits and payments made	(490)
Ending balance	2,433
Returns
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	0
Provision related to sales in the current year	856
Credits and payments made	(324)
Ending balance	$ 532

Revenues - Total Reserves Summa

Revenues - Total Reserves Summarized (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Total revenue-related reserves	$ 3,381	$ 0
Reduction of accounts receivable, net
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Total revenue-related reserves	363
Component of accrued expenses and other current liabilities
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Total revenue-related reserves	$ 3,018	$ 0

Revenues - Additional Informati

Revenues - Additional Information (Details) - USD ($)

1 Months Ended

3 Months Ended

12 Months Ended

Jun. 30, 2019

Dec. 31, 2020

Sep. 30, 2020

Jun. 30, 2020

Mar. 31, 2020

Dec. 31, 2019

Sep. 30, 2019

Jun. 30, 2019

Mar. 31, 2019

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

License Agreement Transactions [Line Items]

Revenues

$ 19,486,000

$ 15,449,000

$ 7,090,000

$ 62,000

$ 0

$ 25,000,000

$ 0

$ 42,087,000

$ 25,000,000

$ 0

Customer One | Revenue from Contract with Customer Benchmark | Customer Concentration Risk

License Agreement Transactions [Line Items]

Concentration risk percentage

57.00%

Customer One | Reduction of accounts receivable, net | Customer Concentration Risk

License Agreement Transactions [Line Items]

Product sales from major customers percentage

59.00%

Customer Two | Revenue from Contract with Customer Benchmark | Customer Concentration Risk

License Agreement Transactions [Line Items]

Concentration risk percentage

24.00%

Customer Two | Reduction of accounts receivable, net | Customer Concentration Risk

License Agreement Transactions [Line Items]

Product sales from major customers percentage

20.00%

Customer Three | Revenue from Contract with Customer Benchmark | Customer Concentration Risk

License Agreement Transactions [Line Items]

Concentration risk percentage

10.00%

Product

License Agreement Transactions [Line Items]

Revenues

$ 39,461,000

Product | UNITED STATES

License Agreement Transactions [Line Items]

Revenues

38,000,000

Product | Non-US [Member]

License Agreement Transactions [Line Items]

Revenues

1,500,000

Collaboration Arrangement

License Agreement Transactions [Line Items]

Revenues

2,626,000

25,000,000

$ 0

Zai License Agreement

License Agreement Transactions [Line Items]

License agreement milestone

5,000,000

Agreement continuation period

10 years

Upfront payment recognized revenue

$ 20,000,000

Collaboration arrangement transaction price

25,000,000

2,000,000

Zai License Agreement | Collaboration Arrangement

License Agreement Transactions [Line Items]

Revenues

2,300,000

$ 25,000,000

Zai License Agreement | Development And Commercial Milestone | Maximum

License Agreement Transactions [Line Items]

License agreement milestone

185,000,000

Zai License Agreement | Development Milestone | Collaboration Arrangement

License Agreement Transactions [Line Items]

Revenues

$ 2,000,000

5,000,000

Zai License Agreement | Development Milestone | Maximum

License Agreement Transactions [Line Items]

License agreement milestone

50,000,000

Zai License Agreement | Commercial Milestone | Maximum

License Agreement Transactions [Line Items]

License agreement milestone

$ 135,000,000

Zai License Agreement | Revenues from Cost Reimbursements | Collaboration Arrangement

License Agreement Transactions [Line Items]

Revenues

300,000

Zai License Agreement | Upfront Payment | Collaboration Arrangement

License Agreement Transactions [Line Items]

Revenues

$ 20,000,000

Zai Supply Agreement | Revenues from Cost Reimbursements | Collaboration Arrangement

License Agreement Transactions [Line Items]

