Gossamer Bio (GOSS) 10-Q 6 May 21 2021 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Mar. 31, 2021	May 03, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Entity File Number	001-38796
Entity Registrant Name	GOSSAMER BIO, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-5461709
Entity Address, Address Line One	3013 Science Park Road
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	684-1300
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	GOSS
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		75,909,708
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001728117
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 439,659	$ 486,055
Marketable securities	13,638	26,573
Restricted cash	565	565
Prepaid expenses and other current assets	11,985	9,129
Total current assets	465,847	522,322
Property and equipment, net	5,920	5,534
Operating lease right-of-use assets	9,692	10,550
Other assets	1,010	1,027
Total assets	482,469	539,433
Current liabilities
Accounts payable	1,073	7,508
Accrued research and development expenses	11,509	10,431
Accrued expenses and other current liabilities	16,862	20,711
Total current liabilities	29,444	38,650
Long-term convertible senior notes	145,168	143,642
Long-term debt	28,823	28,744
Operating lease liabilities - long-term	6,950	7,713
Total liabilities	210,385	218,749
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.0001 par value; 70,000,000 shares authorized; no shares issued or outstanding as of March 31, 2021 and December 31, 2020	0	0
Common stock, $0.0001 par value; 700,000,000 shares authorized as of March 31, 2021 and December 31, 2020; 75,903,538 shares issued and 74,493,150 shares outstanding as of March 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	907,089	897,607
Accumulated deficit	(635,171)	(577,530)
Accumulated other comprehensive income	158	599
Total stockholders' equity	272,084	320,684
Total liabilities and stockholders' equity	$ 482,469	$ 539,433

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, authorized (in shares)	70,000,000	70,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, authorized (in shares)	700,000,000	700,000,000
Common stock, issued (in shares)	75,903,538	75,524,254
Common stock, outstanding (in shares)	74,493,150	73,874,904

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating expenses:
Research and development	$ 41,827	$ 41,414
In process research and development	30	2,805
General and administrative	11,346	10,748
Total operating expenses	53,203	54,967
Loss from operations	(53,203)	(54,967)
Other income (expense), net
Interest income	193	1,598
Interest expense	(4,780)	(707)
Other income	149	2
Total other income (expense), net	(4,438)	893
Net loss	(57,641)	(54,074)
Other comprehensive loss:
Foreign currency translation, net of tax	(372)	(87)
Unrealized loss on marketable securities, net of tax	(69)	(676)
Other comprehensive loss	(441)	(763)
Comprehensive loss	$ (58,082)	$ (54,837)
Net loss per share, basic (in dollars per share)	$ (0.78)	$ (0.87)
Net loss per share, diluted (in dollars per share)	$ (0.78)	$ (0.87)
Weighted average common shares outstanding, basic (in shares)	74,093,526	61,890,323
Weighted average common shares outstanding, diluted (in shares)	74,093,526	61,890,323

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)
Beginning balance (in shares) at Dec. 31, 2019		61,635,477
Beginning balance at Dec. 31, 2019	$ 352,485	$ 7	$ 686,390	$ (334,170)	$ 258
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock (in shares)		404,637
Exercise of stock option (in shares)		4,309
Exercise of stock options	15		15
Stock-based compensation	8,244		8,244
Issuance of common stock pursuant to Employee Stock Purchase Plan (in shares)		49,889
Issuance of common stock pursuant to Employee Stock Purchase Plan	556		556
Net loss	(54,074)			(54,074)
Other comprehensive loss	(763)				(763)
Ending balance (in shares) at Mar. 31, 2020		62,094,312
Ending balance at Mar. 31, 2020	306,463	$ 7	695,205	(388,244)	(505)
Beginning balance (in shares) at Dec. 31, 2020		73,874,904
Beginning 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)		238,962
Exercise of stock option (in shares)	5,721	5,721
Exercise of stock options	$ 15		15
Stock-based compensation	8,708		8,708
Issuance of common stock pursuant to Employee Stock Purchase Plan (in shares)		95,004
Issuance of common stock pursuant to Employee Stock Purchase Plan	759		759
Issuance of common stock for restricted stock units vested (in shares)		278,559
Net loss	(57,641)			(57,641)
Other comprehensive loss	(441)				(441)
Ending balance (in shares) at Mar. 31, 2021		74,493,150
Ending balance at Mar. 31, 2021	$ 272,084	$ 8	$ 907,089	$ (635,171)	$ 158

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net loss	$ (57,641)	$ (54,074)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	416	329
Stock-based compensation expense	8,708	8,244
In process research and development expenses	30	2,805
Amortization of operating lease right-of-use assets	858	566
Amortization of debt discount and issuance costs	1,605	89
Amortization of premium on investments, net of accretion of discounts	66	(65)
Net realized gain on investments	0	(39)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,855)	(1,785)
Other assets	16	925
Operating lease liabilities	117	(566)
Accounts payable	(6,565)	1,609
Accrued expenses	1,771	(2,239)
Accrued research and development expenses	1,078	(2,461)
Accrued compensation and benefits	(6,500)	(5,633)
Net cash used in operating activities	(58,896)	(52,295)
Cash flows from investing activities
Research and development asset acquisitions, net of cash acquired	(30)	(2,805)
Purchase of marketable securities	0	(73,778)
Maturities of marketable securities	12,800	89,083
Sales of marketable securities	0	16,051
Purchase of property and equipment	(802)	(513)
Net cash provided by investing activities	11,968	28,038
Cash flows from financing activities
Proceeds from the exercise of stock options	15	15
Net cash provided by financing activities	774	571
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(242)	(50)
Net decrease in cash, cash equivalents and restricted cash	(46,154)	(23,686)
Cash, cash equivalents and restricted cash, at the beginning of the period	486,620	135,089
Cash, cash equivalents and restricted cash, at the end of the period	440,224	111,353
Supplemental disclosure of cash flow information:
Cash paid for interest	675	618
Supplemental disclosure of noncash investing and financing activities:
Change in unrealized gain on marketable securities, net of tax	(69)	(676)
Unpaid property and equipment	0	60
Employee Stock Purchase Plan
Cash flows from financing activities
Proceeds from issuance of common stock	$ 759	$ 556

