0001728117-23-000134 | 10-Q | XBRL Viewer

Balance Sheet Accounts and Supplemental Disclosures

9 Months Ended

Sep. 30, 2023

Balance Sheets Accounts And Supplemental Disclosures [Abstract]

Balance Sheet Accounts and Supplemental Disclosures

Property and Equipment

Property and equipment, net consisted of the following (in thousands):


	Estimated Useful Life (in years)	September 30, 2023		December 31, 2022
Office equipment	3-7	$	1,097	$	1,097
Computer equipment	5	123		123
Software	3	52		130
Lab equipment	2-5	3,168		6,098
Leasehold improvements	6-7	2,562		2,562
Construction in process	N/A	—		83
Total property and equipment		7,002		10,093
Less: accumulated depreciation		(5,061)		(6,112)
Property and equipment, net		$	1,941	$	3,981

For the three months ended September 30, 2023 and 2022 the Company recorded approximately $0.4 million and $0.5 million, respectively, in depreciation expense, and for the nine months ended September 30, 2023 and 2022, the Company recorded approximately $1.3 million and $1.4 million, respectively, in depreciation expense, which is included in general and administrative expense and research and development expense on the condensed consolidated statements of operations and comprehensive loss.

Accrued Expenses and Other Current Liabilities

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


	As of
	September 30, 2023		December 31, 2022
Accrued compensation and benefits	$	9,051	$	13,534
Operating lease liabilities	3,220		2,983
Accrued consulting fees	637		1,104
Accrued interest	3,495		1,065
Accrued legal fees	127		380

Accrued accounting fees	165		521
Accrued other	767		945
Total accrued expenses and other current liabilities	$	17,462	$	20,532

Licenses, Asset Acquisitions and Contingent Consideration (Details) - Pulmokine, Inc. - License Agreement - In Process Research And Development Seralutinib - USD ($)		1 Months Ended
	Oct. 02, 2017	Oct. 31, 2017	Sep. 30, 2023	Jan. 31, 2021
Business Acquisition [Line Items]
Product license term (in years)	10 years
Upfront payment		$ 5,500,000
Milestones accrued			$ 0	$ 5,000,000
Maximum
Business Acquisition [Line Items]
Development and regulatory milestone payments, payable	$ 58,000,000
Initial phase three payment	10,000,000
Commercial milestone payments, payable	45,000,000
Sales milestone payments, payable	$ 190,000,000

Indebtedness

9 Months Ended

Sep. 30, 2023

Debt Disclosure [Abstract]

Indebtedness

Credit Facility

On May 2, 2019, the Company entered into a credit, guaranty and security agreement, as amended on September 18, 2019, July 2, 2020, December 7, 2022 and February 14, 2023 (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, 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 did not achieve the clinical development milestone required to access one of the $60.0 million tranches, and access to the other $60.0 million tranche expired on December 31, 2022. 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., GB007, Inc., GB008, Inc. and Gossamer Bio Services, Inc., each wholly-owned subsidiaries of the Company, are designated as guarantors. 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) the secured overnight financing rate ("SOFR"), plus corresponding spread, plus (ii) 7.00%, subject to a SOFR 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 began 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.

On December 7, 2022, the Company entered into the Third Amendment to the Credit Facility, with no change to the principal or repayment terms, except with respect to the interest rate applicable to the Credit Facility, with the implementation of a forward-looking term rate based on SOFR as the replacement of LIBOR as the benchmark interest rate. The Company accounted for the change in reference rate as a non-substantial modification as allowed under ASU 2020-04.

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 September 30, 2023, 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.

Debt consisted of the following (in thousands):


	September 30, 2023		December 31, 2022
Debt, current portion	$	11,613	$	11,613
Debt, non-current portion	3,871		12,581
Total debt	15,484		24,194
Less: unamortized debt discount and issuance costs	(237)		(593)
Debt, net	$	15,247	$	23,601

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


	September 30, 2023
2023 (remaining 3 months)	$	2,903
2024	11,613
2025	968
Total	$	15,484

5.00% Convertible Senior Notes due 2027

On May 21, 2020, the Company issued $200.0 million aggregate principal amount of 5.00% convertible senior notes due 2027 in a public offering (the "2027 Notes"). The 2027 Notes were registered pursuant to the Company’s shelf registration statement on Form S-3 filed with the SEC on April 10, 2020. 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 September 30, 2023, 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 September 30, 2023, there were no events or market conditions that would allow holders to convert the 2027 Notes. When the 2027 Notes become convertible within 12 months of the balance sheet date, the carrying value of the 2027 Notes will be reclassified to short-term.

As a result of the adoption of ASU 2020-06, the Company no longer accounts for the 2027 Notes separately as a liability and equity component. The conversion feature of the 2027 Notes was previously represented by an equity component of $53.5 million at issuance, with the excess of the principal amount of the liability component over the carrying amount (“debt discount”) was amortized to interest expense over the term of the 2027 Notes at an effective interest rate of 11.17%.

The Company accounts for the 2027 Notes as a single liability measured at amortized cost. As the equity component is no longer required to be split into a separate component, the Company recorded an adjustment to reflect this update.

The Company recorded $0.4 million of the debt issuance costs related to the 2027 Notes as a reduction to the liability and amortizes these costs to interest expense over the term of the 2027 Notes.

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


	September 30, 2023		December 31, 2022
Principal amount	$	200,000	$	200,000
Unamortized debt discount	(3,405)		(4,021)
Unamortized debt issuance cost	(229)		(270)
Net carrying amount	$	196,366	$	195,709

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


	Three months ended September 30,				Nine months ended September 30,
	2023		2022		2023		2022
Contractual interest expense	$	2,500	$	2,500	$	7,500	$	7,500
Amortization of debt discount	208		197		615		582
Amortization of debt issuance cost	14		13		41		39
Total interest expense related to the 2027 Notes	$	2,722	$	2,710	$	8,156	$	8,121

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
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-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
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-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
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-URI https://asc.fasb.org//470/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1B
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-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
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-Section 50
-Paragraph 1B
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
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-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Section 50
-Paragraph 1I
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2023

Accounting Policies [Abstract]

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, 2022 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 17, 2023. 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, 2022, 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 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.

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, warrants for the purchase of common stock, 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 September 30,
	2023	2022
2027 Notes	12,321,900	12,321,900
Shares issuable upon exercise of stock options	18,358,583	12,789,376
Shares issuable upon exercise of warrants	32,467,360	—
Non-vested shares under restricted stock grants	431,531	1,856,688
Total potentially dilutive securities	63,579,374	26,967,964