Revenues

$ 400,000

Marketable Securities and Fai_3

Marketable Securities and Fair Value Measurements - Schedule of Marketable Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Total
Amortized Cost	$ 425,395	$ 459,145
Gross Unrealized Gains	64	139
Gross Unrealized Losses	(51)	(28)
Estimated Fair Value	425,408	459,256
Commercial paper
Due within one year:
Amortized Cost	62,037	314,292
Gross Unrealized Gains	9	74
Gross Unrealized Losses	15	23
Estimated Fair Value	62,031	314,343
U.S. government securities
Due within one year:
Amortized Cost	298,335	78,612
Gross Unrealized Gains	49	48
Gross Unrealized Losses	1	3
Estimated Fair Value	298,383	78,657
Due after one year through five years:
Amortized Cost	9,370
Gross Unrealized Gains	5
Gross Unrealized Losses	0
Estimated Fair Value	9,375
Total
Estimated Fair Value	307,758	78,657
Certificates of deposit
Due within one year:
Amortized Cost	17,344	66,241
Gross Unrealized Gains	1	17
Gross Unrealized Losses	1	2
Estimated Fair Value	17,344	$ 66,256
Corporate debt securities
Due within one year:
Amortized Cost	38,309
Gross Unrealized Gains	0
Gross Unrealized Losses	34
Estimated Fair Value	$ 38,275

Marketable Securities and Fai_4

Marketable Securities and Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Marketable securities:
Total Marketable securities	$ 425,408	$ 459,256
Total	502,084	507,948
U.S. government securities
Cash equivalents:
Total Cash equivalents	30,000
Marketable securities:
Total Marketable securities	307,758	78,657
Money market funds
Cash equivalents:
Total Cash equivalents	46,676	28,192
Commercial paper
Marketable securities:
Total Marketable securities	62,031	314,343
Certificates of deposit
Cash equivalents:
Total Cash equivalents		20,500
Marketable securities:
Total Marketable securities	17,344	66,256
Corporate debt securities
Marketable securities:
Total Marketable securities	38,275
Level 1
Marketable securities:
Total	0	0
Level 1 \| U.S. government securities
Cash equivalents:
Total Cash equivalents	0
Marketable securities:
Total Marketable securities	0	0
Level 1 \| Money market funds
Cash equivalents:
Total Cash equivalents	0	0
Level 1 \| Commercial paper
Marketable securities:
Total Marketable securities	0	0
Level 1 \| Certificates of deposit
Cash equivalents:
Total Cash equivalents		0
Marketable securities:
Total Marketable securities	0	0
Level 1 \| Corporate debt securities
Marketable securities:
Total Marketable securities	0
Level 2
Marketable securities:
Total	502,084	507,948
Level 2 \| U.S. government securities
Cash equivalents:
Total Cash equivalents	30,000
Marketable securities:
Total Marketable securities	307,758	78,657
Level 2 \| Money market funds
Cash equivalents:
Total Cash equivalents	46,676	28,192
Level 2 \| Commercial paper
Marketable securities:
Total Marketable securities	62,031	314,343
Level 2 \| Certificates of deposit
Cash equivalents:
Total Cash equivalents		20,500
Marketable securities:
Total Marketable securities	17,344	66,256
Level 2 \| Corporate debt securities
Marketable securities:
Total Marketable securities	38,275
Level 3
Marketable securities:
Total	0	0
Level 3 \| U.S. government securities
Cash equivalents:
Total Cash equivalents	0
Marketable securities:
Total Marketable securities	0	0
Level 3 \| Money market funds
Cash equivalents:
Total Cash equivalents	0	0
Level 3 \| Commercial paper
Marketable securities:
Total Marketable securities	0	0
Level 3 \| Certificates of deposit
Cash equivalents:
Total Cash equivalents		0
Marketable securities:
Total Marketable securities	0	$ 0
Level 3 \| Corporate debt securities
Marketable securities:
Total Marketable securities	$ 0

Marketable Securities and Fai_5

Marketable Securities and Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Certificates of deposit \| Letter of Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash balance held to secure letter of credit associated with lease and Company credit card	$ 3.1	$ 1.5

