0000950170-24-027924 | 10-K | XBRL Viewer

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Fair Value Measurement - Summary of Available-for-sale Securities Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale [Line Items]
Less than 12 months, fair value	$ 121,485	$ 253,829
Less than 12 months, unrealized losses	(77)	(716)
Greater than 12 months, fair value	0	0
Greater than 12 months, unrealized losses	0	0
Total, fair value	121,485	253,829
Total, unrealized losses	(77)	(716)
U.S. Treasury Securities
Debt Securities, Available-for-Sale [Line Items]
Less than 12 months, fair value	28,137	99,870
Less than 12 months, unrealized losses	(14)	(318)
Greater than 12 months, fair value	0	0
Greater than 12 months, unrealized losses	0	0
Total, fair value	28,137	99,870
Total, unrealized losses	(14)	(318)
Corporate Bonds
Debt Securities, Available-for-Sale [Line Items]
Less than 12 months, fair value	13,978	2,848
Less than 12 months, unrealized losses	(8)	(3)
Greater than 12 months, fair value	0	0
Greater than 12 months, unrealized losses	0	0
Total, fair value	13,978	2,848
Total, unrealized losses	(8)	(3)
Commercial Paper
Debt Securities, Available-for-Sale [Line Items]
Less than 12 months, fair value	74,599	127,163
Less than 12 months, unrealized losses	(44)	(211)
Greater than 12 months, fair value	0	0
Greater than 12 months, unrealized losses	0	0
Total, fair value	74,599	127,163
Total, unrealized losses	(44)	(211)
U.S. Government Agency Securities
Debt Securities, Available-for-Sale [Line Items]
Less than 12 months, fair value	4,771	23,948
Less than 12 months, unrealized losses	(11)	(184)
Greater than 12 months, fair value	0	0
Greater than 12 months, unrealized losses	0	0
Total, fair value	4,771	23,948
Total, unrealized losses	$ (11)	$ (184)

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ (246,416)	$ (221,102)	$ (165,164)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	852	(635)	(92)
Comprehensive loss	$ (245,564)	$ (221,737)	$ (165,256)

- Definition

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

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+ Details

Accrued Liabilities

12 Months Ended

Dec. 31, 2023

Balance Sheet Related Disclosures [Abstract]

Accrued Liabilities

Note 5. Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):


	December 31,
	2023		2022
Accrued research and development materials and services	$	14,625	$	20,747
Accrued professional services		3,147		1,759
Accrued compensation		13,527		10,920
Other		245		195
Total accrued liabilities	$	31,544	$	33,621

Sanofi Agreement (Tables)

12 Months Ended

Dec. 31, 2023

Sanofi Agreement [Abstract]

Schedule of Regulatory Liabilities [Table Text Block]

The following tables present changes in the Company’s customer contract liabilities for the periods presented (in thousands):


Year Ended December 31, 2023	December 31, 2022		Additions		Deductions			December 31, 2023
Contract liabilities:
Deferred revenue	$	148,931	$	—	$	(2,130	)	$	146,801


Year Ended December 31, 2022	December 31, 2021		Additions		Deductions			December 31, 2022
Contract liabilities:
Deferred revenue	$	—	$	150,000	$	(1,069	)	$	148,931

Stock-Based Compensation - Summary of Restricted Stock Unit Activity (Details)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Granted	1,835,018
Unvested Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Beginning Balance	401,180
Number of Shares, Granted	761,517
Number of Shares, Vested	(358,184)
Number of Shares, Forfeited	(145,721)
Number of Shares, Ending Balance	658,792
Weighted-Average Grant Date Fair Value, Beginning Balance \| $ / shares	$ 33.85
Weighted-Average Grant Date Fair Value, Granted \| $ / shares	12.36
Weighted-Average Grant Date Fair Value, Vested \| $ / shares	32.32
Weighted-Average Grant Date Fair Value, Forfeited \| $ / shares	16.07
Weighted-Average Grant Date Fair Value, Ending Balance \| $ / shares	$ 13.77

Leases - Summary of lease costs and cash paid for the Company's leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Cash paid for operating lease liabilities	$ 8,100	$ 5,548	$ 3,819
Operating lease cost	8,250	6,217	4,137
Variable lease cost	1,084	592	$ 307
Current operating lease liabilities	5,834	5,816
Non-current operating lease liabilities	$ 34,672	$ 35,356
Weighted average remaining lease term in years	8 years 1 month 6 days	8 years 9 months 18 days
Weighted average discount rate	6.50%	6.30%

Stockholders' Equity - Public Offerings and Pre-Funded Warrants - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended
	Jul. 03, 2023	Jun. 26, 2023	Apr. 30, 2022	Dec. 31, 2020	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Class Of Warrant Or Right [Line Items]
Proceeds from issuance of common stock in public offerings, net of offering costs					$ 0	$ 217,987	$ 0
Maximum allowed holding percentage of shares after exercise of warrants				9.99%
Maximum allowed combined voting percentage of shares after exercise of warrants				9.99%
Maximum allowed percentage of pre-funded warrants to exercise				19.99%
Minimum notice term to increase or decrease the holding percentage of pre-funded warrants				61 days
Underwritten Public Offering \| Pre-funded Warrant
Class Of Warrant Or Right [Line Items]
Warrants to purchase an additional shares of common stock				1,334,332
Pre-funded warrant, exercise price				$ 0.01
Non-voting Common Stock
Class Of Warrant Or Right [Line Items]
Issuance of common stock, shares	5,625,000
Common stock, par value					$ 0.01	$ 0.01
Common Stock, Shares, Issued					25,500,383	13,687,883
Non-voting Common Stock \| Private Placement
Class Of Warrant Or Right [Line Items]
Issuance of common stock, shares		2,812,500
Common stock, price per share		$ 8
Public Offering
Class Of Warrant Or Right [Line Items]
Issuance of common stock, shares			10,000,000
Class Of Options Purchase Of Common Stock			1,304,347
Common stock, par value			$ 23
Underwriting discounts and commissions costs		$ 6,500	$ 12,000
Proceeds from issuance of common stock in public offerings, net of offering costs		$ 113,500	$ 218,000
Public Offering \| Non-voting Common Stock
Class Of Warrant Or Right [Line Items]
Issuance of common stock, shares	9,000,000	3,375,000	8,695,653
Common stock, price per share	$ 8
Public Offering \| Common Stock [Member]
Class Of Warrant Or Right [Line Items]
Issuance of common stock, shares	3,187,500	3,187,500
Class Of Options Purchase Of Common Stock	1,589,673

Stock-Based Compensation - Summary of Stock Option (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Outstanding Options, Shares, Beginning balance	5,802,317
Outstanding Options, Shares, Granted	1,835,018
Outstanding Options, Shares, Exercised	(77,762)
Outstanding Options, Shares, Forfeited	(793,233)
Outstanding Options, Shares, Ending balance	6,766,340	5,802,317
Outstanding Options, Shares, Exercisable	4,055,579
Outstanding Options, Weighted-Average Exercise Price, Beginning balance	$ 31.59
Outstanding Options, Weighted-Average Exercise Price, Granted	13.83
Outstanding Options, Weighted-Average Exercise Price, Exercised	1.56
Outstanding Options, Weighted-Average Exercise Price, Forfeited	25.73
Outstanding Options, Weighted-Average Exercise Price, Ending balance	27.81	$ 31.59
Outstanding Options, Weighted-Average Exercise Price, Exercisable	$ 30.14
Outstanding Options, Weighted Average Remaining Contractual Term (Years)	7 years	7 years 10 months 24 days
Outstanding Options, Weighted Average Remaining Contractual Term (Years), Exercisable	5 years 10 months 24 days
Outstanding Options, Aggregate Intrinsic Value, Beginning balance	$ 17,428
Outstanding Options, Aggregate Intrinsic Value, Ending balance	6,823	$ 17,428
Outstanding Options, Aggregate Intrinsic Value, Exercisable	$ 6,697

Fair Value Measurement - Additional Information (Details) $ in Millions	Dec. 31, 2023 USD ($) Instrument	Dec. 31, 2022 USD ($) Instrument
Fair Value Disclosures [Abstract]
Number of financial instruments classified as level 3	0	0
Number of debt securities held	35	69
Accrued interest receivable \| $	$ 0.8	$ 0.5

Restructuring Charges - Summary of Changes in Company's Accrued Restructuring Balance (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 1,826
Severance liability
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance	0
Restructuring Charges	3,732
Payments for Restructuring	(1,335)
Restructuring Reserve, Ending Balance	$ 2,397

- 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

Stock-Based Compensation - Summary of Fair Value of Employee Stock Purchase Plan Estimated Weighted-average Assumptions (Details) - Employee Stock Purchase Plan	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	46.70%	54.40%	60.00%
Risk-free interest rate	5.40%	3.50%	0.10%
Expected dividend yield	0.00%	0.00%	0.00%

- 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

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-Publisher FASB
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+ Details

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2024	Jun. 23, 2023	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance	13,672,764	9,957,462
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation	$ 45.7
Expects to recognize over a remaining weighted-average period	2 years 4 months 24 days
Aggregate intrinsic value of options exercised	$ 0.9	$ 4.6	$ 32.3
Grant date fair value per share	$ 10.62	$ 13.31	$ 56.44
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation	$ 7.1
Expects to recognize over a remaining weighted-average period	3 years
2018 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of exercise price of stock option on estimated fair value of shares	110.00%
Shares reserved for issuance	4,384,000
Outstanding stock including non-voting common stock, percent	4.00%
Shares available for issuance	3,536,312				2,160,000
2018 Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Term of options	10 years
Increase in number of shares	8,768,800
2018 Plan \| Maximum \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares				5,883,557
2018 Plan \| Minimum \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares				2,347,245
2018 Plan \| 10% Stockholder \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Term of options	5 years
2018 Plan \| 10% Stockholder \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of voting power	10.00%
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding stock including non-voting common stock, percent	1.00%
Shares available for issuance	1,376,988					280,000
Discount rate	85.00%
ESPP \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares	560,000
Discount rate	15.00%
ESPP \| Maximum \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares				1,936,988
ESPP \| Minimum \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares				560,000

Leases

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Leases

Note 6. Leases

Operating Leases

The Company leases its headquarters with its main offices and laboratory and manufacturing facilities in Mountain View, California. Additionally, the Company has a lease for office and laboratory space in Doylestown, Pennsylvania. These leases require monthly lease payments that may be subject to annual increases throughout the lease term. Certain of these leases also include renewal options at the election of the Company. These optional periods have not been considered in the determination of the right-of-use assets or lease liabilities associated with these leases as the Company did not consider it reasonably certain it would exercise the options. The Company performed evaluations of its contracts and determined it has only operating leases. Variable lease expense for these leases primarily consists of common area maintenance and other operating costs.

During the year ended December 31, 2022, the Company entered into three new lease agreements for office and laboratory space in Mountain View, California. As of December 31, 2023 and 2022, two of the three new leases had commenced and were included in the right-of-use assets and lease liabilities balances at the respective year ends. The remaining lease with rent payments totaling $9.0 million is expected to commence in September 2024 after the expiration of the existing sublease and therefore has not been included in the right-of-use assets and lease liabilities balances as of December 31, 2023 and 2022.

The following table summarizes the lease costs and cash paid for the Company’s leases (in thousands):


	Year Ended December 31,
	2023		2022		2021
Cash paid for operating lease liabilities	$	8,100	$	5,548	$	3,819
Operating lease cost		8,250		6,217		4,137
Variable lease cost		1,084		592		307

The following table summarizes the weighted-average remaining lease term and discount rates for the Company’s leases:


	December 31,
	2023			2022
Lease term (in years)		8.1			8.8
Discount rate		6.5	%		6.3	%

The maturities of the Company's lease liabilities as of December 31, 2023 were as follows (in thousands):


	Operating
	Lease
Years Ending December 31,	Commitments
2024	$	7,892
2025		6,104
2026		6,208
2027		6,377
2028		6,306
Thereafter		22,303
Total		55,190
Less: imputed interest		(12,333	)
Less: tenant allowances		(2,351	)
Total lease liabilities(1)	$	40,506

(1)

The $9.0 million of future lease commitments for the laboratory lease that will not commence until September 2024 was not included in the lease liabilities balance as of December 31, 2023.

Leases - Additional Information (Details) $ in Thousands	12 Months Ended
Leases - Additional Information (Details) $ in Thousands	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) Agreement	Dec. 31, 2021 USD ($)
Lessee Lease Description [Line Items]
Rent payments	$ 8,100	$ 5,548	$ 3,819
Percentage of employees contribution to annual compensation plan	100.00%
Mountain View, California
Lessee Lease Description [Line Items]
Number of lease agreements \| Agreement		3
Mountain View, California \| Lease Agreements Three
Lessee Lease Description [Line Items]
Rent payments	$ 9,000	$ 9,000

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

Note 13. Income Taxes

Income Taxes

The Company’s income tax provision was $0.7 million for the year ended December 31, 2023, representing an effective tax rate of (0.3)%. There was no tax provision for the years ended December 31, 2022 and 2021. The increase in the income tax provision for the year ended December 31, 2023, as compared to the same period in 2022 was primarily due to recognizing deferred income in 2023 from the $150.0 million Sanofi upfront payment received in 2022 (See Note 9 – Sanofi Agreement).

The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate:


	Year Ended December 31,
	2023			2022			2021
Federal tax at statutory rate		21.0	%		21.0	%		21.0	%
State tax, net of federal benefit		5.8			5.3			7.3
Research and development credits		4.9			4.4			2.7
Stock-based compensation		(1.5	)		(1.1	)		2.6
Other		(0.2	)		—			—
Change in valuation allowance		(30.3	)		(29.6	)		(33.6	)
Effective income tax rate		(0.3	)%		—	%		—	%

Deferred tax assets and liabilities consist of the following (in thousands):


	December 31,
	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	73,437		$	80,507
Accrued liabilities and reserves		5,993			6,691
Stock-based compensation		19,111			12,312
Intangible assets		7,102			8,132
Lease liabilities		11,692			12,682
Research and development credits		44,201			30,208
Capitalized research and development expenses		77,914			49,985
Deferred revenue		40,061			—
Total deferred tax assets		279,511			200,517
Deferred tax liabilities:
Property and equipment		(2,290	)		(532	)
Right-of-use assets		(9,759	)		(10,791	)
Total deferred tax liabilities		(12,049	)		(11,323	)
Valuation allowance		(267,462	)		(189,194	)
Net deferred tax assets	$	—		$	—

The provisions of ASC Topic 740, Accounting for Income Taxes (Topic 740), require an assessment of both positive and negative evidence when determining whether it is more likely than not that deferred tax assets are recoverable. For the years ended December 31, 2023 and 2022, based on all available objective evidence, including the existence of cumulative losses, the Company

determined that it was not more likely than not that the net deferred tax assets were fully realizable. Accordingly, the Company established a full valuation allowance against its deferred tax assets. The Company intends to maintain a full valuation allowance on net deferred tax assets until sufficient positive evidence exists to support reversal of the valuation allowance. During the years ended December 31, 2023 and 2022, the valuation allowance increased by $78.3 million, and $68.8 million, respectively.

