0001728117-24-000019 | 10-K | XBRL Viewer

Print Document View Excel Document

Fair Value Measurements and Available for Sale Investments - Schedule of Contractual Maturities of Available-for-sale Debt Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Less than one year	$ 264,316
Greater than one year	0
Total Fair Value	$ 264,316	$ 143,705

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating expenses:
Research and development	$ 135,304	$ 170,919	$ 170,267
In process research and development	10,000	65	75
General and administrative	38,455	47,609	45,782
Total operating expenses	183,759	218,593	216,124
Loss from operations	(183,759)	(218,593)	(216,124)
Other income (expense)
Interest income	1,997	1,583	761
Interest expense	(13,511)	(13,880)	(19,440)
Other income, net	15,456	1,512	799
Total other income (expense), net	3,942	(10,785)	(17,880)
Net loss	(179,817)	(229,378)	(234,004)
Other comprehensive (loss) income:
Foreign currency translation	33	(544)	(329)
Unrealized income (loss) on marketable securities	191	(75)	(225)
Other comprehensive income (loss)	224	(619)	(554)
Comprehensive loss	$ (179,593)	$ (229,997)	$ (234,558)
Net loss per share, basic (in dollars per share)	$ (1.18)	$ (2.71)	$ (3.13)
Net loss per share, diluted (in dollars per share)	$ (1.18)	$ (2.71)	$ (3.13)
Weighted average common shares outstanding, basic (in shares)	152,621,669	84,574,869	74,843,482
Weighted average common shares outstanding, diluted (in shares)	152,621,669	84,574,869	74,843,482

Licenses, Asset Acquisitions and Contingent Consideration

12 Months Ended

Dec. 31, 2023

Business Combination and Asset Acquisition [Abstract]

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 consolidated statements of operations and comprehensive loss for the years ended December 31, 2023, 2022, and 2021.

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

License from Pulmokine, Inc. (Seralutinib)

On October 2, 2017, the Company entered into a license agreement with Pulmokine, Inc. under which it was granted an exclusive worldwide license and sublicense to certain intellectual property rights owned or controlled by Pulmokine to develop and commercialize seralutinib and certain backup compounds for the treatment, prevention and diagnosis of any and all disease or conditions. The Company also has the right to sublicense its rights under the license agreement, subject to certain conditions. The assets acquired are in the early stages of the FDA approval process, and the Company intends to further develop the assets acquired through potential FDA approval as evidenced by the milestone arrangement in the contract. The

development activities cannot be performed without significant cost and effort by the Company. The agreement will remain in effect from the effective date, unless terminated earlier, until, on a licensed product-by-licensed product and country-by-country basis, the later of ten years from the date of first commercial sale or when there is no longer a valid patent claim covering such licensed product or specified regulatory exclusivity for the licensed product in such country. The Company is obligated to make future development and regulatory milestone payments of up to $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 December 31, 2023, the Company accrued a milestone payment of $10.0 million in connection with the initiation of the Phase 3 clinical trial of seralutinib, which was paid in January 2024. No other milestones had been accrued as the underlying contingencies had not yet been met.

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


	Year Ended December 31,
	2023		2022		2021
Seralutinib	$	10,000	$	—	$	—

Terminated programs	—		65		75
Total in process research and development	$	10,000	$	65	$	75

Description of Business (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended			75 Months Ended
	Jul. 24, 2023	Jul. 15, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2023	May 21, 2020
Subsidiary, Sale of Stock [Line Items]
Retained earnings (accumulated deficit)			$ (1,212,040)	$ (1,032,223)		$ (1,212,040)
Funds raised						$ 1,263,200
Warrants to purchase (in shares)	32,467,360
Offering price (in dollars per share)							$ 13.25
Exercise price of warrants (in dollars per share)	$ 2.04
Warrant term	5 years
Proceeds from issuance of private placement	$ 212,100		$ 201,323	$ 119,946	$ 0
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 \| Officer, Director, Employee Or Consultant
Subsidiary, Sale of Stock [Line Items]
Offering price (in dollars per share)	$ 1.85125

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1.6	$ 1.8	$ 1.7

Licenses, Asset Acquisitions and Contingent Consideration - Additional Information (Details) - Pulmokine, Inc. - License Agreement - Seralutinib - USD ($) $ in Millions		1 Months Ended
	Oct. 02, 2017	Oct. 31, 2017	Dec. 31, 2023	Jan. 31, 2021
Business Acquisition [Line Items]
Product license term	10 years
Upfront payment		$ 5.5
Milestones accrued			$ 10.0	$ 5.0
Maximum
Business Acquisition [Line Items]
Development and regulatory milestone payments, payable	$ 58.0
Initiation of first Phase 3 payments, payable	10.0
Commercial milestone payments, payable	45.0
Sales milestone payments, payable	$ 190.0

Income Taxes - Schedule of Reconciliation of Beginning and Ending Amounts of Unrecognized Tax Benefits, Excluding Interest and Penalties (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of the year	$ 10,572	$ 7,551	$ 5,060
Increase related to current year positions	3,082	3,021	2,491
Balance at the end of the year	$ 13,654	$ 10,572	$ 7,551

Equity Incentive Plans - Schedule of Restricted Stock Activity (Details) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Number of Restricted Stock Units Outstanding
Nonvested beginning balance (in shares)	1,350,035	2,561,219	3,330,821
Granted (in shares)	0	572,901	1,349,885
Vested (in shares)	(779,900)	(1,592,588)	(1,391,476)
Forfeited/cancelled (in shares)	(142,437)	(191,497)	(728,011)
Nonvested ending balance (in shares)	427,698	1,350,035	2,561,219
Weighted- Average Grant Date Fair Value
Nonvested beginning balance (in dollars per share)	$ 10.83	$ 8.67	$ 7.16
Granted (in dollars per share)	0	11.94	10.23
Vested (in dollars per share)	10.67	7.78	5.86
Forfeited/cancelled (in dollars per share)	11.39	10.68	10.03
Nonvested ending balance (in dollars per share)	$ 10.92	$ 10.83	$ 8.67

Fair Value Measurements and Available for Sale Investments - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Significant Other Observable Inputs (Level 2) \| 2027 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	$ 74.9	$ 61.0
Prepaid Expenses and Other Current Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest receivable	$ 0.0	$ 0.0

Commitments and Contingencies - Schedule of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Operating lease cost	$ 3,114	$ 3,097	$ 4,029
Short-term lease cost	52	45	53
Total lease cost	$ 3,166	$ 3,142	$ 4,082

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 7,080	$ 10,093
Less: accumulated depreciation	(5,432)	(6,112)
Property and equipment, net	$ 1,648	3,981
Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	2 years
Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	7 years
Office equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,097	1,097
Office equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Office equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	7 years
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	5 years
Total property and equipment	$ 123	123
Software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Total property and equipment	$ 52	130
Lab equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,246	6,098
Lab equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	2 years
Lab equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 2,562	2,562
Leasehold improvements \| Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	6 years
Leasehold improvements \| Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	7 years
Construction in process
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 0	$ 83

Equity Incentive Plans - Schedule of Fair Value Assumptions Stock Options (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividends yield (in percentage)	0.00%
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	3.36%	1.31%	0.65%
Risk-free interest rate, maximum	4.73%	4.35%	1.30%
Volatility, minimum	70.01%	71.10%	78.80%
Volatility, maximum	170.69%	89.87%	84.79%
Expected dividends yield (in percentage)	0.00%	0.00%	0.00%
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	4.87%	0.60%	0.06%
Risk-free interest rate, maximum	5.47%	3.51%	0.20%
Volatility, minimum	115.19%	64.98%	61.29%
Volatility, maximum	216.45%	121.43%	87.13%
Expected dividends yield (in percentage)	0.00%	0.00%	0.00%
Minimum \| Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected life (in years)	1 year	4 years 4 months 24 days	4 years 7 months 6 days
Minimum \| ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected life (in years)	6 months	6 months	6 months
Maximum \| Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected life (in years)	7 years	6 years 1 month 6 days	6 years 1 month 6 days
Maximum \| ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected life (in years)	2 years	2 years	2 years

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

The amount of net loss before taxes for the years ended December 31, 2023, 2022, and 2021 is as follows (in thousands):


	December 31,
	2023		2022		2021
	(in thousands)
U.S. loss before taxes	$	134,073	$	175,777	$	183,194
Foreign loss before taxes	45,736		53,593		50,802
Pre-tax Loss	$	179,809	$	229,370	$	233,996

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets and liabilities at December 31, 2023, 2022 and 2021 are shown below. The Company has established a valuation allowance against net deferred tax assets due to the uncertainty that such assets will be realized. The Company periodically evaluates the recoverability of the deferred assets. At such time as it is determined that it is more likely than not that the deferred tax asset will be realized, the valuation allowance will be reduced. The change in the valuation allowance for the year ended December 31, 2023 was an increase of $17.3 million.


	December 31,
	2023		2022		2021
	(in thousands)
Deferred tax assets:
Net operating losses	$	122,987	$	128,989	$	116,425
Tax credits, net	45,445		34,193		24,964
Amortization	6,919		8,487		9,190
Stock-based compensation	9,886		8,445		4,917
Lease liability	726		1,354		1,285
Accrued compensation	1,887		2,514		2,238
Section 174	34,268		21,840		—
Other	43		37		18
Total gross deferred tax assets	222,161		205,859		159,037

Deferred tax liabilities:
Convertible senior notes	—		—		(9,395)
Right of use asset	(660)		(1,244)		(1,150)
Property, plant and equipment	(108)		(565)		(790)
Total gross deferred tax liabilities	(768)		(1,809)		(11,335)
Valuation allowance	(221,393)		(204,050)		(147,702)
Net deferred tax asset	$	—	$	—	$	—

As of December 31, 2023, the Company had federal and state NOL carryforwards of approximately $532.1 million and $1.8 million, respectively. The federal NOL carryforwards generated prior to January 1, 2018 begin to expire in 2034, unless previously utilized. The federal NOLs generated in taxable years beginning after December 31, 2017 of $529.1 million can be carried forward indefinitely but may only be used to offset up to 80% of future taxable income each year. The California NOL carryforwards begin to expire in 2036. As of December 31, 2023, the Company also has foreign NOL carryforwards of approximately $89.1 million. The foreign NOL can be carried forward indefinitely. In the current year, the Company determined $140.0 million of foreign NOL carryforwards were relinquished due to liquidation and adjusted the carryforward accordingly.