Description of the Business

Description of the Business	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Description of the Business	Description of the Business Gossamer Bio, Inc. (including its subsidiaries, referred to as “we,” “us,” “our,”, or 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 condensed 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 March 31, 2021, the Company had an accumulated deficit of $635.2 million. From the Company’s inception through March 31, 2021, the Company has funded its operations primarily through equity and debt financings. The Company raised $942.0 million from October 2017 through March 31, 2021 through Series A and Series B convertible preferred stock financings, a convertible note financing, its initial public offering, or IPO, its Credit Facility (as defined in Note 5 below), and concurrent underwritten public offerings of its 5.00% convertible senior notes due 2027 (the “2027 Notes”) and common stock in May 2020. See Note 5 for additional information regarding the Credit Facility and the 2027 Notes. In addition, the Company received $12.8 million in cash in connection with the January 2018 acquisition of AA Biopharma Inc. 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 twelve months from the date these condensed 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 and the impact on the Company’s clinical trials, employees and vendors. At this point, the degree to which COVID-19 has impacted and may continue to impact the Company’s financial condition or results of operations is 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 1b clinical trial in pulmonary arterial hypertension ("PAH") in 2020 as a result of the ongoing COVID-19 pandemic. In addition, due to the challenges of enrolling patients worldwide posed by the COVID-19 pandemic, the Company may experience delays in enrollment of patients in its Phase 2 clinical trials of GB004 in ulcerative colitis and of seralutinib, also known as GB002, in PAH, as well as delays in reporting data results from its ongoing trials.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and with the instructions of the Securities and Exchange Commission (“SEC”) on Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for complete financial statements. In the opinion of management, the condensed consolidated financial statements include all adjustments necessary, which are of a normal and recurring nature, for the fair presentation of the Company’s financial position and of the results of operations and cash flows for the periods presented. These financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2020 included in the Company’s Annual Report on Form 10-K filed with the SEC on February 26, 2021. The results of operations for the interim period shown in this report are not necessarily indicative of the results that may be expected for any other interim period or for the full year. The balance sheet at December 31, 2020, has been derived from the audited financial statements at that date. Use of Estimates The preparation of condensed 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 condensed consolidated financial statements and the reported amounts of expenses during the reporting period. The most significant estimates in the Company’s condensed 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. Recent Accounting Pronouncements In August 2020, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("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 is currently assessing the impact this standard will have on its consolidated financial statements or related financial statement disclosures. 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: As of March 31, 2021 2020 2027 Notes 12,321,900 — Shares issuable upon exercise of stock options 11,390,231 10,192,073 Non-vested shares under restricted stock grants 4,011,189 5,395,550

Balance Sheet Accounts and Supp

Balance Sheet Accounts and Supplemental Disclosures	3 Months Ended
	Mar. 31, 2021
Balance Sheets Accounts And Supplemental Disclosures [Abstract]
Balance Sheet Accounts and Supplemental Disclosures	Balance Sheet Accounts and Supplemental Disclosures Property and Equipment Property and equipment, net consisted of the following (in thousands): Estimated March 31, December 31, Office equipment 3-7 $ 1,153 $ 1,153 Computer equipment 5 123 123 Software 3 130 116 Lab equipment 2-5 4,991 4,210 Leasehold improvements 6-7 2,562 2,540 Construction in process N/A — 15 Total property and equipment 8,959 8,157 Less: accumulated depreciation 3,039 2,623 Property and equipment, net $ 5,920 $ 5,534 Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): As of March 31, December 31, Accrued compensation $ 6,453 $ 12,194 Accrued interest, current 3,594 1,094 Operating lease liabilities, current 3,518 3,633 Accrued professional service fees 2,349 2,823 Accrued other 733 742 Accrued in process research and development 215 225 Total accrued expenses $ 16,862 $ 20,711

Fair Value Measurements and Ava

Fair Value Measurements and Available for Sale Investments	3 Months Ended
	Mar. 31, 2021
Fair Value Measurements And Available For Sale Investments [Abstract]
Fair Value Measurements and Available for Sale Investments	Fair Value Measurements and Available for Sale Investments 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 March 31, 2021 and December 31, 2020 (in thousands): Fair Value Measurements at End of Period Using: Total Quoted Market Significant Significant As of March 31, 2021 Money market funds $ 352,900 $ 352,900 $ — $ — Corporate debt securities 13,638 — 13,638 — 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 March 31, 2021 and December 31, 2020, the carrying amounts of the Company’s financial instruments, which include cash, interest receivable, accounts payable and accrued expenses, approximate fair values because of their short maturities. Interest receivable as of March 31, 2021 and December 31, 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 condensed 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 March 31, 2021, the fair value of the Company’s 2027 Notes was $180.9 million. 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 as interest income or expense. 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 March 31, 2021 are as follows (in thousands): Amortized Gross Gross Total Marketable securities Corporate debt securities $ 13,530 $ 108 $ — $ 13,638 Total marketable securities $ 13,530 $ 108 $ — $ 13,638 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 March 31, 2021, 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 March 31, 2021, were as follows (in thousands): Estimated Due within one year $ 13,638 One to two years — Total $ 13,638 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 condensed consolidated balance sheets.

