0001728117-22-000019 | 10-K | XBRL Viewer

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Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 183,403	$ 486,055
Marketable securities	141,815	26,573
Restricted cash	64	565
Prepaid expenses and other current assets	6,498	9,129
Total current assets	331,780	522,322
Property and equipment, net	5,320	5,534
Operating lease right-of-use assets	5,477	10,550
Other assets	1,080	1,027
Total assets	343,657	539,433
Current liabilities
Accounts payable	3,244	7,508
Accrued research and development expenses	16,205	10,431
Accrued expenses and other current liabilities	20,410	20,711
Total current liabilities	39,859	38,650
Long-term convertible senior notes	150,038	143,642
Long-term debt	29,079	28,744
Operating lease liabilities - long-term	3,218	7,713
Total liabilities	222,194	218,749
Commitments and contingencies
Stockholders' equity (deficit)
Common stock, $0.0001 par value; 700,000,000 shares authorized as of December 31, 2021 and December 31, 2020; 76,470,588 shares issued and 75,752,664 shares outstanding as of December 31, 2021, and 75,524,254 shares issued and 73,874,904 shares outstanding as of December 31, 2020	8	8
Additional paid-in capital	932,944	897,607
Accumulated deficit	(811,534)	(577,530)
Accumulated other comprehensive income	45	599
Total stockholders' equity	121,463	320,684
Total liabilities and stockholders' equity	$ 343,657	$ 539,433

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	700,000,000	700,000,000
Common stock, shares issued (in shares)	76,470,588	75,524,254
Common stock, shares outstanding (in shares)	75,752,664	73,874,904

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating expenses:
Research and development	$ 170,267	$ 160,854	$ 143,403
In process research and development	75	23,380	3,600
General and administrative	45,782	49,728	39,136
Total operating expenses	216,124	233,962	186,139
Loss from operations	(216,124)	(233,962)	(186,139)
Other (expense) income
Interest income	761	3,442	5,563
Interest expense	(19,440)	(12,666)	(1,938)
Other income (expense)	799	(174)	2,207
Total other (expense) income, net	(17,880)	(9,398)	5,832
Net loss	(234,004)	(243,360)	(180,307)
Other comprehensive (loss) income:
Foreign currency translation, net of tax	(329)	441	(12)
Unrealized (loss) gain on marketable securities, net of tax	(225)	(100)	331
Other comprehensive (loss) income	(554)	341	319
Comprehensive loss	$ (234,558)	$ (243,019)	$ (179,988)
Net loss per share, basic (in dollars per share)	$ (3.13)	$ (3.55)	$ (3.29)
Net loss per share, diluted (in dollars per share)	$ (3.13)	$ (3.55)	$ (3.29)
Weighted average common shares outstanding, basic (in shares)	74,843,482	68,510,260	54,740,170
Weighted average common shares outstanding, diluted (in shares)	74,843,482	68,510,260	54,740,170

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)	Series Seed convertible preferred stock	Series A convertible preferred stock	Series B convertible preferred stock
Convertible preferred stock, beginning balance (in shares) at Dec. 31, 2018						20,000,000	45,714,286	71,506,513
Convertible preferred stock, beginning balance at Dec. 31, 2018						$ 29,200	$ 79,615	$ 229,552
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of convertible preferred stock into common stock (in shares)						(20,000,000)	(45,714,286)	(71,506,513)
Conversion of convertible preferred stock into common stock						$ (29,200)	$ (79,615)	$ (229,552)
Convertible preferred stock, ending balance (in shares) at Dec. 31, 2019						0	0	0
Convertible preferred stock, ending balance at Dec. 31, 2019						$ 0	$ 0	$ 0
Beginning balance (in shares) at Dec. 31, 2018		8,051,418
Beginning balance at Dec. 31, 2018	$ (120,069)	$ 2	$ 33,853	$ (153,863)	$ (61)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs (in shares)		19,837,500
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs	291,311	$ 2	291,309
Conversion of convertible preferred stock into common stock (in shares)		30,493,460
Conversion of convertible preferred stock into common stock	$ 338,367	$ 3	338,364
Vesting of restricted stock (in shares)		2,833,506
Exercise of stock options (in shares)	419,593	419,593
Exercise of stock options	$ 2,045		2,045
Stock-based compensation	20,819		20,819
Net loss	(180,307)			(180,307)
Other comprehensive income	319				319
Ending balance (in shares) at Dec. 31, 2019		61,635,477
Ending balance at Dec. 31, 2019	352,485	$ 7	686,390	(334,170)	258
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs (in shares)		9,433,963
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs	117,094	$ 1	117,093
Equity component of convertible note issuance	53,635		53,635
Debt issuance costs attributable to convertible feature	$ (109)		(109)
Vesting of restricted stock (in shares)		2,557,375
Exercise of stock options (in shares)	134,803	134,803
Exercise of stock options	$ 534		534
Stock-based compensation	38,748		38,748
Issuance of common stock pursuant to Employee Stock Purchase Plan (in shares)		113,286
Issuance of common stock pursuant to Employee Stock Purchase Plan	1,300		1,300
Other additional paid-in capital	16		16
Net loss	(243,360)			(243,360)
Other comprehensive income	341				341
Ending balance (in shares) at Dec. 31, 2020		73,874,904
Ending balance at Dec. 31, 2020	$ 320,684	$ 8	897,607	(577,530)	599
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock (in shares)		906,037
Exercise of stock options (in shares)	325,494	325,494
Exercise of stock options	$ 2,014		2,014
Stock-based compensation	32,008		32,008
Issuance of common stock pursuant to Employee Stock Purchase Plan (in shares)		160,790
Issuance of common stock pursuant to Employee Stock Purchase Plan	$ 1,315		1,315
Issuance of common stock for restricted stock units vested (in shares)	485,439
Net loss	$ (234,004)			(234,004)
Other comprehensive income	(554)				(554)
Ending balance (in shares) at Dec. 31, 2021		75,752,664
Ending balance at Dec. 31, 2021	$ 121,463	$ 8	$ 932,944	$ (811,534)	$ 45

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (234,004)	$ (243,360)	$ (180,307)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,740	1,409	917
Stock-based compensation expense	32,008	38,748	20,819
In process research and development expenses	75	23,380	3,600
Amortization of operating lease right-of-use assets	3,427	2,859	2,172
Amortization of long-term debt discount and issuance costs	6,731	3,857	237
Amortization of premium on investments, net of accretion of discounts	339	98	(2,364)
Net realized loss (gain) on investments	0	(256)	(28)
Loss on disposal of property and equipment	20	0	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	2,631	(1,641)	(4,393)
Other assets	(53)	532	2,714
Operating lease liabilities	(3,580)	(2,851)	(2,108)
Accounts payable	(4,428)	6,984	(1,399)
Accrued expenses	736	1,096	1,521
Accrued research and development expenses	5,774	(8,827)	8,605
Accrued compensation and benefits	(278)	1,612	5,180
Accrued interest expense	(28)	0	0
Net cash used in operating activities	(188,890)	(176,360)	(144,834)
Cash flows from investing activities
Research and development asset acquisitions, net of cash acquired	(75)	(23,380)	(3,600)
Purchase of marketable securities	(152,031)	(108,968)	(499,079)
Maturities of marketable securities	36,225	265,678	328,000
Sales of marketable securities	0	83,515	30,501
Purchase of property and equipment	(1,546)	(1,503)	(2,966)
Net cash provided by (used in) investing activities	(117,427)	215,342	(147,144)
Cash flows from financing activities
Proceeds from issuance of common stock	0	117,110	291,311
Proceeds from issuance of convertible senior notes, net	0	193,596	0
Proceeds from the issuance of long-term debt, net of debt discount and issuance costs $1,778	0	0	28,222
Proceeds from Stock Plans	1,315	1,300	0
Proceeds from the exercise of stock options	2,014	534	2,045
Net cash provided by financing activities	3,329	312,540	321,578
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(165)	9	70
Net (decrease) increase in cash, cash equivalents and restricted cash	(303,153)	351,531	29,670
Cash, cash equivalents and restricted cash, at the beginning of the period	486,620	135,089	105,419
Cash, cash equivalents and restricted cash, at the end of the period	183,467	486,620	135,089
Supplemental disclosure of cash flow information:
Cash paid for interest	12,738	7,871	1,475
Supplemental disclosure of noncash investing and financing activities:
Right-of-use assets obtained in exchange for lease liabilities	0	3,106	12,458
Derecognition ROU lease assets obtained in exchange for operating lease liabilities	1,650	0	0
Conversion of convertible preferred stock to common stock	0	0	338,367
Change in unrealized gain (loss) on marketable securities, net of tax	(225)	(100)	331
Purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities	$ 0	$ 15	$ 183

Consolidated Statements of Cash Flows (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Statement of Cash Flows [Abstract]
Debt issuance costs	$ 1,778

Organization and Basis of Presentation	12 Months Ended
Organization and Basis of Presentation	Dec. 31, 2021
Accounting Policies [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation Gossamer Bio, Inc. (including its subsidiaries, referred to as the “Company”) is a clinical-stage biopharmaceutical company focused on discovering, acquiring, developing and commercializing therapeutics in the disease areas of immunology, inflammation and oncology. The Company was incorporated in the state of Delaware on October 25, 2015 (originally as FSG Bio, Inc.) and is based in San Diego, California. The consolidated financial statements include the accounts of Gossamer Bio, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions among the consolidated entity have been eliminated in consolidation. Liquidity and Capital Resources The Company has incurred significant operating losses since its inception. As of December 31, 2021 and 2020, the Company had an accumulated deficit of $811.5 million and $577.5 million, respectively. From the Company’s inception through the year ended December 31, 2021, the Company has funded its operations primarily through equity financings and debt issuance. The Company raised $942.0 million from October 2017 through December 31, 2021 through Series A and Series B convertible preferred stock financings, a convertible note financing, its IPO, its Credit Facility (as defined in Note 5 below), and concurrent underwritten public offerings of its 5.00% convertible senior notes, its 2027 Notes and common stock in May 2020. See Note 5 for additional information regarding the Credit Facility and the 2027 Notes. The Company expects to continue to incur significant operating losses for the foreseeable future and may never become profitable. As a result, the Company will need to raise capital through equity offerings, debt financings and other capital sources, including potential collaborations, licenses and other similar arrangements. Management believes that it has sufficient working capital on hand to fund operations through at least the next 12 months from the date these consolidated financial statements were available to be issued. There can be no assurance that the Company will be successful in acquiring additional funding, that the Company’s projections of its future working capital needs will prove accurate, or that any additional funding would be sufficient to continue operations in future years. COVID-19 The COVID-19 pandemic has caused significant business disruption around the globe. The extent of the impact of COVID-19 on the Company’s operational and financial performance will depend on certain developments, including the duration and spread of the pandemic worldwide and the impact on the Company’s clinical trials, employees and vendors. At this point, the degree to which COVID-19 may continue to impact the Company’s financial condition or results of operations remains uncertain. A prolonged pandemic could have a material and adverse impact on financial results and business operations of the Company, including the timing and ability of the Company to complete certain clinical trials and other efforts required to advance the development of its product candidates and raise additional capital. For example, certain sites temporarily closed enrollment in the Company's Phase 2 clinical trial in pulmonary arterial hypertension ("PAH") in 2020 as a result of the COVID-19 pandemic and related staffing shortages at sites and key vendors. In addition, due to the challenges of enrolling patients worldwide posed by the COVID-19 pandemic and related staffing shortages at sites and key vendors, the Company has experienced and may continue to experience delays in enrollment of patients in its Phase 2 clinical trial of seralutinib, also known as GB002, in PAH, as well as delays in reporting data results from its ongoing trials.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Presentation

The Company’s consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Certain prior period amounts have been reclassified to conform to the current period presentation.

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. The most significant estimates in the Company’s consolidated financial statements relate to the allocation of the 2027 Notes

into liability and equity components and accrued research and development expenses. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results could differ from those estimates.

Segments

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment.

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less to be cash equivalents. The carrying amounts reported in the consolidated balance sheets for cash and cash equivalents are valued at cost, which approximate their fair value.

Marketable Securities

The Company considers securities with original maturities of greater than 90 days to be marketable securities. The Company has the ability, if necessary, to liquidate any of its cash equivalents and marketable securities to meet its liquidity needs in the next 12 months. Accordingly, those investments with contractual maturities greater than one year from the date of purchase are classified as current assets on the accompanying consolidated balance sheets. The Company’s marketable securities consist of commercial paper and corporate debt securities. Marketable securities are recorded at fair value and unrealized gains and losses are recorded within accumulated other comprehensive loss. The estimated fair value of the marketable securities is determined based on quoted market prices or rates for similar instruments. The Company evaluates securities with unrealized losses to determine whether such losses, if any, are due to credit-related factors. The Company records an allowance for credit losses when unrealized losses are due to credit-related factors. Realized gains and losses are calculated using the specific identification method and recorded as interest income or expense. The Company does not generally intend to sell the investments and it is not more likely than not that it will be required to sell the investments before recovery of their amortized cost bases, which may be at maturity. The Company has determined that there were no material declines in fair values of its investments due to credit-related factors as of December 31, 2021.

Restricted Cash

Restricted cash as of December 31, 2021, and 2020 represents cash held as collateral for the Company's facility leases.