Equity Incentive Plans - Additional Information (Details) $ / shares in Units, $ in Thousands					3 Months Ended		9 Months Ended
	Jul. 24, 2023 $ / shares shares	May 05, 2023 USD ($) $ / shares shares	Jul. 15, 2022 $ / shares shares	Feb. 06, 2019 shares	Sep. 30, 2023 USD ($) shares	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($) $ / shares	Dec. 31, 2022 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding awarded (in shares)					18,358,583		18,358,583		17,487,165
Options granted (in shares)		750,000					11,649,890
Options granted (in dollars per share) \| $ / shares		$ 1.36					$ 1.30
Share-based payment arrangement, expense \| $		$ 2,000			$ 6,162	$ 10,122	$ 22,486	$ 31,104
Exercise price (in dollars per share) \| $ / shares		$ 1.36
Share-based payment arrangement, option, exercise price range, shares outstanding		6,817,057
Share-based payment arrangement, plan modification, incremental cost \| $		$ 3,400
Share-based payment arrangement, cancellation percentage		0.33
Share-based payment arrangement, nonvested award, cost not yet recognized, amount \| $		$ 1,400
Number of warrants (in shares)	32,467,360
Exercise price of warrants (in dollars per share) \| $ / shares	$ 2.04
Warrant term	5 years
Warrants outstanding (in shares)					32,467,360		32,467,360
Private Placement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Private placement, number of shares (in shares)	129,869,440		16,649,365
Offering price (in dollars per share) \| $ / shares	$ 1.63125		$ 7.21
Exercise price of warrants (in dollars per share) \| $ / shares	$ 2.04
Warrant term	5 years
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average period of cost expects to recognize (in years)							4 months 24 days
Unrecognized stock-based compensation expense \| $					$ 1,600		$ 1,600
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield							0.00%
Award vesting period		1 year
Award vesting rights, threshold consecutive days		30 days
Share-based payment arrangement, expense \| $		$ 400
Weighted-average period of cost expects to recognize (in years)		2 years 2 months 12 days
Aggregate intrinsic value, options vested in period \| $							$ 0	$ 1,500
Weighted-average grant date fair value (in dollars per share) \| $ / shares							$ 5.38	$ 8.27
Aggregate fair value of stock options vested during period \| $							$ 17,100	$ 26,100
Stock Options \| Tranche 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage		50.00%
Award vesting rights, threshold share price \| $ / shares		$ 5.00
Stock Options \| Tranche 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage		25.00%
Award vesting rights, threshold share price \| $ / shares		$ 7.50
Stock Options \| Tranche 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage		25.00%
Award vesting rights, threshold share price \| $ / shares		$ 10.00
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 2 months 12 days
Unrecognized compensation expense \| $					$ 26,200		$ 26,200
Maximum \| Private Placement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrants (in shares)	32,467,360
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)					4,482,152		4,482,152
Shares outstanding awarded (in shares)					16,605,681		16,605,681		16,199,202
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)					3,058,844		3,058,844
Number of share issued under ESPP							336,795
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)							9 months 18 days
Unrecognized compensation expense \| $					$ 1,300		$ 1,300
2019 Employee Stock Purchase Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase of common stock through payroll deductions, percentage				20.00%
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding awarded (in shares)					2,184,433		2,184,433		2,582,771
2017 Equity Incentive Plan \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards granted (in shares)					0		0

Condensed Consolidated Statements of Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Statement of Stockholders' Equity [Abstract]
Offering costs	$ 10,779	$ 184

Fair Value Measurements and Available for Sale Investments

9 Months Ended

Sep. 30, 2023

Fair Value Measurements And Available For Sale Investments [Abstract]

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 September 30, 2023 and December 31, 2022 (in thousands):


	Fair Value Measurements at End of Period Using:
	Total Fair Value		Quoted Market Prices for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
As of September 30, 2023
Money market funds	$	19,885	$	19,885	$	—	$	—
U.S. Treasury and agency securities	83,790		83,790		—		—
Commercial paper	216,096		—		216,096		—

As of December 31, 2022
Money market funds	$	54,662	$	54,662	$	—	$	—
U.S. Treasury and agency securities	31,458		31,458		—		—
Commercial paper	134,954		—		134,954		—
Corporate debt securities	8,838		—		8,838		—

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 September 30, 2023 and December 31, 2022, the carrying amounts of the Company’s financial instruments, which include cash, prepaid and other current assets, interest receivable, accrued research and development expenses, accounts payable and accrued expenses and other current liabilities, approximate fair values because of their short maturities.

There was no interest receivable as of September 30, 2023, and there was no significant interest receivable as of December 31, 2022. Interest receivable 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 September 30, 2023 and December 31, 2022, the fair value of the Company’s 2027 Notes was $78.9 million and $61.0 million, respectively. The fair value was determined on the basis of market prices observable for similar instruments and is considered Level 2 in the fair value hierarchy (see Note 5).

Available for Sale Investments

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

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 September 30, 2023 and December 31, 2022 are as follows (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Total Fair Value
As of September 30, 2023
U.S. Treasury and agency securities	$	83,766	$	24	$	—	$	83,790
Corporate debt securities	—		—		—		—
Commercial paper	162,535		—		(46)		162,489
Total marketable securities	$	246,301	$	24	$	(46)	$	246,279
Number of securities with unrealized losses					20

As of December 31, 2022
U.S. Treasury and agency securities	$	31,445	$	13	$	—	$	31,458
Corporate debt securities	8,876		—		(38)		8,838
Commercial paper	103,508		—		(99)		103,409
Total marketable securities	$	143,829	$	13	$	(137)	$	143,705
Number of securities with unrealized losses					16

As of September 30, 2023 and December 31, 2022, the Company classified $53.6 million and $31.5 million, respectively, of assets with original maturities of 90 days or less as cash and cash equivalents.

At each reporting date, the Company performs an evaluation of impairment to determine if any unrealized losses are due to credit-related factors. The Company records an allowance for credit losses when unrealized losses are due to credit-related factors. Factors considered when evaluating available-for-sale investments for impairment include the severity of the impairment, changes in underlying credit ratings, the financial condition of the issuer, the probability that the scheduled cash payments will continue to be made and the Company’s intent and ability to hold the investment until recovery of the amortized cost basis. The Company intends and has the ability to hold its investments in unrealized loss positions until their amortized cost basis has been recovered. As of September 30, 2023 and December 31, 2022, 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 September 30, 2023, were as follows (in thousands):


	Estimated Fair Value
Less than one year	$	246,279
Greater than one year	—
Total	$	246,279

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.

Licenses, Asset Acquisitions and Contingent Consideration	9 Months Ended
	Sep. 30, 2023
Business Combination and Asset Acquisition [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 statements of operations and comprehensive loss for the three and nine months ended September 30, 2023 and 2022. The Company accounts for contingent consideration payable upon achievement of certain regulatory, development or sales milestones in such asset acquisitions when the underlying contingency is met. License from Pulmokine, Inc. (Seralutinib) On October 2, 2017, the Company entered into a license agreement with Pulmokine, Inc. under which it was granted an exclusive worldwide license and sublicense to certain intellectual property rights owned or controlled by Pulmokine to develop and commercialize seralutinib and certain backup compounds for the treatment, prevention and diagnosis of any and all disease or conditions. The Company also has the right to sublicense its rights under the license agreement, subject to certain conditions. The assets acquired are in the early stages of the FDA approval process, and the Company intends to further develop the assets acquired through potential FDA approval as evidenced by the milestone arrangement in the contract. The development activities cannot be performed without significant cost and effort by the Company. The agreement will remain in effect from the effective date, unless terminated earlier, until, on a licensed product-by-licensed product and country-by-country basis, the later of ten years from the date of first commercial sale or when there is no longer a valid patent claim covering such licensed product or specified regulatory exclusivity for the licensed product in such country. The Company is obligated to make future development and regulatory milestone payments of up to $58.0 million, which includes a payment of $10.0 million due upon initiation of the first Phase 3 clinical trial, 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. In addition, if the Company chooses to sublicense or assign to any third parties its rights under the agreement with respect to a licensed product, or the Company’s seralutinib operating subsidiary undergoes a change of control, the Company must pay to Pulmokine a specified percentage of all revenue to be received in connection with such transaction. The Company made an upfront payment of $5.5 million in October 2017. The Company made a milestone payment of $5.0 million in connection with the initiation of the first Phase 2 clinical trial of seralutinib in January 2021. As of September 30, 2023, no other milestones had been accrued as the underlying contingencies had not yet been met.