As of December 31, 2023, the Company also had orphan drug credit and federal research tax credit carryforwards of approximately $48.6 million and California research tax credits of $12.4 million. The federal research tax credit carryforwards begin to expire in 2038, and the California research tax credit carryforward does not expire and can be carried forward indefinitely until utilized.

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


	December 31,
	2023		2022		2021
Federal statutory income tax rate	21.00	%	21.00	%	21.00	%
State income taxes, net of federal benefit	—	%	—	%	—	%
Change in valuation allowance	(8.73	%)	(20.25	%)	(19.73	%)
Research and experimentation credits	5.69	%	3.39	%	2.62	%
Foreign rate differential	(2.13	%)	(1.88	%)	(1.95	%)
Stock-based compensation	(1.44	%)	(0.90	%)	(1.56	%)
Nondeductible interest	(1.27	%)	(0.99	%)	(0.96	%)
Foreign Restructuring Impact	(12.49	%)	—	%	—	%
Other	(0.62	%)	(0.37	%)	0.57	%
Provision for income taxes	—	%	—	%	—	%

The NOL carryforward may be subject to an annual limitation under Section 382 and 383 of the Internal Revenue Code of 1986, and similar state provisions if the Company experienced one or more ownership changes which would limit the amount of NOL and tax credit carryforwards that can be utilized to offset future taxable income and tax respectively. In general, an ownership change as defined by Sections 382 and 383, results from the transactions increasing ownership of certain stockholders or public groups in the stock of the corporation of more than 50 percentage points over a three-year period. The Company had an ownership change with the IPO in February of 2019 which resulted in no forfeiture of NOL’s or credits. The Company is completing a review of whether an ownership change occurred for purposes of Sections 382 and 383 Code through 2023. If ownership changes have occurred, including as a result of the Company's private placements of common stock in 2022 and 2023, or additional ownership changes occur in the future as a result of changes in The Company's stock ownership, many of which are outside the Company's control, the NOL and credit carryforwards could be subject to further annual limitations. The Company will update their NOL’s and credits once the analysis is completed. If NOL’s and credits are forfeited, the related asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance. Due to the existence of the valuation allowance, limitations created by future ownership changes, if any, will not impact the Company’s effective tax rate.

The Company files income tax returns in the United States, California, Florida, Ireland, and Luxembourg. Due to the Company’s losses incurred, the Company is subject to the income tax examination by authorities since inception. The Company’s policy is to recognize interest expense and penalties related to income tax matters as tax expense. As of December 31, 2023, 2022, or 2021, there were no accruals for interest related to unrecognized tax benefits or tax penalties.

A reconciliation of the beginning and ending amount of unrecognized tax benefits for 2023, 2022, and 2021, excluding interest and penalties, is as follows:


	December 31,
	2023		2022		2021
	(in thousands)
Balance at beginning of the year	$	10,572	$	7,551	$	5,060
Increase related to current year positions	3,082		3,021		2,491
Balance at the end of the year	$	13,654	$	10,572	$	7,551

Included in the balance of unrecognized tax benefits at December 31, 2023 is $13.7 million that, if recognized, would not impact the Company’s income tax benefit or effective tax rate as long as the Company's deferred tax asset remains subject to a full valuation allowance. The Company does not expect any significant increases or decreases to the Company's unrecognized tax benefits within the next 12 months.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Indebtedness - Schedule of Interest Expense Recognized (Details) - 2027 Notes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Contractual interest expense	$ 10,000	$ 10,000	$ 9,972
Amortization of debt discount	826	782	6,364
Amortization of debt issuance cost	56	53	32
Total interest expense related to the 2027 Notes	$ 10,882	$ 10,835	$ 16,368

- 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
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(a))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-3

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481568/470-20-55-69B

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69C
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481568/470-20-55-69C

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69E
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481568/470-20-55-69E

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69F
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481568/470-20-55-69F

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

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

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

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1D
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1D

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1D
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1D

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1D
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1D

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

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

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1F

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1F

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1F

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1F

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Certain prior period amounts have been reclassified to conform to the current period presentation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. The most significant estimates in the Company’s consolidated financial statements relate to accrued research and development expenses. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results could differ from those estimates.
Segments	Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less to be cash equivalents. The carrying amounts reported in the consolidated balance sheets for cash and cash equivalents are valued at cost, which approximate their fair value.
Marketable Securities	Marketable Securities The Company considers securities with original maturities of greater than 90 days to be marketable securities. The Company has the ability, if necessary, to liquidate any of its marketable securities to meet its liquidity needs in the next 12 months. Accordingly, those investments with contractual maturities greater than one year from the date of purchase are classified as current assets on the accompanying consolidated balance sheets. The Company’s marketable securities consist of U.S. Treasury and agency securities, commercial paper and corporate debt securities. Marketable securities are recorded at fair value and unrealized gains and losses are recorded within accumulated other comprehensive loss. The estimated fair value of the marketable securities is determined based on quoted market prices or rates for similar instruments. The Company evaluates securities with unrealized losses to determine whether such losses, if any, are due to credit-related factors. The Company records an allowance for credit losses when unrealized losses are due to credit-related factors. Realized gains and losses are calculated using the specific identification method and recorded in other income, net in the Company's consolidated statements of operation and comprehensive loss. The Company does not generally intend to sell the investments and it is not more likely than not that it will be required to sell the investments before recovery of their amortized cost bases, which may be at maturity.
Concentrations of Credit Risk and Off-Balance Sheet Risk	Concentrations of Credit Risk and Off-Balance Sheet Risk Cash, cash equivalents and marketable securities are financial instruments that are potentially subject to concentrations of credit risk. The Company’s cash and cash equivalents are deposited in accounts at large financial institutions, and amounts may exceed federally insured limits. The Company believes it is not exposed to significant credit risk due to the financial strength of the depository institutions in which the cash and cash equivalents are held. The Company maintains its cash equivalents in U.S. Treasury and agency securities and commercial paper with maturities less than three months and in money market funds that invest in U.S. Treasury and agency securities. The Company’s available for sale securities are also invested in U.S. Treasury and agency securities. The Company has not recognized any losses from credit risks on such accounts during any of the periods presented. The Company believes it is not exposed to significant credit risk on its cash, cash equivalents and available for sale securities.
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net, which consists mainly of lab equipment and leasehold improvements, are carried at cost less accumulated depreciation. Depreciation is computed over the estimated useful lives of the respective assets, generally two to seven years, using the straight-line method.
Convertible Senior Notes	Convertible Senior Notes Prior to the adoption of ASU 2020-06, the Company accounted for the 2027 Notes as a liability and equity component. The carrying amount of the liability component was calculated by measuring the fair value of similar debt instruments that do not have associated convertible features. The carrying amount of the equity component representing the conversion option was determined by deducting the fair value of the liability component from the par value of the 2027 Notes. The equity component was not re-measured as long as it continued to meet the condition for equity classification. The excess of the principal amount of the liability component over its carrying amount (“debt discount”) was amortized to interest expense over the term of the 2027 Notes. The Company allocated the issuance costs incurred to the liability and equity components of the 2027 Notes based on their relative fair values. Issuance costs attributable to the liability component were recorded as a reduction to the liability portion of the 2027 Notes and were amortized to interest expense over the term of the 2027 Notes. Issuance costs attributable to the equity component, representing the conversion option, were netted with the equity component in stockholders' equity. Effective January 1, 2022 the Company adopted ASU 2020-06. After adoption, the Company now accounts for the 2027 Notes as a single liability measured at amortized cost. The impact upon adoption on the Consolidated Balance Sheets was an increase of approximately $44.8 million in convertible senior notes, net, a write-off of $9.4 million in deferred income tax liabilities and a decrease of $53.5 million in additional paid-in capital. In addition, upon adoption, there was an adjustment of $8.7 million to increase the beginning balance of accumulated deficit on the Consolidated Balance Sheets for previously recognized interest expense related to amortization of debt discount related to the carrying value of the embedded conversion feature upon issuance.
Leases	Leases In accordance with Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842), the Company determines if an arrangement is a lease at inception. Operating leases are included in the balance sheet as right-of-use assets and operating lease liabilities at the present value of the lease payments calculated using the Company’s incremental borrowing rate, unless the implicit rate is readily available. The Company applied the short-term lease recognition exemption for leases with terms at inception not greater than 12 months and elected to not separate lease and non-lease components for its long-term leases. The Company records rent expense on a straight-line basis over the term of the lease.
Research and Development	Research and Development All research and development costs are expensed as incurred. Research and development costs consist primarily of salaries, employee benefits, costs associated with preclinical studies and clinical trials (including amounts paid to clinical research organizations and other professional services). Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received. The Company records accruals for estimated research and development costs, comprising payments for work performed by third party contractors, laboratories, participating clinical trial sites, and others. Some of these contractors bill monthly based on actual services performed, while others bill periodically based upon achieving certain contractual milestones. For the latter, the Company accrues the expenses as goods or services are used or rendered. Clinical trial site costs related to patient enrollment are accrued as patients enter and progress through the trial. Upfront costs, such as costs associated with setting up clinical trial sites for participation in the trials, are expensed immediately once incurred as research and development expenses.
In process research and development	In process research and development In process research and development costs relate to a milestone payment to Pulmokine for the initiation of the Phase 3 clinical trial for seralutinib.
Patent Costs	Patent Costs Costs related to filing and pursuing patent applications are expensed as incurred, as recoverability of such expenditures is uncertain. These costs are included in general and administrative expenses.
Income Taxes	Income Taxes Income taxes are recorded in accordance with Financial Accounting Standards Board (“FASB”) Standards Codification (“ASC”) No. 740, Income Taxes (“ASC 740”), which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit would more likely than not be realized assuming examination by the taxing authority. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. Deferred tax assets and liabilities reflect the future tax consequences of the differences between the financial reporting and tax bases of assets and liabilities using current enacted tax rates. Valuation allowances are recorded when the realizability of such deferred tax assets does not meet a more-likely-than-not threshold. For tax benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by taxing authorities. The Company is subject to taxation in the United States and California, Ireland and Luxembourg. As of December 31, 2023, the Company’s tax years since inception are subject to examination by taxing authorities due to the Company’s unutilized net operating losses ("NOLs") and tax credits.
Stock-Based Compensation	Stock-Based Compensation The Company expenses stock-based compensation to employees and non-employees over the requisite service period based on the estimated grant-date fair value of the awards. The Company records the expense for stock-based compensation awards subject to performance-based milestone vesting over the requisite service period when management determines that achievement of the milestone is probable. Management evaluates when the achievement of a performance-based milestone is probable based on the expected satisfaction of the performance conditions at each reporting date. The Company estimates the fair value of stock option grants and shares purchasable under the Company's 2019 Employee Stock Purchase Plan ("ESPP") using the Black-Scholes option pricing model, and the assumptions used in calculating the fair value of stock-based awards represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment. The Company estimates the fair value of restricted stock units based on the closing price of the Company's common stock on the date of grant. The Company accounts for forfeitures as they occur. All share-based compensation costs are recorded in the statements of operations based upon the underlying employees or non-employee’s roles within the Company.
Foreign Currency	Foreign Currency Assets and liabilities of non-U.S. subsidiaries that operate in a local currency environment, where that local currency is the functional currency, are translated to U.S. dollars at exchange rates in effect at the balance sheet date. Income and expense accounts are translated at average exchange rates during the year which approximate the rates in effect at the transaction dates. The resulting translation adjustments are recorded in accumulated other comprehensive loss in the Company's consolidated balance sheets. Foreign exchange transaction gains and losses are included in other income, net in the Company’s consolidated statement of operations and comprehensive loss.
Recent Accounting Pronouncements - Announced	Recent Accounting Pronouncements - Announced In December 2023, the FASB issued ASU 2023-09 "Income Taxes (Topics 740): Improvements to Income Tax Disclosures" to expand the disclosure requirements for income taxes, specifically related to the rate reconciliation and income taxes paid. ASU 2023-09 is effective for our annual periods beginning January 1, 2025, with early adoption permitted. We are currently evaluating the potential effect that the updated standard will have on our financial statement disclosures.
Net Loss Per Share	Net Loss Per Share Basic net loss per share of common stock is computed by dividing net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. The Company uses the if-converted method for assumed conversion of the 2027 Notes to compute the weighted average shares of common stock outstanding for diluted net loss per share. Diluted net loss per share excludes the potential impact of the Company’s common stock options, 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.