Concentrations of Credit Risk and Off-Balance Sheet Risk

Cash, cash equivalents and marketable securities are financial instruments that are potentially subject to concentrations of credit risk. The Company’s cash and cash equivalents are deposited in accounts at large financial institutions, and amounts may exceed federally insured limits. The Company believes it is not exposed to significant credit risk due to the financial strength of the depository institutions in which the cash and cash equivalents are held. The Company maintains its cash equivalents in U.S. Treasury and agency securities and commercial paper with maturities less than three months and in money market funds that invest in U.S. Treasury and agency securities.

The Company’s available for sale securities are also invested in U.S. Treasury and agency securities. The Company has not recognized any losses from credit risks on such accounts during any of the periods presented. The Company believes it is not exposed to significant credit risk on its cash, cash equivalents and available for sale securities.

Property and Equipment, Net

Property and equipment, net, which consists mainly of office equipment and leasehold improvements, are carried at cost less accumulated depreciation. Depreciation is computed over the estimated useful lives of the respective assets, generally two to seven years, using the straight-line method.

Convertible Senior Notes

instruments that do not have associated convertible features. The carrying amount of the equity component representing the conversion option was determined by deducting the fair value of the liability component from the par value of the 2027 Notes. The equity component is not remeasured as long as it continues to meet the condition for equity classification. The excess of the principal amount of the liability component over its carrying amount (“debt discount”) is amortized to interest expense over the term of the 2027 Notes.

The Company allocated the issuance costs incurred to the liability and equity components of the 2027 Notes based on their relative fair values. Issuance costs attributable to the liability component were recorded as a reduction to the liability portion of the 2027 Notes and are being amortized to interest expense over the term of the 2027 Notes. Issuance costs attributable to the equity component, representing the conversion option, were netted with the equity component in stockholders' equity.

Leases

In accordance with Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842), as adopted on January 1, 2019, the Company determines if an arrangement is a lease at inception. Operating leases are included in the balance sheet as right-of-use assets and operating lease liabilities at the present value of the lease payments calculated using the Company’s incremental borrowing rate, unless the implicit rate is readily available. The Company applied the short-term lease recognition exemption for leases with terms at inception not greater than 12 months and elected to not separate lease and non-lease components for its long-term leases. The Company records rent expense on a straight-line basis over the term of the lease.

Research and Development

All research and development costs are expensed as incurred. Research and development costs consist primarily of salaries, employee benefits, costs associated with preclinical studies and clinical trials (including amounts paid to clinical research organizations and other professional services). Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received.

The Company records accruals for estimated research and development costs, comprising payments for work performed by third party contractors, laboratories, participating clinical trial sites, and others. Some of these contractors bill monthly based on actual services performed, while others bill periodically based upon achieving certain contractual milestones. For the latter, the Company accrues the expenses as goods or services are used or rendered. Clinical trial site costs related to patient enrollment are accrued as patients enter and progress through the trial. Upfront costs, such as costs associated with setting up clinical trial sites for participation in the trials, are expensed immediately once incurred as research and development expenses.

In process research and development

In process research and development costs relate to upfront payment to Aadi in connection with the amendment to the in-license agreement of GB004 and a milestone payment to Pulmokine for the initiation of the Phase 2 clinical trial for seralutinib.

Patent Costs

Costs related to filing and pursuing patent applications are expensed as incurred, as recoverability of such expenditures is uncertain. These costs are included in general and administrative expenses.

Income Taxes

Income taxes are recorded in accordance with Financial Accounting Standards Board (“FASB”) Standards Codification (“ASC”) No. 740, Income Taxes (“ASC 740”), which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit would more likely than not be realized assuming examination by the taxing authority. The determination as to whether the tax benefit will

more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances.

Deferred tax assets and liabilities reflect the future tax consequences of the differences between the financial reporting and tax bases of assets and liabilities using current enacted tax rates. Valuation allowances are recorded when the realizability of such deferred tax assets does not meet a more-likely-than-not threshold. For tax benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by taxing authorities. The Company is subject to taxation in the United States and California, Ireland and Luxembourg. As of December 31, 2021, the Company’s tax years since inception are subject to examination by taxing authorities due to the Company’s unutilized net operating losses ("NOLs") and tax credits.

Stock-Based Compensation

The Company expenses stock-based compensation to employees and non-employees over the requisite service period based on the estimated grant-date fair value of the awards. The Company records the expense for stock-based compensation awards subject to performance-based milestone vesting over the requisite service period when management determines that achievement of the milestone is probable. Management evaluates when the achievement of a performance-based milestone is probable based on the expected satisfaction of the performance conditions at each reporting date. The Company estimates the fair value of stock option grants and shares purchasable under the Company's 2019 Employee Stock Purchase Plan ("ESPP") using the Black-Scholes option pricing model, and the assumptions used in calculating the fair value of stock-based awards represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment. The Company estimates the fair value of restricted stock units based on the closing price of the Company's common stock on the date of grant. The Company accounts for forfeitures as they occur. All share-based compensation costs are recorded in the statements of operations based upon the underlying employees or non-employee’s roles within the Company.

Foreign Currency

Assets and liabilities of non-U.S. subsidiaries that operate in a local currency environment, where that local currency is the functional currency, are translated to U.S. dollars at exchange rates in effect at the balance sheet date. Income and expense accounts are translated at average exchange rates during the year which approximate the rates in effect at the transaction dates. The resulting translation adjustments are recorded in accumulated other comprehensive income in the Company's consolidated balance sheets. Foreign exchange transaction gains and losses are included in other income (expense) in the Company’s consolidated statement of operations and comprehensive loss.

Recent Accounting Pronouncements—To Be Adopted

In August 2020, the FASB issued ASU 2020-06, Debt: Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity's Own Equity (Subtopic 815-40) (“ASU 2020-06”), which simplifies the accounting for convertible instruments and contracts in an entity's own equity. This guidance is effective for annual reporting periods beginning after December 15, 2021, including interim periods within those years, with early adoption permitted only as of annual reporting periods beginning after December 15, 2020.

The Company plans to adopt ASU 2020-06 on January 1, 2022 using the modified retrospective approach, and accordingly the Company will record an adjustment that reflects the 2027 Notes as if the embedded conversion feature had not been separated. The impact upon adoption on the Consolidated Balance Sheets is anticipated to be an increase of approximately $44.8 million in convertible senior notes, net, a write-off of approximately $9.4 million in deferred income tax liabilities and a decrease of approximately $53.5 million in additional paid-in capital. In addition, upon adoption, there is an adjustment to increase the beginning balance of retained earnings on the Consolidated Balance Sheets for previously recognized interest expense, of approximately $8.7 million for amortization of debt discount related to the carrying value of the embedded conversion feature upon issuance. There will be no impact to the Company’s net loss per share calculation. See Note 7. Debt for further information regarding the 2027 Notes.

Net Loss Per Share

Basic net loss per share of common stock is computed by dividing net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. The Company uses the if-converted method for assumed conversion of the 2027 Notes to compute the weighted average shares of common stock outstanding for diluted net loss per share. Diluted net loss per share excludes the potential impact of the Company’s common stock options and unvested shares of restricted stock and the potential shares issuable upon conversion of the 2027 Notes

because their effect would be anti-dilutive due to the Company’s net loss. Since the Company had a net loss in each of the periods presented, basic and diluted net loss per common share are the same.

The table below provides potentially dilutive securities not included in the calculation of the diluted net loss per share because to do so would be anti-dilutive:


	December 31,
	2021	2020	2019
2027 Notes	12,321,900	12,321,900	—
Shares issuable upon exercise of stock options	9,434,660	9,401,082	8,538,060
Non-vested shares under restricted stock grants	2,561,219	3,330,821	4,648,526

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2021

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):


	Years Ended December 31,
	2021		2020
Accrued compensation	$	11,916	$	12,194
Operating lease liabilities	2,902		3,633
Accrued consulting fees	956		1,919
Accrued interest	1,066		1,094
Accrued legal fees	202		619
Accrued litigation liability	2,375		—
Accrued accounting fees	154		285
Accrued in process research and development	—		225
Accrued other	839		742
Total accrued expenses	$	20,410	$	20,711

Fair Value Measurements

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurements

The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows:

Level 1: Observable inputs such as quoted prices in active markets;

Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly; and

Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.

The Company classifies its cash equivalents and available-for-sale investments within Level 1 or Level 2. The fair value of the Company’s investment grade corporate debt securities and commercial paper is determined using proprietary valuation models and analytical tools, which utilize market pricing or prices for similar instruments that are both objective and publicly available, such as matrix pricing or reported trades, benchmark yields, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, and offers.

Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following table presents the hierarchy for assets measured at fair value on a recurring basis as of December 31, 2021 and 2020 (in thousands):


	Fair Value Measurements at End of Period Using:
	Total Fair Value		Quoted Market Prices for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
As of December 31, 2021
Money market funds	$	139,794	$	139,794	$	—	$	—
Commercial paper	113,939		—		113,939		—
Corporate debt securities	37,873		—		37,873		—
As of December 31, 2020
Money market funds	$	411,104	$	411,104	$	—	$	—
U.S. Treasury and agency securities	18,280		18,280		—		—
Corporate debt securities	26,573		—		26,573		—

The Company did not reclassify any investments between levels in the fair value hierarchy during the periods presented.

Fair Value of Other Financial Instruments

As of December 31, 2021 and 2020, the carrying amounts of the Company’s financial instruments, which include cash, restricted cash, prepaid and other current assets, interest receivable, accrued research and development expenses, accounts payable and accrued expenses and other current liabilities, approximate fair values because of their short maturities.

Interest receivable as of December 31, 2021 and 2020 was $0.2 million and $0.2 million, respectively, and is recorded as a component of prepaid expenses and other current assets on the consolidated balance sheets.

The Company believes that its Credit Facility bears interest at a rate that approximates prevailing market rates for instruments with similar characteristics and, accordingly, the carrying value of the Credit Facility approximates fair value. The Company estimates the fair value of long-term debt utilizing an income approach. The Company uses a present value calculation to discount principal and interest payments and the final maturity payment on these liabilities using a discounted cash flow model based on observable inputs. The debt instrument is then discounted based on what the current market rates would be as of the reporting date. Based on the assumptions used to value these liabilities at fair value, the debt instrument is categorized as Level 2 in the fair value hierarchy.

As of December 31, 2021 and 2020 the fair value of the Company's 2027 Notes was $190.5 million and $198.5 million, respectively. The fair value was determined on the basis of market prices observable for similar instruments and is considered Level 2 in the fair value hierarchy (see Note 5).

Available for Sale Investments

The Company invests its excess cash in U.S. Treasury and agency securities and debt instruments of corporations and commercial obligations, which are classified as available-for-sale investments. These investments are carried at fair value and are included in the tables below. The Company evaluates securities with unrealized losses to determine whether such losses, if any, are due to credit-related factors. Realized gains and losses are calculated using the specific identification method and recorded in other income (expense) in the Company’s consolidated statement of operations and comprehensive loss. The Company does not generally intend to sell the investments and it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost bases, which may be at maturity.

The aggregate market value, cost basis, and gross unrealized gains and losses of available-for-sale investments by security type, classified in marketable securities and long-term investments as of December 31, 2021 and 2020 are as follows (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Total Fair Value
As of December 31, 2021
Corporate debt securities	$	37,921	$	—	$	(48)	$	37,873
Commercial paper	$	103,942	$	—	$	—	$	103,942
Total marketable securities	$	141,863	$	—	$	(48)	$	141,815
As of December 31, 2020
Corporate debt securities	$	26,396	$	177	$	—	$	26,573
Total marketable securities	$	26,396	$	177	$	—	$	26,573

As of December 31, 2021 and 2020, the Company classified $10.0 million and $18.3 million, respectively, of assets with original maturities of 90 days or less as cash equivalents.

At each reporting date, the Company performs an evaluation of impairment to determine if any unrealized losses are due to credit-related factors. The Company records an allowance for credit losses when unrealized losses are due to credit-related factors. Factors considered when evaluating available-for-sale investments for impairment include the severity of the impairment, changes in underlying credit ratings, the financial condition of the issuer, the probability that the scheduled cash payments will continue to be made and the Company’s intent and ability to hold the investment until recovery of the amortized cost basis. The Company intends and has the ability to hold its investments in unrealized loss positions until their amortized cost basis has been recovered. As of December 31, 2021 and 2020, there were no material declines in the market value of the Company's available-for-sale investments due to credit-related factors.

Contractual maturities of available-for-sale debt securities, as of December 31, 2021, were as follows (in thousands):


	Estimated Fair Value
Less than one year	$	141,815
Greater than one year	—
Total	$	141,815

The Company has the ability, if necessary, to liquidate any of its cash equivalents and marketable securities to meet its liquidity needs in the next 12 months.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Indebtedness

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Indebtedness

Credit Facility

On May 2, 2019, the Company entered into a credit, guaranty and security agreement, as amended on September 18, 2019 and July 2, 2020 (the “Credit Facility”), with MidCap Financial Trust (“MidCap”), as agent and lender, and the additional lenders party thereto from time to time (together with MidCap, the “Lenders”), pursuant to which the Lenders, including affiliates of MidCap and Silicon Valley Bank, agreed to make term loans available to the Company for working capital and general business purposes, in a principal amount of up to $150.0 million in term loan commitments, including a $30.0 million term loan that was funded at the closing date, with the ability to access the remaining $120.0 million in two additional tranches (each $60.0 million), subject to specified availability periods, the achievement of certain clinical development milestones, minimum cash requirements and other customary conditions. The Company, GB001, Inc., GB002, Inc., and GB004, Inc., each wholly-owned subsidiaries of the Company, are designated as co-borrowers to the Credit Facility, whereas GB003, Inc., GB005, Inc., GB006, Inc., GB007, Inc., GB008, Inc., and Gossamer Bio Services, Inc., each wholly-owned subsidiaries of the Company, are designated as guarantors. The remaining two tranches are available no earlier than the satisfaction of the applicable funding conditions, including the applicable clinical development milestones, and no later than December 31, 2022. As of December 31, 2021, no other tranches under the Credit Facility were available to be drawn. The Credit Facility is secured by substantially all of the Company’s and its domestic subsidiaries’ personal property, including intellectual property.