At December 31, 2023, the Company had net operating loss carryforwards available to reduce future taxable income, if any, for federal and state income tax purposes of approximately $207.6 million and $423.8 million, respectively. The federal net operating loss carryforwards can be carried forward indefinitely, subject to an annual limitation of 80% of taxable income. The state net operating loss carryforwards are subject to expire in various years, with the first expiration beginning in 2036.

At December 31, 2023, the Company also had federal and California research and development tax credit carryforwards of $37.7 million and $20.1 million, respectively, available to offset future income tax, if any. The federal credit carryforwards begin expiring in 2038, and the California credits can be carried forward indefinitely.

Under Section 382 and 383 of the Internal Revenue Code of 1986, as amended, if a corporation undergoes an “ownership change,” the corporation's ability to use its pre-change net operating loss carryforwards and other pre-change attributes, such as research tax credits, to offset its post-change income may be limited. In general, an “ownership change” will occur if there is a cumulative change in the Company's ownership by “5-percent shareholders” that exceeds 50 percentage points over a rolling three-year period. Similar rules may apply under state tax laws. Therefore, certain of the Company's carryforward tax attributes may be subject to an annual limitation regarding their utilization against taxable income in future periods. The Company has completed a Section 382 study and believes it has experienced two changes in ownership. As a result, some of the federal and state NOL carryforwards and tax credit carryforwards may expire before being applied to reduce future income tax liabilities.

Uncertain Tax Positions

The Company adopted the provisions of Topic 740, which requires companies to determine whether it is “more likely than not” that a tax position will be sustained upon examination by the appropriate taxing authorities before any tax benefit can be recorded in the consolidated financial statements. It also provides guidance on the recognition, measurement, classification and interest and penalties related to uncertain tax positions.

The following table summarizes the activity related to the Company’s gross unrecognized tax benefits (in thousands):


	December 31,
	2023		2022			2021
Beginning balance	$	6,916	$	4,075		$	2,429
Increases for tax positions related to prior years		1		—			7
Decreases for tax positions related to prior years		—		(47	)		(94	)
Additions for tax positions related to current year		3,652		2,888			1,733
Ending balance	$	10,569	$	6,916		$	4,075

The unrecognized tax benefits, if recognized, would not affect the effective income tax rate due to the valuation allowance that currently offsets deferred tax assets. No interest or penalties were accrued as of December 31, 2023. The Company does not expect the unrecognized tax benefits to change significantly over the next twelve months.

The Company files U.S. federal and various state income tax returns. For U.S. federal and state income tax purposes, the statute of limitations currently remains open for the years ending December 31, 2020 to present and December 31, 2019 to present, respectively. In addition, all of the net operating losses and research and development credit carryforwards that may be utilized in future years remain subject to examination. The Company is not currently under examination by income tax authorities in any jurisdiction.

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

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 17
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-Publisher FASB
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
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-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

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 Income (Loss)	$ (246,416)	$ (221,102)	$ (165,164)

- Definition

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

+ References

+ Details

Sanofi Agreement (Additional Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued during period value	$ 113,484	$ 217,987
Contract Liabilities	0	0
Deferred Revenue	146,801	148,931	$ 0
Sanofi Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred Revenue	146,800	148,900
Deferred Revenue, Current	3,800	2,700
Revenues	2,100	1,100
Revenue Transaction Price	150,000	$ 150,000
Upfront payment received	150,000
Development and regulatory milestones exchange	1,065,000
Sanofi Agreement [Member] \| European Medicines Agency [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Development and regulatory milestones exchange	$ 940,000
Profit sharing ratio description	50:50

Net Loss Per Share Attributable to Common Stockholders (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Summary of Potentially Dilutive Securities Not Included in the Diluted Per Share Calculations


	December 31,
	2023		2022
Stock options		6,766,340		5,802,317
Estimated shares issuable under the employee stock purchase plan		127,658		54,102
Unvested restricted stock units		658,792		401,180
Total		7,552,790		6,257,599

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
Summary of Significant Accounting Policies	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 2. Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Such management estimates include, but are not limited to, those related to revenue recognition, marketable securities, manufacturing accruals, accrued research and development expenses, stock-based compensation, operating lease right-of-use (ROU) assets and liabilities, income tax uncertainties and the valuation of deferred tax assets. The Company bases its estimates on its historical experience and also on assumptions that it believes are reasonable; however, actual results could significantly differ from those estimates. The most significant estimates and assumptions that management considers in the preparation of our financial statements relate to revenue recognition, accrued research and development costs, and leases. Segments The Company operates and manages its business as one reportable and operating segment, which is the business of developing engineered IgM antibodies for the treatment of cancer and autoimmune and inflammatory diseases. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for allocating and evaluating financial performance. All long-lived assets are maintained in, and all losses are attributable to, the United States of America. Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash, cash equivalents, and marketable securities. The Company invests in money market funds, U.S. treasury securities, corporate bonds, commercial paper, and U.S. government agency securities. The Company maintains bank deposits in federally insured financial institutions and these deposits may exceed federally insured limits. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents, and restricted cash, and bond issuers to the extent recorded on the balance sheets. The Company’s investment policy limits investments to high credit quality securities issued by the U.S. government and its agencies, highly rated banks, and corporate issuers, subject to certain concentration limits and restrictions on maturities. The Company has not experienced any material losses on its deposits of cash, cash equivalents, and marketable securities. The Company’s future results of operations involve a number of other risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, the Company’s early stages of clinical drug development; uncertainties related to the use of engineered IgM antibodies, which is a novel and unproven therapeutic approach; the Company’s ability to advance product candidates into, and successfully complete, clinical trials on the timelines it projects; the Company’s ability to adequately demonstrate sufficient safety and efficacy of its product candidates; the Company’s ability to enroll patients in its ongoing and future clinical trials; the Company’s ability to successfully manufacture and supply its product candidates for clinical trials; the occurrence of any event or circumstance that could give rise to the termination of the Company’s collaborations with third parties; the Company’s ability to obtain additional capital to finance its operations; uncertainties related to the projections of the size of patient populations suffering from the diseases the Company is targeting; the Company’s ability to obtain, maintain, and protect its intellectual property rights; developments relating to the Company’s competitors and its industry, including competing product candidates and therapies; general economic and market conditions; and other risks and uncertainties, including those more fully described in the “Risk Factors” section of this Annual Report on Form 10-K. The Company’s product candidates will require approvals from the U.S. Food and Drug Administration (FDA) and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash and cash equivalents. Cash equivalents consist primarily of amounts invested in money market funds, commercial paper, U.S. treasury securities, and U.S. government agency securities and are stated at fair value. Restricted cash consists of the remaining unused portion of a grant received from a non-profit organization which the Company will continue to utilize as it incurs expenses for services performed under the grant agreement. Marketable Securities The Company’s marketable securities have been classified and accounted for as available-for-sale securities. Fixed income securities consist of U.S. treasury securities, U.S. government agency securities, corporate bonds, and commercial paper. The specific identification method is used to determine the cost basis of fixed income securities sold. These securities are recorded on the consolidated balance sheets at fair value. Unrealized gains and losses on these securities are included as a separate component of accumulated other comprehensive loss. The cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in other income (expense). All available-for-sale securities are considered available to support current operations and are classified as current assets. The Company presents any credit losses identified as an allowance rather than as a reduction in the amortized cost of the available-for-sale securities. For available-for-sale debt securities in an unrealized loss position, the Company first assesses whether it intends to sell, or it is more likely than not that it will be required to sell the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value and recognized in other income (expense) in the statements of operations. If neither criteria is met, the Company evaluates whether the decline in fair value is related to credit-related factors or other factors. In making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and adverse conditions specifically related to the security, among other factors. Credit-related impairment losses, limited by the amount that the fair value is less than the amortized cost basis, are recorded through an allowance for credit losses in other income (expense). Any unrealized losses from declines in fair value below the amortized cost basis as a result of non-credit factors are recognized in accumulated other comprehensive income (loss), net of tax as a separate component of stockholders’ equity, along with unrealized gains. Realized gains and losses and declines in fair value, if any, on available-for-sale securities are included in other income (expense) in the statement operations. For purposes of identifying and measuring credit-related impairments, the Company’s policy is to exclude applicable accrued interest from both the fair value and amortized cost basis of the related security. The Company has elected to write-off uncollectible accrued interest receivable balances in a timely manner, which is defined by the Company as when interest due becomes 90 days delinquent. The accrued interest write-off will be recorded by reversing interest income. Accrued interest receivable is recorded to prepaid expenses and other current assets on the consolidated balance sheets. Property, Plant and Equipment Property, plant and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is determined using the straight-line method over the estimated useful lives of the respective assets, generally three to five years. Leasehold improvements are depreciated using the straight-line method over the shorter of the lease term or the estimated useful economic lives of the related assets. Assets are held in construction in progress until placed in service, upon which date, we begin to depreciate these assets. Upon retirement or sale of the assets, the cost and related accumulated depreciation and amortization are removed from the balance sheets and the resulting gain or loss are recorded to the statements of operations. Repairs and maintenance are charged to the consolidated statements of operations as incurred. Leases The Company determines if an arrangement is a lease at inception. In addition, the Company determines whether leases meet the classification criteria of a finance or operating lease at the lease commencement date considering: (1) whether the lease transfers ownership of the underlying asset to the lessee at the end of the lease term, (2) whether the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise, (3) whether the lease term is for a major part of the remaining economic life of the underlying asset, (4) whether the present value of the sum of the lease payments and residual value guaranteed by the lessee equals or exceeds substantially all of the fair value of the underlying asset, and (5) whether the underlying asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. As of December 31, 2023, the Company's lease population consisted of real estate leases and the Company did not have finance leases. Operating leases are included in operating lease ROU assets and lease liabilities in the Company’s consolidated balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the present value of lease payments, the Company uses its incremental borrowing rate based on the information available at the lease commencement date if the rate implicit in the lease is not readily determinable. The Company determines the incremental borrowing rate based on an analysis of corporate bond yields with a credit rating similar to the Company. The determination of the Company’s incremental borrowing rate requires management judgment including the development of a synthetic credit rating and cost of debt as the Company currently does not carry any debt. The Company believes that the estimates used in determining the incremental borrowing rate are reasonable based upon current facts and circumstances. Applying different judgments to the same facts and circumstances could result in the estimated amounts to vary. The operating lease ROU assets also include adjustments for prepayments and accrued lease payments and exclude lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options. Operating lease cost is recognized on a straight-line basis over the expected lease term. Variable lease costs represent payments that are dependent on usage, a rate or index. Variable lease cost primarily relates to common area maintenance charges. Lease agreements that include lease and non-lease components are accounted for as a single lease component. Lease agreements with a noncancelable term of less than 12 months are not recorded on the Company’s consolidated balance sheets. Impairment of Long-Lived Assets The Company evaluates the carrying amount of its long-lived assets, such as property and equipment, whenever events or changes in circumstances indicate that the assets may not be recoverable. An impairment loss would be recognized when estimated future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount of the asset. During the year ended December 31, 2023, there were impairments on long-lived assets of $0.3 million related to leasehold improvements. There was no impairment of long-lived assets during the years ended December 31, 2022 and 2021. Fair Value Measurement The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements on a recurring basis. Fair value is 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, a three-tier fair value hierarchy has been established, which prioritizes the inputs used in measuring fair value as follows: Level 1—Observable inputs, such as quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2—Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Unobservable inputs which reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. In determining fair value, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible as well as considers counterparty credit risk in its assessment of fair value. Financial instruments classified within Level 2 of the fair value hierarchy are valued based on other observable inputs, including broker or dealer quotations or alternative pricing sources. When quoted prices in active markets for identical assets or liabilities are not available, the Company relies on non-binding quotes from its investment managers, which are based on proprietary valuation models of independent pricing services. These models generally use inputs such as observable market data, quoted market prices for similar instruments, or historical pricing trends of a security relative to its peers. Revenue Recognition For arrangements or transactions between participants determined to be within the scope of Accounting Standard Codification (ASC) Topic 606, “Revenue from Contracts with Customers” (Topic 606) the Company performs the following steps to determine the appropriate amount of revenue to be recognized as the Company fulfills its obligations: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company has entered into and may enter into additional collaboration agreements in the future under which it may obtain upfront payments, milestone payments, royalty payments, profit sharing, and other fees. Promises under these arrangements may include intellectual property licenses, research and development services, and the participation in joint committees. At contract inception, the Company assesses the goods or services promised and enforceable in a contract with a customer and identifies those distinct goods and services that represent a performance obligation. In assessing whether a promised good or service is distinct, and therefore a performance obligation, the Company considers factors such as the nature of the research, stage of development of the targets, manufacturing and commercialization capabilities of the customer and the availability of the associated expertise in the general marketplace. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, the Company combines that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct. Promised goods and services that are not material in the context of the contract are not considered performance obligations. Additional goods or services that are exercisable at a customer’s discretion, including substitution rights, are assessed to determine if they provide a material right to the customer and if so, they are considered performance obligations. The transaction price is the amount of consideration to which the Company expects to be entitled in exchange for transferring promised goods or services to a customer. The consideration promised in a contract with a customer may include fixed amounts, variable amounts, or both. Non-refundable upfront payments are considered fixed consideration and included in the transaction price. If an arrangement includes development, regulatory or commercial milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. The Company includes the amount of estimated variable consideration, including milestones, in the transaction price to the extent that it is probable that a significant reversal of cumulative revenue recognized will not occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and if the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied. If it is determined that multiple performance obligations exist, the transaction price is allocated at the inception of the agreement to all identified performance obligations based on the relative standalone selling prices (SSP), unless the consideration is variable and meets the criteria to be allocated entirely to one or more, but not all, performance obligations in the contract. The relative SSP for each deliverable is estimated using objective evidence if it is available. If SSP is not directly observable the Company estimates the SSP at an amount that would result in the allocation of the transaction price in an amount that depicts the amount of consideration to which the entity expects to be entitled in exchange for transferring the promised goods or services to the customer, using methods such as the expected cost plus margin approach. Once the transaction price has been allocated to a performance obligation using the applicable methodology, it is not subject to reassessment for subsequent changes in standalone selling prices. Collaboration revenue is recognized when, or as, the Company satisfies a performance obligation. The Company recognizes revenue over time by measuring the progress toward complete satisfaction of the relevant performance obligation using an appropriate input method based on the nature of the good or service promised to the customer. After contract inception, the transaction price is reassessed at every period end and updated for changes such as resolution of uncertain events. Management may be required to exercise considerable judgment in estimating revenue to be recognized. Judgment is required in identifying performance obligations, estimating the transaction price, including variable consideration, estimating the standalone selling prices of identified performance obligations, and applying the input method for revenue recognition, including the estimated budgets for each performance obligation. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. If the related performance obligation is expected to be satisfied within the next twelve months this will be classified in current liabilities. Amounts recognized as revenue prior to receipt are recorded as contract assets in the Company’s consolidated balance sheets. If the Company expects to have an unconditional right to receive consideration in the next twelve months, this will be classified in current assets. A net contract asset or liability is presented for each contract with a customer. Collaborative Arrangements The Company analyzes its agreements to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and therefore within the scope of ASC Topic 808, Collaborative Arrangements (Topic 808). These assessments are performed throughout the life of the arrangements based on changes in the responsibilities of all parties in the arrangement. Research and Development Expenses The Company expenses research and development costs as they are incurred. Research and development expenses consist primarily of: (i) personnel-related expenses, including salaries, benefits and stock-based compensation expense, for personnel in the Company’s research and development functions; (ii) fees paid to third parties such as contractors, consultants and contract research organizations (CROs) for conducting clinical trials, and other costs related to clinical and preclinical testing; (iii) costs related to acquiring and manufacturing research and clinical trial materials, including under agreements with third parties such as contract manufacturing organizations (CMOs), and other vendors; (iv) costs related to the preparation of regulatory submissions; (v) expenses related to laboratory supplies and services; (vi) fees under license agreements where no alternative future use exists; and (vii) depreciation of equipment and facilities expenses. Accrued Research and Development Expenses The Company records accruals for estimated costs of research, preclinical studies, clinical trials, and manufacturing, which are significant components of research and development expenses. A substantial portion of the Company’s ongoing research and development activities is conducted by third-party service providers, CROs and CMOs. The Company’s contracts with CROs generally include pass-through fees such as laboratory supplies and services, regulatory expenses, investigator fees, travel costs and other miscellaneous costs, including shipping and printing fees. The Company’s contracts with the CMOs generally include fees such as initiation fees, reservation fees, verification run costs, materials and reagents expenses, taxes, etc. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company accrues the costs incurred under agreements with these third parties based on estimates of actual work completed in accordance with the respective agreements. The Company determines the estimated costs through discussions with internal personnel and external service providers as to the progress, or stage of completion or actual timeline (start-date and end-date) of the services and the agreed-upon fees to be paid for such services. In the event the Company makes advance payments, the payments are recorded as a prepaid expense and recognized as the services are performed. As actual costs become known, the Company adjusts its accruals. Although the Company does not expect its estimates to be materially different from amounts actually incurred, such estimates for the status and timing of services performed relative to the actual status and timing of services performed may vary and could result in the Company reporting amounts that are too high or too low in any particular period. The Company’s accrual is dependent, in part, upon the receipt of timely and accurate reporting from CROs and other third-party vendors. Variations in the assumptions used to estimate accruals including, but not limited to, the number of patients enrolled, the rate of patient enrollment and the actual services performed, may vary from the Company’s estimates, resulting in adjustments to clinical trial expenses in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect its financial condition and results of operations. Through December 31, 2023, there have been no material differences from the Company’s estimated accrued research and development expenses to actual expenses. Acquired In-Process Research and Development Expenses The Company has entered into agreements (see Note 7 – License Agreements) with third parties to acquire the rights to develop and potentially commercialize certain products. Such agreements generally require an initial payment by the Company when the contract is executed. The purchase of license rights for use in research and development activities, including product development, are expensed as incurred and are classified as research and development expense. Additionally, the Company may be obligated to make future royalty payments in the event the Company commercializes the technology and achieves a certain sales volume. In accordance with ASC Topic 730, Research and Development (Topic 730), expenditures for research and development, including upfront licensing fees and milestone payments associated with products not yet been approved by the FDA, are charged to research and development expense as incurred. Future contract milestone and/or royalty payments will be recognized as expense after the achievement of the milestone and the corresponding milestone payment is legally due. Stock-Based Compensation The Company accounts for stock-based compensation by measuring and recognizing compensation expense for all share-based awards made to employees, non-employees and directors based on estimated grant-date fair values. The Company uses the straight-line method to allocate compensation cost to reporting periods over the requisite service period, which is generally the vesting period. The grant date fair value of restricted stock units is estimated based on the closing stock price of the Company’s common stock on the date of grant. The grant date fair value of stock options granted to employees and directors is estimated using the Black-Scholes option-pricing model. The Company accounts for forfeitures as they occur. The fair value of each purchase right under the employee stock purchase plan (ESPP) is estimated at the beginning of the offering period using the Black-Scholes option pricing model and recorded as expense over the service period using the straight-line method. Income Taxes The Company accounts for income taxes using the liability method, whereby deferred tax asset and liability account balances are determined based on differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company provides a valuation allowance when it is more likely than not that some portion, or all of the Company’s deferred tax assets will not be realized. The Company accounts for income tax contingencies using a benefit recognition model. If it considers that a tax position is more likely than not to be sustained upon audit, based solely on the technical merits of the position, it recognizes the benefit. The Company measures the benefit by determining the amount that is greater than 50% likely of being realized upon settlement, presuming that the tax position is examined by the appropriate taxing authority that has full knowledge of all relevant information. The Company is subject to taxation in the United States federal jurisdiction, and various state jurisdictions. Due to the Company’s net operating loss carryforwards, the Company's income tax returns remain subject to examination by federal and state tax authorities for all tax years. The Company’s policy is to recognize interest expense and penalties related to income tax matters as a component of income tax expense. As of December 31, 2023, there were no significant accruals for interest related to unrecognized tax benefits or tax penalties. Comprehensive Loss Comprehensive loss represents the net loss for the period and other comprehensive loss. Other comprehensive loss reflects certain gains and losses that are recorded as a component of stockholders’ equity and are not reflected in the consolidated statements of operations. The Company’s other comprehensive loss consists of changes in unrealized gains and losses on available-for-sale securities. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock (including non-voting common stock and pre-funded warrants) outstanding during the period, without consideration for all other common stock equivalents. Shares of common stock into which the pre-funded warrants may be exercised are considered outstanding for the purposes of computing net loss per share because the shares may be issued for little or no consideration, are fully vested, and are exercisable after the original issuance date. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the net loss for each period presented. Reclassification Certain reclassifications have been made to prior period amounts to conform to current period presentation. These reclassifications did not have an impact on the Company’s results of operations or financial position as of December 31, 2023, 2022, and 2021. Recently Issued Accounting Pronouncements In October 2023, the FASB issued ASU 2023-06, Disclosure Improvements - Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative, which will impact various disclosure areas. The amendments in ASU 2023-06 will be effective on the date the related disclosures are removed from Regulation S-X or Regulation S-K by the SEC, and will no longer be effective if the SEC has not removed the applicable disclosure requirement by June 30, 2027. The Company is currently evaluating the impacts of this standard on its related disclosures. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280), which improves reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. This ASU is effective for fiscal years beginning after December 15, 2023 and is applicable to public entities, including those that have a single reportable segment. Early adoption is permitted. The Company is currently evaluating the impacts of this standard on its consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures, which amends the guidance in ASC 740, Income Taxes. The ASU is intended to improve the transparency of income tax disclosures by requiring (1) consistent categories and greater disaggregation of information in the rate reconciliation and (2) income taxes paid disaggregated by jurisdiction. It also includes certain other amendments to improve the effectiveness of income tax disclosures. The ASU's amendments are effective for public business entities for annual periods beginning after December 15, 2024. Entities are permitted to early adopt the standard for annual financial statements that have not yet been issued or made available for issuance. Adoption is permitted either prospectively or retrospectively. The Company will adopt this ASU on a prospective basis. The Company is currently evaluating the impact of this standard but does not expect any material impacts on its consolidated financial statements and related disclosures. Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. This ASU also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. The Company adopted ASU 2016-13 on January 1, 2023, using the modified retrospective approach, and no cumulative effect adjustment to accumulated deficit was needed as of the adoption date. Additionally, no prior period amounts were adjusted. The adoption of ASU 2016-13 did not have a material impact on the Company’s consolidated financial statements and all current period amounts are reported under the Available-for-Sale Debt Securities Impairment Model (ASC 326-30).