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
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)	225,409,315	94,478,405
Common stock, outstanding (in shares)	225,409,315	94,423,181

Fair Value Measurements and Available for Sale Investments - Schedule of Available for sale Investments by Security Type (Details) $ in Thousands	Sep. 30, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 246,301	$ 143,829
Gross Unrealized Gains	24	13
Gross Unrealized Losses	(46)	(137)
Total Fair Value	$ 246,279	$ 143,705
Number of securities with unrealized losses \| security	20	16
U.S. Treasury and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 83,766	$ 31,445
Gross Unrealized Gains	24	13
Gross Unrealized Losses	0	0
Total Fair Value	83,790	31,458
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	0	8,876
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(38)
Total Fair Value	0	8,838
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	162,535	103,508
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(46)	(99)
Total Fair Value	$ 162,489	$ 103,409

Indebtedness - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Debt, current portion	$ 11,613	$ 11,613
Debt, non-current portion	3,634	11,988
Credit Facility
Debt Instrument [Line Items]
Debt, current portion	11,613	11,613
Debt, non-current portion	3,871	12,581
Total debt	15,484	24,194
Less: unamortized debt discount and issuance costs	(237)	(593)
Debt, net	$ 15,247	$ 23,601

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482900/835-30-50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Paragraph 3
-Subparagraph (SX 210.12-04(a))
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 25: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Cash flows from operating activities
Net loss	$ (131,669)	$ (173,614)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	1,315	1,372
Stock-based compensation expense	22,486	31,104
In process research and development expenses	0	50
Amortization of operating lease right-of-use assets	2,064	1,934
Amortization of long-term debt discount and issuance costs	1,013	893
Amortization of discount on marketable securities, net of accretion of discounts	(5,868)	(261)
Loss on disposal of property and equipment	726	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(6,400)	(1,151)
Other assets	31	451
Operating lease liabilities	(2,216)	(2,030)
Accounts payable	(272)	(2,098)
Accrued expenses and other current liabilities	(1,255)	(1,561)
Accrued research and development expenses	(3,636)	4,541
Accrued compensation and benefits	(4,483)	(1,415)
Accrued interest expense	2,430	2,483
Net cash used in operating activities	(125,734)	(139,302)
Cash flows from investing activities
Research and development asset acquisitions, net of cash acquired	0	(50)
Purchase of marketable securities	(321,404)	(160,641)
Maturities of marketable securities	224,800	151,500
Purchase of property and equipment	0	(308)
Net cash used in investing activities	(96,604)	(9,499)
Cash flows from financing activities
Proceeds from issuance of common stock and common warrants in a private offering, net of offering costs	201,323	119,928
Proceeds from issuance of common stock pursuant to Employee Stock Purchase Plan	444	1,215
Proceeds from the exercise of stock options	0	1,723
Principal repayments of long-term debt	(8,710)	(2,903)
Net cash provided by financing activities	193,057	119,963
Effect of exchange rate changes on cash and cash equivalents	(83)	(1,152)
Net decrease in cash and cash equivalents	(29,364)	(29,990)
Cash, cash equivalents and restricted cash, at the beginning of the period	111,973	183,467
Cash, cash equivalents and restricted cash, at the end of the period	82,609	153,477
Supplemental disclosure of cash flow information:
Cash paid for interest	6,831	7,042
Supplemental disclosure of noncash investing and financing activities:
Operating lease right-of-use asset obtained in exchange for lease liability	0	3,029
Change in unrealized gain (loss) on marketable securities, net	102	(311)
Purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities	$ 0	$ 49

Commitments and Contingencies

9 Months Ended

Sep. 30, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Leases

The Company subleases certain office and laboratory space under a non-cancelable operating lease expiring in January 2025 for the initial leased space and for the expansion space leased pursuant to an amendment to the lease agreement entered into in August 2018. In February 2022, the Company exercised its renewal option to extend the term of the expansion space until January 2025. 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 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.

Monthly rent expense is recognized on a straight-line basis over the term of the leases. The operating leases are included in the condensed consolidated balance sheets 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. As of September 30, 2023, the weighted average remaining lease term was 1.3 years.

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


	Three months ended September 30,				Nine months ended September 30,
	2023		2022		2023		2022
Operating lease cost	$	778	$	778	$	2,335	$	2,318
Short-term lease cost	13		12		39		32
Total lease cost	$	791	$	790	$	2,374	$	2,350

Cash paid for amounts included in the measurement of operating lease liabilities for the three months ended September 30, 2023 and 2022 was $0.6 million and $0.5 million, respectively, and cash paid for amounts included in the measurement of operating lease liabilities for the nine months ended September 30, 2023 and 2022 was $2.5 million and $2.4 million, respectively.

Gross future minimum annual rental commitments as of September 30, 2023, were as follows (in thousands):


	Undiscounted Rent Payments
Year ending December 31
2023 (remaining 3 months)	$	831
2024	3,418
2025	144
Total undiscounted rent payments	$	4,393

Present value discount	(181)
Present value of lease payments	$	4,212
Current portion of operating lease liabilities (included as a component of accrued expenses and other current liabilities)	3,220
Noncurrent operating lease liabilities	992
Total operating lease liability	$	4,212

For the three months ended September 30, 2023 and 2022, the Company recorded $0.9 million and $0.8 million, in rent expense. For the nine months ended September 30, 2023 and 2022, the Company recorded approximately $2.6 million and $2.5 million, respectively, in rent expense. Rent expense is included in research and development and general and administrative expense on the condensed consolidated statements of operations and comprehensive loss.

Fair Value Measurements and Available for Sale Investments - Schedule of Contractual Maturities of Available-for-sale Debt Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value Measurements And Available For Sale Investments [Abstract]
Less than one year	$ 246,279
Greater than one year	0
Total	$ 246,279	$ 143,705

Indebtedness - Schedule of Future Minimum Principal Payments (Details) - Credit Facility $ in Thousands	Sep. 30, 2023 USD ($)
Debt Instrument [Line Items]
2023 (remaining 3 months)	$ 2,903
2024	11,613
2025	968
Total debt	$ 15,484

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Cover - shares	9 Months Ended
Cover - shares	Sep. 30, 2023	Nov. 03, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
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	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		225,409,314
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001728117
Current Fiscal Year End Date	--12-31

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2023

Commitments and Contingencies Disclosure [Abstract]

Schedule of Lease Costs

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


	Three months ended September 30,				Nine months ended September 30,
	2023		2022		2023		2022
Operating lease cost	$	778	$	778	$	2,335	$	2,318
Short-term lease cost	13		12		39		32
Total lease cost	$	791	$	790	$	2,374	$	2,350

Schedule of Gross Future Minimum Annual Rental Commitments

Gross future minimum annual rental commitments as of September 30, 2023, were as follows (in thousands):


	Undiscounted Rent Payments
Year ending December 31
2023 (remaining 3 months)	$	831
2024	3,418
2025	144
Total undiscounted rent payments	$	4,393

Present value discount	(181)
Present value of lease payments	$	4,212
Current portion of operating lease liabilities (included as a component of accrued expenses and other current liabilities)	3,220
Noncurrent operating lease liabilities	992
Total operating lease liability	$	4,212

Stockholders' Equity (Details)							3 Months Ended		9 Months Ended		12 Months Ended
Stockholders' Equity (Details)	Jul. 24, 2023 USD ($) $ / shares shares	Jul. 15, 2022 USD ($) $ / shares shares	Sep. 06, 2018 $ / shares shares	May 21, 2018 $ / shares shares	Jan. 04, 2018 USD ($)	Dec. 03, 2015 USD ($) $ / shares shares	Sep. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) vote $ / shares shares	Sep. 30, 2022 USD ($)	Dec. 31, 2022 $ / shares shares
Stockholders Equity [Line Items]
Common stock number of votes per share \| vote									1
Payments of stock issuance costs \| $	$ 10,700,000	$ 200,000
Number of warrants (in shares)	32,467,360
Exercise price of warrants (in dollars per share) \| $ / shares	$ 2.04
Warrant term	5 years
Proceeds from issuance of common stock and common warrants in a private offering, net of offering costs \| $	$ 212,100,000								$ 201,323,000	$ 119,928,000
Common stock, par value (in dollars per share) \| $ / shares							$ 0.0001		$ 0.0001		$ 0.0001
Issuance of common stock in connection with a public offering net of underwriting discounts, commissions and offering costs \| $							$ 201,323,000	$ 119,928,000
Shares subject to forfeiture (in shares)									0		0
Shares of common stock, repurchase (in shares)							0		0		55,227
Private Placement
Stockholders Equity [Line Items]
Private placement, number of shares (in shares)	129,869,440	16,649,365
Offering price (in dollars per share) \| $ / shares	$ 1.63125	$ 7.21
Aggregate gross proceeds \| $		$ 120,100,000
Payments of stock issuance costs \| $	$ 10,800,000
Exercise price of warrants (in dollars per share) \| $ / shares	$ 2.04
Warrant term	5 years
Private Placement \| Officer, Director, Employee or Consultant
Stockholders Equity [Line Items]
Offering price (in dollars per share) \| $ / shares	$ 1.85125
Private Placement \| Maximum
Stockholders Equity [Line Items]
Number of warrants (in shares)	32,467,360
Founder
Stockholders Equity [Line Items]
Stock issued (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 dollars 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]
Stock issued (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

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2023
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, 2022 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 17, 2023. 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, 2022, 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 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.
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, warrants for the purchase of common stock, 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.