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Net loss	$ (179,817)	$ (229,378)	$ (234,004)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,607	1,832	1,740
Stock-based compensation expense	28,518	42,553	32,008
In process research and development expenses	10,000	65	75
Amortization of operating lease right-of-use assets	2,778	2,597	3,427
Amortization of long-term debt discount and issuance costs	1,321	1,163	6,731
Amortization of discount (premium) on investments, net of accretion of discounts	(9,450)	(1,405)	339
Loss on disposal of property and equipment	726	0	20
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(3,892)	296	2,631
Other assets	62	400	(53)
Operating lease liabilities	(2,982)	(2,721)	(3,580)
Accounts payable	3,990	(1,813)	(4,428)
Accrued expenses	(835)	(1,659)	736
Accrued research and development expenses	(7,847)	(579)	5,774
Accrued compensation and benefits	(3,240)	1,618	(278)
Accrued interest expense	(97)	(1)	(28)
Net cash used in operating activities	(159,158)	(187,032)	(188,890)
Cash flows from investing activities
Research and development asset acquisitions, net of cash acquired	0	(65)	(75)
Purchase of marketable securities	(441,670)	(238,060)	(152,031)
Maturities of marketable securities	330,700	237,500	36,225
Purchase of property and equipment	0	(410)	(1,546)
Net cash used in investing activities	(110,970)	(1,035)	(117,427)
Cash flows from financing activities
Proceeds from issuance of common stock and warrants in a private offering, net of offering costs	201,323	119,946	0
Proceeds from issuance of common stock under Employee Stock Purchase Plan	444	1,214	1,315
Proceeds from the exercise of stock options	0	1,736	2,014
Principal repayments of long-term debt	(11,613)	(5,806)	0
Net cash provided by financing activities	190,154	117,090	3,329
Effect of exchange rate changes on cash, cash equivalents and restricted cash	110	(517)	(165)
Net decrease in cash, cash equivalents and restricted cash	(79,864)	(71,494)	(303,153)
Cash, cash equivalents and restricted cash, at the beginning of the period	111,973	183,467	486,620
Cash, cash equivalents and restricted cash, at the end of the period	32,109	111,973	183,467
Supplemental disclosure of cash flow information:
Cash paid for interest	12,288	12,712	12,738
Supplemental disclosure of noncash investing and financing activities:
Right-of-use assets obtained in exchange for lease liabilities	0	3,029	0
Derecognition ROU lease assets obtained in exchange for operating lease liabilities	0	0	1,650
Change in unrealized loss on marketable securities, net	191	(75)	(225)
Purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities	$ 0	$ 83	$ 0

Stockholders' Equity (Details)								12 Months Ended
Stockholders' Equity (Details)	Jul. 24, 2023 USD ($) $ / shares shares	Jul. 15, 2022 USD ($) $ / shares shares	May 21, 2020 USD ($) $ / shares shares	Sep. 06, 2018 $ / shares shares	May 21, 2018 $ / shares shares	Jan. 04, 2018	Dec. 03, 2015 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) vote shares	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Stockholders Equity Deficit [Line Items]
Common stock, voting right per share \| vote								1
Issuance of common stock (in shares)			9,433,963
Offering price (in dollars per share) \| $ / shares			$ 13.25
Cash flows from financing activities \| $			$ 117,100,000
Payments of stock issuance costs \| $	$ 10,700,000	$ 200,000
Warrants to purchase (in shares)	32,467,360
Exercise price of warrants (in dollars per share) \| $ / shares	$ 2.04
Warrant term	5 years
Proceeds from issuance of private placement \| $	$ 212,100,000							$ 201,323,000	$ 119,946,000	$ 0
Issuance of common stock \| $								$ 201,323,000	$ 119,946,000
Shares of common stock, repurchase (in shares)								0
Private Placement
Stockholders Equity Deficit [Line Items]
Offering price (in dollars per share) \| $ / shares	$ 1.63125	$ 7.21
Private placement, number of shares (in shares)	129,869,440	16,649,365
Net proceeds, after deducting underwriting discounts, commissions, and offering expenses \| $		$ 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 Deficit [Line Items]
Offering price (in dollars per share) \| $ / shares	$ 1.85125
Private Placement \| Maximum
Stockholders Equity Deficit [Line Items]
Warrants to purchase (in shares)	32,467,360
Stock Restriction Agreements
Stockholders Equity Deficit [Line Items]
Shares subject to forfeiture (in shares)								0
Founder
Stockholders Equity Deficit [Line Items]
Issuance of common stock (in shares)				1,795,023	251,547
Issuance price per share (in dollars per share) \| $ / shares				$ 9.63	$ 2.61
Percentage of fully diluted share capital						15.00%
Increased in equity capital amount \| $								$ 300,000,000
Additional shares of restricted stock subject to vesting restrictions (in shares)				1,795,023	251,547
Founder Shares
Stockholders Equity Deficit [Line Items]
Issuance of common stock (in shares)							9,160,888
Issuance price per share (in dollars per share) \| $ / shares							$ 0.0001
Issuance of common stock \| $							$ 4,100
Common stock vesting percentage						50.00%
Common stock vesting period						5 years

Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities not Included in Calculation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
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)	68,843,073	31,159,100	24,317,779
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	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)	23,626,115	17,487,165	9,434,660
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	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)	427,698	1,350,035	2,561,219

Description of Business	12 Months Ended
Description of Business	Dec. 31, 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 the development and commercialization of seralutinib for the treatment of pulmonary arterial hypertension, or PAH. The Company was incorporated in the state of Delaware on October 25, 2015 (originally as FSG Bio, Inc.) and is based in San Diego, California. The consolidated financial statements include the accounts of Gossamer Bio, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions among the consolidated entity have been eliminated in consolidation. Liquidity and Capital Resources The Company has incurred significant operating losses since its inception. As of December 31, 2023 and 2022, the Company had an accumulated deficit of $1,212.0 million and $1,032.2 million, respectively. From the Company’s inception through the year ended December 31, 2023, the Company has funded its operations primarily through equity and debt financings. The Company raised $1,263.2 million from October 2017 through December 31, 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 5 for additional information regarding the Credit Facility and the 2027 Notes. 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 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.

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2023

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

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


	December 31,
	2023		2022
Accrued compensation and benefits	$	10,294	$	13,534
Operating lease liabilities	3,302		2,983
Accrued consulting fees	643		1,104
Accrued interest	968		1,065
Accrued legal fees	385		380
Accrued in process research and development	10,000		—
Accrued accounting fees	234		521
Accrued other	854		945
Total accrued expenses and other current liabilities	$	26,680	$	20,532

Indebtedness (Tables)

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Schedule of Long-Term Debt

Debt consisted of the following (in thousands):


	December 31, 2023
Debt, current portion	$	11,613
Debt, non-current portion	968
Total debt	12,581
Less: unamortized debt discount and issuance costs	(154)
Debt, net	$	12,427

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


	December 31,
	2023		2022
Principal amount	$	200,000	$	200,000
Unamortized debt discount	(3,194)		(4,021)
Unamortized debt issuance cost	(215)		(270)
Net carrying amount	$	196,591	$	195,709

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


	Year Ended December 31,
	2023		2022		2021
Contractual interest expense	$	10,000	$	10,000	$	9,972
Amortization of debt discount	826		782		6,364
Amortization of debt issuance cost	56		53		32
Total interest expense related to the 2027 Notes	$	10,882	$	10,835	$	16,368

Schedule of Future Minimum Principal Payments

The scheduled future minimum principal payments as of December 31, 2023 are as follows (in thousands):