Property, Plant and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment, Net

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


	December 31,
	2023			2022
Manufacturing and laboratory equipment	$	32,712		$	25,631
Office equipment		2,409			631
Leasehold improvements		17,912			14,433
Construction in progress		5,798			5,114
Total property, plant and equipment, gross		58,831			45,809
Less: Accumulated depreciation		(20,599	)		(12,325	)
Total property, plant and equipment, net	$	38,232		$	33,484

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Reconciliation of Statutory Federal Income Tax Rate

The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate:


	Year Ended December 31,
	2023			2022			2021
Federal tax at statutory rate		21.0	%		21.0	%		21.0	%
State tax, net of federal benefit		5.8			5.3			7.3
Research and development credits		4.9			4.4			2.7
Stock-based compensation		(1.5	)		(1.1	)		2.6
Other		(0.2	)		—			—
Change in valuation allowance		(30.3	)		(29.6	)		(33.6	)
Effective income tax rate		(0.3	)%		—	%		—	%

Schedule of Deferred Tax Assets and Liabilities

Deferred tax assets and liabilities consist of the following (in thousands):


	December 31,
	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	73,437		$	80,507
Accrued liabilities and reserves		5,993			6,691
Stock-based compensation		19,111			12,312
Intangible assets		7,102			8,132
Lease liabilities		11,692			12,682
Research and development credits		44,201			30,208
Capitalized research and development expenses		77,914			49,985
Deferred revenue		40,061			—
Total deferred tax assets		279,511			200,517
Deferred tax liabilities:
Property and equipment		(2,290	)		(532	)
Right-of-use assets		(9,759	)		(10,791	)
Total deferred tax liabilities		(12,049	)		(11,323	)
Valuation allowance		(267,462	)		(189,194	)
Net deferred tax assets	$	—		$	—

Summary of Gross Unrecognized Tax Benefits

The following table summarizes the activity related to the Company’s gross unrecognized tax benefits (in thousands):


	December 31,
	2023		2022			2021
Beginning balance	$	6,916	$	4,075		$	2,429
Increases for tax positions related to prior years		1		—			7
Decreases for tax positions related to prior years		—		(47	)		(94	)
Additions for tax positions related to current year		3,652		2,888			1,733
Ending balance	$	10,569	$	6,916		$	4,075

Accrued Liabilities - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Accrued research and development materials and services	$ 14,625	$ 20,747
Accrued professional services	3,147	1,759
Accrued compensation	13,527	10,920
Other	245	195
Total accrued liabilities	$ 31,544	$ 33,621

Stockholders' Equity

12 Months Ended

Dec. 31, 2023

Stockholders' Equity Note [Abstract]

Stockholders' Equity

Note 8. Stockholders' Equity

Common Stock and Non-Voting Common Stock

As of December 31, 2023 and 2022, the Company’s certificate of incorporation authorized the Company to issue 1,200,000,000 shares of common stock (including 200,000,000 shares of non-voting common stock) and 200,000,000 shares of preferred stock, at a par value of $0.01 per share. Each share of common stock (excluding non-voting common stock) is entitled to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the Company’s Board of Directors, subject to prior rights of the preferred stockholders. As of December 31, 2023 and 2022, no dividends have been declared.

The Company had reserved common stock, on an as-converted basis, for future issuance as follows:


	December 31,
	2023		2022
Stock options, issued and outstanding		6,766,340		5,802,317
Restricted stock units		658,792		401,180
Stock options and restricted stock units, future issuance		3,536,312		1,310,601
Employee stock purchase plan, available for future grants		1,376,988		1,109,032
Pre-funded warrants		1,334,332		1,334,332
Total		13,672,764		9,957,462

Stock Offerings

On July 3, 2023, the Company completed an underwritten public offering for the issuance of 3,187,500 shares of voting common stock and 9,000,000 shares of non-voting common stock at a public offering price of $8.00 per share pursuant to a shelf registration statement on Form S-3 (2023 Public Offering). This includes the full exercise by the underwriters of their option to purchase up to 1,589,673 shares of voting common stock. Of the shares sold in the 2023 Public Offering, 3,187,500 shares of voting common stock and 3,375,000 shares of non-voting common stock were issued on June 26, 2023, and the remaining 5,625,000 shares of non-voting common stock were issued on July 3, 2023.

On June 26, 2023, the Company also issued and sold 2,812,500 shares of its non-voting common stock in a concurrent private placement exempt from the registration requirements of the Securities Act at a sale price of $8.00 per share.

The total net proceeds received by the Company from the 2023 Public Offering and concurrent private placement were $113.5 million, after deducting underwriting discounts and commissions and offering costs of $6.5 million.

In April 2022, the Company issued and sold 10,000,000 shares of common stock, including 8,695,653 shares of non-voting common stock and the full exercise of the underwriters' option to purchase 1,304,347 shares of voting common stock, each at a public offering price of $23.00 per share in an underwritten public offering pursuant to a shelf registration statement on Form S-3. The net proceeds to the Company from the offering were $218.0 million, after deducting underwriting discounts and commissions and offering costs of $12.0 million.

Pre-Funded Warrants

In December 2020, the Company issued pre-funded warrants to purchase up to 1,334,332 shares of common stock in an underwritten public offering at the offering price of the common stock, less the $0.01 per share exercise price of each warrant and were issued to two separate related party affiliates. The pre-funded warrants were recorded as a component of stockholders’ equity within additional paid-in-capital and will expire on the date any such warrant is exercised in full.

Subject to applicable law, upon exercise of a pre-funded warrant, a holder may elect to receive the same number of shares of non-voting common stock as the shares of common stock for which the pre-funded warrant is exercisable, provided that (i) at the time of such election there is a sufficient number of authorized but unissued and otherwise unreserved shares of non-voting common stock and (ii) the Company consents to such election.

The outstanding pre-funded warrants to purchase shares of common stock are exercisable at any time after their original issuance. However, the Company may not affect the exercise of any pre-funded warrants, and a holder will not be entitled to exercise any portion of any pre-funded warrants that, upon giving effect to such exercise, would cause: (i) the aggregate number of shares of the Company’s common stock beneficially owned by such holder (together with its affiliates) to exceed 9.99% of the number of shares of the Company’s common stock outstanding immediately after giving effect to the exercise; or (ii) the combined voting power of the Company’s securities beneficially owned by such holder (together with its affiliates) to exceed 9.99% of the combined voting power of all of the Company’s securities outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the pre-funded warrants. However, any holder of a pre-funded warrant may increase or decrease such percentage to any other percentage not in excess of 19.99% upon at least 61 days’ prior notice from the holder to the Company. As of December 31, 2023, no shares underlying the pre-funded warrants had been exercised. All of the outstanding pre-funded warrants are included in the weighted-average number of shares of common stock used to calculate basic net loss per share attributable to common stockholders (see Note 14 – Net Loss Per Share Attributable to Common Stockholders).

- Definition

The entire disclosure for equity.