Balance Sheet Accounts and Supplemental Disclosures (Tables)

9 Months Ended

Sep. 30, 2023

Balance Sheets Accounts And Supplemental Disclosures [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):


	Estimated Useful Life (in years)	September 30, 2023		December 31, 2022
Office equipment	3-7	$	1,097	$	1,097
Computer equipment	5	123		123
Software	3	52		130
Lab equipment	2-5	3,168		6,098
Leasehold improvements	6-7	2,562		2,562
Construction in process	N/A	—		83
Total property and equipment		7,002		10,093
Less: accumulated depreciation		(5,061)		(6,112)
Property and equipment, net		$	1,941	$	3,981

Schedule of Accrued Expenses

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


	As of
	September 30, 2023		December 31, 2022
Accrued compensation and benefits	$	9,051	$	13,534
Operating lease liabilities	3,220		2,983
Accrued consulting fees	637		1,104
Accrued interest	3,495		1,065
Accrued legal fees	127		380

Accrued accounting fees	165		521
Accrued other	767		945
Total accrued expenses and other current liabilities	$	17,462	$	20,532

Indebtedness - Additional Information (Details)			9 Months Ended
Indebtedness - Additional Information (Details)	May 21, 2020 USD ($) tradingDay $ / shares	May 02, 2019 USD ($) tranche	Sep. 30, 2023 USD ($)	Dec. 31, 2022 USD ($) tranche
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
Clinical development milestone unmet, number of tranches \| tranche				1
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 \| Secured Overnight Financing Rate (SOFR)
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		$ 60,000,000
Term Loan \| Tranche Two \| Credit Facility
Debt Instrument [Line Items]
Remaining borrowing capacity		$ 60,000,000		$ 60,000,000
2027 Notes
Debt Instrument [Line Items]
Interest rate	5.00%
Debt instrument aggregate principal amount	$ 200,000,000
Proceeds from convertible debt	$ 193,600,000
Debt instrument conversion ratio	0.0616095
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
Debt instrument, redemption term, threshold trading days	50 days
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
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 \| tradingDay	20
2027 Notes \| 130% Applicable Conversion Price \| Maximum
Debt Instrument [Line Items]
Convertible notes, consecutive trading days \| tradingDay	30
2027 Notes \| 98% Applicable Conversion Price \| Minimum
Debt Instrument [Line Items]
Convertible notes, consecutive trading days \| tradingDay	5
2027 Notes \| 98% Applicable Conversion Price \| Maximum
Debt Instrument [Line Items]
Convertible notes, consecutive trading days \| tradingDay	10

Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities not Included in Calculation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
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)	63,579,374	26,967,964
2027 Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included from calculation of diluted net loss per share (in shares)	12,321,900	12,321,900
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)	18,358,583	12,789,376
Shares issuable upon exercise of warrants
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)	32,467,360	0
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)	431,531	1,856,688

Balance Sheet Accounts and Supplemental Disclosures - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 7,002		$ 7,002		$ 10,093
Less: accumulated depreciation	(5,061)		(5,061)		(6,112)
Property and equipment, net	1,941		1,941		3,981
Depreciation and amortization expense	400	$ 500	1,315	$ 1,372
Office equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,097		$ 1,097		1,097
Office equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	3 years		3 years
Office equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	7 years		7 years
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	5 years		5 years
Total property and equipment	$ 123		$ 123		123
Software
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	3 years		3 years
Total property and equipment	$ 52		$ 52		130
Lab equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,168		$ 3,168		6,098
Lab equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	2 years		2 years
Lab equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	5 years		5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 2,562		$ 2,562		2,562
Leasehold improvements \| Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	6 years		6 years
Leasehold improvements \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	7 years		7 years
Construction in process
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 0		$ 0		$ 83

Equity Incentive Plans

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Equity Incentive Plans

2019 Equity Incentive Plan

In January 2019, the Company’s board of directors and stockholders approved and adopted the 2019 Incentive Award Plan (the “2019 Plan”). The 2019 Plan became effective on February 6, 2019, the day prior to the effectiveness of the registration statement filed in connection with the IPO. Under the 2019 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units, and other stock or cash-based awards to individuals who are then employees, officers, directors or consultants of the Company, and employees and consultants of the Company’s subsidiaries. A total of 5,750,000 shares of common stock were approved to be initially reserved for issuance under the 2019 Plan. The number of shares that remained available for issuance under the 2017 Plan (as defined below) as of the effective date of the 2019 Plan were, and shares subject to outstanding awards under the 2017 Plan as of the effective date of the 2019 Plan that are subsequently canceled, forfeited or repurchased by the Company will be, added to the shares reserved under the 2019 Plan. In addition, the number of shares of common stock available for issuance under the 2019 Plan will be automatically increased on the first day of each calendar year during the ten-year term of the 2019 Plan, beginning with January 1, 2020 and ending with January 1, 2029, by an amount equal to 5% of the outstanding number of shares of the Company’s common stock on December 31 of the preceding calendar year or such lesser amount as determined by the Company’s board of directors. As of September 30, 2023, an aggregate of 4,482,152 shares of common stock were available for issuance under the 2019 Plan. As of September 30, 2023 and December 31, 2022, 16,605,681 and 16,199,202 shares of common stock, respectively, 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 nine months ended September 30, 2023, 336,795 shares were issued pursuant to the ESPP. As of September 30, 2023, an aggregate of 3,058,844 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 September 30, 2023 and December 31, 2022, 2,184,433 and 2,582,771 shares of common stock, respectively, were subject to outstanding options under the 2017 Plan. As of September 30, 2023, no shares of restricted stock awards granted under the 2017 Plan were unvested.

Stock Options

The fair value of each employee and non-employee time-vested stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. The Company uses its own volatility to the extent it has sufficient trading history, and for awards in which sufficient trading history is not available, a peer group is used. 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.

On May 5, 2023, the Company granted to its Chairman and Chief Executive Officer 750,000 options with an exercise price of $1.36 per share. This grant contains both service and market based vesting conditions. The awards vest on the later of the date of achievement and the one-year anniversary of the grant date. The market condition becomes satisfied in 50%, 25% and 25% tranches upon achieving the average per-share closing price of the Company's common stock over any 30 consecutive calendar days following the grant date equal to or exceeding $5.00, $7.50 and $10.00, respectively. In the event a stock price tranche has not vested prior to the fourth anniversary of the grant date, any portion of the option attributable to such tranche will be forfeited. Due to the market condition included in this grant, the Company used the Geometric Brownian Motion/Monte Carlo model to value this award. The total stock-based compensation expense related to this award is $0.4 million, which is included in general and administrative expense on the condensed consolidated statements of operations and comprehensive loss. The Company expects to recognize this expense over a weighted average period of approximately 2.2 years.