Inventory (Details)

Inventory (Details) - USD ($)	12 Months Ended
Inventory (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Raw materials	$ 1,352,000
Work in process	4,142,000
Finished goods	222,000
Total inventory	5,716,000	$ 0
Inventory write-down	$ 0

Property and Equipment, Net - S

Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total cost	$ 13,705	$ 8,163
Less: Accumulated depreciation	(4,122)	(1,830)
Total property and equipment, net	9,583	6,333
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total cost	3,631	2,195
Computer equipment
Property, Plant and Equipment [Line Items]
Total cost	4,795	2,950
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total cost	3,187	1,941
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total cost	1,895	908
Construction in progress
Property, Plant and Equipment [Line Items]
Total cost	$ 197	$ 169

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 2,305	$ 830	$ 317

Leases - Operating Leases in th

Leases - Operating Leases in the Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease assets	$ 36,341	$ 21,158
Operating lease liabilities	2,457	1,747
Operating lease liabilities, net of current portion	28,764	15,904
Total operating lease liabilities	$ 31,221	$ 17,651

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 4,167	$ 1,223
Short-term lease cost	354	520
Variable lease cost	461	427
Total lease expense	$ 4,982	$ 2,170

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Lease Payments under Operating Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Operating Leases, After Adoption
2021	$ 4,143
2022	4,225
2023	4,308
2024	4,390
2025	4,472
Thereafter	18,520
Total future minimum lease payments	40,058
Less: imputed interest	(8,837)
Operating lease liability	$ 31,221	$ 17,651

Leases - Operating Lease Weight

Leases - Operating Lease Weighted Average Remaining Term and Discount Rate (Details)	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Weighted-average remaining lease term in years	8 years 11 months 19 days	9 years 7 months 17 days
Weighted-average discount rate	5.60%	5.36%

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities	$ 2,666	$ 532
Operating lease liabilities arising from obtaining operating lease assets	$ 14,902	$ 17,144

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands	1 Months Ended			12 Months Ended
Leases - Additional Information (Details) $ in Thousands	Aug. 31, 2020renewal_option	Apr. 30, 2019USD ($)ft²renewal_option	May 31, 2018USD ($)renewal_option	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2020USD ($)	Oct. 31, 2019USD ($)
Lessee, Lease, Description [Line Items]
Number of lease options \| renewal_option	2
Lease renewal term	5 years
Operating lease assets				$ 36,341	$ 21,158
Operating lease liability				31,221	17,651
Amounts capitalized under build-to-suit lease transaction				0	0	$ 11,885
Rent expense						1,100
The Initial Space
Lessee, Lease, Description [Line Items]
Number of lease options \| renewal_option			2
Lease renewal term			5 years
Initial annual base rent			$ 2,000
Initial annual base rent increase			$ 22,400
Operating lease assets								$ 21,200
Operating lease liability								$ 17,000
The Additional Space
Lessee, Lease, Description [Line Items]
Number of lease options \| renewal_option		2
Lease renewal term		5 years
Initial annual base rent		$ 1,900
Initial annual base rent increase		$ 18,200
Operating lease assets							$ 16,500
Operating lease liability							13,500
Additional office space \| ft²		38,003
The Premises
Lessee, Lease, Description [Line Items]
Operating lease area \| ft²		82,346
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Amounts capitalized under build-to-suit lease transaction						$ 11,900
Kansas
Lessee, Lease, Description [Line Items]
Operating lease assets							1,400
Operating lease liability							$ 1,400
Certificates of deposit \| The Additional Space
Lessee, Lease, Description [Line Items]
Cash balance to secure letter of credit associated with lease				1,000
Certificates of deposit \| Letter of Credit
Lessee, Lease, Description [Line Items]
Cash balance to secure letter of credit associated with lease				3,100	1,500
Certificates of deposit \| Letter of Credit \| The Premises
Lessee, Lease, Description [Line Items]
Cash balance to secure letter of credit associated with lease				$ 2,100	$ 1,100