Indebtedness

Indebtedness	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Indebtedness	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 March 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 March 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 March 31, 2021 consisted of the following (in thousands): March 31, 2021 Term loan $ 30,000 Debt discount and issuance costs (1,177) Long-term debt $ 28,823 The scheduled future minimum principal payments are as follows (in thousands) March 31, 2021 2021 (remaining 9 months) $ — 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 were registered pursuant to the Company’s Shelf Registration Statement (as defined in Note 7 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 March 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 March 31, 2021, there were no events or market conditions that would allow holders to convert the 2027 Notes. At the time 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): March 31, 2021 December 31, 2020 Principal amount $ 200,000 $ 200,000 Unamortized debt discount (54,562) (56,080) Unamortized debt issuance cost (270) (278) Net carrying amount $ 145,168 $ 143,642 The net carrying amount of the equity component of the 2027 Notes was as follows (in thousands): March 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): Three months ended March 31, 2021 2021 2020 Contractual interest expense $ 2,500 $ — Amortization of debt discount 1,518 — Amortization of debt issuance cost 8 — Total interest expense related to the 2027 Notes $ 4,026 $ —

Licenses, Asset Acquisitions an

Licenses, Asset Acquisitions and Contingent Consideration	3 Months Ended
	Mar. 31, 2021
Business Combinations [Abstract]
Licenses, Asset Acquisitions and Contingent Consideration	Licenses, Asset Acquisitions and Contingent Consideration 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 condensed consolidated statement of operations for the three months ended March 31, 2021. 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 $63.0 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. In December 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. As of March 31, 2021, no other milestones had been accrued as the underlying contingencies had not yet been met. License from Aerpio Pharmaceuticals, Inc. (GB004) On June 24, 2018, the Company entered into a license agreement with Aerpio Pharmaceuticals, Inc. (“Aerpio”) under which the Company was granted an exclusive worldwide license and sublicense to certain intellectual property rights owned or controlled by Aerpio 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 Aerpio pursuant to which the Company made an upfront payment of $15.0 million to Aerpio 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. Aerpio retains its twenty percent (20.00%) participation right on a disposition of GB004. As of March 31, 2021, 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 March 31, 2021, 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 condensed consolidated statements of operations (in thousands): Three months ended March 31, 2021 2020 Seralutinib $ — $ — GB004 — — GB1275 — — Other preclinical programs 30 2,805 Total in process research and development $ 30 $ 2,805

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity 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. In November 2017, in connection with the issuance of the Series A convertible preferred stock, certain employees entered into stock restriction agreements, whereby 1,305,427 shares are subject to forfeiture by the Company upon the stockholder’s termination of employment or service to the Company. For the year ended December 31, 2020, 441,801 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 March 31, 2021 and December 31, 2020, 1,410,385 and 1,649,348 shares of common stock were subject to repurchase by the Company, respectively. The unvested stock liability related to these awards is immaterial to all periods presented.