+ References

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

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+ Details

Property, Plant and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 8,277	$ 6,075	$ 4,484

Defined Contribution Plan (Additional Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
Maximum Employee contribution	100.00%
Defined Contribution Plan, Expenses	$ 1,800	$ 0	$ 0

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 112,520	$ 121,231
Restricted cash	592	689
Marketable securities	225,157	305,931
Prepaid expenses and other current assets	9,328	10,570
Total current assets	347,597	438,421
Property, plant and equipment, net	38,232	33,484
Operating lease right-of-use assets	35,773	39,591
Other non-current assets	1,809	2,003
Total assets	423,411	513,499
Current liabilities:
Accounts payable	1,326	2,512
Accrued liabilities	31,544	33,621
Lease liabilities	5,834	5,816
Deferred revenue	3,777	2,736
Total current liabilities	42,481	44,685
Lease liabilities, non-current	34,672	35,356
Deferred revenue, non-current	143,024	146,195
Total liabilities	220,177	226,236
Commitments and contingencies (Note 7)
Stockholders' equity:
Preferred stock, $0.01 par value; 200,000,000 shares authorized as of December 31, 2023 and 2022; no shares issued and outstanding	0	0
Additional paid-in-capital	1,023,739	862,359
Accumulated other comprehensive income (loss)	151	(701)
Accumulated deficit	(821,242)	(574,826)
Total stockholders’ equity	203,234	287,263
Total liabilities and stockholders’ equity	423,411	513,499
Common Stock Class Undefined
Stockholders' equity:
Common stock, value	331	294
Non-voting Common Stock
Stockholders' equity:
Common stock, value	$ 255	$ 137

Sanofi Agreement

12 Months Ended

Dec. 31, 2023

Sanofi Agreement [Abstract]

Sanofi Agreement

Note 9. Sanofi Agreement

In March 2022, the Company entered into a global collaboration and license agreement (the Sanofi Agreement) with Genzyme Corporation, a wholly owned subsidiary of Sanofi (Sanofi), which became effective in May 2022 upon satisfaction of the closing conditions. Under the terms of the Sanofi Agreement, the Company will generate, develop, manufacture and commercialize IgM antibodies directed to six primary targets, three of which are intended as oncology targets and three of which are intended as immunology targets.

For each oncology target collaboration program, the Company will lead research and development activities, and assume related costs, through receipt of the first marketing approval for a licensed product directed to that oncology target by the Food and Drug Administration (FDA) or European Medicines Agency (EMA) in exchange for up to $940 million in development and regulatory milestones per oncology target. After receipt of the first marketing approval for a licensed product directed to an oncology target, Sanofi will lead all subsequent development and commercialization activities for that oncology target. For each licensed product directed to an oncology target, the companies will share profits 50:50 in certain major markets, subject to certain exceptions, and the Company will be eligible to receive tiered low double-digit to mid-teen royalties on net sales of licensed products in the rest of world, subject to certain reductions and offsets. However, the Company has the right to opt-out of any future research and development responsibilities for each oncology target collaboration program at any time after completion of a Phase 1 clinical trial for an oncology target collaboration program. As a result of exercising this opt-out right, the Company would no longer share profits 50:50 but would instead be eligible for certain sales milestones and tiered royalties on net sales.

For each immunology target collaboration program, the Company will lead research and development activities, and assume related costs, through the completion of the first Phase 1 clinical trials for up to two candidates directed to each immunology target, after which Sanofi will be responsible for all future development and commercialization activities and related costs, in exchange for up to $1.065 billion in aggregate development, regulatory and commercial milestones per immunology target. Following the completion of the first Phase 1 clinical trials for each immunology target, Sanofi will be responsible for subsequent development activities, commercialization efforts, and related costs. The Company is eligible to receive tiered high single-digit to low-teen royalties on global net sales for licensed products related to immunology targets, subject to certain reductions and offsets.

Subject to earlier expiration in certain circumstances, the Sanofi Agreement expires on a licensed product-by-licensed product and country-by-country basis until the expiration of the applicable profit and loss share term or royalty term, as the case may be. Sanofi has the right to terminate the Sanofi Agreement on a collaboration target-by-collaboration target basis or country-by-country basis with or without cause, upon specified prior notice.

After considering the level of involvement and participation in the joint activities and the related exposure to the risks and rewards of the collaboration, the Company determined that at inception, the Sanofi Agreement does not fall within the collaborative arrangement guidance in Topic 808, and that Sanofi is a customer of the Company for all initial promised goods and services and therefore the agreement is directly within the scope of Topic 606.

The Company identified promised goods and services in the Sanofi Agreement related to the grant of intellectual property license, performance of specified research, development and other various activities. The Company determined that for each of the six targets,

the identified promised goods and services are not distinct from each other on a target-by-target basis. The licenses, considered to be functional intellectual property, were determined to not be capable of being distinct due to the specialized nature of the research, development, and other activities to be provided by the Company. Accordingly, the promised goods and services, which consist of the granting of intellectual property licenses and the performance of specified research, development and other various activities, were combined together as one single performance obligation, on a target-by-target basis. The Company determined that the underlying promised goods and services for each of the six targets are both capable of being distinct and distinct within the context of the contract from each of the other targets. Therefore, the Company concluded that there are six performance obligations in the Sanofi Agreement, one for each target, that are comprised of the underlying promised goods and services. Other components and options within the Sanofi Agreement were determined to not provide Sanofi with free or discounted goods or services and therefore did not constitute a material right or were deemed immaterial in the context of the contract.

To determine the transaction price, the Company evaluated all the payments to be received during the duration of the contract. In May 2022, the Company received a $150.0 million upfront payment as part of the Sanofi Agreement. Additionally, in April 2022, Sanofi purchased non-voting common stock in connection with the Company’s public common stock offering (see Note 8 – Stockholders’ Equity). The Company concluded that at inception and as of December 31, 2023, the transaction price was $150.0 million and was comprised solely of the fixed non-refundable upfront payment. No consideration received from Sanofi as part of the April 2022 offering was deemed necessary to include in the transaction price as Sanofi purchased the shares at the same offering price as the other participating investors.

The potential development and regulatory milestone payments that the Company is eligible to receive were excluded from the transaction price, as the milestone amounts were fully constrained, since the milestones relate to successful achievement of certain development results and regulatory approvals, which might not be achieved. The Company determined that the royalties and commercial milestone payments relate predominantly to the license of intellectual property and are therefore excluded from the transaction price under the sales- or usage-based royalty exception of ASC 606. The Company will reevaluate the transaction price, including all constrained amounts, at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and the Company will adjust its estimate of the transaction price as necessary. The Company will recognize the royalties and commercial milestone payments as revenue when the associated sales occur, and relevant sales-based thresholds are met.

The Company allocated the transaction price based on the estimated SSP of each of the six performance obligations. The Company determined the SSP for each of the six performance obligations based on the estimated costs to complete the underlying activities of each performance obligation and included factors such as forecasted internal costs, estimated third-party expenditures, development timelines and scenarios, probability of target failures and selection of substitute targets, and program-specific factors. These estimated cost forecasts were based on observable data for both market and entity specific factors, such as considering the actual and expected costs of the Company’s existing research and development programs and adjusting for factors specific to the targets identified.

The Company recognizes revenue using an input method of costs incurred as a percentage of total estimated costs for each of the performance obligations under the contract. Costs consist primarily of internal personnel costs and third-party contract expenses related to the programs of the Sanofi Agreement. The cumulative effect of revisions to estimated costs to complete the Company’s performance obligations is recorded in the period in which changes are identified and amounts can be reasonably estimated.

For the year ended December 31, 2023 and 2022, the Company recognized collaboration revenue related to the Sanofi Agreement of $2.1 million and $1.1 million. As of December 31, 2023 and 2022, $146.8 million and $148.9 million was recorded as deferred revenue related to the Sanofi Agreement, respectively, of which $3.8 million and $2.7 million was current, on the consolidated balance sheets. The deferred revenue is expected to be recognized over the research and development period of the programs through the completion of Phase 1 clinical trials.

Contract Balances from Customer Contract

The timing of revenue recognition, billings and cash collections results in contract assets and contract liabilities on the consolidated balance sheets. The Company recognizes license and development receivables based on billed services, which are settled upon reimbursement. When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer under the terms of a contract, a contract liability is recorded. Contract liabilities are recognized as revenue after control of the goods or services is transferred to the customer and all revenue recognition criteria have been met.

The following tables present changes in the Company’s customer contract liabilities for the periods presented (in thousands):


Year Ended December 31, 2023	December 31, 2022		Additions		Deductions			December 31, 2023
Contract liabilities:
Deferred revenue	$	148,931	$	—	$	(2,130	)	$	146,801


Year Ended December 31, 2022	December 31, 2021		Additions		Deductions			December 31, 2022
Contract liabilities:
Deferred revenue	$	—	$	150,000	$	(1,069	)	$	148,931

The Company had no customer contract assets during the years ended December 31, 2023 and 2022.

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 73,437	$ 80,507
Accrued liabilities and reserves	5,993	6,691
Stock-based compensation	19,111	12,312
Intangible assets	7,102	8,132
Lease liabilities	11,692	12,682
Research and development credits	44,201	30,208
Capitalized research and development expenses	77,914	49,985
Deferred revenue	40,061	0
Total deferred tax assets	279,511	200,517
Deferred tax liabilities:
Property and equipment	(2,290)	(532)
Right-of-use assets	(9,759)	(10,791)
Total deferred tax liabilities	(12,049)	(11,323)
Valuation allowance	(267,462)	(189,194)
Net deferred tax assets	$ 0	$ 0

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Summary of Investments Measured and Recognized at Fair Value

The following tables set forth the fair value of the Company’s financial assets, which consist of cash equivalents and marketable securities measured and recognized at fair value (in thousands):


		December 31, 2023
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	Level 1	$	21,458	$	—	$	—		$	21,458
U.S. treasury securities	Level 1		25,896		2		—			25,898
Commercial paper	Level 2		54,427		—		(27	)		54,400
U.S. government agency securities	Level 2		4,951		1		—			4,952
Marketable securities:
U.S. treasury securities	Level 1		182,289		214		(14	)		182,489
Corporate bonds	Level 2		13,986		—		(8	)		13,978
Commercial paper	Level 2		20,216		—		(17	)		20,199
U.S. government agency securities	Level 2		8,491		11		(11	)		8,491
Total		$	331,714	$	228	$	(77	)	$	331,865


		December 31, 2022
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	Level 1	$	26,718	$	—	$	—		$	26,718
Commercial paper	Level 2		66,732		—		(16	)		66,716
U.S. government agency securities	Level 2		20,477		7		—			20,484
Marketable securities:
U.S. treasury securities	Level 1		127,234		6		(318	)		126,922
Corporate bonds	Level 2		12,531		2		(3	)		12,530
Commercial paper	Level 2		142,726		—		(195	)		142,531
U.S. government agency securities	Level 2		24,132		—		(184	)		23,948
Total		$	420,550	$	15	$	(716	)	$	419,849

Schedule of Unrealized Loss on Marketable Securities

The following table summarizes the available-for-sale securities in an unrealized loss position for which an allowance for credit losses has not been recorded as of December 31, 2023 and 2022, aggregated by major security type and length of time in a continuous unrealized loss position:


	December 31, 2023
	Less than 12 months					Greater than 12 months				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. treasury securities	$	28,137	$	(14	)	$	—	$	—	$	28,137	$	(14	)
Corporate bonds		13,978		(8	)		—		—		13,978		(8	)
Commercial paper		74,599		(44	)		—		—		74,599		(44	)
U.S. government agency securities		4,771		(11	)		—		—		4,771		(11	)
Total	$	121,485	$	(77	)	$	—	$	—	$	121,485	$	(77	)


	December 31, 2022
	Less than 12 months					Greater than 12 months				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. treasury securities	$	99,870	$	(318	)	$	—	$	—	$	99,870	$	(318	)
Corporate bonds		2,848		(3	)		—		—		2,848		(3	)
Commercial paper		127,163		(211	)		—		—		127,163		(211	)
U.S. government agency securities		23,948		(184	)		—		—		23,948		(184	)
Total	$	253,829	$	(716	)	$	—	$	—	$	253,829	$	(716	)

Summary of Contractual Maturities of Marketable Securities

The following table summarizes the contractual maturities of the Company’s cash equivalents and marketable securities as of December 31, 2023 and 2022 at estimated fair value (in thousands):


	December 31,
	2023		2022
Due in less than one year	$	312,554	$	419,849
Due in more than one year		19,311		—
Total	$	331,865	$	419,849

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Common Stock Non-voting Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at Dec. 31, 2020	$ 381,815	$ 255	$ 64	$ 570,030	$ 26	$ (188,560)
Balance, shares at Dec. 31, 2020		25,542,931	6,431,205
Exercise of stock options, net of shares withheld for taxes and exercise costs	1,571	$ 6		1,565
Exercise of stock options, net of shares withheld for taxes and exercise costs, shares		500,733
Vest of restricted stock units, shares		4,531
Purchases under employee stock purchase plan	905			905
Purchases under employee stock purchase plan, shares		18,623
Stock Issued During Period, Value, Employee Stock Purchase Plan	905			905
Unrealized gain (loss) on marketable securities	(92)				(92)
Stock-based compensation expense	25,873			25,873
Net Income (Loss)	(165,164)					(165,164)
Balance at Dec. 31, 2021	244,908	$ 261	$ 64	598,373	(66)	(353,724)
Balance, shares at Dec. 31, 2021		26,066,818	6,431,205
Exercise of stock options, net of shares withheld for taxes and exercise costs	500	$ 2		498
Exercise of stock options, net of shares withheld for taxes and exercise costs, shares		233,459
Issuance of common stock	217,987	$ 28	$ 73	217,886
Issuance of common stock, shares		1,304,347	8,695,653
Vest of restricted stock units, shares		279,683
Vest of restricted stock units, value		$ 3		(3)
Conversion of convertible preferred stock into common stock and non-voting common stock, shares		1,438,975	(1,438,975)
Purchases under employee stock purchase plan	895			895
Purchases under employee stock purchase plan, shares		71,154
Stock Issued During Period, Value, Employee Stock Purchase Plan	895			895
Unrealized gain (loss) on marketable securities	(635)				(635)
Stock-based compensation expense	44,710			44,710
Net Income (Loss)	(221,102)					(221,102)
Balance at Dec. 31, 2022	287,263	$ 294	$ 137	862,359	(701)	(574,826)
Balance, shares at Dec. 31, 2022		29,394,436	13,687,883
Exercise of stock options, net of shares withheld for taxes and exercise costs	$ 120			120
Exercise of stock options, net of shares withheld for taxes and exercise costs, shares		77,762
Exercise of stock options, shares	77,762
Issuance of common stock	$ 113,484	$ 32	$ 118	113,334
Issuance of common stock, shares		3,187,500	11,812,500
Vest of restricted stock units, shares		358,184
Vest of restricted stock units, value		$ 4		(4)
Purchases under employee stock purchase plan	1,384	$ 1		1,383
Purchases under employee stock purchase plan, shares		162,867
Stock Issued During Period, Value, Employee Stock Purchase Plan	1,384	$ 1		1,383
Unrealized gain (loss) on marketable securities	852				852
Stock-based compensation expense	46,547			46,547
Net Income (Loss)	(246,416)					(246,416)
Balance at Dec. 31, 2023	$ 203,234	$ 331	$ 255	$ 1,023,739	$ 151	$ (821,242)
Balance, shares at Dec. 31, 2023		33,180,749	25,500,383

Income Taxes - Summary of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Beginning balance	$ 6,916	$ 4,075	$ 2,429
Increases for tax positions related to prior years	1	0	7
Decreases for tax positions related to prior years	0	(47)	(94)
Additions for tax positions related to current year	3,652	2,888	1,733
Ending balance	$ 10,569	$ 6,916	$ 4,075

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Collaboration revenue	$ 2,130	$ 1,069	$ 0
Operating expenses:
Research and development	215,519	179,289	127,026
General and administrative	50,072	49,736	38,297
Total operating expenses	265,591	229,025	165,323
Loss from operations	(263,461)	(227,956)	(165,323)
Other income (expense)
Interest income	17,743	7,035	159
Other expense	(20)	(181)	0
Total other income (expense)	17,723	6,854	159
Loss before income tax expense	(245,738)	(221,102)	(165,164)
Income tax expense	(678)	0	0
Net loss	$ (246,416)	$ (221,102)	$ (165,164)
Net loss per share, basic	$ (4.71)	$ (5.32)	$ (4.93)
Net loss per share, diluted	$ (4.71)	$ (5.32)	$ (4.93)
Weighted-average common shares outstanding, basic	52,311,958	41,543,954	33,479,782
Weighted-average common shares outstanding, diluted	52,311,958	41,543,954	33,479,782

Organization - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Subsidiary Sale Of Stock [Line Items]
Accumulated deficit	$ (821,242)	$ (574,826)
Cash, and investments	$ 337,700

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Restructuring Charges

12 Months Ended

Dec. 31, 2023

Restructuring and Related Activities [Abstract]

Restructuring Charges

Note 12. Restructuring Charges

On December 5, 2023, the Company committed to a strategic refocusing (Strategic Refocusing) and suspended clinical development activities for certain product candidates in several indications and reduced its workforce by approximately 22%, with headcount reductions substantially complete by December 31, 2023. The Company is undertaking the effort to focus its resources on the development of IgM Death Receptor 5 agonist antibodies for the treatment of colorectal cancer and IgM T cell engager antibodies for the treatment of autoimmune diseases, while further extending its cash runway. The Company will also continue to focus on the development of oncology and immunology product candidates under its collaboration with Sanofi.