Effective May 5, 2023, and in accordance with the terms of the 2019 Plan, the Company's board of directors approved a stock option repricing (the “Option Repricing”) whereby the exercise price of each Eligible Option (as defined below) was immediately reduced to $1.36 per share, the closing stock price on May 5, 2023. For purposes of the Option Repricing, “Eligible Options” are 6,817,057 outstanding stock options as of May 5, 2023 (vested or unvested) granted under the 2019 Plan prior to November 30, 2022 and held by those eligible employees of the Company identified by the Company's board of directors, including the Company’s executive officers except for the Company’s Chairman and Chief Executive Officer.

The participation of the executive officers of the Company in the Option Repricing was subject to their agreement to cancel a portion of their Eligible Options effective immediately (the “Cancelled Options”). Each executive was required to agree to cancel one-third of his or her Eligible Options, on a grant-by-grant basis. The Cancelled Options were deducted proportionately from the vested and unvested portions of each Repriced Option grant.

To the extent an Eligible Option is exercised prior to the Premium End Date (as defined below), or the eligible employee’s employment terminates prior to the Premium End Date, the eligible employee will be required to pay the original exercise price per share of the Eligible Options in connection with any exercise of the Eligible Option. The “Premium End Date” means the earliest of (i) May 5, 2024, (ii) the date of a change in control, (iii) the eligible employee’s death or disability, or (iv) if an eligible employee is an executive subject to the cancellation of a portion of Eligible Options and is terminated under circumstances giving rise to severance under his or her employment agreement, the date of such termination. Except for the reduction in the exercise prices of the Eligible Options as described above, the Eligible Options will retain their existing terms and conditions as set forth in the 2019 Plan and the applicable award agreements.

The repricing resulted in $3.4 million of incremental cost, which was calculated using the Black-Scholes option-pricing model, of which $2.0 million of the incremental cost was recognized immediately, and $1.4 million of the incremental cost will be recognized on the straight-line basis over the remaining vesting period of the repriced options. The incremental cost is included in general and administrative expense and research and development expense on the condensed consolidated statements of operations and comprehensive loss.

The following table summarizes stock option activity during the nine months ended September 30, 2023:


	Shares Subject to Options Outstanding			Weighted- Average
	Shares	Weighted- Average Exercise Price		Remaining Contractual Life (Years)	Aggregate Intrinsic Value
					(in thousands)
Outstanding as of December 31, 2022	17,487,165	$	9.24	8.1	$	47
Options granted	11,649,890	$	1.30
Options exercised	—	$	—
Options forfeited/cancelled	(10,778,472)	$	11.12
Outstanding as of September 30, 2023	18,358,583	$	3.09	7.5	$	—
Options vested and expected to vest as of September 30, 2023	18,358,583	$	3.09	7.5	$	—
Options exercisable as of September 30, 2023	7,470,969	$	4.72	6.0	$	—

The aggregate intrinsic value in the above table is calculated as the difference between fair value of the Company’s common stock price on September 30, 2023 and the exercise price of the stock options. The aggregate intrinsic value of stock options exercised during the nine months ended September 30, 2023 and 2022 was $0.0 million and $1.5 million, respectively.

The weighted-average grant date fair value per share for the stock option grants during the nine months ended September 30, 2023 and 2022 was $5.38 and $8.27, respectively.

The aggregate fair value of stock options that vested during the nine months ended September 30, 2023 and 2022 was $17.1 million and $26.1 million, respectively.

Warrants

On July 24, 2023, the Company completed a private placement of 129,869,440 shares of the Company’s common stock and accompanying warrants to purchase up to 32,467,360 shares of the Company's common stock at a combined purchase price of $1.63125 per share and accompanying warrant, or with respect to any purchaser that was an officer, director, employee or consultant of the Company $1.85125, per share and accompanying warrant. Each warrant has an exercise price per share of $2.04, was immediately exercisable on the date of issuance and will expire five years from the closing of the private placement.

Given that the warrants are indexed to the Company's shares of common stock (and otherwise meet the requirements to be classified in equity), the Company recorded the consideration received from the issuance of the warrants as additional paid-in capital on the Company's unaudited condensed consolidated balance sheets.

As of September 30, 2023, there were 32,467,360 warrants outstanding.

Restricted Stock

The summary of the Company’s restricted stock activity during the nine months ended September 30, 2023 is as follows:


	Number of Restricted Stock Units Outstanding	Weighted- Average Grant Date Fair Value
Nonvested at December 31, 2022	1,350,035	$	10.83
Granted	—	—
Vested	(779,900)	10.67
Forfeited	(138,604)	11.39
Nonvested at September 30, 2023	431,531	$	10.93

Stock-Based Compensation Expense

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


	Three months ended September 30,				Nine months ended September 30,
	2023		2022		2023		2022
Research and development	$	3,250	$	5,595	$	12,661	$	17,800
General and administrative	2,912		4,527		9,825		13,304
Total stock-based compensation expense	$	6,162	$	10,122	$	22,486	$	31,104

As of September 30, 2023, the total unrecognized compensation expense related to the unvested stock option awards granted was $26.2 million, which the Company expects to recognize over a weighted-average period of approximately 2.2 years.

As of September 30, 2023, the total unrecognized stock-based compensation expense related to the unvested restricted stock awards granted was $1.6 million, which the Company expects to recognize over a weighted-average period of approximately 0.4 years.

As of September 30, 2023, the total unrecognized compensation expense related to the ESPP was $1.3 million, which the Company expects to recognize over a weighted-average period of approximately 0.8 years.

Description of Business	9 Months Ended
Description of Business	Sep. 30, 2023
Accounting Policies [Abstract]
Description of Business	Description of 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 unaudited 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 upon consolidation. Liquidity and Capital Resources The Company has incurred significant operating losses since its inception. As of September 30, 2023, the Company had an accumulated deficit of $1,163.9 million. From the Company’s inception through September 30, 2023, the Company has funded its operations primarily through equity and debt financings. The Company raised $1,263.2 million from October 2017 through September 30, 2023 through the sale of Series A and Series B convertible preferred stock, issuance of convertible notes, its initial public offering ("IPO"), the Credit Facility and 2027 Notes (as defined in Note 5 below), issuance of common stock in May 2020 and July 2022 and issuance of common stock and accompanying warrants in July 2023 (see Note 7). On July 24, 2023, the Company completed a private placement of 129,869,440 shares of the Company’s common stock and accompanying warrants to purchase up to 32,467,360 shares of the Company's common stock at a combined purchase price of $1.63125 per share and accompanying warrant, or with respect to any purchaser that was an officer, director, employee or consultant of the Company $1.85125 per share and accompanying warrant. Each warrant will have an exercise price per share of $2.04, will be immediately exercisable on the date of issuance and will expire five years from the closing of the private placement. The aggregate gross proceeds for the private placement were approximately $212.1 million, before deducting offering expenses, which equaled approximately $10.7 million. 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 additional capital through equity offerings, debt financings or other capital sources, including potential collaborations, licenses and other similar arrangements. Management believes that it has sufficient working capital on hand to fund operations through at least the next 12 months from the date these 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.