2024	$	11,613
2025	968

Total	$	12,581

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Jan. 01, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Number of operating segments \| segment	1
Long-term convertible senior notes	$ 196,591	$ 195,709
Deferred tax liabilities written off	(768)	(1,809)		$ (11,335)
Stockholders' equity attributable to parent increase (decrease)	$ 62,769	12,077		121,463	$ 320,684
Minimum
Debt Instrument [Line Items]
Property and equipment, estimated useful life	2 years
Maximum
Debt Instrument [Line Items]
Property and equipment, estimated useful life	7 years
Additional paid-in capital
Debt Instrument [Line Items]
Stockholders' equity attributable to parent increase (decrease)	$ 1,275,136	1,044,864		932,944	897,607
Accumulated deficit
Debt Instrument [Line Items]
Stockholders' equity attributable to parent increase (decrease)	$ (1,212,040)	$ (1,032,223)		(811,534)	$ (577,530)
Cumulative Effect, Period of Adoption, Adjustment
Debt Instrument [Line Items]
Long-term convertible senior notes			$ 44,800
Deferred tax liabilities written off			9,400
Stockholders' equity attributable to parent increase (decrease)				(44,838)
Cumulative Effect, Period of Adoption, Adjustment \| Additional paid-in capital
Debt Instrument [Line Items]
Stockholders' equity attributable to parent increase (decrease)			(53,500)	(53,527)
Cumulative Effect, Period of Adoption, Adjustment \| Accumulated deficit
Debt Instrument [Line Items]
Stockholders' equity attributable to parent increase (decrease)			$ 8,700	$ 8,689

Indebtedness - Schedule of Net Carrying Amount of Liability Component (Details) - 2027 Notes - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Principal amount	$ 200,000	$ 200,000
Unamortized debt discount	(3,194)	(4,021)
Unamortized debt issuance cost	(215)	(270)
Debt, net	$ 196,591	$ 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

Equity Incentive Plans

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Equity Incentive Plans

2023 Equity Inducement Incentive Plan

In November 2023, the Company approved the 2023 Employment Inducement Incentive Plan (the "2023 Inducement Plan"). The terms of the 2023 Inducement Plan are substantially similar to the terms of the Company’s 2019 Incentive Award Plan (as described below) with the exception that incentive stock options may not be issued under the 2023 Inducement Plan and awards under the 2023 Inducement Plan may only be issued to eligible recipients under the applicable Nasdaq rules. The 2023 Inducement Plan was adopted without stockholder approval pursuant to Rule 5635(c)(4) of the Nasdaq Listing Rules. In accordance with Rule 5635(c)(4) of the Nasdaq Listing Rules, awards under the 2023 Inducement Plan may only be made to an employee who has not previously been an employee or member of the board of directors of the Company or any parent or subsidiary, or following a bona fide period of non-employment by the Company or a parent or subsidiary, if he or she is granted such award in connection with his or her commencement of employment with the Company or a subsidiary and such grant is an inducement material to his or her entering into employment with the Company or such subsidiary. The Company has initially reserved 6,762,279 shares of the Company’s common stock for issuance pursuant to awards granted under the 2023 Inducement Plan. As of December 31, 2023, an aggregate of 5,262,279 shares of common stock were available

for issuance under the 2023 Inducement Plan, and 1,500,000 shares of common stock were subject to outstanding awards under the 2023 Inducement Plan.

2019 Equity Incentive Plan

In January 2019, the Company’s board of directors and stockholders approved and adopted the 2019 Incentive Award Plan (the “2019 Plan”). The 2019 Plan became effective on February 6, 2019, the day prior to the effectiveness of the registration statement filed in connection with the IPO. Under the 2019 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units, and other stock or cash-based awards to individuals who are then employees, officers, directors or consultants of the Company, and employees and consultants of the Company’s subsidiaries. A total of 5,750,000 shares of common stock were approved to be initially reserved for issuance under the 2019 Plan. The number of shares that remained available for issuance under the 2017 Plan (as defined below) as of the effective date of the 2019 Plan were, and shares subject to outstanding awards under the 2017 Plan as of the effective date of the 2019 Plan that are subsequently canceled, forfeited or repurchased by the Company will be added to the shares reserved under the 2019 Plan. In addition, the number of shares of common stock available for issuance under the 2019 Plan will be automatically increased on the first day of each calendar year during the ten-year term of the 2019 Plan, beginning with January 1, 2020 and ending with January 1, 2029, by an amount equal to 5% of the outstanding number of shares of the Company’s common stock on December 31 of the preceding calendar year or such lesser amount as determined by the Company’s board of directors. As of December 31, 2023, an aggregate of 718,453 shares of common stock were available for issuance under the 2019 Plan and 20,374,879 shares of common stock were subject to outstanding awards under the 2019 Plan.

2019 Employee Stock Purchase Plan

In January 2019, the Company’s board of directors and stockholders approved and adopted the 2019 Employee Stock Purchase Plan (the "ESPP"). The ESPP became effective as of February 6, 2019, the day prior to the effectiveness of the registration statement filed in connection with the IPO. The ESPP permits participants to purchase common stock through payroll deductions of up to 20% of their eligible compensation. A total of 700,000 shares of common stock were approved to be initially reserved for issuance under the ESPP. In addition, the number of shares of common stock available for issuance under the ESPP will be automatically increased on the first day of each calendar year during the first ten-years of the term of the ESPP, beginning with January 1, 2020 and ending with January 1, 2029, by an amount equal to 1% of the outstanding number of shares of the Company’s common stock on December 31 of the preceding calendar year or such lesser amount as determined by the Company’s board of directors. During the years ended December 31, 2023 and 2022, 336,795 shares and 157,858 shares were issued pursuant to the ESPP, respectively. As of December 31, 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 December 31, 2023, 2,178,934 shares of common stock were subject to outstanding options under the 2017 Plan, and no shares of restricted stock awards granted under the 2017 Plan were unvested.

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 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 consolidated statements of operations and comprehensive loss.

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


	Year Ended December 31,
	2023	2022	2021
Employee Stock Options
Expected term (in years)	1.0 - 7.0	4.4 - 6.1	4.6 - 6.1
Risk-free interest rate	3.36% - 4.73%	1.31% - 4.35%	0.65% - 1.30%
Volatility	70.01% - 170.69%	71.10% - 89.87%	78.80% - 84.79%
Dividend yield	—	—	—

Employee Stock Purchase Plan
Expected term (in years)	0.5 - 2.0	0.5 - 2.0	0.5 - 2.0
Risk-free interest rate	4.87% -5.47%	0.60% - 3.51%	0.06% - 0.20%
Volatility	115.19% - 216.45%	64.98% - 121.43%	61.29% - 87.13%
Dividend yield	—	—	—

The following table summarizes stock option activity for the years ended December 31, 2023, 2022 and 2021:


	Shares Subject to Options Outstanding			Weighted- Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
	Shares	Weighted- Average Exercise Price
					(in thousands)
Outstanding as of December 31, 2020	9,401,082	$	13.42	8.1	$	10,182
Options granted	3,159,126	$	9.82
Options exercised	(325,494)	$	6.19
Options forfeited/cancelled	(2,800,054)	$	14.14
Outstanding as of December 31, 2021	9,434,660	$	12.24	7.4	$	15,822
Options granted	9,271,272	$	6.75
Options exercised	(270,707)	$	6.41
Options forfeited/cancelled	(948,060)	$	15.69
Outstanding as of December 31, 2022	17,487,165	$	9.24	8.1	$	47
Options granted	17,159,617	$	1.16
Options exercised	—	$	—
Options forfeited/cancelled	(11,020,667)	$	11.07
Outstanding as of December 31, 2023	23,626,115	$	2.52	7.9	$	369
Options vested and expected to vest as of December 31, 2023	23,626,115	$	2.52	7.9	$	369
Options exercisable as of December 31, 2023	8,952,067	$	4.17	6.3	$	1

The weighted-average grant date fair value per share for the stock options granted during the year ended December 31, 2023, 2022 and 2021 was $3.88, $4.77 and $6.93, respectively.

The aggregate fair value of stock options that vested during the years ended December 31, 2023, 2022 and 2021 was $22.7 million, $20.7 million and $21.9 million, respectively.

The aggregate intrinsic value in the above table is calculated as the difference between fair value of the Company’s common stock price and the exercise price of the stock options. The aggregate intrinsic value of stock options exercised during the year ended December 31, 2023, 2022 and 2021 was $0.0 million, $1.5 million and $1.6 million, respectively.

At December 31, 2023, the total unrecognized compensation related to unvested stock option awards granted was $25.3 million, which the Company expects to recognize over a weighted-average period of approximately 2.7 years.

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 consolidated balance sheets. As of December 31, 2023, there were 32,467,360 warrants outstanding.

Restricted Stock

The summary of the Company’s restricted stock activity during the years ended December 31, 2023, 2022 and 2021 is as follows:


	Number of Restricted Stock Units Outstanding	Weighted- Average Grant Date Fair Value
Nonvested at December 31, 2020	3,330,821	$	7.16
Granted	1,349,885	10.23
Vested	(1,391,476)	5.86
Forfeited / cancelled	(728,011)	10.03
Nonvested at December 31, 2021	2,561,219	$	8.67
Granted	572,901	11.94
Vested	(1,592,588)	7.78
Forfeited / cancelled	(191,497)	10.68
Nonvested at December 31, 2022	1,350,035	$	10.83
Granted	—	—
Vested	(779,900)	10.67
Forfeited / cancelled	(142,437)	11.39
Nonvested at December 31, 2023	427,698	$	10.92

At December 31, 2023, the total unrecognized compensation related to unvested restricted stock awards granted was $0.5 million, which the Company expects to recognize over a weighted-average period of approximately 0.1 years.

Stock-Based Compensation Expense

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


	Year Ended December 31,
	2023		2022		2021
Research and development	$	15,871	$	24,415	$	18,943
General and administrative	12,647		18,138		13,065
Total stock-based compensation expense	$	28,518	$	42,553	$	32,008

As of December 31, 2023, total unrecognized compensation expense related to the ESPP was $0.9 million, which the Company expects to recognize over a weighted-average period of approximately 0.8 years.