Each term loan under the Credit Facility bears interest at an annual rate equal to the sum of (i) one-month LIBOR (customarily defined, with a change to prime rate if LIBOR funding becomes unlawful or impractical) plus (ii) 7.00%, subject to a LIBOR floor of 2.00%. The borrower is required to make interest-only payments on the term loan for all payment dates prior to July 1, 2022. The term loans under the Credit Facility will begin amortizing on July 1, 2022, with equal monthly payments of principal plus interest being made by the Company to the Lenders in consecutive monthly installments following such interest-only period until the Credit Facility matures on January 1, 2025. Upon final repayment of the term loans, the borrower must pay an exit fee of 1.75% of the amount borrowed under the Credit Facility, less any partial exit fees previously paid. Upon partial prepayment of a portion of the term loans, the borrower must pay a partial exit fee of 1.75% of the principal being prepaid. At the borrower’s option, the borrower may prepay the outstanding principal balance of the term loan in whole or in part, subject to a prepayment fee of 3.00% of any amount prepaid if the prepayment occurs through and including the first anniversary of the second amendment effective date, 2.00% of the amount prepaid if the prepayment occurs after the first anniversary of the second amendment effective date through and including the second anniversary of the second amendment effective date, and 1.00% of any amount prepaid after the second anniversary of the second amendment effective date and prior to January 1, 2025.

The Credit Facility includes affirmative and negative covenants applicable to the Company and certain of its subsidiaries. The affirmative covenants include, among others, covenants requiring such entities to maintain their legal existence and governmental approvals, deliver certain financial reports, maintain insurance coverage, maintain property, pay taxes, satisfy certain requirements regarding accounts and comply with laws and regulations. The negative covenants include, among others, restrictions on such entities from transferring collateral, incurring additional indebtedness, engaging in mergers or acquisitions, paying dividends or making other distributions, making investments, creating liens, amending material agreements and organizational documents, selling assets and suffering a change in control, in each case subject to certain exceptions. The Company and certain of its subsidiaries are also subject to an ongoing minimum cash financial covenant in which they must maintain unrestricted cash in an amount not less than 25% of the outstanding principal amount of the term loans. As of December 31, 2021, the Company was in compliance with these covenants.

The Credit Facility also includes events of default, the occurrence and continuation of which could cause interest to be charged at the rate that is otherwise applicable plus 3.00% and would provide MidCap, as agent, with the right to exercise remedies against the Company and/or certain of its subsidiaries, and the collateral securing the Credit Facility, including foreclosure against the properties securing the credit facilities, including cash. These events of default include, among other things, failure to pay any amounts due under the Credit Facility, a breach of covenants under the Credit Facility, insolvency or the occurrence of insolvency events, the occurrence of a change in control, the occurrence of certain U.S. Food and Drug Administration ("FDA") and regulatory events, failure to remain registered with the SEC and listed for trading on Nasdaq, the occurrence of a material adverse change, the occurrence of a default under a material agreement reasonably expected to result in a material adverse change, the occurrence of certain defaults under certain other indebtedness in an amount greater than $2.5 million and the occurrence of certain defaults under subordinated indebtedness and convertible indebtedness.

Long-term debt as of December 31, 2021 consisted of the following (in thousands):


	December 31, 2021
Term loan	$	30,000
Debt discount and issuance costs	(921)
Long-term debt	$	29,079

The scheduled future minimum principal payments are as follows (in thousands):


	December 31, 2021
2022	5,806
2023	11,613
2024	11,613
2025	968
Total	$	30,000

5.00% Convertible Senior Notes due 2027

On May 21, 2020, the Company issued $200.0 million aggregate principal amount of 5.00% convertible senior notes due 2027 in a public offering (the "2027 Notes"). The 2027 Notes were registered pursuant to the Company’s Shelf Registration Statement (as defined in Note 8 below). The interest rate on the 2027 Notes is fixed at 5.00% per annum. Interest is payable semi-annually in arrears on June 1 and December 1 of each year, commencing on December 1, 2020. The 2027 Notes will mature on June 1, 2027. The net proceeds from the offering, after deducting the underwriting discounts and commissions and other offering costs, were approximately $193.6 million. The 2027 Notes may be settled in cash, shares of the Company’s common stock, or a combination thereof, solely at the Company’s election. The initial conversion rate of the 2027 Notes is 61.6095 shares per $1,000 principal amount, which is equivalent to a conversion price of approximately $16.23 per share, subject to adjustments. In addition, following certain corporate events that occur prior to the maturity date or if the Company issues a notice of redemption, the Company will increase the conversion rate for a holder who elects to convert its 2027 Notes in connection with such a corporate event during the related redemption period in certain circumstances.

The 2027 Notes are senior unsecured obligations of the Company, ranking senior in right of payment to any of the Company’s indebtedness that is expressly subordinated in right of payment to the 2027 Notes, and are effectively subordinated to the Company’s existing and future secured indebtedness, to the extent of the value of the collateral securing that indebtedness, including all indebtedness under the Credit Facility.

Holders may convert their notes at their option only in the following circumstances: (1) during any calendar quarter (and only during such calendar quarter) commencing after the calendar quarter ending on September 30, 2020, if the last reported sale price per share of the Company’s common stock exceeds 130% of the conversion price for each of at least 20 trading days (whether or not consecutive) during the 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter; (2) during the five consecutive business days immediately after any 10 consecutive trading day period (such 10 consecutive trading day period, the “measurement period”) in which the trading price per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of the Company’s common stock on such trading day and the conversion rate on such trading day; (3) upon the occurrence of certain corporate events or distributions on the Company’s common stock; (4) if the Company calls such notes for redemption; and (5) at any time from, and including, March 1, 2027 until the close of business on the scheduled trading day immediately before the maturity date.

The Company will not have the right to redeem the 2027 Notes prior to June 6, 2024. On or after June 6, 2024 and on or before the 50th scheduled trading day immediately before the maturity date, the Company may redeem the 2027 Notes, in whole or in part, if the last reported sale price of the Company’s common stock has been at least 130% of the conversion price then in effect on (1) each of at least 20 trading days (whether or not consecutive) during the 30 consecutive trading days ending on, and including, the trading day immediately before the date the Company sends the related redemption notice; and (2) the trading day immediately before the date the Company sends such notice. In the case of any optional redemption, the Company will redeem the 2027 Notes at a redemption price equal to 100% of the principal amount of such Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date.

If the Company undergoes a fundamental change prior to the maturity date of the 2027 Notes, holders of the 2027 Notes may require the Company to repurchase for cash all or part of their 2027 Notes at a repurchase price equal to 100% of the principal amount of the 2027 Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

The indenture governing the 2027 Notes provides for customary terms and covenants, including that upon certain events of default, either the trustee or the holders of not less than 25% in aggregate principal amount of the 2027 Notes then outstanding may declare the unpaid principal amount of the 2027 Notes and accrued and unpaid interest, if any, thereon immediately due and payable. As of December 31, 2021, the Company was in compliance with these covenants. In the case of certain events of bankruptcy, insolvency or reorganization, the principal amount of the 2027 Notes together with accrued and unpaid interest, if any, thereon will automatically become and be immediately due and payable.

As of December 31, 2021 and 2020, there were no events or market conditions that would allow holders to convert the 2027 Notes. When the 2027 Notes become convertible within 12 months of the balance sheet date, the carrying value of the 2027 Notes will be reclassified to short-term.

In accounting for the issuance of the 2027 Notes, the Company separated the 2027 Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of similar debt instruments that do not have associated convertible features. The carrying amount of the equity component representing the conversion option was $53.5 million and was determined by deducting the fair value of the liability component from the par

value of the 2027 Notes. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. The debt discount is amortized to interest expense over the term of the 2027 Notes at an effective interest rate of 11.17% over the contractual terms of the 2027 Notes.

In accounting for the debt issuance costs of $0.4 million related to the 2027 Notes, the Company allocated the total amount incurred to the liability and equity components of the 2027 Notes based on their relative fair values. Issuance costs attributable to the liability component were $0.3 million and will be amortized to interest expense using the effective interest method over the contractual terms of the 2027 Notes. Issuance costs attributable to the equity component were netted with the equity component in stockholders’ equity.

The net carrying amount of the liability component of the 2027 Notes was as follows (in thousands):


	December 31, 2021		December 31, 2020
Principal amount	$	200,000	$	200,000
Unamortized debt discount	(49,716)		(56,080)
Unamortized debt issuance cost	(246)		(278)
Net carrying amount	$	150,038	$	143,642

The net carrying amount of the equity component of the 2027 Notes was as follows (in thousands):


	December 31, 2021		December 31, 2020
Debt discount related to the value of conversion option	$	53,635	$	53,635
Debt issuance cost	(109)		(109)
Net carrying amount	$	53,526	$	53,526

The following table sets forth the interest expense recognized related to the 2027 Notes (in thousands):


	Years Ended December 31,
	December 31, 2021		December 31, 2020		December 31, 2019
Contractual interest expense	$	9,972	$	6,139	$	—
Amortization of debt discount	6,364		3,555		—
Amortization of debt issuance cost	32		17		—
Total interest expense related to the 2027 Notes	$	16,368	$	9,711	$	—

License and Asset Acquisitions

12 Months Ended

Dec. 31, 2021

Business Combination and Asset Acquisition [Abstract]

License and Asset Acquisitions

The following purchased assets were accounted for as asset acquisitions as substantially all of the fair value of the assets acquired were concentrated in a group of similar assets and/or the acquired assets were not capable of producing outputs due to the lack of employees and early stage of development. Because the assets had not yet received regulatory approval, the fair value attributable to these assets was recorded as in process research and development (“IPR&D”) expenses in the Company’s consolidated statement of operations for the years ended December 31, 2021, 2020, and 2019.

The Company accounts for contingent consideration payable upon achievement of certain regulatory, development or sales milestones in such asset acquisitions when the underlying contingency is met.

License from Pulmokine, Inc. (Seralutinib)

On October 2, 2017, the Company, entered into a license agreement with Pulmokine, Inc. under which it was granted an exclusive worldwide license and sublicense to certain intellectual property rights owned or controlled by Pulmokine to develop and commercialize seralutinib and certain backup compounds for the treatment, prevention and diagnosis of any and all disease or conditions. The Company also has the right to sublicense its rights under the license agreement, subject to certain conditions. The assets acquired are in the early stages of the FDA approval process, and the Company intends to further develop the assets acquired through potential FDA approval as evidenced by the milestone arrangement in the contract. The development activities cannot be performed without significant cost and effort by the Company. The agreement will remain in effect from the effective date, unless terminated earlier, until, on a licensed product-by-licensed product and country-by-country

basis, the later of ten years from the date of first commercial sale or when there is no longer a valid patent claim covering such licensed product or specified regulatory exclusivity for the licensed product in such country. The Company is obligated to make future development and regulatory milestone payments of up to $58.0 million, commercial milestone payments of up to $45.0 million, and sales milestone payments of up to $190.0 million. The Company is also obligated to pay tiered royalties on sales for each licensed product, at percentages ranging from the mid-single digits to the high single-digits. The Company made an upfront payment of $5.5 million in October 2017. As of December 31, 2020, the Company accrued a milestone payment of $5.0 million in connection with the initiation of the first Phase 2 clinical trial of seralutinib, which was paid in January 2021. As of December 31, 2021, no other milestones had been accrued as the underlying contingencies had not yet been met.

License from Aadi Biosciences, Inc. (GB004)

On June 24, 2018, the Company entered into a license agreement with Aerpio Pharmaceuticals, Inc., now known as Aadi Biosciences, Inc. ("Aadi"), under which the Company was granted an exclusive worldwide license and sublicense to certain intellectual property rights owned or controlled by Aadi to develop and commercialize GB004, and certain other related compounds for all applications. The Company made an upfront payment of $20.0 million in June 2018, which represented the purchase consideration for an asset acquisition. On May 11, 2020, the Company entered into an amendment to the license agreement with Aadi pursuant to which the Company made an upfront payment of $15.0 million to Aadi for a reduction in future milestone payments and royalties. Under the amended license agreement, the Company is obligated to make future approval milestone payments of up to $40.0 million and a sales milestone payment of $50.0 million. The Company also has the right to sublicense its rights under the license agreement, subject to certain conditions. The Company is also obligated to pay tiered royalties on sales for each licensed product, at percentages ranging from low- to mid-single digits, subject to certain customary reductions. Aadi retains its twenty percent (20.00%) participation right on a disposition of GB004. As of December 31, 2021and 2020, no milestones had been accrued as the underlying contingencies had not yet been met.

Adhaere Pharmaceuticals, Inc. Acquisition (GB1275)

On September 21, 2018, the Company acquired Adhaere Pharmaceuticals, Inc. ("Adhaere") pursuant to a merger agreement for an upfront payment of $7.5 million in cash, and with the acquisition acquired the rights to GB1275 and certain backup compounds. The Company is obligated to make future regulatory, development and sales milestone payments of up to $62.0 million and pay tiered royalties on worldwide net sales, at percentages ranging from low to mid-single digits, subject to customary reductions. The Company recorded IPR&D of $7.5 million in connection with the acquisition of Adhaere. In May 2019, the Company made a milestone payment of $1.0 million in connection with the filing of the Investigational New Drug application for the GB1275 program. As of December 31, 2021 and 2020, no other milestones had been accrued as the underlying contingencies had not yet been met.