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts Payable and Accrued Liabilities [Abstract]
External research and development expenses	$ 31,259	$ 20,462
Payroll and related expenses	17,255	12,902
Professional fees	3,306	3,810
Revenue-related reserves	3,381	0
Other	389	1,542
Total accrued expenses and other current liabilities	$ 55,227	$ 38,716

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 25, 2020	Feb. 19, 2020	Sep. 03, 2019	Aug. 19, 2019	Jun. 20, 2018	Jun. 11, 2018	Aug. 31, 2020	Feb. 29, 2020	Jun. 30, 2018	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions, and offering costs											$ 206,276	$ 431,780	$ 185,259
Common Shares
Class of Stock [Line Items]
Number of additional shares issued and sold (in shares)											3,953,365	12,432,431	4,945,000
Issuance of common stock sold in public offering, net of underwriting discounts, commissions, and offering costs											$ 40	$ 124	$ 50
Follow On Offering \| Common Shares
Class of Stock [Line Items]
Number of additional shares issued and sold (in shares)	477,272	3,181,818	1,621,621	10,810,810	645,000	4,300,000		3,659,090	4,945,000	12,432,431
Additional offering price of common stock (in dollars per share)	$ 55	$ 55	$ 37	$ 37	$ 40	$ 40		$ 55	$ 40	$ 37
Issuance of common stock sold in public offering, net of underwriting discounts, commissions, and offering costs	$ 24,700	$ 163,700	$ 56,400	$ 375,400	$ 24,300	$ 161,000		$ 188,400	$ 185,300	$ 431,800
Open Market Sale Agreement
Class of Stock [Line Items]
Authorized aggregate offering proceeds							$ 200,000
Available for future issuance											$ 181,300
Open Market Sale Agreement \| Common Shares
Class of Stock [Line Items]
Number of additional shares issued and sold (in shares)											294,275
Issuance of common stock sold in public offering, net of underwriting discounts, commissions, and offering costs											$ 17,900

Stock-Based Awards - Summary of

Stock-Based Awards - Summary of Assumptions used to Determine the Fair Value of Options Granted to Employees and Directors (Details) - Stock options	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.20%	2.20%	2.80%
Expected term (in years)	6 years 1 month 6 days	6 years 2 months 12 days	6 years 1 month 6 days
Expected volatility	77.20%	74.50%	73.30%
Expected dividend yield	0.00%	0.00%	0.00%

Stock-Based Awards - Summary _2

Stock-Based Awards - Summary of Option Activity (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)$ / sharesshares
Number of Shares
Outstanding, beginning balance, number of shares (in shares) \| shares	6,750,939
Granted \| shares	1,331,148
Exercised \| shares	(1,881,892)
Forfeited/Expired \| shares	487,856
Outstanding, ending balance, number of shares (in shares) \| shares	5,712,339
Options vested and expected to vest (in shares) \| shares	5,712,339
Options exercisable (in shares) \| shares	2,873,038
Weighted Average Exercise Price
Outstanding, beginning balance (in dollars per share) \| $ / shares	$ 19.36
Granted (in dollars per share) \| $ / shares	54.79
Exercised (in dollars per share) \| $ / shares	9.96
Forfeited/Expired (in dollars per share) \| $ / shares	33.27
Outstanding, ending balance (in dollars per share) \| $ / shares	29.53
Options vested and expected to vest (in dollars per share) \| $ / shares	29.53
Options exercisable (in dollars per share) \| $ / shares	$ 20.60
Additional Disclosures
Outstanding, weighted average remaining contractual term	7 years 9 months 18 days
Options vested and expected to vest, weighted average remaining contractual term	7 years 9 months 18 days
Options exercisable, weighted average remaining contractual term	7 years 1 month 6 days
Outstanding, aggregate intrinsic value \| $	$ 158,204
Options vested and expected to vest, aggregate intrinsic value \| $	158,204
Options exercisable, aggregate intrinsic value \| $	$ 104,889