Equity Incentive Plans

Equity Incentive Plans	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Equity Incentive Plans	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 March 31, 2021, an aggregate of 2,088,506 shares of common stock were available for issuance under the 2019 Plan and 10,114,815 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 2019 Employee Stock Purchase Plan (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 three months ended March 31, 2021, 95,004 shares were issued pursuant to the ESPP. As of March 31, 2021, an aggregate of 1,909,793 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 March 31, 2021, 3,876,219 shares of common stock were subject to outstanding options under the 2017 Plan, and 195,432 shares of restricted stock awards granted under the 2017 plan were unvested. Stock Options 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 table summarizes stock option activity during the three months ended March 31, 2021: Shares Subject to Weighted- Shares Weighted- Remaining Aggregate (in thousands) Outstanding as of December 31, 2020 9,401,082 $ 13.42 8.1 $ 10,182 Options granted 2,215,526 $ 9.82 Options exercised (5,721) $ 2.61 Options forfeited/cancelled (220,656) $ 16.06 Outstanding as of March 31, 2021 11,390,231 $ 13.83 8.1 $ 9,464 Options vested and exercisable as of March 31, 2021 4,431,654 $ 12.76 7.3 $ 6,558 The aggregate intrinsic value in the above table is calculated as the difference between fair value of the Company’s common stock price on March 31, 2021 and the exercise price of the stock options. The weighted-average grant date fair value per share for the stock option grants during the three months ended March 31, 2021 was $6.97. The aggregate fair value of stock options that vested during the three months ended March 31, 2021 was $7.3 million. Restricted Stock The summary of the Company’s restricted stock activity is as follows: Number of Weighted- Nonvested at December 31, 2020 3,330,821 $ 7.16 Granted 1,243,045 $ 10.41 Vested (517,521) $ 7.58 Forfeited (45,156) $ 10.24 Nonvested at March 31, 2021 4,011,189 $ 8.08 At March 31, 2021, the total unrecognized compensation related to unvested restricted stock awards granted was $28.7 million, which the Company expects to recognize over a weighted-average period of approximately 1.9 years. Stock-Based Compensation Expense Stock-based compensation expense has been reported in the Company’s condensed consolidated statements of operations as follows (in thousands): Three months ended March 31, 2021 2020 Research and development $ 5,442 $ 4,586 General and administrative 3,266 3,658 Total stock-based compensation $ 8,708 $ 8,244 At March 31, 2021, the total unrecognized compensation related to unvested stock option awards granted was $56.8 million, which the Company expects to recognize over a weighted-average period of approximately 2.6 years. As of March 31, 2021, total unrecognized compensation expense related to the ESPP was $2.5 million, which the Company expects to recognize over a weighted-average period of approximately 1.2 years.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	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 December 2022 for 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. The lease agreement also includes a one-time termination option for the expansion space only whereby the Company can terminate the lease with advance written notice. The termination option was not determined to be reasonably certain to be executed. 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 expiring on December 31, 2021. The lease agreement includes a lease for temporary space commencing on January 1, 2020 and expiring on the commencement date of the lease of the permanent space. The monthly base rent for the permanent and temporary space is $63,425 and $28,745, respectively. The lease agreement included an option to extend the term of the permanent space for twelve months. The option to extend must be exercised nine months prior to the termination of the original lease agreement. The period covered by the option was not included in the non-cancellable lease term as it was not determined to be reasonably certain to be executed. 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. 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 expires on December 31, 2021. The sublessee pays the monthly base rent of $63,425, subject to an annual 3% increase, and is 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 will continue to account for the permanent space as it did before the commencement of the sublease. The Company recognized $0.3 million in sublease income for the three months ended March 31, 2021 and no sublease income for the three months ended March 31, 2020. 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. The lease term expires on December 31, 2026 and the Company has the option to extend the term of the lease by up to five years. The period covered by the option was not included in the non-cancellable lease term as it was not determined to be reasonably certain to be executed. The monthly base rent for the space is $28,495. The lease is subject to charges for common area maintenance and other costs, and base rent is subject to an annual 2.5% increase on January 1 of each year. 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 3.2 years. Lease costs were comprised of the following (in thousands): Three months ended March 31, 2021 2020 Operating lease cost $ 1,038 $ 753 Short-term lease cost 9 22 Total lease cost $ 1,047 $ 775 Cash paid for amounts included in the measurement of operating lease liabilities for the three months ended March 31, 2021 and 2020 was $1.1 million and $0.8 million, respectively. Gross future minimum annual rental commitments as of March 31, 2021, were as follows (in thousands): Undiscounted Rent Year ending December 31 2021 (remaining 9 months) $ 3,213 2022 3,579 2023 2,063 2024 2,123 2025 387 2026 397 Total undiscounted rent payments $ 11,762 Present value discount (1,294) Present value $ 10,468 Current portion of operating lease liability (included as a component of accrued expenses) 3,518 Noncurrent operating lease liabilities 6,950 Total operating lease liability $ 10,468 For the three months ended March 31, 2021 and 2020 the Company recorded approximately $1.0 million and $0.8 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 first amended complaint was filed on August 31, 2020, and the second amended complaint was filed on November 20, 2020. The second amended 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 second amended complaint alleges 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 seeks damages, interest, costs, attorneys’ fees, and other unspecified equitable relief. The Company moved to dismiss the second amended 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. The Company intends to vigorously defend this matter. Given the uncertainty of litigation, the preliminary stage of the case, and the legal standards that must be met for, among other things, class certification and success on the merits, the Company cannot estimate the reasonably possible loss or range of loss that may result from this action.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of PresentationThe accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and with the instructions of the Securities and Exchange Commission (“SEC”) on Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for complete financial statements. In the opinion of management, the condensed consolidated financial statements include all adjustments necessary, which are of a normal and recurring nature, for the fair presentation of the Company’s financial position and of the results of operations and cash flows for the periods presented. These financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2020 included in the Company’s Annual Report on Form 10-K filed with the SEC on February 26, 2021. The results of operations for the interim period shown in this report are not necessarily indicative of the results that may be expected for any other interim period or for the full year. The balance sheet at December 31, 2020, has been derived from the audited financial statements at that date.
Use of Estimates	Use of Estimates The preparation of condensed 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 condensed consolidated financial statements and the reported amounts of expenses during the reporting period. The most significant estimates in the Company’s condensed 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.
Recent Accounting Pronouncements - To be Adopted	Recent Accounting Pronouncements In August 2020, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("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 is currently assessing the impact this standard will have on its consolidated financial statements or related financial statement disclosures.
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 Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 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: As of March 31, 2021 2020 2027 Notes 12,321,900 — Shares issuable upon exercise of stock options 11,390,231 10,192,073 Non-vested shares under restricted stock grants 4,011,189 5,395,550

Balance Sheet Accounts and Su_2

Balance Sheet Accounts and Supplemental Disclosures (Tables)	3 Months Ended
	Mar. 31, 2021
Balance Sheets Accounts And Supplemental Disclosures [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): Estimated March 31, December 31, Office equipment 3-7 $ 1,153 $ 1,153 Computer equipment 5 123 123 Software 3 130 116 Lab equipment 2-5 4,991 4,210 Leasehold improvements 6-7 2,562 2,540 Construction in process N/A — 15 Total property and equipment 8,959 8,157 Less: accumulated depreciation 3,039 2,623 Property and equipment, net $ 5,920 $ 5,534
Schedule of Accrued Expenses	Accrued expenses and other current liabilities consisted of the following (in thousands): As of March 31, December 31, Accrued compensation $ 6,453 $ 12,194 Accrued interest, current 3,594 1,094 Operating lease liabilities, current 3,518 3,633 Accrued professional service fees 2,349 2,823 Accrued other 733 742 Accrued in process research and development 215 225 Total accrued expenses $ 16,862 $ 20,711