Indebtedness - Schedule of Future Minimum Principal Payments (Details) - Credit Facility $ in Thousands	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
2024	$ 11,613
2025	968
Total	$ 12,581

- 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 - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lessee, Lease, Description [Line Items]
Weighted average discount rate, operating leases	7.00%
Weighted average remaining lease term	1 year
Cash paid for operating lease liabilities	$ 3.3	$ 3.2
Rent expense	$ 3.4	$ 3.3	$ 4.3
Non-cancelable Lease Agreement Entered in August 2018
Lessee, Lease, Description [Line Items]
Operating sublease, annual increase percentage for base rent	3.00%

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2023
Auditor Information [Abstract]
Auditor name	Ernst & Young LLP
Auditor location	San Diego, California
Auditor Firm ID	42

Property and Equipment, Net

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

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


	Estimated Useful Life (in years)	December 31, 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	3,246		6,098
Leasehold improvements	6-7	2,562		2,562
Construction in process	N/A	—		83
Total property and equipment		7,080		10,093
Less: accumulated depreciation		(5,432)		(6,112)
Property and equipment, net		$	1,648	$	3,981

Depreciation expense for the years ended December 31, 2023, 2022 and 2021 was approximately $1.6 million, $1.8 million and $1.7 million, respectively, and was recorded in general and administrative expense and research and development expense, respectively, on the consolidated statements of operations and comprehensive loss.

Fair Value Measurements and Available for Sale Investments (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [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 December 31, 2023 and 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 December 31, 2023
Money market funds	$	25,222	$	25,222	$	—	$	—
U.S. Treasury and agency securities	92,309		92,309		—		—
Commercial paper	168,534		—		168,534		—
Corporate debt securities	3,473		—		3,473		—
As of December 31, 2022
Money market funds	$	54,662	$	54,662	$	—	$	—
U.S. Treasury and agency securities	31,458		31,458		—		—
Commercial paper	103,409		—		103,409		—
Corporate debt securities	8,838		—		8,838		—

Schedule of Available for Sale Investments by Security Type

The aggregate market value, cost basis, and gross unrealized gains and losses of available-for-sale investments by security type, classified in marketable securities as of December 31, 2023 and 2022 are as follows (in thousands except securities amounts):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Total Fair Value
As of December 31, 2023
U.S Treasury and agency securities	$	92,294	$	20	$	(5)	$	92,309
Corporate debt securities	3,467		6		—		3,473
Commercial paper	168,488		76		(30)		168,534
Total marketable securities	$	264,249	$	102	$	(35)	$	264,316
Number of securities with unrealized losses					12
As of December 31, 2022
U.S. Treasury and agency securities	$	31,445	$	15	$	(2)	$	31,458
Corporate debt securities	8,876		$	—	(38)		8,838
Commercial paper	103,508		1		(100)		103,409
Total marketable securities	$	143,829	$	16	$	(140)	$	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 December 31, 2023, were as follows (in thousands):


	Estimated Fair Value
Less than one year	$	264,316
Greater than one year	—
Total	$	264,316

Consolidated Statements of Stockholders' Equity - 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, 2020			73,874,904
Beginning balance at Dec. 31, 2020	$ 320,684		$ 8	$ 897,607		$ (577,530)		$ 599
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2020-06 [Member]
Vesting of restricted stock (in shares)			906,037
Exercise of stock options (in shares)	325,494		325,494
Exercise of stock options	$ 2,014			2,014
Stock-based compensation	32,008			32,008
Issuance of common stock pursuant to Employee Stock Purchase Plan (in shares)			160,790
Issuance of common stock pursuant to Employee Stock Purchase Plan	1,315			1,315
Issuance of common stock for restricted stock units vested (in shares)			485,439
Net loss	(234,004)					(234,004)
Other comprehensive income (loss)	(554)							(554)
Ending balance (in shares) at Dec. 31, 2021			75,752,664
Ending 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]
Issuance of common stock (in shares)			16,649,365
Issuance of common stock	$ 119,946		$ 2	119,944
Vesting of restricted stock (in shares)			662,700
Exercise of stock options (in shares)	270,707		270,707
Exercise of stock options	$ 1,736			1,736
Stock-based compensation	42,553			42,553
Issuance of common stock pursuant to Employee Stock Purchase Plan (in shares)			157,858
Issuance of common stock pursuant to Employee Stock Purchase Plan	1,214			1,214
Issuance of common stock for restricted stock units vested (in shares)			929,887
Net loss	(229,378)					(229,378)
Other comprehensive income (loss)	$ (619)							(619)
Ending balance (in shares) at Dec. 31, 2022	94,423,181		94,423,181
Ending balance at Dec. 31, 2022	$ 12,077		$ 10	1,044,864		(1,032,223)		(574)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)			129,869,440
Issuance of common stock	$ 201,323		$ 13	201,310
Vesting of restricted stock (in shares)			55,225
Exercise of stock options (in shares)	0
Stock-based compensation	$ 28,518			28,518
Issuance of common stock pursuant to Employee Stock Purchase Plan (in shares)			336,795
Issuance of common stock pursuant to Employee Stock Purchase Plan	444			444
Issuance of common stock for restricted stock units vested (in shares)			724,674
Net loss	(179,817)					(179,817)
Other comprehensive income (loss)	$ 224							224
Ending balance (in shares) at Dec. 31, 2023	225,409,315		225,409,315
Ending balance at Dec. 31, 2023	$ 62,769		$ 23	$ 1,275,136		$ (1,212,040)		$ (350)

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	700,000,000	700,000,000
Common stock, shares issued (in shares)	225,409,315	94,478,405
Common stock, shares outstanding (in shares)	225,409,315	94,423,181

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Accrued compensation and benefits	$ 10,294	$ 13,534
Operating lease liabilities	3,302	2,983
Accrued consulting fees	643	1,104
Accrued interest	968	1,065
Accrued legal fees	385	380
Accrued in process research and development	10,000	0
Accrued accounting fees	234	521
Accrued other	854	945
Total accrued expenses and other current liabilities	$ 26,680	$ 20,532
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Total accrued expenses and other current liabilities	Total accrued expenses and other current liabilities

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Presentation

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

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. The most significant estimates in the Company’s consolidated financial statements relate to accrued research and development expenses. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results could differ from those estimates.

Segments

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

Cash and Cash Equivalents

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

Marketable Securities

The Company considers securities with original maturities of greater than 90 days to be marketable securities. The Company has the ability, if necessary, to liquidate any of its marketable securities to meet its liquidity needs in the next 12 months. Accordingly, those investments with contractual maturities greater than one year from the date of purchase are classified as current assets on the accompanying consolidated balance sheets. The Company’s marketable securities consist of U.S. Treasury and agency securities, commercial paper and corporate debt securities. Marketable securities are recorded at fair value and unrealized gains and losses are recorded within accumulated other comprehensive loss. The estimated fair value of the marketable securities is determined based on quoted market prices or rates for similar instruments. The Company evaluates securities with unrealized losses to determine whether such losses, if any, are due to credit-related factors. The Company records an allowance for credit losses when unrealized losses are due to credit-related factors. Realized gains and losses are calculated using the specific identification method and recorded in other income, net in the Company's consolidated statements of operation and comprehensive loss. The Company does not generally intend to sell the investments and it is not more likely than not that it will be required to sell the investments before recovery of their amortized cost bases, which may be at maturity. The Company has determined that there were no material declines in fair values of its investments due to credit-related factors as of December 31, 2023.

Concentrations of Credit Risk and Off-Balance Sheet Risk

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

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

Property and Equipment, Net

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

Convertible Senior Notes

Prior to the adoption of ASU 2020-06, the Company accounted for the 2027 Notes as a liability and equity component. The carrying amount of the liability component was calculated by measuring the fair value of similar debt instruments that do not have associated convertible features. The carrying amount of the equity component representing the conversion option was determined by deducting the fair value of the liability component from the par value of the 2027 Notes. The equity component was not re-measured as long as it continued to meet the condition for equity classification. The excess of the principal amount of the liability component over its carrying amount (“debt discount”) was amortized to interest expense over the term of the 2027 Notes.

The Company allocated the issuance costs incurred to the liability and equity components of the 2027 Notes based on their relative fair values. Issuance costs attributable to the liability component were recorded as a reduction to the liability portion of the 2027 Notes and were amortized to interest expense over the term of the 2027 Notes. Issuance costs

attributable to the equity component, representing the conversion option, were netted with the equity component in stockholders' equity.

Effective January 1, 2022 the Company adopted ASU 2020-06. After adoption, the Company now accounts for the 2027 Notes as a single liability measured at amortized cost. The impact upon adoption on the Consolidated Balance Sheets was an increase of approximately $44.8 million in convertible senior notes, net, a write-off of $9.4 million in deferred income tax liabilities and a decrease of $53.5 million in additional paid-in capital. In addition, upon adoption, there was an adjustment of $8.7 million to increase the beginning balance of accumulated deficit on the Consolidated Balance Sheets for previously recognized interest expense related to amortization of debt discount related to the carrying value of the embedded conversion feature upon issuance.

Leases

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

Research and Development

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

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

In process research and development

In process research and development costs relate to a milestone payment to Pulmokine for the initiation of the Phase 3 clinical trial for seralutinib.

Patent Costs

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

Income Taxes

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

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit would more likely than not be realized assuming examination by the taxing authority. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances.

Deferred tax assets and liabilities reflect the future tax consequences of the differences between the financial reporting and tax bases of assets and liabilities using current enacted tax rates. Valuation allowances are recorded when the realizability of such deferred tax assets does not meet a more-likely-than-not threshold. For tax benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by taxing authorities. The Company is subject to taxation in the United States and California, Ireland and Luxembourg. As of December 31, 2023, the Company’s tax years since inception are subject to examination by taxing authorities due to the Company’s unutilized net operating losses ("NOLs") and tax credits.

Stock-Based Compensation

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

Foreign Currency

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

Recent Accounting Pronouncements - Announced

In December 2023, the FASB issued ASU 2023-09 "Income Taxes (Topics 740): Improvements to Income Tax Disclosures" to expand the disclosure requirements for income taxes, specifically related to the rate reconciliation and income taxes paid. ASU 2023-09 is effective for our annual periods beginning January 1, 2025, with early adoption permitted. We are currently evaluating the potential effect that the updated standard will have on our financial statement disclosures.