The Company recorded the following IPR&D expense on the consolidated statements of operations (in thousands):


	Years Ended December 31,
	2021		2020		2019
Seralutinib	$	—	$	5,000	$	—
GB004	—		15,000		—
GB1275	—		—		1,000
Other preclinical programs	75		3,380		2,600
Total in process research and development	$	75	$	23,380	$	3,600

Income Taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

The amount of net loss before taxes for the years ended December 31, 2021, 2020, and 2019 is as follows (in thousands):


	December 31,
	2021		2020		2019
	(in thousands)
U.S. loss before taxes	$	183,194	$	186,888	$	138,342
Foreign loss before taxes	50,802		56,472		41,965
Loss before income taxes	$	233,996	$	243,360	$	180,307

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets and liabilities at December 31, 2021, 2020 and 2019 are shown below. The Company has established a valuation allowance against net deferred tax assets due to the uncertainty that such assets will be realized. The Company periodically evaluates the recoverability of the deferred assets. At such time as it is determined that it is more likely than not that the deferred tax asset will be realized, the valuation allowance will be reduced. The change in the valuation allowance for the year ended December 31, 2021 was an increase of $46.0 million.


	December 31,
	2021		2020		2019
	(in thousands)
Deferred tax assets:
Net operating losses	$	116,425	$	77,946	$	43,626
Tax credits, net	24,964		17,372		9,196
Amortization	9,190		10,939		6,597
Stock-based compensation	4,917		4,448		1,388
Lease liability	1,285		2,383		2,329
Accrued compensation	2,238		2,137		1,476
Other	18		16		383
Total gross deferred tax assets	159,037		115,241		64,995

Deferred tax liabilities:
Convertible senior notes	(9,395)		(10,592)		—
Right of use asset	(1,150)		(2,215)		(2,164)
Property, plant and equipment	(790)		(776)		(57)
Total gross deferred tax liabilities	(11,335)		(13,583)		(2,221)

Valuation allowance	(147,702)		(101,658)		(62,774)
Net deferred tax asset	$	—	$	—	$	—

As of December 31, 2021, the Company had federal and state NOL carryforwards of approximately $460.4 million and $1.1 million, respectively. The federal and state NOL carryforwards that are subject to expiration will begin to expire in 2034, unless previously utilized. The federal NOL generated after 2017 of $457.5 million can be carried forward indefinitely but may only be used to offset up to 80% of future taxable income each year. The California NOL carryforwards begin to expire in 2036. As of December 31, 2021, the Company also has foreign NOL carryforwards of approximately $157.2 million. The foreign NOL can be carried forward indefinitely.

As of December 31, 2021, the Company also had orphan drug credit and federal research tax credit carryforwards of approximately $25.7 million and California research tax credits of $8.0 million. The federal research tax credit carryforwards begin to expire in 2038 and the California research tax credit carryforward does not expire and can be carried forward indefinitely until utilized.

A reconciliation of the federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	December 31,
	2021		2020		2019
Federal statutory income tax rate	21.00	%	21.00	%	21.00	%
State income taxes, net of federal benefit	—	%	—	%	—	%
Change in valuation allowance	(19.73	%)	(19.50	%)	(22.12	%)
Research and experimentation credits	2.62	%	2.76	%	3.81	%
Foreign rate differential	(1.95	%)	(1.64	%)	(1.84	%)
Stock-based compensation	(1.56	%)	(1.81	%)	—	%
Nondeductible interest	(0.96	%)	—	%	—	%
Other	0.57	%	(0.80	%)	(0.85	%)
Provision for income taxes	—	%	—	%	—	%

The NOL and credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. Under Section 382 and 383 of the Code, the NOL and credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders (or groups of stockholders) in excess of 50 percentage points over a rolling three-year period. Similar rules may apply under state and foreign tax laws. In connection with the Company’s IPO in February 2019, the Company experienced an ownership change for the purposes of Section 382 and 383 of the Code. Consequently, the Company’s federal and state NOLs and tax credits generated through February 2019 will be subject to annual limitations. However, the Company’s NOLs and tax credits are not expected to expire unused as a result of such annual limitations, assuming we otherwise have taxable income or income tax liabilities in future periods. If a change in ownership occurs in the future as a result of changes in the Company’s stock ownership, many of which are outside the Company’s control, the NOL and credit carryforwards could be subject to further annual limitations. If the Company earns taxable income, such annual limitations could result in increased future tax liability to the Company and its future cash flows could be adversely affected. The Company has recorded a full valuation allowance related to its NOLs and other deferred tax assets due to the uncertainty of the ultimate realization of the future benefits of those assets.

The Company files income tax returns in the United States, California, Ireland, and Luxembourg. Due to the Company’s losses incurred, the Company is subject to the income tax examination by authorities since inception. The Company’s policy is to recognize interest expense and penalties related to income tax matters as tax expense. As of December 31, 2021, 2020, or 2019, there were no accruals for interest related to unrecognized tax benefits or tax penalties.

A reconciliation of the beginning and ending amount of unrecognized tax benefits for 2021, 2020, and 2019, excluding interest and penalties, is as follows:


	December 31,
	2021		2020		2019
	(in thousands)
Balance at beginning of the year	$	5,060	$	2,754	$	408
Increase related to current year positions	2,491		2,306		2,346
Balance at the end of the year	$	7,551	$	5,060	$	2,754

Included in the balance of unrecognized tax benefits at December 31, 2021 is $7.6 million that, if recognized, would not impact the Company’s income tax benefit or effective tax rate as long as the Company's deferred tax asset remains subject to a full valuation allowance. The Company does not expect any significant increases or decreases to the Company's unrecognized tax benefits within the next 12 months.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI http://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2021
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Common stock In connection with the Company’s IPO, the outstanding shares of the Company’s Series Seed, Series A, and Series B convertible preferred stock automatically converted into 30,493,460 shares of common stock. Each share of common stock is entitled to one vote. Common stock owners are entitled to dividends when funds are legally available and declared by the Board. Shelf Registration Statement and Stock Offering On April 10, 2020, the Company filed a universal shelf registration statement on Form S-3, covering the offering from time to time of common stock, preferred stock, debt securities, warrants and units, which registration statement became automatically effective on April 10, 2020 (the “Shelf Registration Statement”). On May 21, 2020, the Company completed a public offering of 9,433,963 shares of its common stock at a public offering price of $13.25 per share. The net proceeds from the offering, after deducting underwriting discounts and commissions and other offering costs, were approximately $117.1 million. The shares sold in the offering were registered pursuant to the Company’s Shelf Registration Statement. Shares of Common Stock Subject to Repurchase On December 3, 2015, the Company issued 9,160,888 shares of common stock as founder shares for services rendered to the Company, valued at $0.0001 par value per share, for a total of approximately $4,100 (the “founder shares”). On January 4, 2018, incremental vesting conditions were placed on the previously issued founder shares. Fifty percent of the previously issued founder shares vested on January 4, 2018, and the remaining founder shares are subject to vesting restrictions over a period of five years. These shares are subject to repurchase by the Company upon a founder's termination of employment or service to the Company. Pursuant to the employment agreements with the Company’s founders executed January 4, 2018, the Company provided for certain potential additional issuances of common stock (the “anti-dilution shares”) to each of the founders to ensure the total number of shares of common stock held by them and their affiliates (inclusive of any shares subject to equity awards granted by the Company) would represent 15% of the Company’s fully-diluted capitalization until such time as the Company raised $300.0 million in equity capital, including the capital raised in the Series A financing. In furtherance of this obligation, on May 21, 2018, the Company issued 251,547 shares of common stock to the founders for services rendered to the Company, valued at $2.61 per share with an additional 251,547 shares of restricted stock subject to the same vesting restrictions and vesting period as the founder shares. In addition, on September 6, 2018, the Company issued 1,795,023 shares of common stock to the founders for services rendered to the Company, valued at $9.63 per share, with an additional 1,795,023 shares of restricted stock subject to the same vesting restrictions and vesting period as the founder shares. For the year ended December 31, 2021, 25,383 shares were forfeited due to termination of employment. Any shares subject to repurchase by the Company are not deemed, for accounting purposes, to be outstanding until those shares vest. As such, the Company recognizes the measurement date fair value of the restricted stock over the vesting period as compensation expense. As of December 31, 2021, 2020 and 2019, 717,927 shares, 1,649,348 shares and 4,648,526 shares of common stock, respectively, were subject to repurchase by the Company. The unvested stock liability related to these awards is immaterial to all periods presented.

Equity Incentive Plans

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Equity Incentive Plans

2019 Equity Incentive Plan

In January 2019, the Company’s board of directors and stockholders approved and adopted the 2019 Incentive Award Plan (the “2019 Plan”). The 2019 Plan became effective on February 6, 2019, the day prior to the effectiveness of the registration statement filed in connection with the IPO. Under the 2019 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units, and other stock or cash-based awards to individuals who are then employees, officers, directors or consultants of the Company, and employees and consultants of the Company’s subsidiaries. A total of 5,750,000 shares of common stock were approved to be initially reserved for issuance under the 2019 Plan. The number of shares that remained available for issuance under the 2017 Plan (as defined below) as of the effective date of the 2019 Plan were, and shares subject to outstanding awards under the 2017 Plan as of the effective date of the 2019 Plan that are subsequently canceled, forfeited or repurchased by the Company will be added to the shares reserved under the 2019 Plan. In addition, the number of shares of common stock available for issuance under the 2019 Plan will be automatically increased on the first day of each calendar year during the ten-year term of the 2019 Plan, beginning with January 1, 2020 and ending with January 1, 2029, by an amount equal to 5% of the outstanding number of shares of the Company’s common stock on December 31 of the preceding calendar year or such lesser amount as determined by the Company’s board of directors. As of December 31, 2021, an aggregate of 5,388,985 shares of common stock were available for issuance under the 2019 Plan and 8,402,621 shares of common stock were subject to outstanding awards under the 2019 Plan.

2019 Employee Stock Purchase Plan

In January 2019, the Company’s board of directors and stockholders approved and adopted the ESPP. The ESPP became effective as of February 6, 2019, the day prior to the effectiveness of the registration statement filed in connection with the IPO. The ESPP permits participants to purchase common stock through payroll deductions of up to 20% of their eligible compensation. A total of 700,000 shares of common stock were approved to be initially reserved for issuance under the ESPP. In addition, the number of shares of common stock available for issuance under the ESPP will be automatically increased on the first day of each calendar year during the first ten-years of the term of the ESPP, beginning with January 1, 2020 and ending with January 1, 2029, by an amount equal to 1% of the outstanding number of shares of the Company’s common stock on December 31 of the preceding calendar year or such lesser amount as determined by the Company’s board of directors. During the year ended December 31, 2021, 160,790 shares were issued pursuant to the ESPP. As of December 31, 2021, an aggregate of 1,844,007 shares of common stock were available for issuance under the ESPP.

2017 Equity Incentive Plan

The Company’s 2017 Equity Incentive Plan (the “2017 Plan”) permitted the granting of incentive stock options, non-statutory stock options, restricted stock, restricted stock units and other stock-based awards. Subsequent to the adoption of the 2019 Plan, no additional equity awards can be made under the 2017 Plan. As of December 31, 2021, 2,875,330 shares of common stock were subject to outstanding options under the 2017 Plan, and no shares of restricted stock awards granted under the 2017 plan were unvested.

Fair Value of Stock Option Awards

The fair value of each employee and non-employee stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. The Company estimates its expected volatility based on the historical volatility of a publicly traded set of peer companies. Due to the lack of historical exercise history, the expected term of the Company’s stock options for employees has been determined utilizing the “simplified” method for awards. The expected term of stock options granted to non-employees is equal to the contractual term of the option award. 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 zero based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

The following assumptions were used to estimate the fair value of stock option awards granted to employees under the Company’s equity incentive plans and the shares purchasable under the ESPP during the periods presented:


	Year Ended December 31,
	2021	2020	2019
Employee Stock Options
Expected term (in years)	4.6 - 6.1	4.6 - 6.1	4.6 - 6.1
Risk-free interest rate	0.65% - 1.30%	0.22% - 1.67%	1.38% - 2.58%
Volatility	78.80% - 84.79%	84.38% - 87.23%	70.25% - 86.92%
Dividend yield	—	—	—

Employee Stock Purchase Plan
Expected term (in years)	0.49 - 2.00	0.49 - 2.00	0.49 - 1.99
Risk-free interest rate	0.06% -0.20%	0.12% - 0.95%	1.46% - 1.87%
Volatility	61.29% - 87.13%	85.50% - 99.13%	72.08% - 78.70%
Dividend yield	—	—	—

Stock Options

The following table summarizes stock option activity for the years ended December 31, 2021, 2020 and 2019:


	Shares Subject to Options Outstanding			Weighted- Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
	Shares	Weighted- Average Exercise Price
					(in thousands)
Outstanding as of December 31, 2018	5,107,329	$	7.51	9.7	$	16,343
Options granted	4,194,624	$	20.11
Options exercised	(419,593)	$	4.87
Options forfeited/cancelled	(344,300)	$	11.64
Outstanding as of December 31, 2019	8,538,060	$	13.67	9.0	$	35,385
Options granted	2,712,372	$	13.78
Options exercised	(134,803)	$	3.96
Options forfeited/cancelled	(1,714,547)	$	15.99
Outstanding as of December 31, 2020	9,401,082	$	13.42	8.1	$	10,182
Options granted	3,159,126	$	9.82
Options exercised	(325,494)	$	6.19
Options forfeited/cancelled	(2,800,054)	$	14.14
Outstanding as of December 31, 2021	9,434,660	$	12.24	7.4	$	15,822
Options vested and expected to vest as of December 31, 2021	9,434,660	$	12.24	7.4	15,822
Options exercisable as of December 31, 2021	4,780,459	$	12.63	6.5	10,221

The weighted-average grant date fair value per share for the stock options granted during the year ended December 31, 2021, 2020 and 2019 was $6.93, $9.82 and $13.17, respectively.