Stock-Based Awards - Summary _3

Stock-Based Awards - Summary of TRSU Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Time-based restricted stock units
Number of Shares
Outstanding shares, beginning balance (in shares)	99,500
Granted (in shares)	426,155
Vested (in shares)	(50,750)		0
Forfeited (in shares)	(36,280)
Outstanding shares, ending balance (in shares)	438,625	99,500
Weighted Average Exercise Price
Weighted average grant date fair value, beginning balance (in dollars per share)	$ 29.58
Weighted average grant date fair value, granted (in dollars per share)	51.74
Weighted average grant date fair value, vested (in dollars per share)	28.93
Weighted average grant date fair value, forfeited (in dollars per share)	52.66
Weighted average grant date fair value, ending balance (in dollars per share)	$ 49.28	$ 29.58
Performance-based restricted stock units
Number of Shares
Granted (in shares)	0	57,400	0
Vested (in shares)	(55,200)
Forfeited (in shares)	(2,200)
Outstanding shares, ending balance (in shares)	0
Weighted Average Exercise Price
Weighted average grant date fair value, granted (in dollars per share)		$ 34.43
Weighted average grant date fair value, vested (in dollars per share)	$ 34.43
Weighted average grant date fair value, forfeited (in dollars per share)	$ 34.43

Stock-Based Awards - Classifica

Stock-Based Awards - Classification of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 37,137	$ 20,410	$ 9,688
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	17,443	7,934	4,021
Selling, general, and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	19,694	12,476	5,667
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	29,925	19,328	9,578
Time-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	4,424	1,082	110
Performance-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	1,907	0	0
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 881	$ 0	$ 0

Stock-Based Awards - Additional

Stock-Based Awards - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 01, 2021	Sep. 21, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock issued under ESPP (in shares)			37,298
Intrinsic value of stock options exercised			$ 86	$ 53.2	$ 4.4
Weighted average grant-date fair value per share of options granted (in dollars per share)			$ 36.71	$ 19.22	$ 19.68
Unrecognized compensation cost related to unvested share-based awards			$ 85
Unrecognized compensation cost related to unvested share-based awards, period for recognition			2 years 6 months
President And Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense				$ 2.4
Time-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, granted (in shares)			426,155
Weighted average grant date fair value, granted (in dollars per share)			$ 51.74
Vested (in shares)			50,750		0
Weighted average grant date fair value, vested (in dollars per share)			$ 28.93
Fair-value of units			$ 2.3	$ 0.5
Forfeited (in shares)			36,280
Weighted average grant date fair value, forfeited (in dollars per share)			$ 52.66
Nonvested shares outstanding (in shares)			438,625	99,500
Time-based restricted stock units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, vesting period			4 years	4 years	4 years
Time-based restricted stock units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, vesting period			1 year	1 year	1 year
Performance-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, granted (in shares)			0	57,400	0
Weighted average grant date fair value, granted (in dollars per share)				$ 34.43
Vested (in shares)			55,200
Weighted average grant date fair value, vested (in dollars per share)			$ 34.43
Fair-value of units			$ 3.6
Forfeited (in shares)			2,200
Weighted average grant date fair value, forfeited (in dollars per share)			$ 34.43
Nonvested shares outstanding (in shares)			0
Unvested employee stock purchase plan shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value of common stock			85.00%
Discount percentage			15.00%
Purchase period			6 months
2015 Equity Incentive Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)			10 years
2015 Equity Incentive Plan \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value of common stock			100.00%
2015 Equity Incentive Plan \| Employees and Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, vesting period			4 years
Common Shares \| 2017 Stock Option and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares reserved for issuance (in shares)		2,655,831	1,828,021
Effective date from which automatic annual increase in number of shares reserved for future issuance		Jan. 1, 2018
Percentage of automatic annual increase in number of shares reserved for future issuance		4.00%
Common Shares \| 2017 Stock Option and Incentive Plan \| Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares reserved for issuance (in shares)	2,303,845
Common Shares \| 2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares reserved for issuance (in shares)		306,750	1,372,135
Effective date from which automatic annual increase in number of shares reserved for future issuance		Jan. 1, 2018
Date until which automatic annual increase in number of shares reserved for future issuance		Jan. 1, 2027
Common Shares \| 2017 Employee Stock Purchase Plan \| Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares reserved for issuance (in shares)	400,000
Common Shares \| 2017 Employee Stock Purchase Plan \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of automatic annual increase in number of shares reserved for future issuance		1.00%
Automatic annual increase in number of shares reserved for future issuance (in shares)		400,000