In connection with the Strategic Refocusing, the Company recognized restructuring charges of $1.8 million during the year ended December 31, 2023. These restructuring charges were primarily related to severance and one-time termination payments of $3.7 million, partially offset by a $1.9 million reversal of previously recognized non-cash incentive and stock-based compensation expense. As of December 31, 2023, accrued severance of $2.4 million remained unpaid and is expected to be paid within one year. The Company recorded these restructuring charges to the respective research and development and general and administrative operating expense categories on its consolidated statements of operations and comprehensive loss.

The following table summarizes the changes in the Company's accrued restructuring balance (in thousands):


	Beginning Balance December 31, 2022		Charges		Payments			Ending Balance December 31, 2023
Severance liability	$	—	$	3,732	$	(1,335	)	$	2,397

A summary of the charges related to the restructuring activities as of December 31, 2023 is as follows (in thousands):


	Severance and Related Compensation		Incentive and Stock-Based Compensation			Total Restructuring Costs
Research and development	$	3,260	$	(1,531	)	$	1,729
General and administrative		472		(375	)		97
Total	$	3,732	$	(1,906	)	$	1,826

Net Loss Per Share Attributable to Common Stockholders - Schedule of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net Income (Loss)	$ (246,416)	$ (221,102)	$ (165,164)

- Definition

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

+ References

+ Details

Organization	12 Months Ended
Organization	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Note 1. Organization Description of the Business IGM Biosciences, Inc. (the Company) was incorporated in the state of Delaware in August 1993 under the name Palingen, Inc. and the name was subsequently changed to IGM Biosciences, Inc. in 2010. The Company’s headquarters are in Mountain View, California. IGM Biosciences, Inc. is a biotechnology company engaged in the development of IgM antibody therapeutics for the treatment of cancer and autoimmune and inflammatory diseases. Basis of Presentation These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP), as defined by the Financial Accounting Standards Board (FASB) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. All U.S. dollar (USD) amounts presented, except per share amounts, are stated in thousands, unless otherwise indicated. Liquidity The Company has incurred net operating losses and negative cash flows from operations since its inception and had an accumulated deficit of $821.2 million as of December 31, 2023. As of December 31, 2023, the Company had cash, cash equivalents, and marketable securities of $337.7 million. Management believes that the existing financial resources are sufficient to continue operating activities at least one year past the issuance date of these consolidated financial statements. The Company has historically financed its operations primarily through the sale of common stock and pre-funded warrants in its public offerings and private placement, the sale of convertible preferred stock and issuance of unsecured promissory notes in private placements, and funding received from our collaboration partners. To date, none of the Company’s product candidates have been approved for sale, and the Company has not generated any product revenue since inception. Management expects operating losses to continue and increase for the foreseeable future, as the Company progresses its planned research and development activities for its product candidates. The Company’s prospects are subject to risks, expenses and uncertainties frequently encountered by companies in the biotechnology industry as discussed below. While the Company has been able to raise multiple rounds of financing, there can be no assurance that in the event the Company requires additional financing, such financing will be available on terms which are favorable or at all. Failure to raise sufficient capital when needed or generate sufficient cash flow from operations would impact the ability to pursue business strategies and could require the Company to delay, scale back or discontinue one or more product development programs, or other aspects of the Company's business objectives.

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax [Line Items]
Income tax expense	$ 678	$ 0	$ 0
Increase in valuation allowance amount	$ 78,300	68,800
Operating loss carryforwards limitations on use, percentage of taxable income	80.00%
Research and development credits	$ 44,201	30,208
Interest or penalties charged in relation to unrecognized tax benefits	0
Income tax provision	$ 700	$ 0	$ 0
Effective income tax rate	(0.30%)	0.00%	0.00%
SanofiAgreement [Member]
Income Tax [Line Items]
Revenue Transaction Price	$ 150,000	$ 150,000
Federal
Income Tax [Line Items]
Operating loss carryforwards	$ 207,600
Federal credit carryforwards expiration period	2038
Research and development credits	$ 37,700
California
Income Tax [Line Items]
Operating loss carryforwards	423,800
Research and development credits	$ 20,100

Stock-Based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

Note 10. Stock-Based Compensation

2010 Stock Plan (as Amended and Restated)

The 2010 Stock Plan (the 2010 Plan) was originally adopted by the Company’s Board of Directors and approved by the Company’s stockholders in November 2010. The 2010 Plan was amended and restated in December 2017 and April 2019. The 2010 Plan allowed the Company to provide incentive stock options, within the meaning of Section 422 of the Code, nonstatutory stock options and stock purchase rights to eligible employees, consultants and directors and any parent or subsidiary of the Company. The 2010 Plan was terminated in 2019 and the Company will not grant any additional awards under the 2010 Plan. However, the 2010 Plan will continue to govern the terms and conditions of the outstanding awards previously granted under the 2010 Plan.

2018 Omnibus Incentive Plan (as Amended and Restated)

In September 2019, the Company adopted an amendment and restatement of the 2018 Omnibus Incentive Plan (the 2018 Plan) which provides for the grant of incentive stock options, within the meaning of Section 422 of the Code to employees, and for the grant of nonstatutory stock options, restricted stock, restricted stock units (RSUs), stock appreciation rights, performance units, and performance shares to employees, directors, and consultants of the Company.

Options granted under the 2018 Plan expire no later than 10 years from the date of grant. The exercise price of options granted under the 2018 Plan must at least be equal to the fair market value of the Company’s common stock on the date of grant. With respect to any participant who owns more than 10% of the voting power of all classes of the Company’s outstanding stock, the term of an incentive stock option granted to such participant must not exceed five years and the exercise price must equal at least 110% of the fair market value on the grant date. Employee stock options generally vest over a four year period.

Awards granted under the 2018 Plan expire no later than 10 years from the date of the grant. Awards outstanding as of December 31, 2023 vest over four years.

Subject to an annual evergreen increase and adjustment in the case of certain capitalization events, the Company initially reserved 4,384,000 shares of the Company’s common stock for issuance pursuant to awards under the 2018 Plan. The 2018 Plan is administered by the Compensation Committee of the Company’s Board of Directors. The number of shares of the Company’s common stock available for issuance under the 2018 Plan will also include an annual increase on the first day of each fiscal year beginning with the 2020 fiscal year, equal to the least of (i) 8,768,800 shares, (ii) 4% of the Company’s common stock and non-voting common stock outstanding at December 31 of the immediately preceding year, or (iii) such number of shares as determined by the Company’s Board of Directors. On June 23, 2023, the Company’s stockholders approved an amendment and restatement to the 2018 Plan, which provided for an increase in the number of shares of common stock reserved for issuance thereunder by 2,160,000 shares.

As of December 31, 2023, 3,536,312 shares of common stock remained available for issuance under the 2018 Plan. Effective January 1, 2024, the number of shares of common stock available under the 2018 Plan increased by 2,347,245 shares to 5,883,557 shares pursuant to the evergreen provision of the 2018 Plan.

2019 Employee Stock Purchase Plan

The 2019 Employee Stock Purchase Plan (the ESPP) became effective in September 2019. The ESPP is intended to have two components: a component that is intended to qualify as an “employee stock purchase plan” under Section 423 of the Code (the 423 Component) and a component that is not intended to qualify (the Non-423 Component). The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation. At the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock at the beginning of the offering period or at the end of each applicable purchase period.

Subject to adjustment in the case of certain capitalization events, a total of 280,000 common shares of the Company were available for purchase at adoption of the ESPP. Pursuant to the ESPP, the annual share increase pursuant to the evergreen provision is determined based on the least of (i) 560,000 shares, (ii) 1% of the Company’s common stock and non-voting common stock outstanding at December 31 of the immediately preceding year, or (iii) such number of shares as determined by the Company’s Board of Directors.

As of December 31, 2023, 1,376,988 shares of common stock remained available for issuance under the ESPP. Effective January 1, 2024, the number of shares of common stock available under the ESPP increased by 560,000 shares to 1,936,988 shares pursuant to the evergreen provision of the ESPP.

Stock Options

The following table summarizes stock option activity:


	Shares Issuable Under Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2022		5,802,317		$	31.59		7.9	$	17,428
Granted		1,835,018		$	13.83
Exercised		(77,762	)	$	1.56
Forfeited		(793,233	)	$	25.73
Outstanding as of December 31, 2023		6,766,340		$	27.81		7.0	$	6,823
Options exercisable as of December 31, 2023		4,055,579		$	30.14		5.9	$	6,697

Stock-Based Compensation Expense

Stock-based compensation expense recorded related to the 2010 Plan, 2018 Plan, and ESPP was recorded in the statements of operations and allocated as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Research and development	$	27,499	$	25,620	$	12,264
General and administrative		19,048		19,090		13,609
Total stock-based compensation expense	$	46,547	$	44,710	$	25,873

As of December 31, 2023, the Company had a total of $45.7 million of unrecognized stock-based compensation expense for options outstanding, which is expected to be recognized over a weighted-average period of 2.4 years.

The aggregate intrinsic value of options exercised for the years ended December 31, 2023, 2022, and 2021 was $0.9 million, $4.6 million, and $32.3 million, respectively. Intrinsic values of options exercised are calculated as the difference between the exercise price of the underlying options and the fair value of the common stock on the date of exercise. Intrinsic values of options outstanding are calculated as the difference between the exercise price of the underlying options and the fair value of the common stock as of the reporting date.

For the years ended December 31, 2023, 2022, and 2021, the weighted-average grant date fair value of options granted was $10.62, $13.31, and $56.44, respectively.

In determining the fair value of the stock-based awards, the Company uses the Black-Scholes option-pricing model and assumptions discussed below. Each of these inputs is subjective and generally requires judgment to determine.

Expected Term

The Company’s expected term represents the period that the Company’s stock-based awards are expected to be outstanding and is determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term). The Company utilizes this method due to lack of historical exercise data and the plain-vanilla nature of the Company’s stock-based awards.

Expected Volatility

Since the Company was privately held through September 2019, it alone does not have the relevant company-specific historical data to support its expected volatility. As such, the Company has used an average of expected volatilities based on the volatilities of a representative group of publicly traded biopharmaceutical companies over a period equal to the expected term of the stock option grants. Subsequent to the Company’s initial public offering, it began to consider the Company’s own historic volatility. However, due to its limited history as a public company, the Company still uses peer company data to assist in this analysis. For purposes of identifying comparable companies, the Company selected companies with comparable characteristics to it, including enterprise value, risk profiles, position within the industry, and with historical share price information sufficient to meet the expected life of the stock-based awards. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. The Company intends to consistently apply this process using the same or similar comparable entities until a sufficient amount of historical information regarding the volatility of the Company’s own share price becomes available.

Risk-Free Interest Rate

The risk-free interest rate is based on the Treasury Constant Maturities as provided by the Federal Reserve in effect at the time of grant for periods corresponding with the expected term of option.

Expected Dividend

The Company has never paid dividends on its common stock and has no plans to pay dividends on its common stock. Therefore, the Company used an expected dividend yield of zero.

The fair value of employee stock options granted under the 2018 Plan and the shares available for purchase under the ESPP were determined using the Black-Scholes option-pricing model. The following summarizes the weighted-average assumptions used in calculating the fair value of the awards:


	Year Ended December 31,
	2023			2022			2021
2018 Plan
Expected term (in years)		6.0			6.0			6.0
Expected volatility		92.3	%		87.1	%		87.5	%
Risk-free interest rate		3.5	%		2.3	%		0.9	%
Expected dividend yield		—			—			—
ESPP
Expected term (in years)		0.5			0.5			0.5
Expected volatility		46.7	%		54.4	%		60.0	%
Risk-free interest rate		5.4	%		3.5	%		0.1	%
Expected dividend yield		—			—			—

Restricted Stock Units (RSUs)

The following table summarizes restricted stock unit activity:


	Shares			Weighted- Average Grant Date Fair Value
Unvested restricted stock units as of December 31, 2022		401,180		$	33.85
Granted		761,517		$	12.36
Vested		(358,184	)	$	32.32
Forfeited		(145,721	)	$	16.07
Unvested restricted stock units as of December 31, 2023		658,792		$	13.77