Fair Value Measurements and A_2

Fair Value Measurements and Available for Sale Investments (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Measurements And Available For Sale Investments [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 March 31, 2021 and December 31, 2020 (in thousands): Fair Value Measurements at End of Period Using: Total Quoted Market Significant Significant As of March 31, 2021 Money market funds $ 352,900 $ 352,900 $ — $ — Corporate debt securities 13,638 — 13,638 — 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	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 March 31, 2021 are as follows (in thousands): Amortized Gross Gross Total Marketable securities Corporate debt securities $ 13,530 $ 108 $ — $ 13,638 Total marketable securities $ 13,530 $ 108 $ — $ 13,638
Schedule of Contractual Maturities of Available-for-sale Debt Securities	Contractual maturities of available-for-sale debt securities, as of March 31, 2021, were as follows (in thousands): Estimated Due within one year $ 13,638 One to two years — Total $ 13,638

Indebtedness (Tables)

Indebtedness (Tables)	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Schedule of Long-Term Debt	Long-term debt as of March 31, 2021 consisted of the following (in thousands): March 31, 2021 Term loan $ 30,000 Debt discount and issuance costs (1,177) Long-term debt $ 28,823
Schedule of Future Minimum Principal Payments	The scheduled future minimum principal payments are as follows (in thousands) March 31, 2021 2021 (remaining 9 months) $ — 2022 5,806 2023 11,613 2024 11,613 2025 968 Total $ 30,000
Schedule of Net Carrying Amount of Liability Component	The net carrying amount of the liability component of the 2027 Notes was as follows (in thousands): March 31, 2021 December 31, 2020 Principal amount $ 200,000 $ 200,000 Unamortized debt discount (54,562) (56,080) Unamortized debt issuance cost (270) (278) Net carrying amount $ 145,168 $ 143,642
Schedule of Equity Components	The net carrying amount of the equity component of the 2027 Notes was as follows (in thousands): March 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
Schedule of Interest Expense Recognized	The following table sets forth the interest expense recognized related to the 2027 Notes (in thousands): Three months ended March 31, 2021 2021 2020 Contractual interest expense $ 2,500 $ — Amortization of debt discount 1,518 — Amortization of debt issuance cost 8 — Total interest expense related to the 2027 Notes $ 4,026 $ —

Licenses, Asset Acquisitions _2

Licenses, Asset Acquisitions and Contingent Consideration (Tables)	3 Months Ended
	Mar. 31, 2021
Business Combinations [Abstract]
Schedule of IPR&D Expense	The Company recorded the following IPR&D expense on the condensed consolidated statements of operations (in thousands): Three months ended March 31, 2021 2020 Seralutinib $ — $ — GB004 — — GB1275 — — Other preclinical programs 30 2,805 Total in process research and development $ 30 $ 2,805

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Summary of Stock Option Activity	The following table summarizes stock option activity during the three months ended March 31, 2021: Shares Subject to Weighted- Shares Weighted- Remaining Aggregate (in thousands) Outstanding as of December 31, 2020 9,401,082 $ 13.42 8.1 $ 10,182 Options granted 2,215,526 $ 9.82 Options exercised (5,721) $ 2.61 Options forfeited/cancelled (220,656) $ 16.06 Outstanding as of March 31, 2021 11,390,231 $ 13.83 8.1 $ 9,464 Options vested and exercisable as of March 31, 2021 4,431,654 $ 12.76 7.3 $ 6,558
Summary of Restricted Stock Activity	The summary of the Company’s restricted stock activity is as follows: Number of Weighted- Nonvested at December 31, 2020 3,330,821 $ 7.16 Granted 1,243,045 $ 10.41 Vested (517,521) $ 7.58 Forfeited (45,156) $ 10.24 Nonvested at March 31, 2021 4,011,189 $ 8.08
Stock-Based Compensation Expense Reported in Condensed Consolidated Statements of Operations	Stock-based compensation expense has been reported in the Company’s condensed consolidated statements of operations as follows (in thousands): Three months ended March 31, 2021 2020 Research and development $ 5,442 $ 4,586 General and administrative 3,266 3,658 Total stock-based compensation $ 8,708 $ 8,244

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Schedule of Lease Costs	Lease costs were comprised of the following (in thousands): Three months ended March 31, 2021 2020 Operating lease cost $ 1,038 $ 753 Short-term lease cost 9 22 Total lease cost $ 1,047 $ 775
Schedule of Gross Future Minimum Annual Rental Commitments	Gross future minimum annual rental commitments as of March 31, 2021, were as follows (in thousands): Undiscounted Rent Year ending December 31 2021 (remaining 9 months) $ 3,213 2022 3,579 2023 2,063 2024 2,123 2025 387 2026 397 Total undiscounted rent payments $ 11,762 Present value discount (1,294) Present value $ 10,468 Current portion of operating lease liability (included as a component of accrued expenses) 3,518 Noncurrent operating lease liabilities 6,950 Total operating lease liability $ 10,468

Description of the Business - A

Description of the Business - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 04, 2018	Mar. 31, 2021	Dec. 31, 2020	May 21, 2020
Description Of Business [Line Items]
Accumulated deficit		$ (635,171)	$ (577,530)
Funds raised through Series A and Series B Convertible Preferred Stock, convertible note financings and completed IPO		$ 942,000
AA Biopharma Inc.
Description Of Business [Line Items]
Cash received in connection with acquisition	$ 12,800
2027 Notes
Description Of Business [Line Items]
Debt instrument interest rate percentage		5.00%		5.00%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities not Included in Calculation of Diluted Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
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	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)	11,390,231	10,192,073
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)	4,011,189	5,395,550