The aggregate fair value of stock options that vested during the years ended December 31, 2021, 2020 and 2019 was $21.9 million, $29.9 million and $7.2 million, respectively.

The aggregate intrinsic value in the above table is calculated as the difference between fair value of the Company’s common stock price and the exercise price of the stock options. The aggregate intrinsic value of stock options exercised during the year ended December 31, 2021, 2020 and 2019 was $1.6 million, $1.1 million and $6.9 million, respectively.

At December 31, 2021, the total unrecognized compensation related to unvested stock option awards granted was $34.1 million, which the Company expects to recognize over a weighted-average period of approximately 2.3 years.

Restricted Stock

The summary of the Company’s restricted stock activity during the years ended December 31, 2021, 2020 and 2019 is as follows:


	Number of Restricted Stock Units Outstanding	Weighted- Average Grant Date Fair Value
Nonvested at December 31, 2018	7,482,032	$	4.01
Granted	—	—
Vested	(2,833,506)	4.05
Forfeited / cancelled	—	—
Nonvested at December 31, 2019	4,648,526	$	3.98
Granted	2,003,900	10.96
Vested	(2,557,377)	4.00
Forfeited / cancelled	(764,228)	8.30
Nonvested at December 31, 2020	3,330,821	$	7.16
Granted	1,349,885	10.23
Vested	(1,391,476)	5.86
Forfeited / cancelled	(728,011)	10.03
Nonvested at December 31, 2021	2,561,219	$	8.67

At December 31, 2021, the total unrecognized compensation related to unvested restricted stock awards granted was $15.0 million, which the Company expects to recognize over a weighted-average period of approximately 1.5 years.

Stock-Based Compensation Expense

Stock-based compensation expense has been reported in the Company’s consolidated statements of operations as follows (in thousands):


	Year Ended December 31,
	2021		2020		2019
Research and development	$	18,943	$	18,997	$	10,227
General and administrative	13,065		19,751		10,592
Total stock-based compensation	$	32,008	$	38,748	$	20,819

In connection with the departure of the Company's former President and Chief Executive Officer in November 2020, the Company recognized $5.5 million of incremental stock-based compensation expense during the year ended December 31, 2020, due to a modification of the executive's existing restricted stock award, which included 18 months of accelerated vesting of the executive's outstanding restricted stock in accordance with the terms of the executive's transition agreement.

As of December 31, 2021, total unrecognized compensation expense related to the ESPP was $1.0 million, which the Company expects to recognize over a weighted-average period of approximately 0.9 years.

Property and Equipment, Net

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

The Company’s property and equipment, net consisted of the following (in thousands):


	Estimated Useful Life (in years)	December 31, 2021		December 31, 2020
Office equipment	3-7	$	1,097	$	1,153
Computer equipment	5	123		123
Software	3	130		116
Lab equipment	2-5	5,688		4,210
Leasehold improvements	6-7	2,562		2,540
Construction in process	N/A	—		15
Total property and equipment		9,600		8,157
Less: accumulated depreciation		4,280		2,623
Property and equipment, net		$	5,320	$	5,534

Depreciation expense for the years ended December 31, 2021, 2020 and 2019 was approximately $1.7 million, $1.4 million and $0.9 million, respectively, and was recorded in general and administrative expense and research and development expense, respectively, on the consolidated statements of operations.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2021

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Leases

The Company subleases certain office and laboratory space under a non-cancelable operating lease expiring in January 2025 for the initial leased space and for the expansion space leased pursuant to an amendment to the lease agreement entered into in August 2018. The sublease agreement included options to extend for the entire premises through October 2028. The options to extend must be exercised prior to the termination of the original lease agreement. The period covered by the options was not included in the non-cancellable lease term as it was not determined to be reasonably certain to be executed. In February 2022, the Company exercised its renewal option to extend the term of the expansion space until January 2025. The lease is subject to charges for common area maintenance and other costs, and base rent is subject to an annual 3% increase each subsequent year. Costs determined to be variable and not based on an index or rate were not included in the measurement of the operating lease liabilities.

In November 2019, the Company entered into an additional non-cancelable lease agreement for certain office and laboratory space (the “Permanent Space”) in San Diego, California, commencing on May 1, 2020 and expired on December 31, 2021. The lease agreement included a lease for temporary space commencing on January 1, 2020 and expired on the commencement date of the lease of the Permanent Space. The monthly base rent for the permanent and temporary space was $63,425 and $28,745, respectively. The lease was subject to charges for common area maintenance and other costs, and base rent is subject to an annual 3% increase each subsequent year.

In June 2020, the Company entered into a sublease agreement for the Permanent Space with a third party. The sublease commenced on July 1, 2020 and expired on December 31, 2021. The sublessee paid the monthly base rent of $63,425, subject to an annual 3% increase, and was obligated to pay for common area maintenance and other costs. The sublessee received a 6 months base rent abatement. The Company determined that there was no impairment on the original right-of-use asset and continued to account for the Permanent Space as it did before the commencement of the sublease. The Company recognized $1.1 million and $0.2 million in sublease income for the years ended December 31, 2021 and 2020, respectively.

On July 29, 2020, the Company entered into a lease assignment agreement, whereby it became the assignee to a lease for certain office and laboratory space in Ann Arbor, Michigan. On August 4, 2021, the Company entered into a lease assignment agreement, whereby it assigned the lease to another assignee. The Company derecognized the related operating lease obligation and right-of-use asset of $1.7 million.

Monthly rent expense is recognized on a straight-line basis over the term of the leases. The operating leases are included in the balance sheet at the present value of the lease payments at a weighted average discount rate of 7% using the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment as the leases do not provide an implicit rate. The weighted average remaining lease term was 2.1 years.

Lease costs were comprised of the following (in thousands):


	Year Ended December 31,
	2021		2020		2019
Operating lease cost	$	4,029	$	3,615	$	3,011
Short-term lease cost	53		78		133
Total lease cost	$	4,082	$	3,693	$	3,144

Cash paid for amounts included in the measurement of operating lease liabilities for the years ended December 31, 2021 and 2020 was $4.0 million and $3.6 million, respectively.

Gross future minimum annual rental commitments as of December 31, 2021, were as follows (in thousands):


	Undiscounted Rent Payments
Year ending December 31,
2022	$	3,220
2023	1,694
2024	1,745
Total undiscounted rent payments	$	6,659

Present value discount	(539)
Present value of lease payments	$	6,120
Current portion of operating lease liabilities (included as a component of accrued expenses and other current liabilities)	2,902
Noncurrent operating lease liabilities	3,218
Total operating lease liability	$	6,120

For the years ended December 31, 2021, 2020 and 2019, the Company recorded approximately $4.3 million, $4.0 million and $3.1 million, respectively, in rent expense.

Litigation

Kuhne vs. Gossamer Bio, Inc., et. al.

On April 3, 2020, Scott Kuhne, individually and on behalf of all others similarly situated, filed a putative class action lawsuit against the Company, certain of its executive officers and directors, and the underwriters of its IPO in the United States District Court for the Southern District of California (Case No. 3:20-cv-00649-DMS-DEB). The second amended complaint was filed on November 20, 2020. The complaint was filed on behalf of all investors who purchased the Company's securities pursuant to or traceable to the Company's February 8, 2019 IPO. The complaint alleged that the Company, certain of its executive officers and directors, and the underwriters of its IPO made false and/or misleading statements and failed to disclose material adverse facts about its business, operations and prospects in violation of Sections 11 and 15 of the Securities Act of 1933, as amended. The plaintiff sought damages, interest, costs, attorneys’ fees, and other unspecified equitable relief. The Company moved to dismiss the complaint on January 19, 2021. On April 19, 2021, the Court granted the Company's motion to dismiss in substantial part without leave to amend, and denied the motion to dismiss as to single claim. On October 29, 2021, the parties informed the Court that they had reached a settlement in principle, and the Court vacated all deadlines. The parties entered a settlement agreement on February 1, 2022. Pursuant to the agreement, the Company has agreed to pay approximately $2.4 million, in exchange for customary releases and settlement terms. The lead plaintiff filed a motion for preliminary approval of the settlement and authorization of dissemination of notice to the class on February 2, 2022, which remains pending. In accordance with the authoritative guidance on the evaluation of loss contingencies, the Company recorded a $2.4 million litigation charge related to this matter in the third quarter of 2021, which is included as a component of General and Administrative expense in the Consolidated Statements of Operations and Comprehensive Loss for the year ended December 31, 2021.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Certain prior period amounts have been reclassified to conform to the current period presentation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. The most significant estimates in the Company’s consolidated financial statements relate to the allocation of the 2027 Notes into liability and equity components and accrued research and development expenses. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results could differ from those estimates.
Segments	Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less to be cash equivalents. The carrying amounts reported in the consolidated balance sheets for cash and cash equivalents are valued at cost, which approximate their fair value.
Marketable Securities	Marketable SecuritiesThe Company considers securities with original maturities of greater than 90 days to be marketable securities. The Company has the ability, if necessary, to liquidate any of its cash equivalents and marketable securities to meet its liquidity needs in the next 12 months. Accordingly, those investments with contractual maturities greater than one year from the date of purchase are classified as current assets on the accompanying consolidated balance sheets. The Company’s marketable securities consist of commercial paper and corporate debt securities. Marketable securities are recorded at fair value and unrealized gains and losses are recorded within accumulated other comprehensive loss. The estimated fair value of the marketable securities is determined based on quoted market prices or rates for similar instruments. The Company evaluates securities with unrealized losses to determine whether such losses, if any, are due to credit-related factors. The Company records an allowance for credit losses when unrealized losses are due to credit-related factors. Realized gains and losses are calculated using the specific identification method and recorded as interest income or expense. The Company does not generally intend to sell the investments and it is not more likely than not that it will be required to sell the investments before recovery of their amortized cost bases, which may be at maturity.
Restricted Cash	Restricted Cash Restricted cash as of December 31, 2021, and 2020 represents cash held as collateral for the Company's facility leases.
Concentrations of Credit Risk and Off-Balance Sheet Risk	Concentrations of Credit Risk and Off-Balance Sheet Risk Cash, cash equivalents and marketable securities are financial instruments that are potentially subject to concentrations of credit risk. The Company’s cash and cash equivalents are deposited in accounts at large financial institutions, and amounts may exceed federally insured limits. The Company believes it is not exposed to significant credit risk due to the financial strength of the depository institutions in which the cash and cash equivalents are held. The Company maintains its cash equivalents in U.S. Treasury and agency securities and commercial paper with maturities less than three months and in money market funds that invest in U.S. Treasury and agency securities. The Company’s available for sale securities are also invested in U.S. Treasury and agency securities. The Company has not recognized any losses from credit risks on such accounts during any of the periods presented. The Company believes it is not exposed to significant credit risk on its cash, cash equivalents and available for sale securities.
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net, which consists mainly of office equipment and leasehold improvements, are carried at cost less accumulated depreciation. Depreciation is computed over the estimated useful lives of the respective assets, generally two to seven years, using the straight-line method.
Convertible Senior Notes	Convertible Senior Notes In accounting for the issuance of the 2027 Notes, the Company separated the 2027 Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of similar debt instruments that do not have associated convertible features. The carrying amount of the equity component representing the conversion option was determined by deducting the fair value of the liability component from the par value of the 2027 Notes. The equity component is not remeasured as long as it continues to meet the condition for equity classification. The excess of the principal amount of the liability component over its carrying amount (“debt discount”) is amortized to interest expense over the term of the 2027 Notes. The Company allocated the issuance costs incurred to the liability and equity components of the 2027 Notes based on their relative fair values. Issuance costs attributable to the liability component were recorded as a reduction to the liability portion of the 2027 Notes and are being amortized to interest expense over the term of the 2027 Notes. Issuance costs attributable to the equity component, representing the conversion option, were netted with the equity component in stockholders' equity.
Leases	Leases In accordance with Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842), as adopted on January 1, 2019, the Company determines if an arrangement is a lease at inception. Operating leases are included in the balance sheet as right-of-use assets and operating lease liabilities at the present value of the lease payments calculated using the Company’s incremental borrowing rate, unless the implicit rate is readily available. The Company applied the short-term lease recognition exemption for leases with terms at inception not greater than 12 months and elected to not separate lease and non-lease components for its long-term leases. The Company records rent expense on a straight-line basis over the term of the lease.
Research and Development	Research and Development All research and development costs are expensed as incurred. Research and development costs consist primarily of salaries, employee benefits, costs associated with preclinical studies and clinical trials (including amounts paid to clinical research organizations and other professional services). Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received. The Company records accruals for estimated research and development costs, comprising payments for work performed by third party contractors, laboratories, participating clinical trial sites, and others. Some of these contractors bill monthly based on actual services performed, while others bill periodically based upon achieving certain contractual milestones. For the latter, the Company accrues the expenses as goods or services are used or rendered. Clinical trial site costs related to patient enrollment are accrued as patients enter and progress through the trial. Upfront costs, such as costs associated with setting up clinical trial sites for participation in the trials, are expensed immediately once incurred as research and development expenses.
In process research and development	In process research and development In process research and development costs relate to upfront payment to Aadi in connection with the amendment to the in-license agreement of GB004 and a milestone payment to Pulmokine for the initiation of the Phase 2 clinical trial for seralutinib.
Patent Costs	Patent Costs Costs related to filing and pursuing patent applications are expensed as incurred, as recoverability of such expenditures is uncertain. These costs are included in general and administrative expenses.
Income Taxes	Income Taxes Income taxes are recorded in accordance with Financial Accounting Standards Board (“FASB”) Standards Codification (“ASC”) No. 740, Income Taxes (“ASC 740”), which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit would more likely than not be realized assuming examination by the taxing authority. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. Deferred tax assets and liabilities reflect the future tax consequences of the differences between the financial reporting and tax bases of assets and liabilities using current enacted tax rates. Valuation allowances are recorded when the realizability of such deferred tax assets does not meet a more-likely-than-not threshold. For tax benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by taxing authorities. The Company is subject to taxation in the United States and California, Ireland and Luxembourg. As of December 31, 2021, the Company’s tax years since inception are subject to examination by taxing authorities due to the Company’s unutilized net operating losses ("NOLs") and tax credits.
Stock-Based Compensation	Stock-Based Compensation The Company expenses stock-based compensation to employees and non-employees over the requisite service period based on the estimated grant-date fair value of the awards. The Company records the expense for stock-based compensation awards subject to performance-based milestone vesting over the requisite service period when management determines that achievement of the milestone is probable. Management evaluates when the achievement of a performance-based milestone is probable based on the expected satisfaction of the performance conditions at each reporting date. The Company estimates the fair value of stock option grants and shares purchasable under the Company's 2019 Employee Stock Purchase Plan ("ESPP") using the Black-Scholes option pricing model, and the assumptions used in calculating the fair value of stock-based awards represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment. The Company estimates the fair value of restricted stock units based on the closing price of the Company's common stock on the date of grant. The Company accounts for forfeitures as they occur. All share-based compensation costs are recorded in the statements of operations based upon the underlying employees or non-employee’s roles within the Company.
Foreign Currency	Foreign Currency Assets and liabilities of non-U.S. subsidiaries that operate in a local currency environment, where that local currency is the functional currency, are translated to U.S. dollars at exchange rates in effect at the balance sheet date. Income and expense accounts are translated at average exchange rates during the year which approximate the rates in effect at the transaction dates. The resulting translation adjustments are recorded in accumulated other comprehensive income in the Company's consolidated balance sheets. Foreign exchange transaction gains and losses are included in other income (expense) in the Company’s consolidated statement of operations and comprehensive loss.
Recent Accounting Pronouncements - To Be Adopted	Recent Accounting Pronouncements—To Be Adopted In August 2020, the FASB issued ASU 2020-06, Debt: Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity's Own Equity (Subtopic 815-40) (“ASU 2020-06”), which simplifies the accounting for convertible instruments and contracts in an entity's own equity. This guidance is effective for annual reporting periods beginning after December 15, 2021, including interim periods within those years, with early adoption permitted only as of annual reporting periods beginning after December 15, 2020. The Company plans to adopt ASU 2020-06 on January 1, 2022 using the modified retrospective approach, and accordingly the Company will record an adjustment that reflects the 2027 Notes as if the embedded conversion feature had not been separated. The impact upon adoption on the Consolidated Balance Sheets is anticipated to be an increase of approximately $44.8 million in convertible senior notes, net, a write-off of approximately $9.4 million in deferred income tax liabilities and a decrease of approximately $53.5 million in additional paid-in capital. In addition, upon adoption, there is an adjustment to increase the beginning balance of retained earnings on the Consolidated Balance Sheets for previously recognized interest expense, of approximately $8.7 million for amortization of debt discount related to the carrying value of the embedded conversion feature upon issuance. There will be no impact to the Company’s net loss per share calculation. See Note 7. Debt for further information regarding the 2027 Notes.
Net Loss Per Share	Net Loss Per Share Basic net loss per share of common stock is computed by dividing net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. The Company uses the if-converted method for assumed conversion of the 2027 Notes to compute the weighted average shares of common stock outstanding for diluted net loss per share. Diluted net loss per share excludes the potential impact of the Company’s common stock options and unvested shares of restricted stock and the potential shares issuable upon conversion of the 2027 Notes because their effect would be anti-dilutive due to the Company’s net loss. Since the Company had a net loss in each of the periods presented, basic and diluted net loss per common share are the same.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Schedule of Potentially Dilutive Securities not Included in Calculation of Diluted Net Loss Per Share