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Lessee, Lease, Description [Line Items]
Operating lease, weighted average discount rate	7.00%		7.00%
Weighted average remaining lease term (in years)	1 year 3 months 18 days		1 year 3 months 18 days
Cash paid for operating lease liabilities	$ 0.6	$ 0.5	$ 2.5	$ 2.4
Rent expense	$ 0.9	$ 0.8	$ 2.6	$ 2.5
Non-cancelable Lease Agreement Entered in August 2018
Lessee, Lease, Description [Line Items]
Operating sublease, annual increase percentage for base rent			3.00%

Equity Incentive Plans - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended	12 Months Ended
	May 05, 2023	Sep. 30, 2023	Dec. 31, 2022
Shares Subject to Options Outstanding, Shares
Outstanding as of beginning balance (in shares)		17,487,165
Options granted (in shares)	750,000	11,649,890
Option exercised (in shares)		0
Options forfeited/cancelled (in shares)		(10,778,472)
Outstanding as ending balance (in shares)		18,358,583	17,487,165
Options vested and expected to vest as of ending balance (in shares)		18,358,583
Options exercisable as of ending balance (in shares)		7,470,969
Shares Subject to Options Outstanding, Weighted Average Exercise Price
Outstanding as of beginning balance (in dollars per share)		$ 9.24
Options granted (in dollars per share)	$ 1.36	1.30
Option exercised (in dollars per share)		0
Options forfeited/cancelled (in dollars per share)		11.12
Outstanding as of ending balance (in dollars per share)		3.09	$ 9.24
Options vested and expected to vest as of ending balance (in dollars per share)		3.09
Options exercisable as of ending balance (in dollars per share)		$ 4.72
Weighted-Average Remaining Contractual Life (in years)		7 years 6 months	8 years 1 month 6 days
Weighted-Average Remaining Contractual Life (in years), Options vested and expected to vest as of end of period		7 years 6 months
Weighted-Average Remaining Contractual Life (in years), Options exercisable as of end of period		6 years
Aggregate Intrinsic Value		$ 0	$ 47
Aggregate Intrinsic Value, Options vested and expected to vest as of end of period		0
Aggregate Intrinsic Value, Options exercisable as of end of period		$ 0

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current assets
Cash and cash equivalents	$ 82,609	$ 111,973
Marketable securities	246,279	143,705
Prepaid expenses and other current assets	12,602	6,202
Total current assets	341,490	261,880
Property and equipment, net	1,941	3,981
Operating lease right-of-use assets	3,845	5,909
Other assets	649	680
Total assets	347,925	272,450
Current liabilities
Accounts payable	1,251	1,459
Accrued research and development expenses	11,990	15,626
Current portion of long-term debt	11,613	11,613
Accrued expenses and other current liabilities	17,462	20,532
Total current liabilities	42,316	49,230
Long-term convertible senior notes	196,366	195,709
Long-term debt	3,634	11,988
Operating lease liabilities - long-term	992	3,446
Total liabilities	243,308	260,373
Commitments and contingencies (Note 9)
Stockholders' equity
Common stock, $0.0001 par value; 700,000,000 shares authorized as of September 30, 2023 and December 31, 2022; 225,409,315 shares issued and outstanding as of September 30, 2023, and 94,478,405 shares issued and 94,423,181 shares outstanding as of December 31, 2022	23	10
Additional paid-in capital	1,269,104	1,044,864
Accumulated deficit	(1,163,892)	(1,032,223)
Accumulated other comprehensive loss	(618)	(574)
Total stockholders' equity	104,617	12,077
Total liabilities and stockholders' equity	$ 347,925	$ 272,450

Equity Incentive Plans - Stock-Based Compensation Expense Reported in Condensed Consolidated Statements of Operations (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	May 05, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based payment arrangement, expense	$ 2,000	$ 6,162	$ 10,122	$ 22,486	$ 31,104
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based payment arrangement, expense		3,250	5,595	12,661	17,800
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based payment arrangement, expense		$ 2,912	$ 4,527	$ 9,825	$ 13,304

Indebtedness (Tables)

9 Months Ended

Sep. 30, 2023

Debt Disclosure [Abstract]

Schedule of Long-term Debt

Debt consisted of the following (in thousands):


	September 30, 2023		December 31, 2022
Debt, current portion	$	11,613	$	11,613
Debt, non-current portion	3,871		12,581
Total debt	15,484		24,194
Less: unamortized debt discount and issuance costs	(237)		(593)
Debt, net	$	15,247	$	23,601

Schedule of Future Minimum Principal Payments

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


	September 30, 2023
2023 (remaining 3 months)	$	2,903
2024	11,613
2025	968
Total	$	15,484

Schedule of Net Carrying Amount of 2027 Notes

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


	September 30, 2023		December 31, 2022
Principal amount	$	200,000	$	200,000
Unamortized debt discount	(3,405)		(4,021)
Unamortized debt issuance cost	(229)		(270)
Net carrying amount	$	196,366	$	195,709

Schedule of Interest Expense Recognized

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


	Three months ended September 30,				Nine months ended September 30,
	2023		2022		2023		2022
Contractual interest expense	$	2,500	$	2,500	$	7,500	$	7,500
Amortization of debt discount	208		197		615		582
Amortization of debt issuance cost	14		13		41		39
Total interest expense related to the 2027 Notes	$	2,722	$	2,710	$	8,156	$	8,121

Condensed Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common stock	Additional paid-in capital	Additional paid-in capital Cumulative Effect, Period of Adoption, Adjustment	Accumulated deficit	Accumulated deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated other comprehensive income (loss)
Beginning balance (in shares) at Dec. 31, 2021			75,752,664
Beginning balance at Dec. 31, 2021	$ 121,463	$ (44,838)	$ 8	$ 932,944	$ (53,527)	$ (811,534)	$ 8,689	$ 45
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock (in shares)			165,675
Stock-based compensation	10,983			10,983
Issuance of common stock pursuant to Employee Stock Purchase Plan (in shares)			77,496
Issuance of common stock pursuant to Employee Stock Purchase Plan	595			595
Issuance of common stock for restricted stock units vested (in shares)			518,577
Net loss	(57,785)					(57,785)
Other comprehensive income	(385)							(385)
Exercise of stock options (in shares)			39,525
Exercise of stock options	126			126
Ending balance (in shares) at Mar. 31, 2022			76,553,937
Ending balance at Mar. 31, 2022	30,159		$ 8	891,121		(860,630)		(340)
Beginning balance (in shares) at Dec. 31, 2021			75,752,664
Beginning balance at Dec. 31, 2021	121,463	$ (44,838)	$ 8	932,944	$ (53,527)	(811,534)	$ 8,689	45
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(173,614)
Other comprehensive income	(630)
Ending balance (in shares) at Sep. 30, 2022			93,914,200
Ending balance at Sep. 30, 2022	56,351		$ 10	1,033,385		(976,459)		(585)
Beginning balance (in shares) at Mar. 31, 2022			76,553,937
Beginning balance at Mar. 31, 2022	30,159		$ 8	891,121		(860,630)		(340)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock (in shares)			165,675
Stock-based compensation	9,999			9,999
Issuance of common stock for restricted stock units vested (in shares)			8,607
Net loss	(56,466)					(56,466)
Other comprehensive income	(174)							(174)
Exercise of stock options (in shares)			8,005
Exercise of stock options	21			21
Ending balance (in shares) at Jun. 30, 2022			76,736,224
Ending balance at Jun. 30, 2022	(16,461)		$ 8	901,141		(917,096)		(514)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock (in shares)			165,676
Stock-based compensation	10,122			10,122
Issuance of common stock pursuant to Employee Stock Purchase Plan (in shares)			80,362
Issuance of common stock pursuant to Employee Stock Purchase Plan	620			620
Issuance of common stock for restricted stock units vested (in shares)			63,000
Net loss	(59,363)					(59,363)
Other comprehensive income	(71)							(71)
Issuance of common stock and accompanying warrants in connection with a private offering, net of offering costs of $184 (in shares)			16,649,365
Issuance of common stock and accompanying warrants in connection with a private offering, net of offering costs of $10,779	119,928		$ 2	119,926
Exercise of stock options (in shares)			219,573
Exercise of stock options	1,576			1,576
Ending balance (in shares) at Sep. 30, 2022			93,914,200
Ending balance at Sep. 30, 2022	$ 56,351		$ 10	1,033,385		(976,459)		(585)
Beginning balance (in shares) at Dec. 31, 2022	94,423,181		94,423,181
Beginning balance at Dec. 31, 2022	$ 12,077		$ 10	1,044,864		(1,032,223)		(574)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock (in shares)			55,225
Stock-based compensation	8,127			8,127
Issuance of common stock pursuant to Employee Stock Purchase Plan (in shares)			249,623
Issuance of common stock pursuant to Employee Stock Purchase Plan	367			367
Issuance of common stock for restricted stock units vested (in shares)			716,067
Net loss	(49,165)					(49,165)
Other comprehensive income	138							138
Ending balance (in shares) at Mar. 31, 2023			95,444,096
Ending balance at Mar. 31, 2023	$ (28,456)		$ 10	1,053,358		(1,081,388)		(436)
Beginning balance (in shares) at Dec. 31, 2022	94,423,181		94,423,181
Beginning balance at Dec. 31, 2022	$ 12,077		$ 10	1,044,864		(1,032,223)		(574)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(131,669)
Other comprehensive income	$ (44)
Exercise of stock options (in shares)	0
Ending balance (in shares) at Sep. 30, 2023	225,409,315		225,409,315
Ending balance at Sep. 30, 2023	$ 104,617		$ 23	1,269,104		(1,163,892)		(618)
Beginning balance (in shares) at Mar. 31, 2023			95,444,096
Beginning balance at Mar. 31, 2023	(28,456)		$ 10	1,053,358		(1,081,388)		(436)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	8,197			8,197
Issuance of common stock for restricted stock units vested (in shares)			8,607
Net loss	(42,496)					(42,496)
Other comprehensive income	(45)							(45)
Ending balance (in shares) at Jun. 30, 2023			95,452,703
Ending balance at Jun. 30, 2023	(62,800)		$ 10	1,061,555		(1,123,884)		(481)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	6,162			6,162
Issuance of common stock pursuant to Employee Stock Purchase Plan (in shares)			87,172
Issuance of common stock pursuant to Employee Stock Purchase Plan	77			77
Net loss	(40,008)					(40,008)
Other comprehensive income	(137)							(137)
Issuance of common stock and accompanying warrants in connection with a private offering, net of offering costs of $184 (in shares)			129,869,440
Issuance of common stock and accompanying warrants in connection with a private offering, net of offering costs of $10,779	$ 201,323		$ 13	201,310
Ending balance (in shares) at Sep. 30, 2023	225,409,315		225,409,315
Ending balance at Sep. 30, 2023	$ 104,617		$ 23	$ 1,269,104		$ (1,163,892)		$ (618)