Balance Sheet Accounts and Su_3

Balance Sheet Accounts and Supplemental Disclosures - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 8,959	$ 8,157
Less: accumulated depreciation	3,039	2,623
Property and equipment, net	5,920	5,534
Office equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,153	1,153
Office equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	3 years
Office equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	7 years
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	5 years
Total property and equipment	$ 123	123
Software
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	3 years
Total property and equipment	$ 130	116
Lab equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 4,991	4,210
Lab equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	2 years
Lab equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	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]
Estimated Useful Life (in years)	6 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	7 years
Construction in process
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 0	$ 15

Balance Sheet Accounts and Su_4

Balance Sheet Accounts and Supplemental Disclosures - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Balance Sheets Accounts And Supplemental Disclosures [Abstract]
Accrued compensation	$ 6,453	$ 12,194
Accrued interest, current	3,594	1,094
Operating lease liabilities, current	3,518	3,633
Accrued professional service fees	2,349	2,823
Accrued other	733	742
Accrued in process research and development	215	225
Total accrued expenses	$ 16,862	$ 20,711

Fair Value Measurements and A_3

Fair Value Measurements and Available for Sale Investments - Assets Measured at Fair Value on Recurring Basis (Details) - Recurring Basis - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	$ 352,900	$ 411,104
U.S. Treasury and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis		18,280
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	13,638	26,573
Quoted Market Prices for Identical Assets (Level 1) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	352,900	411,104
Quoted Market Prices for Identical Assets (Level 1) | U.S. Treasury and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis		18,280
Quoted Market Prices for Identical Assets (Level 1) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	0	0
Significant Other Observable Inputs (Level 2) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	0	0
Significant Other Observable Inputs (Level 2) | U.S. Treasury and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis		0
Significant Other Observable Inputs (Level 2) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	13,638	26,573
Significant Unobservable Inputs (Level 3) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	0	0
Significant Unobservable Inputs (Level 3) | U.S. Treasury and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis		0
Significant Unobservable Inputs (Level 3) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	$ 0	$ 0

Fair Value Measurements and A_4

Fair Value Measurements and Available for Sale Investments - Additional Information (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value hierarchy level 1 to level 2	$ 0	$ 0
Fair value hierarchy level 2 to level 1	0	0
2027 Notes | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of convertible senior notes	180,900,000
Prepaid Expenses and Other Current Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest and securities receivable	$ 200,000	$ 200,000

Fair Value Measurements and A_5

Fair Value Measurements and Available for Sale Investments - Schedule of Available for sale Investments by Security Type (Details) $ in Thousands	Mar. 31, 2021USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Investments, Amortized Cost	$ 13,530
Available-for-sale Investments, Gross Unrealized Gains	108
Available-for-sale Investments, Gross Unrealized Losses	0
Available-for-sale Investments, Total Fair Value	13,638
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Investments, Amortized Cost	13,530
Available-for-sale Investments, Gross Unrealized Gains	108
Available-for-sale Investments, Gross Unrealized Losses	0
Available-for-sale Investments, Total Fair Value	$ 13,638

Fair Value Measurements and A_6

Fair Value Measurements and Available for Sale Investments - Schedule of Contractual Maturities of Available-for-sale Debt Securities (Details) $ in Thousands	Mar. 31, 2021USD ($)
Fair Value Measurements And Available For Sale Investments [Abstract]
Due within one year	$ 13,638
One to two years	0
Total	$ 13,638

Indebtedness - Additional Infor

Indebtedness - Additional Information (Details)	May 21, 2020USD ($)day$ / shares	May 02, 2019USD ($)tranche	Mar. 31, 2021USD ($)
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 | Credit Facility | Prepayment Occurs through First Anniversary of Closing Date
Debt Instrument [Line Items]
Percentage of prepayment fee		3.00%
Term Loan | Credit Facility | First Anniversary of Closing Date through Second Anniversary of Closing Date
Debt Instrument [Line Items]
Percentage of prepayment fee		2.00%
Term Loan | Credit Facility | Second Anniversary of Closing Date and Prior to Jan 1, 2025
Debt Instrument [Line Items]
Percentage of prepayment fee		1.00%
Term Loan | Credit Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		7.00%
Interest rate		2.00%
Term Loan | Credit Facility | MidCap Financial Trust
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%		5.00%
Debt instrument aggregate principal amount	$ 200,000,000
Proceeds from convertible debt	$ 193,600,000
Debt instrument conversion ratio	0.0616
Convertible notes, initial conversion price (in dollars per share) | $ / shares	$ 16.23
Convertible notes, percentage of conversion price	130.00%
Debt conversion, converted instrument	$ 1,000
Convertible notes, redemption percentage	100.00%
Percentage of repurchase price is equal to principal amount of convertible notes	100.00%
Percentage in aggregate principal amount (not less than)	0.25
Carrying amount of the equity component	$ 53,500,000
Convertible notes, effective interest rate	11.17%
Debt issuance costs	$ 400,000
Amortization of debt issuance cost	$ 300,000
2027 Notes | Maximum
Debt Instrument [Line Items]
Convertible notes, percentage of last reported sale price of common stock	98.00%
2027 Notes | 130% Applicable Conversion Price | Minimum
Debt Instrument [Line Items]
Convertible notes, consecutive trading days | day	20
2027 Notes | 130% Applicable Conversion Price | Maximum
Debt Instrument [Line Items]
Convertible notes, consecutive trading days | day	30
2027 Notes | 98% Applicable Conversion Price | Minimum
Debt Instrument [Line Items]
Convertible notes, consecutive trading days | day	5
2027 Notes | 98% Applicable Conversion Price | Maximum
Debt Instrument [Line Items]
Convertible notes, consecutive trading days | day	10