The table below provides potentially dilutive securities not included in the calculation of the diluted net loss per share because to do so would be anti-dilutive:


	December 31,
	2021	2020	2019
2027 Notes	12,321,900	12,321,900	—
Shares issuable upon exercise of stock options	9,434,660	9,401,082	8,538,060
Non-vested shares under restricted stock grants	2,561,219	3,330,821	4,648,526

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2021

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):


	Years Ended December 31,
	2021		2020
Accrued compensation	$	11,916	$	12,194
Operating lease liabilities	2,902		3,633
Accrued consulting fees	956		1,919
Accrued interest	1,066		1,094
Accrued legal fees	202		619
Accrued litigation liability	2,375		—
Accrued accounting fees	154		285
Accrued in process research and development	—		225
Accrued other	839		742
Total accrued expenses	$	20,410	$	20,711

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Assets Measured at Fair Value on Recurring Basis

The following table presents the hierarchy for assets measured at fair value on a recurring basis as of December 31, 2021 and 2020 (in thousands):


	Fair Value Measurements at End of Period Using:
	Total Fair Value		Quoted Market Prices for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
As of December 31, 2021
Money market funds	$	139,794	$	139,794	$	—	$	—
Commercial paper	113,939		—		113,939		—
Corporate debt securities	37,873		—		37,873		—
As of December 31, 2020
Money market funds	$	411,104	$	411,104	$	—	$	—
U.S. Treasury and agency securities	18,280		18,280		—		—
Corporate debt securities	26,573		—		26,573		—

Schedule of Available for Sale Investments by Security Type


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Total Fair Value
As of December 31, 2021
Corporate debt securities	$	37,921	$	—	$	(48)	$	37,873
Commercial paper	$	103,942	$	—	$	—	$	103,942
Total marketable securities	$	141,863	$	—	$	(48)	$	141,815
As of December 31, 2020
Corporate debt securities	$	26,396	$	177	$	—	$	26,573
Total marketable securities	$	26,396	$	177	$	—	$	26,573

Schedule of Contractual Maturities of Available-for-sale Debt Securities

Contractual maturities of available-for-sale debt securities, as of December 31, 2021, were as follows (in thousands):


	Estimated Fair Value
Less than one year	$	141,815
Greater than one year	—
Total	$	141,815

Indebtedness (Tables)

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Schedule of Long-Term Debt

Long-term debt as of December 31, 2021 consisted of the following (in thousands):


	December 31, 2021
Term loan	$	30,000
Debt discount and issuance costs	(921)
Long-term debt	$	29,079

The net carrying amount of the liability component of the 2027 Notes was as follows (in thousands):


	December 31, 2021		December 31, 2020
Principal amount	$	200,000	$	200,000
Unamortized debt discount	(49,716)		(56,080)
Unamortized debt issuance cost	(246)		(278)
Net carrying amount	$	150,038	$	143,642

The net carrying amount of the equity component of the 2027 Notes was as follows (in thousands):


	December 31, 2021		December 31, 2020
Debt discount related to the value of conversion option	$	53,635	$	53,635
Debt issuance cost	(109)		(109)
Net carrying amount	$	53,526	$	53,526

The following table sets forth the interest expense recognized related to the 2027 Notes (in thousands):


	Years Ended December 31,
	December 31, 2021		December 31, 2020		December 31, 2019
Contractual interest expense	$	9,972	$	6,139	$	—
Amortization of debt discount	6,364		3,555		—
Amortization of debt issuance cost	32		17		—
Total interest expense related to the 2027 Notes	$	16,368	$	9,711	$	—

Schedule of Future Minimum Principal Payments

The scheduled future minimum principal payments are as follows (in thousands):


	December 31, 2021
2022	5,806
2023	11,613
2024	11,613
2025	968
Total	$	30,000

License and Asset Acquisitions (Tables)

12 Months Ended

Dec. 31, 2021

Business Combination and Asset Acquisition [Abstract]

Schedule of IPR&D Expense

The Company recorded the following IPR&D expense on the consolidated statements of operations (in thousands):


	Years Ended December 31,
	2021		2020		2019
Seralutinib	$	—	$	5,000	$	—
GB004	—		15,000		—
GB1275	—		—		1,000
Other preclinical programs	75		3,380		2,600
Total in process research and development	$	75	$	23,380	$	3,600

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Schedule of Amount of Net Loss Before Taxes

The amount of net loss before taxes for the years ended December 31, 2021, 2020, and 2019 is as follows (in thousands):


	December 31,
	2021		2020		2019
	(in thousands)
U.S. loss before taxes	$	183,194	$	186,888	$	138,342
Foreign loss before taxes	50,802		56,472		41,965
Loss before income taxes	$	233,996	$	243,360	$	180,307

Schedule of Deferred Tax Assets and Liabilities


	December 31,
	2021		2020		2019
	(in thousands)
Deferred tax assets:
Net operating losses	$	116,425	$	77,946	$	43,626
Tax credits, net	24,964		17,372		9,196
Amortization	9,190		10,939		6,597
Stock-based compensation	4,917		4,448		1,388
Lease liability	1,285		2,383		2,329
Accrued compensation	2,238		2,137		1,476
Other	18		16		383
Total gross deferred tax assets	159,037		115,241		64,995

Deferred tax liabilities:
Convertible senior notes	(9,395)		(10,592)		—
Right of use asset	(1,150)		(2,215)		(2,164)
Property, plant and equipment	(790)		(776)		(57)
Total gross deferred tax liabilities	(11,335)		(13,583)		(2,221)

Valuation allowance	(147,702)		(101,658)		(62,774)
Net deferred tax asset	$	—	$	—	$	—

Reconciliation of the Federal Statutory Income Tax Rate to Effective Income Tax Rate

A reconciliation of the federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	December 31,
	2021		2020		2019
Federal statutory income tax rate	21.00	%	21.00	%	21.00	%
State income taxes, net of federal benefit	—	%	—	%	—	%
Change in valuation allowance	(19.73	%)	(19.50	%)	(22.12	%)
Research and experimentation credits	2.62	%	2.76	%	3.81	%
Foreign rate differential	(1.95	%)	(1.64	%)	(1.84	%)
Stock-based compensation	(1.56	%)	(1.81	%)	—	%
Nondeductible interest	(0.96	%)	—	%	—	%
Other	0.57	%	(0.80	%)	(0.85	%)
Provision for income taxes	—	%	—	%	—	%

Schedule of Reconciliation of Beginning and Ending Amounts of Unrecognized Tax Benefits, Excluding Interest and Penalties

A reconciliation of the beginning and ending amount of unrecognized tax benefits for 2021, 2020, and 2019, excluding interest and penalties, is as follows:


	December 31,
	2021		2020		2019
	(in thousands)
Balance at beginning of the year	$	5,060	$	2,754	$	408
Increase related to current year positions	2,491		2,306		2,346
Balance at the end of the year	$	7,551	$	5,060	$	2,754

Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Summary of Fair Value of Stock Option Award Granted


	Year Ended December 31,
	2021	2020	2019
Employee Stock Options
Expected term (in years)	4.6 - 6.1	4.6 - 6.1	4.6 - 6.1
Risk-free interest rate	0.65% - 1.30%	0.22% - 1.67%	1.38% - 2.58%
Volatility	78.80% - 84.79%	84.38% - 87.23%	70.25% - 86.92%
Dividend yield	—	—	—

Employee Stock Purchase Plan
Expected term (in years)	0.49 - 2.00	0.49 - 2.00	0.49 - 1.99
Risk-free interest rate	0.06% -0.20%	0.12% - 0.95%	1.46% - 1.87%
Volatility	61.29% - 87.13%	85.50% - 99.13%	72.08% - 78.70%
Dividend yield	—	—	—

Summary of Stock Option Activity

The following table summarizes stock option activity for the years ended December 31, 2021, 2020 and 2019:


	Shares Subject to Options Outstanding			Weighted- Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
	Shares	Weighted- Average Exercise Price
					(in thousands)
Outstanding as of December 31, 2018	5,107,329	$	7.51	9.7	$	16,343
Options granted	4,194,624	$	20.11
Options exercised	(419,593)	$	4.87
Options forfeited/cancelled	(344,300)	$	11.64
Outstanding as of December 31, 2019	8,538,060	$	13.67	9.0	$	35,385
Options granted	2,712,372	$	13.78
Options exercised	(134,803)	$	3.96
Options forfeited/cancelled	(1,714,547)	$	15.99
Outstanding as of December 31, 2020	9,401,082	$	13.42	8.1	$	10,182
Options granted	3,159,126	$	9.82
Options exercised	(325,494)	$	6.19
Options forfeited/cancelled	(2,800,054)	$	14.14
Outstanding as of December 31, 2021	9,434,660	$	12.24	7.4	$	15,822
Options vested and expected to vest as of December 31, 2021	9,434,660	$	12.24	7.4	15,822
Options exercisable as of December 31, 2021	4,780,459	$	12.63	6.5	10,221