Fair Value Measurements and Available for Sale Investments (Tables)

9 Months Ended

Sep. 30, 2023

Fair Value Measurements And Available For Sale Investments [Abstract]

Schedule of 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 September 30, 2023 and December 31, 2022 (in thousands):


	Fair Value Measurements at End of Period Using:
	Total Fair Value		Quoted Market Prices for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
As of September 30, 2023
Money market funds	$	19,885	$	19,885	$	—	$	—
U.S. Treasury and agency securities	83,790		83,790		—		—
Commercial paper	216,096		—		216,096		—

As of December 31, 2022
Money market funds	$	54,662	$	54,662	$	—	$	—
U.S. Treasury and agency securities	31,458		31,458		—		—
Commercial paper	134,954		—		134,954		—
Corporate debt securities	8,838		—		8,838		—

Schedule of Available for Sale Investments by Security Type


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Total Fair Value
As of September 30, 2023
U.S. Treasury and agency securities	$	83,766	$	24	$	—	$	83,790
Corporate debt securities	—		—		—		—
Commercial paper	162,535		—		(46)		162,489
Total marketable securities	$	246,301	$	24	$	(46)	$	246,279
Number of securities with unrealized losses					20

As of December 31, 2022
U.S. Treasury and agency securities	$	31,445	$	13	$	—	$	31,458
Corporate debt securities	8,876		—		(38)		8,838
Commercial paper	103,508		—		(99)		103,409
Total marketable securities	$	143,829	$	13	$	(137)	$	143,705
Number of securities with unrealized losses					16

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

Contractual maturities of available-for-sale debt securities, as of September 30, 2023, were as follows (in thousands):


	Estimated Fair Value
Less than one year	$	246,279
Greater than one year	—
Total	$	246,279

Equity Incentive Plans (Tables)

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

The following table summarizes stock option activity during the nine months ended September 30, 2023:


	Shares Subject to Options Outstanding			Weighted- Average
	Shares	Weighted- Average Exercise Price		Remaining Contractual Life (Years)	Aggregate Intrinsic Value
					(in thousands)
Outstanding as of December 31, 2022	17,487,165	$	9.24	8.1	$	47
Options granted	11,649,890	$	1.30
Options exercised	—	$	—
Options forfeited/cancelled	(10,778,472)	$	11.12
Outstanding as of September 30, 2023	18,358,583	$	3.09	7.5	$	—
Options vested and expected to vest as of September 30, 2023	18,358,583	$	3.09	7.5	$	—
Options exercisable as of September 30, 2023	7,470,969	$	4.72	6.0	$	—

Schedule of Restricted Stock Activity

The summary of the Company’s restricted stock activity during the nine months ended September 30, 2023 is as follows:


	Number of Restricted Stock Units Outstanding	Weighted- Average Grant Date Fair Value
Nonvested at December 31, 2022	1,350,035	$	10.83
Granted	—	—
Vested	(779,900)	10.67
Forfeited	(138,604)	11.39
Nonvested at September 30, 2023	431,531	$	10.93

Schedule of 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 and comprehensive loss as follows (in thousands):


	Three months ended September 30,				Nine months ended September 30,
	2023		2022		2023		2022
Research and development	$	3,250	$	5,595	$	12,661	$	17,800
General and administrative	2,912		4,527		9,825		13,304
Total stock-based compensation expense	$	6,162	$	10,122	$	22,486	$	31,104

Fair Value Measurements and Available for Sale Investments - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest receivable	$ 0.0	$ 0.0
Cash equivalents, at carrying value	53.6	31.5
2027 Notes \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of convertible senior notes	$ 78.9	$ 61.0

Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2023

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 September 30,
	2023	2022
2027 Notes	12,321,900	12,321,900
Shares issuable upon exercise of stock options	18,358,583	12,789,376
Shares issuable upon exercise of warrants	32,467,360	—
Non-vested shares under restricted stock grants	431,531	1,856,688
Total potentially dilutive securities	63,579,374	26,967,964

Label	Element	Value
Accounting Standards Update [Extensible Enumeration]	us-gaap_AccountingStandardsUpdateExtensibleList	Accounting Standards Update 2020-06 [Member]

- Definition

Indicates amendment to accounting standards.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 34: http://www.xbrl.org/2003/role/disclosureRef
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Reference 43: http://www.xbrl.org/2003/role/disclosureRef
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Reference 46: http://www.xbrl.org/2003/role/disclosureRef
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Reference 47: http://www.xbrl.org/2003/role/disclosureRef
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Reference 48: http://www.xbrl.org/2003/role/disclosureRef
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Reference 49: http://www.xbrl.org/2003/role/disclosureRef
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Reference 51: http://www.xbrl.org/2003/role/disclosureRef
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Reference 52: http://www.xbrl.org/2003/role/disclosureRef
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Reference 53: http://www.xbrl.org/2003/role/disclosureRef
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Reference 55: http://www.xbrl.org/2003/role/disclosureRef
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Reference 56: http://www.xbrl.org/2003/role/disclosureRef
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Reference 57: http://www.xbrl.org/2003/role/disclosureRef
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Reference 58: http://www.xbrl.org/2003/role/disclosureRef
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Reference 59: http://www.xbrl.org/2003/role/disclosureRef
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Reference 62: http://www.xbrl.org/2003/role/disclosureRef
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Reference 66: http://www.xbrl.org/2003/role/disclosureRef
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Reference 67: http://www.xbrl.org/2003/role/disclosureRef
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Reference 68: http://www.xbrl.org/2003/role/disclosureRef
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Reference 69: http://www.xbrl.org/2003/role/disclosureRef
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Reference 70: http://www.xbrl.org/2003/role/disclosureRef
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Reference 71: http://www.xbrl.org/2003/role/disclosureRef
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Reference 72: http://www.xbrl.org/2009/role/commonPracticeRef
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-URI https://asc.fasb.org//1943274/2147483443/250-10-50-1