401(k) Savings Plan - Additiona

401(k) Savings Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan description	Effective January 1, 2018, the Company adopted the 2018 401(k) Plan, a defined contribution plan under Section 401(k) of the Internal Revenue Code, whereby the Company provides matching contributions of 100% of each employee's contribution up to a maximum matching contribution of 3% of the employee's eligible compensation and at a rate of 50% of each employee's contribution in excess of 3% up to a maximum of 5% of the employee's eligible compensation.
Matching contributions to the plan by employer	$ 2.3	$ 0.9	$ 0.4
Up to Three Percent of Compensation
Defined Contribution Plan Disclosure [Line Items]
Percentage of matching contribution to plan	100.00%
Three to Five Percent of Compensation
Defined Contribution Plan Disclosure [Line Items]
Percentage of matching contribution to plan	50.00%
Maximum \| First Tier of Matching
Defined Contribution Plan Disclosure [Line Items]
Employee earnings subject to employer match	3.00%
Maximum \| Second Tier of Matching
Defined Contribution Plan Disclosure [Line Items]
Percentage of salary for matching contribution per employee on time-based vesting	5.00%
Minimum \| Second Tier of Matching
Defined Contribution Plan Disclosure [Line Items]
Percentage of salary for matching contribution per employee on time-based vesting	3.00%

Net Loss per Share - Summary of

Net Loss per Share - Summary of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss									$ (266,489)	$ (192,256)	$ (99,854)
Denominator:
Weighted average common shares outstanding—basic and diluted (in shares)									55,780,982	42,869,058	35,390,480
Net loss per share—basic and diluted (in dollars per share)	$ (1.10)	$ (1.13)	$ (1.20)	$ (1.36)	$ (1.31)	$ (1.28)	$ (0.56)	$ (1.25)	$ (4.78)	$ (4.48)	$ (2.82)

Net Loss per Share - Summary _2

Net Loss per Share - Summary of Potential Dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share (in shares)	6,181,790	6,907,839	5,812,151
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share (in shares)	5,712,339	6,750,939	5,787,151
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share (in shares)	438,625	156,900	25,000
Unvested employee stock purchase plan shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share (in shares)	30,826	0	0

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate (Details)	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	35.00%	21.00%	21.00%	21.00%
State taxes, net of federal benefit			2.40%	7.00%	6.10%
Research and orphan drug credit			2.10%	5.40%	9.60%
Stock-based compensation			5.40%	4.70%	0.70%
Permanent adjustments and other			0.50%	(0.90%)	0.00%
Increase in deferred tax asset valuation allowance			(31.40%)	(37.20%)	(37.40%)
Effective income tax rate			0.00%	0.00%	0.00%

Income Taxes - Schedule of Net

Income Taxes - Schedule of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets (liabilities):
Net operating loss carryforwards	$ 159,192	$ 85,632
Research and orphan drug credit carryforwards	31,142	25,267
Stock-based compensation	8,928	5,535
Accrued expenses	3,779	2,951
Operating lease liabilities	9,321	5,841
Operating lease assets	(8,811)	(5,515)
Property and equipment	(387)	0
Other	16
Other		(64)
Total gross deferred tax assets	203,180	119,647
Valuation allowance	(203,180)	(119,647)	$ (48,191)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Schedule of Chan