As of December 31, 2023, the Company had a total of $7.1 million of unrecognized stock-based compensation expense for restricted stock unit awards, which is expected to be recognized over a weighted-average period of 3.0 years.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2023
Accounting Policies [Abstract]
Description of the Business	Description of the Business IGM Biosciences, Inc. (the Company) was incorporated in the state of Delaware in August 1993 under the name Palingen, Inc. and the name was subsequently changed to IGM Biosciences, Inc. in 2010. The Company’s headquarters are in Mountain View, California. IGM Biosciences, Inc. is a biotechnology company engaged in the development of IgM antibody therapeutics for the treatment of cancer and autoimmune and inflammatory diseases.
Basis of Presentation	Basis of Presentation These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP), as defined by the Financial Accounting Standards Board (FASB) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. All U.S. dollar (USD) amounts presented, except per share amounts, are stated in thousands, unless otherwise indicated.
Liquidity	Liquidity The Company has incurred net operating losses and negative cash flows from operations since its inception and had an accumulated deficit of $821.2 million as of December 31, 2023. As of December 31, 2023, the Company had cash, cash equivalents, and marketable securities of $337.7 million. Management believes that the existing financial resources are sufficient to continue operating activities at least one year past the issuance date of these consolidated financial statements. The Company has historically financed its operations primarily through the sale of common stock and pre-funded warrants in its public offerings and private placement, the sale of convertible preferred stock and issuance of unsecured promissory notes in private placements, and funding received from our collaboration partners. To date, none of the Company’s product candidates have been approved for sale, and the Company has not generated any product revenue since inception. Management expects operating losses to continue and increase for the foreseeable future, as the Company progresses its planned research and development activities for its product candidates. The Company’s prospects are subject to risks, expenses and uncertainties frequently encountered by companies in the biotechnology industry as discussed below. While the Company has been able to raise multiple rounds of financing, there can be no assurance that in the event the Company requires additional financing, such financing will be available on terms which are favorable or at all. Failure to raise sufficient capital when needed or generate sufficient cash flow from operations would impact the ability to pursue business strategies and could require the Company to delay, scale back or discontinue one or more product development programs, or other aspects of the Company's business objectives.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Such management estimates include, but are not limited to, those related to revenue recognition, marketable securities, manufacturing accruals, accrued research and development expenses, stock-based compensation, operating lease right-of-use (ROU) assets and liabilities, income tax uncertainties and the valuation of deferred tax assets. The Company bases its estimates on its historical experience and also on assumptions that it believes are reasonable; however, actual results could significantly differ from those estimates. The most significant estimates and assumptions that management considers in the preparation of our financial statements relate to revenue recognition, accrued research and development costs, and leases.
Segments	Segments The Company operates and manages its business as one reportable and operating segment, which is the business of developing engineered IgM antibodies for the treatment of cancer and autoimmune and inflammatory diseases. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for allocating and evaluating financial performance. All long-lived assets are maintained in, and all losses are attributable to, the United States of America.
Concentration of Credit Risk and Other Risks and Uncertainties	Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash, cash equivalents, and marketable securities. The Company invests in money market funds, U.S. treasury securities, corporate bonds, commercial paper, and U.S. government agency securities. The Company maintains bank deposits in federally insured financial institutions and these deposits may exceed federally insured limits. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents, and restricted cash, and bond issuers to the extent recorded on the balance sheets. The Company’s investment policy limits investments to high credit quality securities issued by the U.S. government and its agencies, highly rated banks, and corporate issuers, subject to certain concentration limits and restrictions on maturities. The Company has not experienced any material losses on its deposits of cash, cash equivalents, and marketable securities. The Company’s future results of operations involve a number of other risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, the Company’s early stages of clinical drug development; uncertainties related to the use of engineered IgM antibodies, which is a novel and unproven therapeutic approach; the Company’s ability to advance product candidates into, and successfully complete, clinical trials on the timelines it projects; the Company’s ability to adequately demonstrate sufficient safety and efficacy of its product candidates; the Company’s ability to enroll patients in its ongoing and future clinical trials; the Company’s ability to successfully manufacture and supply its product candidates for clinical trials; the occurrence of any event or circumstance that could give rise to the termination of the Company’s collaborations with third parties; the Company’s ability to obtain additional capital to finance its operations; uncertainties related to the projections of the size of patient populations suffering from the diseases the Company is targeting; the Company’s ability to obtain, maintain, and protect its intellectual property rights; developments relating to the Company’s competitors and its industry, including competing product candidates and therapies; general economic and market conditions; and other risks and uncertainties, including those more fully described in the “Risk Factors” section of this Annual Report on Form 10-K. The Company’s product candidates will require approvals from the U.S. Food and Drug Administration (FDA) and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash and cash equivalents. Cash equivalents consist primarily of amounts invested in money market funds, commercial paper, U.S. treasury securities, and U.S. government agency securities and are stated at fair value. Restricted cash consists of the remaining unused portion of a grant received from a non-profit organization which the Company will continue to utilize as it incurs expenses for services performed under the grant agreement.
Marketable Securities	Marketable Securities The Company’s marketable securities have been classified and accounted for as available-for-sale securities. Fixed income securities consist of U.S. treasury securities, U.S. government agency securities, corporate bonds, and commercial paper. The specific identification method is used to determine the cost basis of fixed income securities sold. These securities are recorded on the consolidated balance sheets at fair value. Unrealized gains and losses on these securities are included as a separate component of accumulated other comprehensive loss. The cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in other income (expense). All available-for-sale securities are considered available to support current operations and are classified as current assets. The Company presents any credit losses identified as an allowance rather than as a reduction in the amortized cost of the available-for-sale securities. For available-for-sale debt securities in an unrealized loss position, the Company first assesses whether it intends to sell, or it is more likely than not that it will be required to sell the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value and recognized in other income (expense) in the statements of operations. If neither criteria is met, the Company evaluates whether the decline in fair value is related to credit-related factors or other factors. In making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and adverse conditions specifically related to the security, among other factors. Credit-related impairment losses, limited by the amount that the fair value is less than the amortized cost basis, are recorded through an allowance for credit losses in other income (expense). Any unrealized losses from declines in fair value below the amortized cost basis as a result of non-credit factors are recognized in accumulated other comprehensive income (loss), net of tax as a separate component of stockholders’ equity, along with unrealized gains. Realized gains and losses and declines in fair value, if any, on available-for-sale securities are included in other income (expense) in the statement operations. For purposes of identifying and measuring credit-related impairments, the Company’s policy is to exclude applicable accrued interest from both the fair value and amortized cost basis of the related security. The Company has elected to write-off uncollectible accrued interest receivable balances in a timely manner, which is defined by the Company as when interest due becomes 90 days delinquent. The accrued interest write-off will be recorded by reversing interest income. Accrued interest receivable is recorded to prepaid expenses and other current assets on the consolidated balance sheets.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is determined using the straight-line method over the estimated useful lives of the respective assets, generally three to five years. Leasehold improvements are depreciated using the straight-line method over the shorter of the lease term or the estimated useful economic lives of the related assets. Assets are held in construction in progress until placed in service, upon which date, we begin to depreciate these assets. Upon retirement or sale of the assets, the cost and related accumulated depreciation and amortization are removed from the balance sheets and the resulting gain or loss are recorded to the statements of operations. Repairs and maintenance are charged to the consolidated statements of operations as incurred.
Leases	Leases The Company determines if an arrangement is a lease at inception. In addition, the Company determines whether leases meet the classification criteria of a finance or operating lease at the lease commencement date considering: (1) whether the lease transfers ownership of the underlying asset to the lessee at the end of the lease term, (2) whether the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise, (3) whether the lease term is for a major part of the remaining economic life of the underlying asset, (4) whether the present value of the sum of the lease payments and residual value guaranteed by the lessee equals or exceeds substantially all of the fair value of the underlying asset, and (5) whether the underlying asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. As of December 31, 2023, the Company's lease population consisted of real estate leases and the Company did not have finance leases. Operating leases are included in operating lease ROU assets and lease liabilities in the Company’s consolidated balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the present value of lease payments, the Company uses its incremental borrowing rate based on the information available at the lease commencement date if the rate implicit in the lease is not readily determinable. The Company determines the incremental borrowing rate based on an analysis of corporate bond yields with a credit rating similar to the Company. The determination of the Company’s incremental borrowing rate requires management judgment including the development of a synthetic credit rating and cost of debt as the Company currently does not carry any debt. The Company believes that the estimates used in determining the incremental borrowing rate are reasonable based upon current facts and circumstances. Applying different judgments to the same facts and circumstances could result in the estimated amounts to vary. The operating lease ROU assets also include adjustments for prepayments and accrued lease payments and exclude lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options. Operating lease cost is recognized on a straight-line basis over the expected lease term. Variable lease costs represent payments that are dependent on usage, a rate or index. Variable lease cost primarily relates to common area maintenance charges. Lease agreements that include lease and non-lease components are accounted for as a single lease component. Lease agreements with a noncancelable term of less than 12 months are not recorded on the Company’s consolidated balance sheets.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company evaluates the carrying amount of its long-lived assets, such as property and equipment, whenever events or changes in circumstances indicate that the assets may not be recoverable. An impairment loss would be recognized when estimated future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount of the asset. During the year ended December 31, 2023, there were impairments on long-lived assets of $0.3 million related to leasehold improvements. There was no impairment of long-lived assets during the years ended December 31, 2022 and 2021.
Fair Value Measurement	Fair Value Measurement The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements on a recurring basis. Fair value is 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, a three-tier fair value hierarchy has been established, which prioritizes the inputs used in measuring fair value as follows: Level 1—Observable inputs, such as quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2—Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Unobservable inputs which reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. In determining fair value, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible as well as considers counterparty credit risk in its assessment of fair value. Financial instruments classified within Level 2 of the fair value hierarchy are valued based on other observable inputs, including broker or dealer quotations or alternative pricing sources. When quoted prices in active markets for identical assets or liabilities are not available, the Company relies on non-binding quotes from its investment managers, which are based on proprietary valuation models of independent pricing services. These models generally use inputs such as observable market data, quoted market prices for similar instruments, or historical pricing trends of a security relative to its peers.
Revenue Recognition	Revenue Recognition For arrangements or transactions between participants determined to be within the scope of Accounting Standard Codification (ASC) Topic 606, “Revenue from Contracts with Customers” (Topic 606) the Company performs the following steps to determine the appropriate amount of revenue to be recognized as the Company fulfills its obligations: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company has entered into and may enter into additional collaboration agreements in the future under which it may obtain upfront payments, milestone payments, royalty payments, profit sharing, and other fees. Promises under these arrangements may include intellectual property licenses, research and development services, and the participation in joint committees. At contract inception, the Company assesses the goods or services promised and enforceable in a contract with a customer and identifies those distinct goods and services that represent a performance obligation. In assessing whether a promised good or service is distinct, and therefore a performance obligation, the Company considers factors such as the nature of the research, stage of development of the targets, manufacturing and commercialization capabilities of the customer and the availability of the associated expertise in the general marketplace. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, the Company combines that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct. Promised goods and services that are not material in the context of the contract are not considered performance obligations. Additional goods or services that are exercisable at a customer’s discretion, including substitution rights, are assessed to determine if they provide a material right to the customer and if so, they are considered performance obligations. The transaction price is the amount of consideration to which the Company expects to be entitled in exchange for transferring promised goods or services to a customer. The consideration promised in a contract with a customer may include fixed amounts, variable amounts, or both. Non-refundable upfront payments are considered fixed consideration and included in the transaction price. If an arrangement includes development, regulatory or commercial milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. The Company includes the amount of estimated variable consideration, including milestones, in the transaction price to the extent that it is probable that a significant reversal of cumulative revenue recognized will not occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and if the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied. If it is determined that multiple performance obligations exist, the transaction price is allocated at the inception of the agreement to all identified performance obligations based on the relative standalone selling prices (SSP), unless the consideration is variable and meets the criteria to be allocated entirely to one or more, but not all, performance obligations in the contract. The relative SSP for each deliverable is estimated using objective evidence if it is available. If SSP is not directly observable the Company estimates the SSP at an amount that would result in the allocation of the transaction price in an amount that depicts the amount of consideration to which the entity expects to be entitled in exchange for transferring the promised goods or services to the customer, using methods such as the expected cost plus margin approach. Once the transaction price has been allocated to a performance obligation using the applicable methodology, it is not subject to reassessment for subsequent changes in standalone selling prices. Collaboration revenue is recognized when, or as, the Company satisfies a performance obligation. The Company recognizes revenue over time by measuring the progress toward complete satisfaction of the relevant performance obligation using an appropriate input method based on the nature of the good or service promised to the customer. After contract inception, the transaction price is reassessed at every period end and updated for changes such as resolution of uncertain events. Management may be required to exercise considerable judgment in estimating revenue to be recognized. Judgment is required in identifying performance obligations, estimating the transaction price, including variable consideration, estimating the standalone selling prices of identified performance obligations, and applying the input method for revenue recognition, including the estimated budgets for each performance obligation. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. If the related performance obligation is expected to be satisfied within the next twelve months this will be classified in current liabilities. Amounts recognized as revenue prior to receipt are recorded as contract assets in the Company’s consolidated balance sheets. If the Company expects to have an unconditional right to receive consideration in the next twelve months, this will be classified in current assets. A net contract asset or liability is presented for each contract with a customer.
Collaborative Arrangements	Collaborative Arrangements The Company analyzes its agreements to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and therefore within the scope of ASC Topic 808, Collaborative Arrangements (Topic 808). These assessments are performed throughout the life of the arrangements based on changes in the responsibilities of all parties in the arrangement.
Research and Development Expenses	Research and Development Expenses The Company expenses research and development costs as they are incurred. Research and development expenses consist primarily of: (i) personnel-related expenses, including salaries, benefits and stock-based compensation expense, for personnel in the Company’s research and development functions; (ii) fees paid to third parties such as contractors, consultants and contract research organizations (CROs) for conducting clinical trials, and other costs related to clinical and preclinical testing; (iii) costs related to acquiring and manufacturing research and clinical trial materials, including under agreements with third parties such as contract manufacturing organizations (CMOs), and other vendors; (iv) costs related to the preparation of regulatory submissions; (v) expenses related to laboratory supplies and services; (vi) fees under license agreements where no alternative future use exists; and (vii) depreciation of equipment and facilities expenses.
Accrued Research and Development Expenses	Accrued Research and Development Expenses The Company records accruals for estimated costs of research, preclinical studies, clinical trials, and manufacturing, which are significant components of research and development expenses. A substantial portion of the Company’s ongoing research and development activities is conducted by third-party service providers, CROs and CMOs. The Company’s contracts with CROs generally include pass-through fees such as laboratory supplies and services, regulatory expenses, investigator fees, travel costs and other miscellaneous costs, including shipping and printing fees. The Company’s contracts with the CMOs generally include fees such as initiation fees, reservation fees, verification run costs, materials and reagents expenses, taxes, etc. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company accrues the costs incurred under agreements with these third parties based on estimates of actual work completed in accordance with the respective agreements. The Company determines the estimated costs through discussions with internal personnel and external service providers as to the progress, or stage of completion or actual timeline (start-date and end-date) of the services and the agreed-upon fees to be paid for such services. In the event the Company makes advance payments, the payments are recorded as a prepaid expense and recognized as the services are performed. As actual costs become known, the Company adjusts its accruals. Although the Company does not expect its estimates to be materially different from amounts actually incurred, such estimates for the status and timing of services performed relative to the actual status and timing of services performed may vary and could result in the Company reporting amounts that are too high or too low in any particular period. The Company’s accrual is dependent, in part, upon the receipt of timely and accurate reporting from CROs and other third-party vendors. Variations in the assumptions used to estimate accruals including, but not limited to, the number of patients enrolled, the rate of patient enrollment and the actual services performed, may vary from the Company’s estimates, resulting in adjustments to clinical trial expenses in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect its financial condition and results of operations. Through December 31, 2023, there have been no material differences from the Company’s estimated accrued research and development expenses to actual expenses.
Acquired In-Process Research and Development Expenses	Acquired In-Process Research and Development Expenses The Company has entered into agreements (see Note 7 – License Agreements) with third parties to acquire the rights to develop and potentially commercialize certain products. Such agreements generally require an initial payment by the Company when the contract is executed. The purchase of license rights for use in research and development activities, including product development, are expensed as incurred and are classified as research and development expense. Additionally, the Company may be obligated to make future royalty payments in the event the Company commercializes the technology and achieves a certain sales volume. In accordance with ASC Topic 730, Research and Development (Topic 730), expenditures for research and development, including upfront licensing fees and milestone payments associated with products not yet been approved by the FDA, are charged to research and development expense as incurred. Future contract milestone and/or royalty payments will be recognized as expense after the achievement of the milestone and the corresponding milestone payment is legally due.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation by measuring and recognizing compensation expense for all share-based awards made to employees, non-employees and directors based on estimated grant-date fair values. The Company uses the straight-line method to allocate compensation cost to reporting periods over the requisite service period, which is generally the vesting period. The grant date fair value of restricted stock units is estimated based on the closing stock price of the Company’s common stock on the date of grant. The grant date fair value of stock options granted to employees and directors is estimated using the Black-Scholes option-pricing model. The Company accounts for forfeitures as they occur. The fair value of each purchase right under the employee stock purchase plan (ESPP) is estimated at the beginning of the offering period using the Black-Scholes option pricing model and recorded as expense over the service period using the straight-line method.
Income Taxes	Income Taxes The Company accounts for income taxes using the liability method, whereby deferred tax asset and liability account balances are determined based on differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company provides a valuation allowance when it is more likely than not that some portion, or all of the Company’s deferred tax assets will not be realized. The Company accounts for income tax contingencies using a benefit recognition model. If it considers that a tax position is more likely than not to be sustained upon audit, based solely on the technical merits of the position, it recognizes the benefit. The Company measures the benefit by determining the amount that is greater than 50% likely of being realized upon settlement, presuming that the tax position is examined by the appropriate taxing authority that has full knowledge of all relevant information. The Company is subject to taxation in the United States federal jurisdiction, and various state jurisdictions. Due to the Company’s net operating loss carryforwards, the Company's income tax returns remain subject to examination by federal and state tax authorities for all tax years. The Company’s policy is to recognize interest expense and penalties related to income tax matters as a component of income tax expense. As of December 31, 2023, there were no significant accruals for interest related to unrecognized tax benefits or tax penalties.
Comprehensive Loss	Comprehensive Loss Comprehensive loss represents the net loss for the period and other comprehensive loss. Other comprehensive loss reflects certain gains and losses that are recorded as a component of stockholders’ equity and are not reflected in the consolidated statements of operations. The Company’s other comprehensive loss consists of changes in unrealized gains and losses on available-for-sale securities.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock (including non-voting common stock and pre-funded warrants) outstanding during the period, without consideration for all other common stock equivalents. Shares of common stock into which the pre-funded warrants may be exercised are considered outstanding for the purposes of computing net loss per share because the shares may be issued for little or no consideration, are fully vested, and are exercisable after the original issuance date. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the net loss for each period presented.
Reclassification	Reclassification Certain reclassifications have been made to prior period amounts to conform to current period presentation. These reclassifications did not have an impact on the Company’s results of operations or financial position as of December 31, 2023, 2022, and 2021.
Recently Adopted Accounting Standards and Accounting Pronouncements	Recently Issued Accounting Pronouncements In October 2023, the FASB issued ASU 2023-06, Disclosure Improvements - Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative, which will impact various disclosure areas. The amendments in ASU 2023-06 will be effective on the date the related disclosures are removed from Regulation S-X or Regulation S-K by the SEC, and will no longer be effective if the SEC has not removed the applicable disclosure requirement by June 30, 2027. The Company is currently evaluating the impacts of this standard on its related disclosures. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280), which improves reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. This ASU is effective for fiscal years beginning after December 15, 2023 and is applicable to public entities, including those that have a single reportable segment. Early adoption is permitted. The Company is currently evaluating the impacts of this standard on its consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures, which amends the guidance in ASC 740, Income Taxes. The ASU is intended to improve the transparency of income tax disclosures by requiring (1) consistent categories and greater disaggregation of information in the rate reconciliation and (2) income taxes paid disaggregated by jurisdiction. It also includes certain other amendments to improve the effectiveness of income tax disclosures. The ASU's amendments are effective for public business entities for annual periods beginning after December 15, 2024. Entities are permitted to early adopt the standard for annual financial statements that have not yet been issued or made available for issuance. Adoption is permitted either prospectively or retrospectively. The Company will adopt this ASU on a prospective basis. The Company is currently evaluating the impact of this standard but does not expect any material impacts on its consolidated financial statements and related disclosures. Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. This ASU also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. The Company adopted ASU 2016-13 on January 1, 2023, using the modified retrospective approach, and no cumulative effect adjustment to accumulated deficit was needed as of the adoption date. Additionally, no prior period amounts were adjusted. The adoption of ASU 2016-13 did not have a material impact on the Company’s consolidated financial statements and all current period amounts are reported under the Available-for-Sale Debt Securities Impairment Model (ASC 326-30).