Summary of Restricted Stock Activity

The summary of the Company’s restricted stock activity during the years ended December 31, 2021, 2020 and 2019 is as follows:


	Number of Restricted Stock Units Outstanding	Weighted- Average Grant Date Fair Value
Nonvested at December 31, 2018	7,482,032	$	4.01
Granted	—	—
Vested	(2,833,506)	4.05
Forfeited / cancelled	—	—
Nonvested at December 31, 2019	4,648,526	$	3.98
Granted	2,003,900	10.96
Vested	(2,557,377)	4.00
Forfeited / cancelled	(764,228)	8.30
Nonvested at December 31, 2020	3,330,821	$	7.16
Granted	1,349,885	10.23
Vested	(1,391,476)	5.86
Forfeited / cancelled	(728,011)	10.03
Nonvested at December 31, 2021	2,561,219	$	8.67

Stock-Based Compensation Expense Reported in Condensed Consolidated Statements of Operations

Stock-based compensation expense has been reported in the Company’s consolidated statements of operations as follows (in thousands):


	Year Ended December 31,
	2021		2020		2019
Research and development	$	18,943	$	18,997	$	10,227
General and administrative	13,065		19,751		10,592
Total stock-based compensation	$	32,008	$	38,748	$	20,819

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment, Net

The Company’s property and equipment, net consisted of the following (in thousands):


	Estimated Useful Life (in years)	December 31, 2021		December 31, 2020
Office equipment	3-7	$	1,097	$	1,153
Computer equipment	5	123		123
Software	3	130		116
Lab equipment	2-5	5,688		4,210
Leasehold improvements	6-7	2,562		2,540
Construction in process	N/A	—		15
Total property and equipment		9,600		8,157
Less: accumulated depreciation		4,280		2,623
Property and equipment, net		$	5,320	$	5,534

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2021

Commitments and Contingencies Disclosure [Abstract]

Schedule of Lease Costs

Lease costs were comprised of the following (in thousands):


	Year Ended December 31,
	2021		2020		2019
Operating lease cost	$	4,029	$	3,615	$	3,011
Short-term lease cost	53		78		133
Total lease cost	$	4,082	$	3,693	$	3,144

Schedule of Gross Future Minimum Annual Rental Commitments

Gross future minimum annual rental commitments as of December 31, 2021, were as follows (in thousands):


	Undiscounted Rent Payments
Year ending December 31,
2022	$	3,220
2023	1,694
2024	1,745
Total undiscounted rent payments	$	6,659

Present value discount	(539)
Present value of lease payments	$	6,120
Current portion of operating lease liabilities (included as a component of accrued expenses and other current liabilities)	2,902
Noncurrent operating lease liabilities	3,218
Total operating lease liability	$	6,120

Organization and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	51 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	May 21, 2020
Organization and Basis of Presentation [Line Items]
Retained earnings (accumulated deficit)	$ (811,534)	$ (577,530)
Funds raised through Series A and Series B Convertible Preferred Stock, convertible note financings and completed IPO	$ 942,000
2027 Notes
Organization and Basis of Presentation [Line Items]
Interest rate			5.00%

- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

+ References + Details

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) segment	Jan. 01, 2022 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Number of operating segments \| segment	1
Long-term convertible senior notes	$ 150,038		$ 143,642
Deferred tax liabilities written off	11,335		13,583	$ 2,221
Stockholders' equity attributable to parent	$ 121,463		320,684	352,485	$ (120,069)
Minimum
Debt Instrument [Line Items]
Property and equipment, estimated useful life	2 years
Maximum
Debt Instrument [Line Items]
Property and equipment, estimated useful life	7 years
Additional paid-in capital
Debt Instrument [Line Items]
Stockholders' equity attributable to parent	$ 932,944		897,607	686,390	33,853
Accumulated deficit
Debt Instrument [Line Items]
Stockholders' equity attributable to parent	$ (811,534)		$ (577,530)	$ (334,170)	$ (153,863)
Subsequent Event \| Cumulative Effect, Period of Adoption, Adjustment
Debt Instrument [Line Items]
Long-term convertible senior notes		$ 44,800
Deferred tax liabilities written off		(9,400)
Subsequent Event \| Cumulative Effect, Period of Adoption, Adjustment \| Additional paid-in capital
Debt Instrument [Line Items]
Stockholders' equity attributable to parent		(53,500)
Subsequent Event \| Cumulative Effect, Period of Adoption, Adjustment \| Accumulated deficit
Debt Instrument [Line Items]
Stockholders' equity attributable to parent		$ 8,700

Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities not Included in Calculation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
2027 Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included from calculation of diluted net loss per share (in shares)	12,321,900	12,321,900	0
Shares issuable upon exercise of stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included from calculation of diluted net loss per share (in shares)	9,434,660	9,401,082	8,538,060
Non-vested shares under restricted stock grants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included from calculation of diluted net loss per share (in shares)	2,561,219	3,330,821	4,648,526

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued compensation	$ 11,916	$ 12,194
Operating lease liabilities	$ 2,902	$ 3,633
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued expenses and other current liabilities	Accrued expenses and other current liabilities
Accrued consulting fees	$ 956	$ 1,919
Accrued interest	1,066	1,094
Accrued legal fees	202	619
Accrued litigation liability	2,375	0
Accrued accounting fees	154	285
Accrued in process research and development	0	225
Accrued other	839	742
Accrued expenses and other current liabilities	$ 20,410	$ 20,711

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 10,000	$ 18,300
Significant Other Observable Inputs (Level 2) \| 2027 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	190,500	198,500
Prepaid Expenses and Other Current Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest receivable	$ 200	$ 200

Fair Value Measurements - Schedule of Available for sale Investments by Security Type (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 141,863	$ 26,396
Gross Unrealized Gains	0	177
Gross Unrealized Losses	(48)	0
Total Fair Value	141,815	26,573
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	37,921	26,396
Gross Unrealized Gains	0	177
Gross Unrealized Losses	(48)	0
Total Fair Value	37,873	$ 26,573
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	103,942
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total Fair Value	$ 103,942

Fair Value Measurements - Schedule of Contractual Maturities of Available-for-sale Debt Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Less than one year	$ 141,815
Greater than one year	0
Total Fair Value	$ 141,815	$ 26,573

Indebtedness - Additional Information (Details)			12 Months Ended
Indebtedness - Additional Information (Details)	May 21, 2020 USD ($) tradingDay $ / shares	May 02, 2019 USD ($) tranche	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Amount funded			$ 0	$ 0	$ 28,222,000
Proceeds from issuance of convertible senior notes, net			0	$ 193,596,000	$ 0
Term Loan \| Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 150,000,000
Amount funded		30,000,000
Remaining borrowing capacity		$ 120,000,000
Number of additional tranches \| tranche		2
Percentage of exit fee on amount borrowed on final repayment		1.75%
Percentage of exit fee on amount borrowed on partial prepayment		1.75%
Debt covenant minimum unrestricted cash percentage		25.00%
Debt instrument, default trigger amount			$ 2,500,000
Term Loan \| Prepayment Occurs through First Anniversary of Closing Date \| Credit Facility
Debt Instrument [Line Items]
Percentage of prepayment fee		3.00%
Term Loan \| First Anniversary of Closing Date through Second Anniversary of Closing Date \| Credit Facility
Debt Instrument [Line Items]
Percentage of prepayment fee		2.00%
Term Loan \| Second Anniversary of Closing Date and Prior to January 1, 2025 \| Credit Facility
Debt Instrument [Line Items]
Percentage of prepayment fee		1.00%
Term Loan \| LIBOR \| Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate		7.00%
Interest rate		2.00%
Term Loan \| MidCap Financial Trust \| Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate			3.00%
Term Loan \| Tranche One \| Credit Facility
Debt Instrument [Line Items]
Remaining borrowing capacity		$ 60,000,000
Term Loan \| Tranche Two \| Credit Facility
Debt Instrument [Line Items]
Remaining borrowing capacity		$ 60,000,000
2027 Notes
Debt Instrument [Line Items]
Interest rate	5.00%
Debt instrument aggregate principal amount	$ 200,000,000
Proceeds from issuance of convertible senior notes, net	$ 193,600,000
Debt instrument, convertible, conversion ratio	0.0616
Debt instrument, conversion price (in dollars per share) \| $ / shares	$ 16.23
Debt instrument, conversion price (in percentage)	130.00%
Debt conversion, converted instrument, amount	$ 1,000
Debt instrument, redemption price (in percentage)	100.00%
Percentage of repurchase price is equal to principal amount of convertible notes	100.00%
Long-term debt, percentage in aggregate principal amount	0.25
Debt instrument, convertible, carrying amount of equity component	$ 53,500,000
Effective interest rate	11.17%
Debt issuance costs	$ 400,000
Amortization of debt issuance cost	$ 300,000
2027 Notes \| Minimum \| One Hundred Thirty Percent Applicable Conversion Price
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days \| tradingDay	20
2027 Notes \| Minimum \| Ninety Eight Percent Applicable Conversion Price
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days \| tradingDay	5
2027 Notes \| Maximum
Debt Instrument [Line Items]
Debt instrument convertible conversion last reported sale price (in percentage)	98.00%
2027 Notes \| Maximum \| One Hundred Thirty Percent Applicable Conversion Price
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days \| tradingDay	30
2027 Notes \| Maximum \| Ninety Eight Percent Applicable Conversion Price
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days \| tradingDay	10

Indebtedness - Schedule of Long-term Debt (Details) - Credit Facility $ in Thousands	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
Term loan	$ 30,000
Debt discount and issuance costs	(921)
Long-term debt	$ 29,079

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References + Details

Indebtedness - Schedule of Future Minimum Principal Payments (Details) - Credit Facility $ in Thousands	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
2022	$ 5,806
2023	11,613
2024	11,613
2025	968
Total	$ 30,000

Indebtedness - Schedule of Net Carrying Amount of Liability Component (Details) - 2027 Notes - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Principal amount	$ 200,000	$ 200,000
Unamortized debt discount	(49,716)	(56,080)
Unamortized debt issuance cost	(246)	(278)
Long-term debt	$ 150,038	$ 143,642

- Definition

+ References + Details

Indebtedness - Schedule of Equity Components (Details) - 2027 Notes - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt discount related to the value of conversion option	$ 53,635	$ 53,635
Debt issuance cost	(109)	(109)
Net carrying amount	$ 53,526	$ 53,526

Indebtedness - Schedule of Interest Expense Recognized (Details) - 2027 Notes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Contractual interest expense	$ 9,972	$ 6,139	$ 0
Amortization of debt discount	6,364	3,555	0
Amortization of debt issuance cost	32	17	0
Total interest expense related to the 2027 Notes	$ 16,368	$ 9,711	$ 0

License and Asset Acquisitions - Additional Information (Details) - USD ($)				1 Months Ended			12 Months Ended
	May 11, 2020	Sep. 21, 2018	Oct. 02, 2017	May 31, 2019	Jun. 30, 2018	Oct. 31, 2017	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
In process research and development							$ 75,000	$ 23,380,000	$ 3,600,000
Seralutinib
Business Acquisition [Line Items]
In process research and development							0	5,000,000	0
GB004
Business Acquisition [Line Items]
In process research and development							0	15,000,000	0
GB1275
Business Acquisition [Line Items]
In process research and development							0	0	$ 1,000,000
Pulmokine, Inc. \| License Agreement \| Seralutinib
Business Acquisition [Line Items]
Product license term			10 years
Upfront payment						$ 5,500,000
Milestones accrued							0	5,000,000
Pulmokine, Inc. \| License Agreement \| Seralutinib \| Maximum
Business Acquisition [Line Items]
Development and regulatory milestone payments, payable			$ 58,000,000
Commercial milestone payments, payable			45,000,000
Sales milestone payments, payable			$ 190,000,000
Aadi Biosciences, Inc. \| License Agreement \| GB004
Business Acquisition [Line Items]
Upfront payment	$ 15,000,000
Milestones accrued							0	0
Upfront payment, purchase consideration paid					$ 20,000,000
Participation right (in percentage)					20.00%
Aadi Biosciences, Inc. \| License Agreement \| GB004 \| Maximum
Business Acquisition [Line Items]
Development and regulatory milestone payments, payable	40,000,000
Sales milestone payments, payable	$ 50,000,000
Adhaere Pharmaceuticals, Inc. \| GB1275
Business Acquisition [Line Items]
Milestones accrued							$ 0	$ 0
Upfront payment, purchase consideration paid		$ 7,500,000
In process research and development		7,500,000
Milestones payment				$ 1,000,000
Adhaere Pharmaceuticals, Inc. \| GB1275 \| Maximum
Business Acquisition [Line Items]
Regulatory, development and sales milestone payments payable		$ 62,000,000

License and Asset Acquisitions - Schedule of IPR&D Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development	$ 75	$ 23,380	$ 3,600
Seralutinib
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development	0	5,000	0
GB004
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development	0	15,000	0
GB1275
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development	0	0	1,000
Other preclinical programs
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development	$ 75	$ 3,380	$ 2,600

Income Taxes - Schedule of Amount of Net Loss Before Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
U.S. loss before taxes	$ 183,194	$ 186,888	$ 138,342
Foreign loss before taxes	50,802	56,472	41,965
Loss before income taxes	$ 233,996	$ 243,360	$ 180,307

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Paragraph 30
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-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Section 25
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
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Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
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Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 942
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-Section S99
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-Subparagraph (SX 210.9-05(b)(2))
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Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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+ Details