+ Details

Balance Sheet Accounts and Supplemental Disclosures - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Balance Sheets Accounts And Supplemental Disclosures [Abstract]
Accrued compensation and benefits	$ 9,051	$ 13,534
Operating lease liabilities	3,220	2,983
Accrued consulting fees	637	1,104
Accrued interest	3,495	1,065
Accrued legal fees	127	380
Accrued accounting fees	165	521
Accrued other	767	945
Total accrued expenses and other current liabilities	$ 17,462	$ 20,532

Commitments and Contingencies - Schedule of Gross Future Minimum Annual Rental Commitments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
2023 (remaining 3 months)	$ 831
2024	3,418
2025	144
Total undiscounted rent payments	4,393
Present value discount	(181)
Present value of lease payments	4,212
Current portion of operating lease liabilities (included as a component of accrued expenses and other current liabilities)	3,220	$ 2,983
Noncurrent operating lease liabilities	992	$ 3,446
Total operating lease liability	$ 4,212

Fair Value Measurements and Available for Sale Investments - Assets Measured at Fair Value on Recurring Basis (Details) - Recurring Basis - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	$ 19,885	$ 54,662
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	83,790	31,458
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	216,096	134,954
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis		8,838
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	19,885	54,662
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	83,790	31,458
Quoted Market Prices for Identical Assets (Level 1) \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	0	0
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
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	0
Significant Other Observable Inputs (Level 2) \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	216,096	134,954
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		8,838
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	0
Significant Unobservable Inputs (Level 3) \| Commercial paper
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) \| 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

Indebtedness - Schedule of Interest Expense Recognized (Details) - 2027 Notes - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Debt Instrument [Line Items]
Contractual interest expense	$ 2,500	$ 2,500	$ 7,500	$ 7,500
Amortization of debt discount	208	197	615	582
Amortization of debt issuance cost	14	13	41	39
Total interest expense related to the 2027 Notes	$ 2,722	$ 2,710	$ 8,156	$ 8,121

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Commitments and Contingencies - Schedule of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 778	$ 778	$ 2,335	$ 2,318
Short-term lease cost	13	12	39	32
Total lease cost	$ 791	$ 790	$ 2,374	$ 2,350

Description of Business (Details) - USD ($) $ / shares in Units, $ in Thousands			9 Months Ended		72 Months Ended
	Jul. 24, 2023	Jul. 15, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Dec. 31, 2022
Subsidiary, Sale of Stock [Line Items]
Accumulated deficit			$ 1,163,892		$ 1,163,892	$ 1,032,223
Funds raised					$ 1,263,200
Number of warrants (in shares)	32,467,360
Exercise price of warrants (in dollars per share)	$ 2.04
Warrant term	5 years
Proceeds from issuance of private placement	$ 212,100		$ 201,323	$ 119,928
Payments of stock issuance costs	$ 10,700	$ 200
Private Placement
Subsidiary, Sale of Stock [Line Items]
Private placement, number of shares (in shares)	129,869,440	16,649,365
Offering price (in dollars per share)	$ 1.63125	$ 7.21
Exercise price of warrants (in dollars per share)	$ 2.04
Warrant term	5 years
Payments of stock issuance costs	$ 10,800
Private placement with officer, director, employee, or consultant
Subsidiary, Sale of Stock [Line Items]
Offering price (in dollars per share)	$ 1.85125

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Operating expenses:
Research and development	$ 31,200	$ 44,509	$ 105,334	$ 129,411
In process research and development	0	15	0	50
General and administrative	9,290	11,497	29,398	34,775
Total operating expenses	40,490	56,021	134,732	164,236
Loss from operations	(40,490)	(56,021)	(134,732)	(164,236)
Other income (expense)
Interest income	405	465	1,687	989
Interest expense	(3,343)	(3,475)	(10,272)	(10,423)
Other income (expense), net	3,420	(332)	11,648	56
Total other income (expense), net	482	(3,342)	3,063	(9,378)
Net loss	(40,008)	(59,363)	(131,669)	(173,614)
Other comprehensive income (loss):
Foreign currency translation	(170)	(173)	(146)	(319)
Unrealized gain (loss) on marketable securities	33	102	102	(311)
Other comprehensive loss	(137)	(71)	(44)	(630)
Comprehensive loss	$ (40,145)	$ (59,434)	$ (131,713)	$ (174,244)
Net loss per share, basic (in dollars per share)	$ (0.21)	$ (0.65)	$ (1.03)	$ (2.14)
Net loss per share, diluted (in dollars per share)	$ (0.21)	$ (0.65)	$ (1.03)	$ (2.14)
Weighted average common shares outstanding, basic (in shares)	192,883,209	91,181,427	128,092,499	81,304,089
Weighted average common shares outstanding, diluted (in shares)	192,883,209	91,181,427	128,092,499	81,304,089

Equity Incentive Plans - Schedule of Restricted Stock Activity (Details) - Restricted Stock	9 Months Ended
	Sep. 30, 2023 $ / shares shares
Number of Restricted Stock Units Outstanding
Nonvested beginning balance (in shares) \| shares	1,350,035
Granted (in shares) \| shares	0
Vested (in shares) \| shares	(779,900)
Forfeited (in shares) \| shares	(138,604)
Nonvested ending balance (in shares) \| shares	431,531
Weighted- Average Grant Date Fair Value
Nonvested beginning balance (in dollars per share) \| $ / shares	$ 10.83
Granted (in dollars per share) \| $ / shares	0
Vested (in dollars per share) \| $ / shares	10.67
Forfeited (in dollars per share) \| $ / shares	11.39
Nonvested ending balance (in dollars per share) \| $ / shares	$ 10.93

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2023
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 Company's board of directors. Private Placement Financing On July 15, 2022, the Company completed a private placement of 16,649,365 shares of the Company's common stock at purchase price of $7.21 per share. The gross proceeds for the private placement were $120.1 million, before deducting offering expenses, which equaled $0.2 million. On August 9, 2022, the Company filed a registration statement on Form S-3 registering the shares of common stock issued in the private placement, which registration statement became automatically effective on August 9, 2022. On July 24, 2023, the Company completed a private placement of 129,869,440 shares of the Company’s common stock and accompanying warrants to purchase up to 32,467,360 shares of the Company's common stock at a combined purchase price of $1.63125 per share and accompanying warrant, or with respect to any purchaser that was an officer, director, employee or consultant of the Company $1.85125, per share and accompanying warrant. Each warrant has an exercise price per share of $2.04, was immediately exercisable on the date of issuance and will expire five years from the closing of the private placement. The aggregate gross proceeds for the private placement were approximately $212.1 million, before deducting offering expenses, which equaled $10.8 million. On August 18, 2023, the Company filed a registration statement on Form S-3 registering the shares of common stock and shares of common stock issuable upon the exercise of warrants issued in the private placement, which registration statement became effective on August 28, 2023. 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. During the nine months ended September 30, 2023 and the year ended December 31, 2022, no 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 September 30, 2023 and December 31, 2022, no shares and 55,227 shares of common stock, respectively, were subject to repurchase by the Company. The unvested stock liability related to these awards is immaterial to all periods presented.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

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+ Details

Indebtedness - Schedule of Net Carrying Amount of 2027 Notes (Details) - 2027 Notes - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Principal amount	$ 200,000	$ 200,000
Unamortized debt discount	(3,405)	(4,021)
Unamortized debt issuance cost	(229)	(270)
Debt, net	$ 196,366	$ 195,709

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details