Leases - Schedule of Maturities of Lease Liabilities (Details)
$ in Thousands

Dec. 31, 2023

USD ($)

Leases [Abstract]

$ 7,892

6,104

6,208

6,377

6,306

22,303

55,190

Less imputed interest

(12,333)

Less: tenant allowances

(2,351)

Total lease liabilities

$ 40,506

^[1]

[1]	The $9.0 million of future lease commitments for the laboratory lease that will not commence until September 2024 was not included in the lease liabilities balance as of December 31, 2023.

Restructuring Charges (Additional Information) (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Restructuring Cost and Reserve [Line Items]
Workforce Reduced, Percent	22.00%
Restructuring Charges		$ 1,826
Severance		3,732
Reversal of Stock-based Compensation Expense		(1,906)
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		3,732
Restructuring Reserve to be Paid within One Year	$ 2,400	$ 2,400

- 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

License Agreements

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

License Agreements

Note 7. License Agreements

The Company enters into arrangements to in-license research and development technology rights with third parties relating to its clinical and pre-clinical programs and product candidates. These arrangements may include non-refundable, upfront payments, payments for options to acquire additional rights relating to its product candidates, as well as contingent obligations for potential development, regulatory and commercial performance milestone payments, and royalty payments. The Company’s obligation to make payments for contingent obligations is contingent upon the respective milestones being achieved as well as its continued involvement in the programs and/or the lack of any adverse events which could cause the discontinuance of the programs. The activities under these license agreements are performed with no guarantee of either technological or commercial success.

During the years ended December 31, 2023, 2022, and 2021 the Company recorded $1.9 million, $3.3 million and $5.3 million, respectively, as research and development expense in our consolidated statements of operations related to license agreements.

As of December 31, 2023, the Company’s license agreements for technologies optioned by the Company, including the Medivir agreement described below, included potential future payments for development, regulatory, and sales milestones totaling approximately $361.9 million plus royalties on net sales that range from single digits to mid-teens. No milestones were achieved or deemed probable as of December 31, 2023.

Medivir Agreement

In January 2021, the Company entered into an exclusive license agreement with Medivir AB (Medivir) through which the Company received global, exclusive development and commercialization rights for birinapant, a clinical-stage Second Mitochondrial-derived Activator of Caspases (SMAC) mimetic. Under the terms of the agreement, the Company made an upfront payment of $1.0 million upon signing the agreement, and made an additional $1.5 million payment in November 2021 due to the Company's initiation of a Phase 1 clinical trial of aplitabart in combination with birinapant. Under the terms of the agreement, should birinapant be successfully developed and approved, the Company would be obligated to make additional milestone payments up to a total of approximately $348.5 million, plus tiered royalties from the mid-single digits up to mid-teens on net sales. No milestones were achieved or deemed probable as of December 31, 2023.

Stock-Based Compensation - Summary of Fair Value of Employee Stock Options and Employee Stock Purchase Plan Estimated Weighted-average Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
2018 Plan and 2010 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average fair value of share-based awards granted per share	$ 6	$ 6	$ 6
Expected volatility	92.30%	87.10%	87.50%
Risk-free interest rate	3.50%	2.30%	0.90%
Expected dividend yield	0.00%	0.00%	0.00%
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average fair value of share-based awards granted per share	$ 0.5	$ 0.5	$ 0.5
Expected volatility	46.70%	54.40%	60.00%
Risk-free interest rate	5.40%	3.50%	0.10%
Expected dividend yield	0.00%	0.00%	0.00%

- 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

Net Loss Per Share Attributable to Common Stockholders - Summary of Potentially Dilutive Securities Not Included in the Diluted Per Share Calculations (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	7,552,790	6,257,599
Employee Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	6,766,340	5,802,317
Estimated Shares Issuable Under The Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	127,658	54,102
Unvested Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	658,792	401,180

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of reportable segment \| Segment	1
Number of operating segment \| Segment	1
Impairment of long-lived assets \| $	$ 300	$ 0	$ 0
Interest or penalties charged in relation to unrecognized tax benefits \| $	$ 0
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life	3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life	5 years

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Details) - 2010 Plan, 2018 Plan and ESPP - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 46,547	$ 44,710	$ 25,873
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	27,499	25,620	12,264
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 19,048	$ 19,090	$ 13,609

Net Loss Per Share Attributable to Common Stockholders

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

Note 14. Net Loss Per Share Attributable to Common Stockholders

Basic and diluted net loss per share is computed by dividing net loss by the weighted-average number of common stock and pre-funded warrants outstanding for the period. Shares of common stock into which the pre-funded warrants may be exercised are considered outstanding for the purposes of computing net loss per share because the shares may be issued for little or no consideration, are fully vested, and are exercisable after the original issuance date. For periods in which the Company generated a net loss, the Company does not include the potential impact of dilutive securities in diluted net loss per share, as the impact of these items is anti-dilutive.

The following equity instruments were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented:


	December 31,
	2023		2022
Stock options		6,766,340		5,802,317
Estimated shares issuable under the employee stock purchase plan		127,658		54,102
Unvested restricted stock units		658,792		401,180
Total		7,552,790		6,257,599

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Common stock, shares authorized	1,200,000,000	1,200,000,000
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	200,000,000	200,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common Stock Class Undefined
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	33,180,749	29,394,436
Common stock, shares outstanding	33,180,749	29,394,436
Non-voting Common Stock
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	25,500,383	13,687,883
Common stock, shares outstanding	25,500,383	13,687,883

Document And Entity Information - USD ($) $ in Millions	12 Months Ended
Document And Entity Information - USD ($) $ in Millions	Dec. 31, 2023	Mar. 01, 2024	Jun. 30, 2023
Document And Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Registrant Name	IGM Biosciences, Inc.
Entity Central Index Key	0001496323
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 132.1
Entity Shell Company	false
Document Financial Statement Error Correction [Flag]	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	IGMS
Security Exchange Name	NASDAQ
Entity File Number	001-39045
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0349194
Entity Address, Address Line One	325 E. Middlefield Road
Entity Address, City or Town	Mountain View
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94043
City Area Code	650
Local Phone Number	965-7873
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Certain sections of the Registrant’s definitive Proxy Statement to be filed in connection with the Registrant’s 2022 Annual Meeting of Stockholders are incorporated by reference into Part III of this Annual Report on Form 10-K where indicated. Such definitive Proxy Statement will be filed with the Securities and Exchange Commission pursuant to Regulation 14A within 120 days of the Registrant’s fiscal year ended December 31, 2023.
Auditor Firm ID	34
Auditor Name	Deloitte & Touche LLP
Auditor Location	San Francisco, California
Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		33,286,205
Non-voting Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		25,500,383

Fair Value Measurement - Summary of Investments Measured and Recognized at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 331,714	$ 420,550
Gross Unrealized Gains	228	15
Gross Unrealized Losses	(77)	(716)
Fair Value	331,865	419,849
Financial Assets Included Within Cash and Cash Equivalents \| U.S. Treasury Securities \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	25,896
Financial assets included within cash and cash equivalents, Gross Unrealized Gains	2
Financial assets included within cash and cash equivalents, Gross Unrealized Losses	0
Financial assets included within cash and cash equivalents, Fair Value	25,898
Financial Assets Included Within Cash and Cash Equivalents \| Money Market Funds \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	21,458	26,718
Financial assets included within cash and cash equivalents, Gross Unrealized Gains	0	0
Financial assets included within cash and cash equivalents, Gross Unrealized Losses	0	0
Financial assets included within cash and cash equivalents, Fair Value	21,458	26,718
Financial Assets Included Within Cash and Cash Equivalents \| Commercial Paper \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	54,427	66,732
Financial assets included within cash and cash equivalents, Gross Unrealized Gains	0	0
Financial assets included within cash and cash equivalents, Gross Unrealized Losses	(27)	(16)
Financial assets included within cash and cash equivalents, Fair Value	54,400	66,716
Financial Assets Included Within Cash and Cash Equivalents \| U.S. Government Agency Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	4,951	20,477
Financial assets included within cash and cash equivalents, Gross Unrealized Gains	1	7
Financial assets included within cash and cash equivalents, Gross Unrealized Losses	0	0
Financial assets included within cash and cash equivalents, Fair Value	4,952	20,484
Financial Assets Included Within Marketable Securities Member \| U.S. Treasury Securities \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	182,289	127,234
Financial assets included within cash and cash equivalents, Gross Unrealized Gains	214	6
Financial assets included within cash and cash equivalents, Gross Unrealized Losses	(14)	(318)
Financial assets included within cash and cash equivalents, Fair Value	182,489	126,922
Financial Assets Included Within Marketable Securities Member \| Corporate Bonds \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	13,986	12,531
Financial assets included within cash and cash equivalents, Gross Unrealized Gains	0	2
Financial assets included within cash and cash equivalents, Gross Unrealized Losses	(8)	(3)
Financial assets included within cash and cash equivalents, Fair Value	13,978	12,530
Financial Assets Included Within Marketable Securities Member \| Commercial Paper \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	20,216	142,726
Financial assets included within cash and cash equivalents, Gross Unrealized Gains	0	0
Financial assets included within cash and cash equivalents, Gross Unrealized Losses	(17)	(195)
Financial assets included within cash and cash equivalents, Fair Value	20,199	142,531
Financial Assets Included Within Marketable Securities Member \| U.S. Government Agency Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	8,491	24,132
Financial assets included within cash and cash equivalents, Gross Unrealized Gains	11	0
Financial assets included within cash and cash equivalents, Gross Unrealized Losses	(11)	(184)
Financial assets included within cash and cash equivalents, Fair Value	$ 8,491	$ 23,948

Property, Plant and Equipment, Net

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment, Net

Note 4. Property, Plant and Equipment, Net

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


	December 31,
	2023			2022
Manufacturing and laboratory equipment	$	32,712		$	25,631
Office equipment		2,409			631
Leasehold improvements		17,912			14,433
Construction in progress		5,798			5,114
Total property, plant and equipment, gross		58,831			45,809
Less: Accumulated depreciation		(20,599	)		(12,325	)
Total property, plant and equipment, net	$	38,232		$	33,484

Depreciation expense was approximately $8.3 million, $6.1 million and $4.5 million for the years ended December 31, 2023, 2022 and 2021, respectively.

Sanofi Agreement - Schedule of Contract liabilities for the periods (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Sanofi Agreement [Abstract]
Deferred revenue Begining Balnce	$ 148,931	$ 0
Deferred Revenue, Additions	0	150,000
Deductions	(2,130)	(1,069)
Deferred revenue Ending Balance	$ 146,801	$ 148,931

Leases (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Summary of lease costs and cash paid for the Company's leases

The following table summarizes the lease costs and cash paid for the Company’s leases (in thousands):


	Year Ended December 31,
	2023		2022		2021
Cash paid for operating lease liabilities	$	8,100	$	5,548	$	3,819
Operating lease cost		8,250		6,217		4,137
Variable lease cost		1,084		592		307

The following table summarizes the weighted-average remaining lease term and discount rates for the Company’s leases:


	December 31,
	2023			2022
Lease term (in years)		8.1			8.8
Discount rate		6.5	%		6.3	%

Schedule of Maturities of Lease Liabilities

The maturities of the Company's lease liabilities as of December 31, 2023 were as follows (in thousands):


	Operating
	Lease
Years Ending December 31,	Commitments
2024	$	7,892
2025		6,104
2026		6,208
2027		6,377
2028		6,306
Thereafter		22,303
Total		55,190
Less: imputed interest		(12,333	)
Less: tenant allowances		(2,351	)
Total lease liabilities(1)	$	40,506

(1)

The $9.0 million of future lease commitments for the laboratory lease that will not commence until September 2024 was not included in the lease liabilities balance as of December 31, 2023.