Indebtedness - Schedule of Long

Indebtedness - Schedule of Long-term Debt (Details) - Credit Facility $ in Thousands	Mar. 31, 2021USD ($)
Debt Instrument [Line Items]
Term loan	$ 30,000
Debt discount and issuance costs	(1,177)
Long-term debt	$ 28,823

Indebtedness - Schedule of Futu

Indebtedness - Schedule of Future Minimum Principal Payments (Details) - Credit Facility $ in Thousands	Mar. 31, 2021USD ($)
Debt Instrument [Line Items]
2021 (remaining 9 months)	$ 0
2022	5,806
2023	11,613
2024	11,613
2025	968
Term loan	$ 30,000

Indebtedness - Schedule of Net

Indebtedness - Schedule of Net Carrying Amount of Liability Component (Details) - 2027 Notes - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Principal amount	$ 200,000	$ 200,000
Unamortized debt discount	(54,562)	(56,080)
Unamortized debt issuance cost	(270)	(278)
Long-term debt	$ 145,168	$ 143,642

Indebtedness - Schedule of Equi

Indebtedness - Schedule of Equity Components (Details) - 2027 Notes - USD ($) $ in Thousands	Mar. 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 Inte

Indebtedness - Schedule of Interest Expense Recognized (Details) - 2027 Notes - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Debt Instrument [Line Items]
Contractual interest expense	$ 2,500	$ 0
Amortization of debt discount	1,518	0
Amortization of debt issuance cost	8	0
Total interest expense related to the 2027 Notes	$ 4,026	$ 0

Licenses, Asset Acquisitions _3

Licenses, Asset Acquisitions and Contingent Consideration - Additional Information (Details) - USD ($)	May 11, 2020	Sep. 21, 2018	Jun. 24, 2018	Oct. 02, 2017	May 31, 2019	Jun. 30, 2018	Oct. 31, 2017	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Business Acquisition [Line Items]
In process research and development						$ 20,000,000		$ 30,000	$ 2,805,000
Seralutinib
Business Acquisition [Line Items]
In process research and development								0	0
GB004
Business Acquisition [Line Items]
In process research and development								0	0
GB1275
Business Acquisition [Line Items]
In process research and development								0	$ 0
Pulmokine, Inc. | License Agreement | Seralutinib
Business Acquisition [Line Items]
Product license term (in years)				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				$ 63,000,000
Commercial milestone payments, payable				45,000,000
Sales milestone payments, payable				$ 190,000,000
Aerpio Pharmaceuticals, Inc. | License Agreement | GB004
Business Acquisition [Line Items]
Upfront payment	$ 15,000,000
Milestones accrued								0
Participation rights (as a percent)			20.00%
Aerpio Pharmaceuticals, 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
In process research and development		$ 7,500,000
Upfront payment, purchase consideration paid		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

Licenses, Asset Acquisitions _4

Licenses, Asset Acquisitions and Contingent Consideration - Schedule of IPR&D Expense (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Jun. 30, 2018	Mar. 31, 2021	Mar. 31, 2020
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development	$ 20,000	$ 30	$ 2,805
Seralutinib
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development		0	0
GB004
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development		0	0
GB1275
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development		0	0
Other preclinical programs
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development		$ 30	$ 2,805

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details)	May 21, 2020USD ($)$ / sharesshares	Sep. 06, 2018$ / sharesshares	May 21, 2018$ / sharesshares	Jan. 04, 2018USD ($)	Dec. 03, 2015USD ($)$ / sharesshares	Nov. 30, 2017shares	Mar. 31, 2021vote$ / sharesshares	Dec. 31, 2020$ / sharesshares
Stockholders Equity [Line Items]
Common stock number of votes per share | vote							1
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs (in shares)	9,433,963
Offering price (in dollars per share) | $ / shares	$ 13.25
Proceeds from issuance of common stock | $	$ 117,100,000
Common stock, par value (in dollars per share) | $ / shares							$ 0.0001	$ 0.0001
Shares of common stock, repurchase (in shares)							1,410,385	1,649,348
Stock Restriction Agreements
Stockholders Equity [Line Items]
Shares subject to forfeiture (in shares)								441,801
Series A Convertible Preferred Stock | Stock Restriction Agreements
Stockholders Equity [Line Items]
Shares subject to forfeiture (in shares)						1,305,427
Founder
Stockholders Equity [Line Items]
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs (in shares)		1,795,023	251,547
Percentage of fully diluted share capital				15.00%
Increased in equity capital amount | $				$ 300,000,000
Common stock issued price per share (in USD per share) | $ / shares		$ 9.63	$ 2.61
Additional shares of restricted stock subject to vesting restrictions (in shares)		1,795,023	251,547
Founder Shares
Stockholders Equity [Line Items]
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs (in shares)					9,160,888
Common stock, par value (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 (in years)				5 years

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 06, 2019	Mar. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding awarded (in shares)		11,390,231	9,401,082
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs		$ 28.7
Weighted-average period of cost expects to recognize (in years)		1 year 10 months 24 days
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield (as a percent)		0.00%
Weighted-average grant date fair value (in dollars per share)		$ 6.97
Aggregate fair value of stock options vested during period		$ 7.3
Stock-Based Compensation Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average period of cost expects to recognize (in years)		2 years 7 months 6 days
Unrecognized compensation expense related to the ESPP		$ 56.8
2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)	5,750,000
Term of awards (in years)	10 years
Percentage of amount increase in outstanding shares	5.00%
Common stock available for issuance (in shares)		2,088,506
Shares outstanding awarded (in shares)		10,114,815
2019 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)	700,000
Term of awards (in years)	10 years
Percentage of amount increase in outstanding shares	1.00%
Common stock available for issuance (in shares)		1,909,793
Number of share issued under ESPP		95,004
2019 Employee Stock Purchase Plan | Stock-Based Compensation Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average period of cost expects to recognize (in years)		1 year 2 months 12 days
Unrecognized compensation expense related to the ESPP		$ 2.5
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)		3,876,219
2017 Equity Incentive Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards granted (in shares)		195,432