Income Taxes - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)
Operating Loss Carryforwards [Line Items]
Increase (decrease) in valuation allowance	$ 46.0
Unrecognized tax benefits that would not impact effective tax rate	7.6
Orphan Drug Credit
Operating Loss Carryforwards [Line Items]
Research and development credit	$ 25.7
Maximum
Operating Loss Carryforwards [Line Items]
Net operating losses carryforward available to offset future federal taxable income , percentage	80.00%
Federal
Operating Loss Carryforwards [Line Items]
Net operating losses (“NOL”) carryforwards	$ 460.4
Net operating losses (“NOL”) that can be carried forward indefinitely	457.5
Research and development credit	25.7
California
Operating Loss Carryforwards [Line Items]
Net operating losses (“NOL”) carryforwards	1.1
Research and development credit	8.0
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Net operating losses (“NOL”) carryforwards	$ 157.2

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating losses	$ 116,425	$ 77,946	$ 43,626
Tax credits, net	24,964	17,372	9,196
Amortization	9,190	10,939	6,597
Stock-based compensation	4,917	4,448	1,388
Lease liability	1,285	2,383	2,329
Accrued compensation	2,238	2,137	1,476
Other	18	16	383
Total gross deferred tax assets	159,037	115,241	64,995
Deferred tax liabilities:
Convertible senior notes	(9,395)	(10,592)	0
Right of use asset	(1,150)	(2,215)	(2,164)
Property, plant and equipment	(790)	(776)	(57)
Total gross deferred tax liabilities	(11,335)	(13,583)	(2,221)
Valuation allowance	(147,702)	(101,658)	(62,774)
Net deferred tax asset	$ 0	$ 0	$ 0

Income Taxes - Reconciliation of Federal Statutory Income Tax Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal benefit	0.00%	0.00%	0.00%
Change in valuation allowance	(19.73%)	(19.50%)	(22.12%)
Research and experimentation credits	2.62%	2.76%	3.81%
Foreign rate differential	(1.95%)	(1.64%)	(1.84%)
Stock-based compensation	(1.56%)	(1.81%)	0.00%
Nondeductible interest	(0.96%)	0.00%	0.00%
Other	0.57%	(0.80%)	(0.85%)
Provision for income taxes	0.00%	0.00%	0.00%

Income Taxes - Schedule of Reconciliation of Beginning and Ending Amounts of Unrecognized Tax Benefits, Excluding Interest and Penalties (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of the year	$ 5,060	$ 2,754	$ 408
Increase related to current year positions	2,491	2,306	2,346
Balance at the end of the year	$ 7,551	$ 5,060	$ 2,754

Stockholders' Equity - Additional Information (Details)						3 Months Ended	12 Months Ended
Stockholders' Equity - Additional Information (Details)	May 21, 2020 USD ($) $ / shares shares	Sep. 06, 2018 $ / shares shares	May 21, 2018 $ / shares shares	Jan. 04, 2018	Dec. 03, 2015 USD ($) $ / shares shares	Mar. 31, 2019 shares	Dec. 31, 2021 USD ($) vote shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares
Stockholders Equity Deficit [Line Items]
Common stock, voting right per share \| vote							1
Sale of shares of common stock (in shares)	9,433,963
Offering price (in dollars per share) \| $ / shares	$ 13.25
Proceeds from issuance of common stock \| $	$ 117,100,000						$ 0	$ 117,110,000	$ 291,311,000
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs \| $								$ 117,094,000	$ 291,311,000
Shares of common stock, repurchase (in shares)							717,927	1,649,348	4,648,526
Stock Restriction Agreements
Stockholders Equity Deficit [Line Items]
Shares subject to forfeiture (in shares)							25,383
Founder
Stockholders Equity Deficit [Line Items]
Sale of shares of common stock (in shares)		1,795,023	251,547
Issuance price per share (in dollars per share) \| $ / shares		$ 9.63	$ 2.61
Percentage of fully diluted share capital							15.00%
Increased in equity capital amount \| $							$ 300,000,000
Additional shares of restricted stock subject to vesting restrictions (in shares)		1,795,023	251,547
Founder Shares
Stockholders Equity Deficit [Line Items]
Sale of shares of common stock (in shares)					9,160,888
Issuance price per share (in dollars per share) \| $ / shares					$ 0.0001
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs \| $					$ 4,100
Common Stock vesting percentage				50.00%
Common stock vesting period				5 years
Common stock
Stockholders Equity Deficit [Line Items]
Conversion of convertible preferred stock into common stock (in shares)						30,493,460			30,493,460
Sale of shares of common stock (in shares)								9,433,963	19,837,500
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs \| $								$ 1,000	$ 2,000

Equity Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Feb. 06, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding awarded (in shares)		9,434,660	9,401,082	8,538,060	5,107,329
Expected dividends yield (in percentage)		0.00%
Total stock-based compensation		$ 32,008	$ 38,748	$ 20,819
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation, recognition period		1 year 6 months
Unrecognized compensation related to unvested restricted stock awards		$ 15,000
Restricted Stock \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation		$ 5,500
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividends yield (in percentage)		0.00%	0.00%	0.00%
Weighted-average grant date fair value (in dollars per share)		$ 6.93	$ 9.82	$ 13.17
Aggregate fair value of stock options vested		$ 21,900	$ 29,900	$ 7,200
Aggregate intrinsic value, options vested in period		1,600	$ 1,100	$ 6,900
Unrecognized compensation related to unvested stock option		$ 34,100
Unrecognized compensation, recognition period		2 years 3 months 18 days
2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share reserved for future issuance (in shares)	5,750,000
Term of awards	10 years
Percentage of amount increase in outstanding shares	5.00%
Common stock available for issuance (in shares)		5,388,985
Shares reserved for issuance on granting of outstanding awards (in shares)		8,402,621
2019 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share reserved for future issuance (in shares)	700,000
Percentage of amount increase in outstanding shares	1.00%
Number of shares issued under ESPP plan		160,790
Number of share reserved for future issuance (in shares)		1,844,007
2019 Employee Stock Purchase Plan \| Stock-Based Compensation Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation related to unvested stock option		$ 1,000
Unrecognized compensation, recognition period		10 months 24 days
2019 Employee Stock Purchase Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase of common stock through payroll deductions, percentage	20.00%
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding awarded (in shares)		2,875,330
2017 Equity Incentive Plan \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards granted (in shares)		0

Equity Incentive Plans - Schedule of Fair Value Assumptions Stock Options (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividends yield (in percentage)	0.00%
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	0.65%	0.22%	1.38%
Risk-free interest rate, maximum	1.30%	1.67%	2.58%
Volatility, minimum	78.80%	84.38%	70.25%
Volatility, maximum	84.79%	87.23%	86.92%
Expected dividends yield (in percentage)	0.00%	0.00%	0.00%
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	0.06%	0.12%	1.46%
Risk-free interest rate, maximum	0.20%	0.95%	1.87%
Volatility, minimum	61.29%	85.50%	72.08%
Volatility, maximum	87.13%	99.13%	78.70%
Expected dividends yield (in percentage)	0.00%	0.00%	0.00%
Minimum \| Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected life (in years)	4 years 7 months 6 days	4 years 7 months 6 days	4 years 7 months 6 days
Minimum \| ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected life (in years)	5 months 26 days	5 months 26 days	5 months 26 days
Maximum \| Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected life (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days
Maximum \| ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected life (in years)	2 years	2 years	1 year 11 months 26 days

Equity Incentive Plans - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares Subject to Options Outstanding, Beginning (in shares)	9,401,082	8,538,060	5,107,329
Shares Subject to Options Outstanding, Options granted (in shares)	3,159,126	2,712,372	4,194,624
Shares Subject to Options Outstanding, Option exercised (in shares)	(325,494)	(134,803)	(419,593)
Shares Subject to Options Outstanding, Options forfeited/cancelled (in shares)	(2,800,054)	(1,714,547)	(344,300)
Shares Subject to Options Outstanding, Ending (in shares)	9,434,660	9,401,082	8,538,060	5,107,329
Options vested and expected to vest as of period end (in shares)	9,434,660
Options vested and exercisable as of period end (in shares)	4,780,459
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-Average Exercise Price, Outstanding, beginning (in dollars per share)	$ 13.42	$ 13.67	$ 7.51
Weighted-Average Exercise Price, Options granted (in dollars per share)	9.82	13.78	20.11
Weighted-Average Exercise Price, Option exercised (in dollars per share)	6.19	3.96	4.87
Weighted-Average Exercise Price, Options forfeited/cancelled (in dollars per share)	14.14	15.99	11.64
Weighted-Average Exercise Price, Outstanding, ending (in dollars per share)	12.24	$ 13.42	$ 13.67	$ 7.51
Weighted-Average Exercise Price, Options vested and expected to vest as of period end (in dollars per share)	12.24
Weighted-Average Exercise Price, Options vested and exercisable as of period end (in dollars per share)	$ 12.63
Weighted-Average Remaining Contractual Life (Years), Outstanding	7 years 4 months 24 days	8 years 1 month 6 days	9 years	9 years 8 months 12 days
Weighted-Average Remaining Contractual Life (Years), Options vested and expected to vest	7 years 4 months 24 days
Weighted-Average Remaining Contractual Life (Years), Options vested and exercisable	6 years 6 months
Aggregate Intrinsic Value	$ 15,822	$ 10,182	$ 35,385	$ 16,343
Options vested and expected to vest, aggregate intrinsic value	15,822
Options vested and exercisable, aggregate intrinsic value	$ 10,221

Equity Incentive Plans - Summary of Restricted Stock Activity (Details) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of Restricted Stock Units Outstanding, Nonvested, beginning (in shares)	3,330,821	4,648,526	7,482,032
Number of Restricted Stock Units Outstanding, Granted (in shares)	1,349,885	2,003,900	0
Number of Restricted Stock Units Outstanding, Vested (in shares)	(1,391,476)	(2,557,377)	(2,833,506)
Number of Restricted Stock Units Outstanding, Forfeited/cancelled (in shares)	(728,011)	(764,228)	0
Number of Restricted Stock Units Outstanding, Nonvested, ending (in shares)	2,561,219	3,330,821	4,648,526
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-Average Grant Date Fair Value, Nonvested (in dollars per share)	$ 7.16	$ 3.98	$ 4.01
Weighted-Average Grant Date Fair Value, Granted (in dollars per share)	10.23	10.96	0
Weighted-Average Grant Date Fair Value, Vested (in dollars per share)	5.86	4.00	4.05
Weighted-Average Grant Date Fair Value, Forfeited/cancelled (in dollars per share)	10.03	8.30	0
Weighted-Average Grant Date Fair Value, Nonvested (in dollars per share)	$ 8.67	$ 7.16	$ 3.98

Equity Incentive Plans - Stock-Based Compensation Expense Reported in Condensed Consolidated Statements of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Incremental stock compensation expense	$ 32,008	$ 38,748	$ 20,819
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Incremental stock compensation expense	18,943	18,997	10,227
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Incremental stock compensation expense	$ 13,065	$ 19,751	$ 10,592

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 9,600	$ 8,157
Less: accumulated depreciation	4,280	2,623
Property and equipment, net	$ 5,320	5,534
Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	2 years
Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	7 years
Office equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,097	1,153
Office equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Office equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	7 years
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	5 years
Total property and equipment	$ 123	123
Software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Total property and equipment	$ 130	116
Lab equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 5,688	4,210
Lab equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	2 years
Lab equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 2,562	2,540
Leasehold improvements \| Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	6 years
Leasehold improvements \| Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	7 years
Construction in process
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 0	$ 15

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1.7	$ 1.4	$ 0.9

Commitments and Contingencies - Additional Information (Details) - USD ($)			1 Months Ended		12 Months Ended
	Oct. 29, 2021	Aug. 04, 2021	Jun. 30, 2020	Nov. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Weighted average discount rate, operating leases					7.00%
Weighted average remaining lease term					2 years 1 month 6 days
Derecognition ROU lease assets obtained in exchange for operating lease liabilities					$ 1,650,000	$ 0	$ 0
Cash paid for operating lease liabilities					4,000,000	3,600,000
Rent expense					$ 4,300,000	4,000,000	$ 3,100,000
Gain (loss) on litigation settlement	$ 2,400,000
Non-cancelable Lease Agreement Entered in August 2018
Lessee, Lease, Description [Line Items]
Operating sublease, annual increase percentage for base rent					3.00%
Additional Non-cancelable Lease Agreement In Nov 2019
Lessee, Lease, Description [Line Items]
Monthly base rent for permanent space				$ 63,425
Monthly base rent for temporary space				$ 28,745
Annual increase percentage for lease charges				3.00%
Sublease Agreement Entered in June 2020
Lessee, Lease, Description [Line Items]
Sublease temporary monthly base rent			$ 63,425
Weighted average discount rate, operating leases			3.00%
Weighted average remaining lease term			6 months
Sublease Income					$ 1,100,000	$ 200,000
Lease Assignment Agreement Entered in July 2020
Lessee, Lease, Description [Line Items]
Derecognition ROU lease assets obtained in exchange for operating lease liabilities		$ 1,700,000

Commitments and Contingencies - Schedule of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 4,029	$ 3,615	$ 3,011
Short-term lease cost	53	78	133
Total lease cost	$ 4,082	$ 3,693	$ 3,144

Commitments and Contingencies - Schedule of Gross Future Minimum Annual Rental Commitments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
2022	$ 3,220
2023	1,694
2024	1,745
Total undiscounted rent payments	6,659
Present value discount	(539)
Present value of lease payments	6,120
Operating lease liabilities	2,902	$ 3,633
Operating lease liabilities - long-term	3,218	$ 7,713
Total operating lease liability	$ 6,120