Net Loss Per Share

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


	December 31,
	2023	2022	2021
2027 Notes	12,321,900	12,321,900	12,321,900
Shares issuable upon exercise of stock options	23,626,115	17,487,165	9,434,660
Shares issuable upon exercise of warrants	32,467,360	—	—
Non-vested shares under restricted stock grants	427,698	1,350,035	2,561,219
Total potentially dilutive securities	68,843,073	31,159,100	24,317,779

Commitments and Contingencies

12 Months Ended

Dec. 31, 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. 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 balance sheet at the present value of the lease payments at a weighted average discount rate of 7% using the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment as the leases do not provide an implicit rate. As of December 31, 2023, the weighted average remaining lease term was 1.0 year.

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


	Year Ended December 31,
	2023		2022		2021
Operating lease cost	$	3,114	$	3,097	$	4,029
Short-term lease cost	52		45		53
Total lease cost	$	3,166	$	3,142	$	4,082

Cash paid for amounts included in the measurement of operating lease liabilities as of December 31, 2023 and 2022 was $3.3 million and $3.2 million, respectively.

Gross future minimum annual rental commitments as of December 31, 2023, were as follows (in thousands):


	Undiscounted Rent Payments
Year ending December 31,
2024	$	3,419
2025	144

Total undiscounted rent payments	$	3,563

Present value discount	(117)
Present value of lease payments	$	3,446
Current portion of operating lease liabilities (included as a component of accrued expenses and other current liabilities)	3,302
Noncurrent operating lease liabilities	144
Total operating lease liability	$	3,446

For the years ended December 31, 2023, 2022 and 2021, the Company recorded approximately $3.4 million, $3.3 million and $4.3 million, respectively, in rent expense. Rent expense is included in research and development and general and administrative expense on the consolidated statements of operations and comprehensive loss.

Subsequent events

The Company has evaluated all subsequent events and transactions through the filing date. There were no material events that impacted the audited consolidated financial statements or disclosures.

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2023

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

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


	December 31,
	2023		2022
Accrued compensation and benefits	$	10,294	$	13,534
Operating lease liabilities	3,302		2,983
Accrued consulting fees	643		1,104
Accrued interest	968		1,065
Accrued legal fees	385		380
Accrued in process research and development	10,000		—
Accrued accounting fees	234		521
Accrued other	854		945
Total accrued expenses and other current liabilities	$	26,680	$	20,532

Licenses, Asset Acquisitions and Contingent Consideration - Schedule of IPR&D Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development	$ 10,000	$ 65	$ 75
Seralutinib
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development	10,000	0	0
Terminated programs
Acquired Finite-Lived Intangible Assets [Line Items]
Total in process research and development	$ 0	$ 65	$ 75

Commitments and Contingencies - Schedule of Gross Future Minimum Annual Rental Commitments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
2024	$ 3,419
2025	144
Total undiscounted rent payments	3,563
Present value discount	(117)
Present value of lease payments	3,446
Current portion of operating lease liabilities (included as a component of accrued expenses and other current liabilities)	3,302	$ 2,983
Noncurrent operating lease liabilities	144	$ 3,446
Total operating lease liability	$ 3,446

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 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. Shelf Registration Statement and Stock Offering On April 10, 2020, the Company filed a universal shelf registration statement on Form S-3, covering the offering from time to time of common stock, preferred stock, debt securities, warrants and units, which registration statement became automatically effective on April 10, 2020 (the “Shelf Registration Statement”). On May 21, 2020, the Company completed a public offering of 9,433,963 shares of its common stock at a public offering price of $13.25 per share. The net proceeds from the offering, after deducting underwriting discounts and commissions and other offering costs, were approximately $117.1 million. The shares sold in the offering were registered pursuant to the Company’s Shelf Registration Statement. 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 $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 was declared 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. For the year ended December 31, 2023, 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 December 31, 2023, there were no shares of common stock subject to repurchase by the Company. The unvested stock liability related to these awards is immaterial to all periods presented.

Equity Incentive Plans - Schedule of Stock-Based Compensation Expense Reported in Condensed Consolidated Statements of Operations (Details) - USD ($) $ in Thousands		12 Months Ended
	May 05, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Incremental stock compensation expense	$ 2,000	$ 28,518	$ 42,553	$ 32,008
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Incremental stock compensation expense		15,871	24,415	18,943
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Incremental stock compensation expense		$ 12,647	$ 18,138	$ 13,065

Fair Value Measurements and Available for Sale Investments - Schedule of Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and agency securities and corporate debt securities	$ 264,316	$ 143,705
U.S. Treasury and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and agency securities and corporate debt securities	92,309	31,458
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and agency securities and corporate debt securities	3,473	8,838
Recurring Basis \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	25,222	54,662
Recurring Basis \| U.S. Treasury and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and agency securities and corporate debt securities	92,309	31,458
Recurring Basis \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper	168,534	103,409
Recurring Basis \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and agency securities and corporate debt securities	3,473	8,838
Recurring Basis \| Quoted Market Prices for Identical Assets (Level 1) \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	25,222	54,662
Recurring Basis \| 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]
U.S. Treasury and agency securities and corporate debt securities	92,309	31,458
Recurring Basis \| Quoted Market Prices for Identical Assets (Level 1) \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper	0	0
Recurring Basis \| Quoted Market Prices for Identical Assets (Level 1) \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and agency securities and corporate debt securities	0	0
Recurring Basis \| Significant Other Observable Inputs (Level 2) \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
Recurring Basis \| 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]
U.S. Treasury and agency securities and corporate debt securities	0	0
Recurring Basis \| Significant Other Observable Inputs (Level 2) \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper	168,534	103,409
Recurring Basis \| Significant Other Observable Inputs (Level 2) \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and agency securities and corporate debt securities	3,473	8,838
Recurring Basis \| Significant Unobservable Inputs (Level 3) \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
Recurring Basis \| Significant Unobservable Inputs (Level 3) \| U.S. Treasury and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and agency securities and corporate debt securities	0	0
Recurring Basis \| Significant Unobservable Inputs (Level 3) \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper	0	0
Recurring Basis \| Significant Unobservable Inputs (Level 3) \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury and agency securities and corporate debt securities	$ 0	$ 0

Equity Incentive Plans - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	May 05, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Shares Subject to Options Outstanding, Shares
Outstanding as of beginning balance (in shares)		17,487,165	9,434,660	9,401,082
Options granted (in shares)	750,000	17,159,617	9,271,272	3,159,126
Option exercised (in shares)		0	(270,707)	(325,494)
Options forfeited/cancelled (in shares)		(11,020,667)	(948,060)	(2,800,054)
Outstanding as of ending balance (in shares)		23,626,115	17,487,165	9,434,660	9,401,082
Options vested and expected to vest as of ending balance (in shares)		23,626,115
Options exercisable as of ending balance (in shares)		8,952,067
Shares Subject to Options Outstanding, Weighted Average Exercise Price
Outstanding as of beginning balance (in dollars per share)		$ 9.24	$ 12.24	$ 13.42
Options granted (in dollars per share)	$ 1.36	1.16	6.75	9.82
Option exercised (in dollars per share)		0	6.41	6.19
Options forfeited/cancelled (in dollars per share)		11.07	15.69	14.14
Outstanding as of ending balance (in dollars per share)		2.52	$ 9.24	$ 12.24	$ 13.42
Options vested and expected to vest as of ending balance (in dollars per share)		2.52
Options exercisable as of ending balance (in dollars per share)		$ 4.17
Weighted-Average Remaining Contractual Life (Years), Outstanding		7 years 10 months 24 days	8 years 1 month 6 days	7 years 4 months 24 days	8 years 1 month 6 days
Weighted-Average Remaining Contractual Life (Years), Options vested and expected to vest		7 years 10 months 24 days
Weighted-Average Remaining Contractual Life (Years), Options vested and exercisable		6 years 3 months 18 days
Aggregate Intrinsic Value		$ 369	$ 47	$ 15,822	$ 10,182
Options vested and expected to vest, aggregate intrinsic value		369
Options vested and exercisable, aggregate intrinsic value		$ 1

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 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:


	December 31,
	2023	2022	2021
2027 Notes	12,321,900	12,321,900	12,321,900
Shares issuable upon exercise of stock options	23,626,115	17,487,165	9,434,660
Shares issuable upon exercise of warrants	32,467,360	—	—
Non-vested shares under restricted stock grants	427,698	1,350,035	2,561,219
Total potentially dilutive securities	68,843,073	31,159,100	24,317,779

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets
Cash and cash equivalents	$ 32,109	$ 111,973
Marketable securities	264,316	143,705
Prepaid expenses and other current assets	10,094	6,202
Total current assets	306,519	261,880
Property and equipment, net	1,648	3,981
Operating lease right-of-use assets	3,131	5,909
Other assets	618	680
Total assets	311,916	272,450
Current liabilities
Accounts payable	5,526	1,459
Accrued research and development expenses	7,779	15,626
Current portion of long-term debt	11,613	11,613
Accrued expenses and other current liabilities	26,680	20,532
Total current liabilities	51,598	49,230
Long-term convertible senior notes	196,591	195,709
Long-term debt	814	11,988
Operating lease liabilities - long-term	144	3,446
Total liabilities	249,147	260,373
Commitments and contingencies (Note 11)
Stockholders' equity (deficit)
Common stock, $0.0001 par value; 700,000,000 shares authorized as of December 31, 2023 and December 31, 2022; 225,409,315 shares issued and outstanding as of December 31, 2023, and 94,478,405 shares issued and 94,423,181 shares outstanding as of December 31, 2022	23	10
Additional paid-in capital	1,275,136	1,044,864
Accumulated deficit	(1,212,040)	(1,032,223)
Accumulated other comprehensive loss	(350)	(574)
Total stockholders' equity	62,769	12,077
Total liabilities and stockholders' equity	$ 311,916	$ 272,450

Cover - USD ($) $ in Millions	12 Months Ended
Cover - USD ($) $ in Millions	Dec. 31, 2023	Feb. 27, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
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 Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 98.0
Entity Common Stock, Shares Outstanding		225,582,250
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Certain sections of the registrant’s definitive proxy statement for the 2024 annual meeting of stockholders to be filed with the Securities and Exchange Commission pursuant to Regulation 14A not later than 120 days after end of this fiscal year covered by this Form 10-K are incorporated by reference into Part III of this Form 10-K.
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Central Index Key	0001728117