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Shares
Shares Subject to Options Outstanding, Outstanding as of December 31, 2020 (in shares)	9,401,082
Shares Subject to Options Outstanding, Options granted (in shares)	2,215,526
Shares Subject to Options Outstanding, Option exercised (in shares)	(5,721)
Shares Subject to Options Outstanding, Options forfeited/cancelled (in shares)	(220,656)
Shares Subject to Options Outstanding, Outstanding as of March 31, 2021 (in shares)	11,390,231	9,401,082
Shares Subject to Options Outstanding, Options vested and exercisable as of March 31, 2021 (in shares)	4,431,654
Weighted- Average Exercise Price
Weighted-Average Exercise Price, Outstanding as of December 31, 2020 (in USD per share)	$ 13.42
Weighted-Average Exercise Price, Options granted (in USD per share)	9.82
Weighted-Average Exercise Price, Option exercised (in USD per share)	2.61
Weighted-Average Exercise Price, Options forfeited/cancelled (in USD per share)	16.06
Weighted-Average Exercise Price, Outstanding as of March 31, 2021 (in USD per share)	13.83	$ 13.42
Weighted-Average Exercise Price, Options vested and exercisable as of March 31, 2021 (in USD per share)	$ 12.76
Weighted-Average Remaining Contractual Life (in years)	8 years 1 month 6 days	8 years 1 month 6 days
Weighted-Average Remaining Contractual Life (in years), Options vested and exercisable as of March 31, 2021	7 years 3 months 18 days
Aggregate Intrinsic Value	$ 9,464	$ 10,182
Aggregate Intrinsic Value, Options vested and exercisable as of March 31, 2021	$ 6,558

Equity Incentive Plans - Summ_2

Equity Incentive Plans - Summary of Restricted Stock Activity (Details)	3 Months Ended
	Mar. 31, 2021$ / sharesshares
Weighted- Average Grant Date Fair Value
Weighted-Average Grant Date Fair Value, Nonvested at March 31, 2021 (in USD per share) | $ / shares	$ 8.08
Restricted Stock
Number of Restricted Stock Units Outstanding
Number of Restricted Stock Units Outstanding, Nonvested at December 31, 2020 (in shares) | shares	3,330,821
Number of Restricted Stock Units Outstanding, Granted (in shares) | shares	1,243,045
Number of Restricted Stock Units Outstanding, Vested (in shares) | shares	(517,521)
Number of Restricted Stock Units Outstanding, Forfeited (in shares) | shares	(45,156)
Number of Restricted Stock Units Outstanding, Nonvested at March 31, 2021 (in shares) | shares	4,011,189
Weighted- Average Grant Date Fair Value
Weighted-Average Grant Date Fair Value, Nonvested at December 31, 2020 (in USD per share) | $ / shares	$ 7.16
Weighted-Average Grant Date Fair Value, Granted (in USD per share) | $ / shares	10.41
Weighted-Average Grant Date Fair Value, Vested (in USD per share) | $ / shares	7.58
Weighted-Average Grant Date Fair Value, Forfeited (in USD per share) | $ / shares	$ 10.24

Equity Incentive Plans - Stock-

Equity Incentive Plans - Stock-Based Compensation Expense Reported in Condensed Consolidated Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 8,708	$ 8,244
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	5,442	4,586
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 3,266	$ 3,658

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	Jul. 29, 2020	Jun. 30, 2020	Nov. 30, 2019	Mar. 31, 2021	Mar. 31, 2020
Lessee, Lease, Description [Line Items]
Exercise period (in months)			9 months
Sublease income					$ 0
Operating lease, weighted average discount rate				7.00%
Weighted average remaining lease term (in years)				3 years 2 months 12 days
Cash paid for operating lease liabilities				$ 1,100,000	800,000
Rent expense				$ 1,000,000	$ 800,000
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 Entered in November 2019
Lessee, Lease, Description [Line Items]
Monthly base rent for permanent space			$ 63,425
Monthly base rent for temporary space			$ 28,745
Option to extend lease term of permanent space (in months)			12 months
Annual increase percentage for lease charges			3.00%
Sublease Agreement Entered in June 2020
Lessee, Lease, Description [Line Items]
Sublease monthly base rent		$ 63,425
Sublease annual increase percentage for lease charges		3.00%
Sublease period of base rent abatement (in months)		6 months
Sublease income				$ 300,000
Lease Assignment Agreement Entered in July 2020
Lessee, Lease, Description [Line Items]
Annual increase percentage for lease charges	2.50%
Operating lease, renewal term (in years)	5 years
Lease assignment agreement, monthly base rent expense	$ 28,495

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 1,038	$ 753
Short-term lease cost	9	22
Total lease cost	$ 1,047	$ 775

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Gross Future Minimum Annual Rental Commitments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
2021 (remaining 9 months)	$ 3,213
2022	3,579
2023	2,063
2024	2,123
2025	387
2026	397
Total undiscounted rent payments	11,762
Present value discount	(1,294)
Present value	10,468
Current portion of operating lease liability (included as a component of accrued expenses)	3,518	$ 3,633
Noncurrent operating lease liabilities	6,950	$ 7,713
Total operating lease liability	$ 10,468