Income Taxes - Schedule of Changes in Valuation Allowance for Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Valuation allowance as of beginning of year	$ (119,647)	$ (48,191)
Net increases recorded to income tax provision	(83,533)	(71,456)
Valuation allowance as of end of year	$ (203,180)	$ (119,647)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details)	Jan. 01, 2018	Dec. 31, 2017	Oct. 02, 2017	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Income Tax Disclosure [Line Items]
Conversion ratio			5.65
Income tax benefits				$ 0	$ 0	$ 0
Federal statutory income tax rate	21.00%	35.00%		21.00%	21.00%	21.00%
Percentage of net operating loss carry forward deductible from current year taxable income	80.00%
Coronavirus Aid Relief And Economic Security Act Taxable Income Limitation Percentage Eliminated				80.00%
Coronavirus Aid Relief And Economic Security Act Carryback Period Allowed for NOLs				5 years
Coronavirus Aid Relief And Economic Security Act Interest Deductible Percentage Of Adjusted Taxable Income				50.00%
Coronavirus Aid Relief And Economic Security Act Charitable Deduction Limitation Percentage				25.00%
Coronavirus Aid Relief And Economic Security Act Qualified Improvement Property Recovery Period				15 years
Coronavirus Aid Relief And Economic Security Act Bonus Depreciation Percentage				100.00%
Research and orphan drug credit carryforwards				$ 31,142,000	$ 25,267,000
Unrecognized tax benefits				$ 0
Income tax examination, description				There are currently no pending income tax examinations. The Company's tax years that are open under statute are from October 2, 2017 to the present.
Accrued interest or penalties related to uncertain tax positions				$ 0	0
Income Tax Examination, Penalties and Interest Expense				0	$ 0	$ 0
Federal
Income Tax Disclosure [Line Items]
Net operating loss carryforwards				643,600,000
Net operating loss carryforwards, subject to expiration				$ 16,600,000
Net operating loss carryforwards expiration year				2037
Net operating loss carryforwards, carried forward indefinitely				$ 627,000,000
Research and orphan drug credit carryforwards				$ 28,800,000
Tax credit carryforwards expiration year				2037
State
Income Tax Disclosure [Line Items]
Net operating loss carryforwards				$ 479,200,000
Net operating loss carryforwards expiration year				2037
Research and orphan drug credit carryforwards				$ 3,000,000
Tax credit carryforwards expiration year				2032	2032

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - Supply Commitment $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Other Commitments [Line Items]
Supply commitment, remaining minimum amount committed	$ 8.8
Supply commitment expected to be paid within one year	7
Supply commitment expected to be paid after one year	$ 1.8
Supply commitment payment period, year one	1 year
Supply commitment amount paid	$ 3.7
Minimum
Other Commitments [Line Items]
Supply commitment payment period, after year one	1 year
Maximum
Other Commitments [Line Items]
Supply commitment payment period, after year one	3 years

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) - Schedule of Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statements of Operations Data:
Revenues	$ 19,486	$ 15,449	$ 7,090	$ 62	$ 0	$ 0	$ 25,000	$ 0	$ 42,087	$ 25,000	$ 0
Gross profit	19,359	15,359	7,082	62	0	0	25,000	0
Operating Income (Loss)	(62,999)	(63,997)	(68,932)	(75,262)	(70,373)	(58,353)	(22,975)	(49,025)	(271,190)	(200,726)	(104,099)
Net loss	$ (62,740)	$ (63,701)	$ (67,241)	$ (72,807)	$ (67,216)	$ (56,196)	$ (21,460)	$ (47,384)	$ (266,489)	$ (192,256)	$ (99,854)
Net loss per share—basic and diluted (in dollars per share)	$ (1.10)	$ (1.13)	$ (1.20)	$ (1.36)	$ (1.31)	$ (1.28)	$ (0.56)	$ (1.25)	$ (4.78)	$ (4.48)	$ (2.82)