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	$ (246,416)	$ (221,102)	$ (165,164)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	8,277	6,075	4,484
Stock-based compensation expense	46,547	44,710	25,873
Purchase net discount (premium) on marketable securities	9,481	7,368	(643)
Net (accretion of discounts) amortization of premiums on marketable securities	(9,140)	(2,713)	624
Non-cash lease expense	5,414	4,527	3,240
Other	299	112	157
Changes in assets and liabilities:
Prepaid expenses and other current assets	1,711	359	(3,298)
Other non-current assets	194	(967)	(488)
Accounts payable	(992)	(3,002)	652
Accrued liabilities	(3,214)	13,705	12,569
Lease liabilities, net	(2,262)	(3,856)	(2,988)
Deferred revenue	(2,130)	148,931	0
Net cash used in operating activities	(192,231)	(5,853)	(124,982)
Cash flows from investing activities:
Purchase of property, plant and equipment	(12,381)	(10,206)	(13,244)
Purchases of marketable securities	(365,039)	(540,022)	(128,705)
Proceeds from maturities of marketable securities	445,775	324,584	157,410
Net cash provided by (used in) investing activities	68,355	(225,644)	15,461
Cash flows from financing activities:
Payment of employee taxes and exercise costs for shares withheld	0	0	(1,555)
Proceeds from exercise of stock options	120	500	3,126
Proceeds from purchases under the employee stock purchase plan	1,384	895	905
Proceeds from issuance of common stock in public offering and private placement, net of offering costs	113,564	0	0
Proceeds from issuance of common stock in public offerings, net of offering costs	0	217,987	0
Net cash provided by financing activities	115,068	219,382	2,476
Net decrease in cash, cash equivalents and restricted cash	(8,808)	(12,115)	(107,045)
Cash, cash equivalents, and restricted cash Beginning of period	121,920	134,035	241,080
Cash, cash equivalents, and restricted cash, End of period	113,112	121,920	134,035
Cash and cash equivalents	112,520	121,231	133,334
Restricted cash	592	689	701
Cash, cash equivalents, and restricted cash	113,112	121,920	134,035
Supplemental cash flow data:
Cash paid for income taxes	625	0	0
Supplemental disclosure of non-cash investing and financing activities:
Right-of-use assets recognized in exchange for lease obligations	1,596	16,269	19,503
Unpaid amounts related to purchase of property, plant and equipment	$ 2,408	$ 1,465	$ 495

Fair Value Measurement

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurement

Note 3. Fair Value Measurement

The Company measures and reports certain financial instruments as assets and liabilities at fair value on a recurring basis. The following tables set forth the fair value of the Company’s financial assets, which consist of cash equivalents and marketable securities measured and recognized at fair value (in thousands):


		December 31, 2023
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	Level 1	$	21,458	$	—	$	—		$	21,458
U.S. treasury securities	Level 1		25,896		2		—			25,898
Commercial paper	Level 2		54,427		—		(27	)		54,400
U.S. government agency securities	Level 2		4,951		1		—			4,952
Marketable securities:
U.S. treasury securities	Level 1		182,289		214		(14	)		182,489
Corporate bonds	Level 2		13,986		—		(8	)		13,978
Commercial paper	Level 2		20,216		—		(17	)		20,199
U.S. government agency securities	Level 2		8,491		11		(11	)		8,491
Total		$	331,714	$	228	$	(77	)	$	331,865


		December 31, 2022
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	Level 1	$	26,718	$	—	$	—		$	26,718
Commercial paper	Level 2		66,732		—		(16	)		66,716
U.S. government agency securities	Level 2		20,477		7		—			20,484
Marketable securities:
U.S. treasury securities	Level 1		127,234		6		(318	)		126,922
Corporate bonds	Level 2		12,531		2		(3	)		12,530
Commercial paper	Level 2		142,726		—		(195	)		142,531
U.S. government agency securities	Level 2		24,132		—		(184	)		23,948
Total		$	420,550	$	15	$	(716	)	$	419,849

The Company evaluates transfers between levels at the end of each reporting period. There were no transfers between Levels 1, 2 and 3 during the years ended December 31, 2023 and 2022. As of December 31, 2023 and 2022, there were no financial instruments classified as Level 3.


	December 31, 2023
	Less than 12 months					Greater than 12 months				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. treasury securities	$	28,137	$	(14	)	$	—	$	—	$	28,137	$	(14	)
Corporate bonds		13,978		(8	)		—		—		13,978		(8	)
Commercial paper		74,599		(44	)		—		—		74,599		(44	)
U.S. government agency securities		4,771		(11	)		—		—		4,771		(11	)
Total	$	121,485	$	(77	)	$	—	$	—	$	121,485	$	(77	)


	December 31, 2022
	Less than 12 months					Greater than 12 months				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. treasury securities	$	99,870	$	(318	)	$	—	$	—	$	99,870	$	(318	)
Corporate bonds		2,848		(3	)		—		—		2,848		(3	)
Commercial paper		127,163		(211	)		—		—		127,163		(211	)
U.S. government agency securities		23,948		(184	)		—		—		23,948		(184	)
Total	$	253,829	$	(716	)	$	—	$	—	$	253,829	$	(716	)

As of December 31, 2023 and 2022, the Company held 35 and 69 debt securities, respectively, with an unrealized loss position. The Company evaluated its securities for credit losses and considered the decline in market value to be primarily attributable to current economic and market conditions and not to a credit loss or other factors. Additionally, the Company does not intend to sell the securities in an unrealized loss position and does not expect it will be required to sell the securities before recovery of the unamortized cost basis. As of December 31, 2023 and 2022, an allowance for credit losses has not been recognized. Given the Company's intent and ability to hold such securities until recovery, and the lack of significant change in credit risk of these investments, it does not consider these marketable securities impaired as of December 31, 2023 and 2022.

There were no realized gains or losses on marketable securities for years ended December 31, 2023 and 2022. Interest on marketable securities is included in interest income. As of December 31, 2023 and 2022, the Company had accrued interest receivable of $0.8 million and $0.5 million, respectively, which was included in prepaid expenses and other current assets on the consolidated balance sheets.

The following table summarizes the contractual maturities of the Company’s cash equivalents and marketable securities as of December 31, 2023 and 2022 at estimated fair value (in thousands):


	December 31,
	2023		2022
Due in less than one year	$	312,554	$	419,849
Due in more than one year		19,311		—
Total	$	331,865	$	419,849

- 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

Accrued Liabilities (Tables)

12 Months Ended

Dec. 31, 2023

Balance Sheet Related Disclosures [Abstract]

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):


	December 31,
	2023		2022
Accrued research and development materials and services	$	14,625	$	20,747
Accrued professional services		3,147		1,759
Accrued compensation		13,527		10,920
Other		245		195
Total accrued liabilities	$	31,544	$	33,621

Restructuring Charges - Summary of Charges Related to Restructuring Activities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Restructuring Cost and Reserve [Line Items]
Severance and Related Compensation	$ 3,732
Incentive and Stock-Based Compensation	(1,906)
Restructuring Charges, Total	1,826
Research and Development
Restructuring Cost and Reserve [Line Items]
Severance and Related Compensation	3,260
Incentive and Stock-Based Compensation	(1,531)
Restructuring Charges, Total	1,729
General and Administrative
Restructuring Cost and Reserve [Line Items]
Severance and Related Compensation	472
Incentive and Stock-Based Compensation	(375)
Restructuring Charges, Total	$ 97

- 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

Leases - Schedule of Maturities of Lease Liabilities (Parenthetical) (Details)
$ in Thousands

Dec. 31, 2023

USD ($)

Lessee, Lease, Description [Line Items]

Future lease commitments

$ 40,506

^[1]

Laboratory [Member]

Lessee, Lease, Description [Line Items]

Future lease commitments

$ 9,000

[1]	The $9.0 million of future lease commitments for the laboratory lease that will not commence until September 2024 was not included in the lease liabilities balance as of December 31, 2023.

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2023

Stockholders' Equity Note [Abstract]

Schedule of Number of Common Stock Reserved for Future Issuance

The Company had reserved common stock, on an as-converted basis, for future issuance as follows:


	December 31,
	2023		2022
Stock options, issued and outstanding		6,766,340		5,802,317
Restricted stock units		658,792		401,180
Stock options and restricted stock units, future issuance		3,536,312		1,310,601
Employee stock purchase plan, available for future grants		1,376,988		1,109,032
Pre-funded warrants		1,334,332		1,334,332
Total		13,672,764		9,957,462

Defined Contribution Plan

12 Months Ended

Dec. 31, 2023

Retirement Benefits [Abstract]

Defined Contribution Plan

Note 11. Defined Contribution Plan

The Company sponsors a 401(k) retirement plan for its employees. This plan provides for tax-deferred salary deductions for all employees. Employee contributions are voluntary. Employees may contribute up to 100% of their annual compensation to this plan, as limited by an annual maximum amount as determined by the IRS. During the year ended December 31, 2023, the Company provided $1.8 million in matching contributions to the 401(k) plan. There were no matching contributions in the years ended December 31, 2022 and 2021.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 70
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480794/715-70-50-1

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480482/715-20-55-17

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(03)
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-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (q)
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-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1
-Subparagraph (l)
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-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//715/tableOfContent

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 1
-Subparagraph (o)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480126/715-20-S99-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 60
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480266/715-60-50-3

+ Details

License Agreements - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment based on achievement of specified development	$ 0
Research and Development Expenses
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized	1,900	$ 3,300	$ 5,300
License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment based on achievement of specified development	361,900
License Agreement \| Medivir AB
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional milestone payment				$ 1,500
Milestone payment based on achievement of specified development	$ 0
Upfront payment				1,000
License Agreement \| Medivir AB \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment based on achievement of specified development				$ 348,500

Stockholders' Equity - Schedule of Number of Common Stock Reserved for Future Issuance (Details) - shares	Dec. 31, 2023	Dec. 31, 2022
Stockholders' Equity Note [Abstract]
Stock options, issued and outstanding	6,766,340	5,802,317
Restricted stock units	658,792	401,180
Stock options and restricted stock units, future issuance	3,536,312	1,310,601
Employee stock purchase plan, available for future grants	1,376,988	1,109,032
Pre-funded warrants	1,334,332	1,334,332
Total	13,672,764	9,957,462

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of Stock-Based Compensation Expense

Stock-based compensation expense recorded related to the 2010 Plan, 2018 Plan, and ESPP was recorded in the statements of operations and allocated as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Research and development	$	27,499	$	25,620	$	12,264
General and administrative		19,048		19,090		13,609
Total stock-based compensation expense	$	46,547	$	44,710	$	25,873

Summary of Stock Option

The following table summarizes stock option activity:


	Shares Issuable Under Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2022		5,802,317		$	31.59		7.9	$	17,428
Granted		1,835,018		$	13.83
Exercised		(77,762	)	$	1.56
Forfeited		(793,233	)	$	25.73
Outstanding as of December 31, 2023		6,766,340		$	27.81		7.0	$	6,823
Options exercisable as of December 31, 2023		4,055,579		$	30.14		5.9	$	6,697

Summary of Fair Value of Employee Stock Options and Employee Stock Purchase Plan Estimated Weighted-average Assumptions


	Year Ended December 31,
	2023			2022			2021
2018 Plan
Expected term (in years)		6.0			6.0			6.0
Expected volatility		92.3	%		87.1	%		87.5	%
Risk-free interest rate		3.5	%		2.3	%		0.9	%
Expected dividend yield		—			—			—
ESPP
Expected term (in years)		0.5			0.5			0.5
Expected volatility		46.7	%		54.4	%		60.0	%
Risk-free interest rate		5.4	%		3.5	%		0.1	%
Expected dividend yield		—			—			—

Summary of Restricted Stock Unit Activity

The following table summarizes restricted stock unit activity:


	Shares			Weighted- Average Grant Date Fair Value
Unvested restricted stock units as of December 31, 2022		401,180		$	33.85
Granted		761,517		$	12.36
Vested		(358,184	)	$	32.32
Forfeited		(145,721	)	$	16.07
Unvested restricted stock units as of December 31, 2023		658,792		$	13.77

Property, Plant and Equipment, Net - Schedule of Property, Plant and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	$ 58,831	$ 45,809
Less: Accumulated depreciation	(20,599)	(12,325)
Total property, plant and equipment, net	38,232	33,484
Manufacturing and Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	32,712	25,631
Office Equipment
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	2,409	631
Leasehold Improvement
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	17,912	14,433
Construction In Progress
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	$ 5,798	$ 5,114

Restructuring Charges (Tables)

12 Months Ended

Dec. 31, 2023

Restructuring and Related Activities [Abstract]

Summary of Changes in Company's Accrued Restructuring Balance

The following table summarizes the changes in the Company's accrued restructuring balance (in thousands):


	Beginning Balance December 31, 2022		Charges		Payments			Ending Balance December 31, 2023
Severance liability	$	—	$	3,732	$	(1,335	)	$	2,397

Summary of Charges Related to Restructuring Activities

A summary of the charges related to the restructuring activities as of December 31, 2023 is as follows (in thousands):


	Severance and Related Compensation		Incentive and Stock-Based Compensation			Total Restructuring Costs
Research and development	$	3,260	$	(1,531	)	$	1,729
General and administrative		472		(375	)		97
Total	$	3,732	$	(1,906	)	$	1,826

Stockholders' Equity - Common Stock and Non-Voting Common Stock - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) Vote $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares
Class Of Stock [Line Items]
Common stock, shares authorized	1,200,000,000	1,200,000,000
Preferred stock, shares authorized	200,000,000	200,000,000
Preferred stock, par value \| $ / shares	$ 0.01	$ 0.01
Common stock, voting rights	Each share of common stock (excluding non-voting common stock) is entitled to one vote
Number of common stock voting rights held \| Vote	1
Common stock, dividends declared \| $	$ 0	$ 0
Non-voting Common Stock
Class Of Stock [Line Items]
Common stock, shares authorized	200,000,000	200,000,000

- 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/exampleRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 272
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483014/272-10-45-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 272
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482987/272-10-50-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(d))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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+ Details

Fair Value Measurement - Summary of Contractual Maturities of Cash and Investments (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Due in less than one year	$ 312,554	$ 419,849
Due in more than one year	19,311	0
Total	$ 331,865	$ 419,849

Income Taxes - Reconciliation of Statutory Federal Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Federal tax at statutory rate	21.00%	21.00%	21.00%
State tax, net of federal benefit	5.80%	5.30%	7.30%
Research and development credits	4.90%	4.40%	2.70%
Stock-based compensation	(1.50%)	(1.10%)	2.60%
Other	(0.20%)	0.00%	0.00%
Change in valuation allowance	(30.30%)	(29.60%)	(33.60%)
Effective income tax rate	(0.30%)	0.00%	0.00%