Fair Value Measurements and Available for Sale Investments - Schedule of Available for sale Investments by Security Type (Details) $ in Thousands	Dec. 31, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 264,249	$ 143,829
Gross Unrealized Gains	102	16
Gross Unrealized Losses	(35)	(140)
Total Fair Value	$ 264,316	$ 143,705
Number of securities with unrealized losses \| security	12	16
U.S. Treasury and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 92,294	$ 31,445
Gross Unrealized Gains	20	15
Gross Unrealized Losses	(5)	(2)
Total Fair Value	92,309	31,458
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	3,467	8,876
Gross Unrealized Gains	6	0
Gross Unrealized Losses	0	(38)
Total Fair Value	3,473	8,838
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	168,488	103,508
Gross Unrealized Gains	76	1
Gross Unrealized Losses	(30)	(100)
Total Fair Value	$ 168,534	$ 103,409

Indebtedness

12 Months Ended

Dec. 31, 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 December 31, 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):


	December 31, 2023
Debt, current portion	$	11,613
Debt, non-current portion	968
Total debt	12,581
Less: unamortized debt discount and issuance costs	(154)
Debt, net	$	12,427

The scheduled future minimum principal payments as of December 31, 2023 are as follows (in thousands):


2024	$	11,613
2025	968

Total	$	12,581

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 December 31, 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 December 31, 2023 and 2022, 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 liability component of the 2027 Notes was as follows (in thousands):


	December 31,
	2023		2022
Principal amount	$	200,000	$	200,000
Unamortized debt discount	(3,194)		(4,021)
Unamortized debt issuance cost	(215)		(270)
Net carrying amount	$	196,591	$	195,709

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


	Year Ended December 31,
	2023		2022		2021
Contractual interest expense	$	10,000	$	10,000	$	9,972
Amortization of debt discount	826		782		6,364
Amortization of debt issuance cost	56		53		32
Total interest expense related to the 2027 Notes	$	10,882	$	10,835	$	16,368

Equity Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended
	Jul. 24, 2023	May 05, 2023	Jul. 15, 2022	Feb. 06, 2019	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Nov. 30, 2023	Dec. 31, 2020	May 21, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock were subject to outstanding options (in shares)					23,626,115	17,487,165	9,434,660		9,401,082
Expected dividends yield (in percentage)					0.00%
Options granted (in shares)		750,000			17,159,617	9,271,272	3,159,126
Options granted (in dollars per share)		$ 1.36			$ 1.16	$ 6.75	$ 9.82
Share-based payment arrangement, expense		$ 2,000			$ 28,518	$ 42,553	$ 32,008
Exercise price (in dollars per share)		$ 1.36
Share-based payment arrangement, option, exercise price range, shares outstanding (in shares)		6,817,057
Share-based payment arrangement, option, required cancellation percentage		33.00%
Share-based payment arrangement, plan modification, incremental cost		$ 3,400
Share-based payment arrangement, nonvested award, cost not yet recognized, amount		$ 1,400
Warrants to purchase (in shares)	32,467,360
Offering price (in dollars per share)										$ 13.25
Class of warrant or right, exercise price of warrants or rights	$ 2.04
Warrant term	5 years
Warrants outstanding (in shares)					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)	$ 1.63125		$ 7.21
Class of warrant or right, exercise price of warrants or rights	$ 2.04
Warrant term	5 years
Private Placement \| Officer, Director, Employee Or Consultant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Offering price (in dollars per share)	$ 1.85125
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average period of cost expects to recognize (in years)					1 month 6 days
Unrecognized compensation related to unvested restricted stock awards					$ 500
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividends yield (in percentage)					0.00%	0.00%	0.00%
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			2 years 8 months 12 days
Weighted-average grant date fair value (in dollars per share)					$ 3.88	$ 4.77	$ 6.93
Aggregate fair value of stock options vested					$ 22,700	$ 20,700	$ 21,900
Aggregate intrinsic value, options vested in period					0	$ 1,500	$ 1,600
Unrecognized compensation related to unvested stock option					$ 25,300
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		$ 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		$ 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		$ 10.00
Maximum \| Private Placement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants to purchase (in shares)	32,467,360
2023 Inducement Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share reserved for future issuance (in shares)								6,762,279
Common stock available for issuance (in shares)					5,262,279
Shares reserved for issuance on granting of outstanding awards (in shares)					1,500,000
2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share reserved for future issuance (in shares)				5,750,000
Common stock available for issuance (in shares)					718,453
Shares reserved for issuance on granting of outstanding awards (in shares)					20,374,879
Term of awards				10 years
Percentage of amount increase in outstanding shares				5.00%
2019 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share reserved for future issuance (in shares)				700,000
Percentage of amount increase in outstanding shares				1.00%
ESPP program, stock available for issuance, automatic increase term				10 years
Number of shares issued under ESPP plan					336,795	157,858
Number of share reserved for future issuance (in shares)					3,058,844
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 related to unvested stock option					$ 900
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]
Common stock were subject to outstanding options (in shares)					2,178,934
2017 Equity Incentive Plan \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards granted (in shares)					0

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Amount of Net Loss Before Taxes

The amount of net loss before taxes for the years ended December 31, 2023, 2022, and 2021 is as follows (in thousands):


	December 31,
	2023		2022		2021
	(in thousands)
U.S. loss before taxes	$	134,073	$	175,777	$	183,194
Foreign loss before taxes	45,736		53,593		50,802
Pre-tax Loss	$	179,809	$	229,370	$	233,996

Schedule of Deferred Tax Assets and Liabilities


	December 31,
	2023		2022		2021
	(in thousands)
Deferred tax assets:
Net operating losses	$	122,987	$	128,989	$	116,425
Tax credits, net	45,445		34,193		24,964
Amortization	6,919		8,487		9,190
Stock-based compensation	9,886		8,445		4,917
Lease liability	726		1,354		1,285
Accrued compensation	1,887		2,514		2,238
Section 174	34,268		21,840		—
Other	43		37		18
Total gross deferred tax assets	222,161		205,859		159,037

Deferred tax liabilities:
Convertible senior notes	—		—		(9,395)
Right of use asset	(660)		(1,244)		(1,150)
Property, plant and equipment	(108)		(565)		(790)
Total gross deferred tax liabilities	(768)		(1,809)		(11,335)
Valuation allowance	(221,393)		(204,050)		(147,702)
Net deferred tax asset	$	—	$	—	$	—

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

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


	December 31,
	2023		2022		2021
Federal statutory income tax rate	21.00	%	21.00	%	21.00	%
State income taxes, net of federal benefit	—	%	—	%	—	%
Change in valuation allowance	(8.73	%)	(20.25	%)	(19.73	%)
Research and experimentation credits	5.69	%	3.39	%	2.62	%
Foreign rate differential	(2.13	%)	(1.88	%)	(1.95	%)
Stock-based compensation	(1.44	%)	(0.90	%)	(1.56	%)
Nondeductible interest	(1.27	%)	(0.99	%)	(0.96	%)
Foreign Restructuring Impact	(12.49	%)	—	%	—	%
Other	(0.62	%)	(0.37	%)	0.57	%
Provision for income taxes	—	%	—	%	—	%

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

A reconciliation of the beginning and ending amount of unrecognized tax benefits for 2023, 2022, and 2021, excluding interest and penalties, is as follows:


	December 31,
	2023		2022		2021
	(in thousands)
Balance at beginning of the year	$	10,572	$	7,551	$	5,060
Increase related to current year positions	3,082		3,021		2,491
Balance at the end of the year	$	13,654	$	10,572	$	7,551

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Statement of Stockholders' Equity [Abstract]
Offering costs	$ 10,779	$ 184

Fair Value Measurements and Available for Sale Investments

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [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 December 31, 2023 and 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 December 31, 2023
Money market funds	$	25,222	$	25,222	$	—	$	—
U.S. Treasury and agency securities	92,309		92,309		—		—
Commercial paper	168,534		—		168,534		—
Corporate debt securities	3,473		—		3,473		—
As of December 31, 2022
Money market funds	$	54,662	$	54,662	$	—	$	—
U.S. Treasury and agency securities	31,458		31,458		—		—
Commercial paper	103,409		—		103,409		—
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 December 31, 2023 and 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-term maturities.

There was no significant interest receivable as of December 31, 2023 and 2022, and is recorded as a component of prepaid expenses and other current assets on the consolidated balance sheets.

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

As of December 31, 2023 and 2022 the fair value of the Company's 2027 Notes was $74.9 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, net in the Company's consolidated statements 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.


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Total Fair Value
As of December 31, 2023
U.S Treasury and agency securities	$	92,294	$	20	$	(5)	$	92,309
Corporate debt securities	3,467		6		—		3,473
Commercial paper	168,488		76		(30)		168,534
Total marketable securities	$	264,249	$	102	$	(35)	$	264,316
Number of securities with unrealized losses					12
As of December 31, 2022
U.S. Treasury and agency securities	$	31,445	$	15	$	(2)	$	31,458
Corporate debt securities	8,876		$	—	(38)		8,838
Commercial paper	103,508		1		(100)		103,409
Total marketable securities	$	143,829	$	16	$	(140)	$	143,705
Number of securities with unrealized losses					16

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


	Estimated Fair Value
Less than one year	$	264,316
Greater than one year	—
Total	$	264,316

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

- Definition

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

+ References + Details

Licenses, Asset Acquisitions and Contingent Consideration (Tables)

12 Months Ended

Dec. 31, 2023

Business Combination and Asset Acquisition [Abstract]

Schedule of IPR&D Expense

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


	Year Ended December 31,
	2023		2022		2021
Seralutinib	$	10,000	$	—	$	—

Terminated programs	—		65		75
Total in process research and development	$	10,000	$	65	$	75

Income Taxes - Schedule of Amount of Net Loss Before Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
U.S. loss before taxes	$ 134,073	$ 175,777	$ 183,194
Foreign loss before taxes	45,736	53,593	50,802
Pre-tax Loss	$ 179,809	$ 229,370	$ 233,996

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(11))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479557/942-235-S99-1

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 25
-Paragraph 1
-SubTopic 20
-Topic 940
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481913/940-20-25-1

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Fair Value of Stock Option Award Granted


	Year Ended December 31,
	2023	2022	2021
Employee Stock Options
Expected term (in years)	1.0 - 7.0	4.4 - 6.1	4.6 - 6.1
Risk-free interest rate	3.36% - 4.73%	1.31% - 4.35%	0.65% - 1.30%
Volatility	70.01% - 170.69%	71.10% - 89.87%	78.80% - 84.79%
Dividend yield	—	—	—

Employee Stock Purchase Plan
Expected term (in years)	0.5 - 2.0	0.5 - 2.0	0.5 - 2.0
Risk-free interest rate	4.87% -5.47%	0.60% - 3.51%	0.06% - 0.20%
Volatility	115.19% - 216.45%	64.98% - 121.43%	61.29% - 87.13%
Dividend yield	—	—	—

Schedule of Stock Option Activity

The following table summarizes stock option activity for the years ended December 31, 2023, 2022 and 2021:


	Shares Subject to Options Outstanding			Weighted- Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
	Shares	Weighted- Average Exercise Price
					(in thousands)
Outstanding as of December 31, 2020	9,401,082	$	13.42	8.1	$	10,182
Options granted	3,159,126	$	9.82
Options exercised	(325,494)	$	6.19
Options forfeited/cancelled	(2,800,054)	$	14.14
Outstanding as of December 31, 2021	9,434,660	$	12.24	7.4	$	15,822
Options granted	9,271,272	$	6.75
Options exercised	(270,707)	$	6.41
Options forfeited/cancelled	(948,060)	$	15.69
Outstanding as of December 31, 2022	17,487,165	$	9.24	8.1	$	47
Options granted	17,159,617	$	1.16
Options exercised	—	$	—
Options forfeited/cancelled	(11,020,667)	$	11.07
Outstanding as of December 31, 2023	23,626,115	$	2.52	7.9	$	369
Options vested and expected to vest as of December 31, 2023	23,626,115	$	2.52	7.9	$	369
Options exercisable as of December 31, 2023	8,952,067	$	4.17	6.3	$	1

Schedule of Restricted Stock Activity

The summary of the Company’s restricted stock activity during the years ended December 31, 2023, 2022 and 2021 is as follows:


	Number of Restricted Stock Units Outstanding	Weighted- Average Grant Date Fair Value
Nonvested at December 31, 2020	3,330,821	$	7.16
Granted	1,349,885	10.23
Vested	(1,391,476)	5.86
Forfeited / cancelled	(728,011)	10.03
Nonvested at December 31, 2021	2,561,219	$	8.67
Granted	572,901	11.94
Vested	(1,592,588)	7.78
Forfeited / cancelled	(191,497)	10.68
Nonvested at December 31, 2022	1,350,035	$	10.83
Granted	—	—
Vested	(779,900)	10.67
Forfeited / cancelled	(142,437)	11.39
Nonvested at December 31, 2023	427,698	$	10.92

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

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


	Year Ended December 31,
	2023		2022		2021
Research and development	$	15,871	$	24,415	$	18,943
General and administrative	12,647		18,138		13,065
Total stock-based compensation expense	$	28,518	$	42,553	$	32,008

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net loss	$ (179,817)	$ (229,378)	$ (234,004)

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-28

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482765/220-10-50-6

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-3

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480175/815-40-65-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-8

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-9

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-4

Reference 13: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 830
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480167/946-830-55-10

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483581/946-220-45-7

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(9))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(1)(d))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-3

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 20: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-60B

Reference 32: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483499/205-20-50-7

Reference 35: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-28

Reference 36: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1A

Reference 37: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1B

Reference 38: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 39: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

Income Taxes - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Operating Loss Carryforwards [Line Items]
Increase (decrease) in valuation allowance	$ 17.3
Net operating loss carryforwards relinquished due to liquidation and adjusted	140.0
Unrecognized tax benefits that would not impact effective tax rate	13.7
Orphan Drug Credit
Operating Loss Carryforwards [Line Items]
Research and development credit	$ 48.6
Maximum
Operating Loss Carryforwards [Line Items]
Net operating losses carryforward available to offset future federal taxable income , percentage	80.00%
Federal
Operating Loss Carryforwards [Line Items]
Net operating losses (“NOL”) carryforwards	$ 532.1
Net operating losses (“NOL”) that can be carried forward indefinitely	529.1
Research and development credit	48.6
California
Operating Loss Carryforwards [Line Items]
Net operating losses (“NOL”) carryforwards	1.8
Research and development credit	12.4
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Net operating losses (“NOL”) carryforwards	$ 89.1

Income Taxes - Schedule of Reconciliation of Federal Statutory Income Tax Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal benefit	0.00%	0.00%	0.00%
Change in valuation allowance	(8.73%)	(20.25%)	(19.73%)
Research and experimentation credits	5.69%	3.39%	2.62%
Foreign rate differential	(2.13%)	(1.88%)	(1.95%)
Stock-based compensation	(1.44%)	(0.90%)	(1.56%)
Nondeductible interest	(1.27%)	(0.99%)	(0.96%)
Foreign Restructuring Impact	(12.49%)	0.00%	0.00%
Other	(0.62%)	(0.37%)	0.57%
Provision for income taxes	0.00%	0.00%	0.00%

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment, Net

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


	Estimated Useful Life (in years)	December 31, 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	3,246		6,098
Leasehold improvements	6-7	2,562		2,562
Construction in process	N/A	—		83
Total property and equipment		7,080		10,093
Less: accumulated depreciation		(5,432)		(6,112)
Property and equipment, net		$	1,648	$	3,981

Indebtedness - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Debt, current portion	$ 11,613	$ 11,613
Debt, non-current portion	814	$ 11,988
Credit Facility
Debt Instrument [Line Items]
Debt, current portion	11,613
Debt, non-current portion	968
Total	12,581
Less: unamortized debt discount and issuance costs	(154)
Debt, net	$ 12,427

- 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

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Schedule of Lease Costs

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


	Year Ended December 31,
	2023		2022		2021
Operating lease cost	$	3,114	$	3,097	$	4,029
Short-term lease cost	52		45		53
Total lease cost	$	3,166	$	3,142	$	4,082

Schedule of Gross Future Minimum Annual Rental Commitments

Gross future minimum annual rental commitments as of December 31, 2023, were as follows (in thousands):


	Undiscounted Rent Payments
Year ending December 31,
2024	$	3,419
2025	144

Total undiscounted rent payments	$	3,563

Present value discount	(117)
Present value of lease payments	$	3,446
Current portion of operating lease liabilities (included as a component of accrued expenses and other current liabilities)	3,302
Noncurrent operating lease liabilities	144
Total operating lease liability	$	3,446

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating losses	$ 122,987	$ 128,989	$ 116,425
Tax credits, net	45,445	34,193	24,964
Amortization	6,919	8,487	9,190
Stock-based compensation	9,886	8,445	4,917
Lease liability	726	1,354	1,285
Accrued compensation	1,887	2,514	2,238
Section 174	34,268	21,840	0
Other	43	37	18
Total gross deferred tax assets	222,161	205,859	159,037
Deferred tax liabilities:
Convertible senior notes	0	0	(9,395)
Right of use asset	(660)	(1,244)	(1,150)
Property, plant and equipment	(108)	(565)	(790)
Total gross deferred tax liabilities	(768)	(1,809)	(11,335)
Valuation allowance	(221,393)	(204,050)	(147,702)
Net deferred tax asset	$ 0	$ 0	$ 0

Indebtedness - Additional Information (Details) $ / shares in Units, $ in Millions			12 Months Ended
	May 21, 2020 USD ($) tradingDay $ / shares	May 02, 2019 USD ($) tranche	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) tranche
Term Loan \| Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 150.0
Amount funded		30.0
Remaining borrowing capacity		$ 120.0
Number of additional tranches \| tranche		2
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			$ 2.5
Term Loan \| Prepayment Occurs through First Anniversary of Closing Date \| Credit Facility
Debt Instrument [Line Items]
Percentage of prepayment fee		3.00%
Term Loan \| First Anniversary of Closing Date through Second Anniversary of Closing Date \| Credit Facility
Debt Instrument [Line Items]
Percentage of prepayment fee		2.00%
Term Loan \| Second Anniversary of Closing Date and Prior to January 1, 2025 \| Credit Facility
Debt Instrument [Line Items]
Percentage of prepayment fee		1.00%
Term Loan \| Secured Overnight Financing Rate (SOFR) \| Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate		7.00%
Interest rate		2.00%
Term Loan \| MidCap Financial Trust \| Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate			3.00%
Term Loan \| Tranche One \| Credit Facility
Debt Instrument [Line Items]
Remaining borrowing capacity		$ 60.0		$ 60.0
Term Loan \| Tranche Two \| Credit Facility
Debt Instrument [Line Items]
Remaining borrowing capacity		$ 60.0		$ 60.0
2027 Notes
Debt Instrument [Line Items]
Interest rate	5.00%
Debt instrument aggregate principal amount	$ 200.0
Proceeds from issuance of convertible senior notes, net	$ 193.6
Debt instrument, convertible, conversion ratio	0.0616095
Debt instrument, conversion price (in dollars per share) \| $ / shares	$ 16.23
Debt instrument, conversion price (in percentage)	130.00%
Debt instrument, redemption term, number of trading days before maturity \| tradingDay	50
Debt instrument, redemption price (in percentage)	100.00%
Percentage of repurchase price is equal to principal amount of convertible notes	100.00%
Long-term debt, percentage in aggregate principal amount	0.25
Debt instrument, convertible, carrying amount of equity component	$ 53.5
Effective interest rate	11.17%
Debt issuance costs	$ 0.4
2027 Notes \| Minimum \| One Hundred Thirty Percent Applicable Conversion Price
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days \| tradingDay	20
2027 Notes \| Minimum \| Ninety Eight Percent Applicable Conversion Price
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days \| tradingDay	5
2027 Notes \| Maximum
Debt Instrument [Line Items]
Debt instrument convertible conversion last reported sale price (in percentage)	98.00%
2027 Notes \| Maximum \| One Hundred Thirty Percent Applicable Conversion Price
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days \| tradingDay	30
2027 Notes \| Maximum \| Ninety Eight Percent Applicable Conversion Price
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days \| tradingDay	10