0000950170-24-025855 | 10-K | XBRL Viewer

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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Jun. 29, 2020	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Summary Of Significant Accounting Policies [Line Items]
Marketable securities recognition of other-than-temporary impairment		$ 0	$ 0	$ 0
Impairment losses		$ 0	$ 0	$ 0
Percentage of realization of tax benefit upon ultimate settlement		50.00%
Use of net operating losses suspension period for medium and large business	3 years
Use of business incentive tax credits period cap	3 years
40 Erie Street [Member]
Summary Of Significant Accounting Policies [Line Items]
Asset Impairment Charges		$ 2,000
Taxable Years 2020 and 2021 [Member]
Summary Of Significant Accounting Policies [Line Items]
Minimum amount of taxable income where use of net operating losses is suspended	$ 1,000
Taxable Years 2020 and 2021 [Member] \| Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Business incentive tax credits to offset against taxes	$ 5,000

Income Taxes - Schedule of Activity Related Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Beginning of year—unrecognized tax benefits	$ 6,715	$ 5,481	$ 4,025
Decrease for tax positions taken during prior periods	(77)	0	0
Increases for tax positions taken during current period	8,213	1,234	1,456
End of year—unrecognized tax benefits	$ 14,851	$ 6,715	$ 5,481

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	ATM Equity Offering Program [Member]	Private Investment in Public Equity [Member]	Common Stock [Member]	Common Stock [Member] ATM Equity Offering Program [Member]	Common Stock [Member] Private Investment in Public Equity [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] ATM Equity Offering Program [Member]	Additional Paid-In Capital [Member] Private Investment in Public Equity [Member]	Accumulated Other Comprehensive Gain/(Loss) [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2020	$ 166,739			$ 18			$ 493,023				$ (326,302)
Balance, shares at Dec. 31, 2020				47,552,693
Issuance of stock, net of issuance costs		$ 36,595	$ 52,653			$ 1		$ 36,595	$ 52,652
Issuance of stock, net of issuance costs, shares					3,990,869	5,000,000
Offering costs related to the sale of common stock and pre-funded warrants	(451)						(451)
Issuance of common stock under the ESPP	914						914
Issuance of common stock under the ESPP, shares				183,111
Unrealized gain (loss) on marketable securities	(73)									$ (73)
Issuance of common stock upon exercise of stock options	3,360						3,360
Issuance of common stock upon exercise of stock options, shares				692,038
Issuance of common stock for warrant exercises, Share				10,459,576
Issuance of common stock for warrant exercises, Value	49			$ 1			48
Issuance of common stock under Sales Purchase Agreement, net of issuance costs, shares				1,169,591
Issuance of common stock under Sales Purchase Agreement, net of issuance costs	20,830						20,830
Issuance of common stock upon exercise of warrants	49			$ 1			48
Issuance of common stock upon exercise of warrants, shares				10,459,576
Stock-based compensation	10,552						10,552
Net Income (Loss)	(75,082)										(75,082)
Balance at Dec. 31, 2021	216,086			$ 20			617,523			(73)	(401,384)
Balance, shares at Dec. 31, 2021				69,047,878
Issuance of stock, net of issuance costs		19,592	14,121		$ 1	$ 1		19,591	14,120
Issuance of stock, net of issuance costs, shares					7,034,948	6,637,165
Issuance of common stock under the ESPP	549						549
Issuance of common stock under the ESPP, shares				322,646
Unrealized gain (loss) on marketable securities	(7)									(7)
Issuance of common stock upon exercise of stock options	186						186
Issuance of common stock upon exercise of stock options, shares				194,347
Issuance of pre-funded warrants, net of issuance costs			28,240						$ 28,240
Issuance of common stock for warrant exercises, Share				3,442,567
Issuance of common stock for warrant exercises, Value	34						34
Issuance of common stock upon exercise of warrants	34						34
Issuance of common stock upon exercise of warrants, shares				3,442,567
Issuance of common stock upon restricted stock units vesting, shares				215,350
Tax payments related to shares withheld for vested restricted stock units	(890)						(890)
Stock-based compensation	12,557						12,557
Net Income (Loss)	(119,687)										(119,687)
Balance at Dec. 31, 2022	170,781			$ 22			691,910			(80)	(521,071)
Balance, shares at Dec. 31, 2022				86,894,901
Issuance of stock, net of issuance costs		$ 7,964						$ 7,964
Issuance of stock, net of issuance costs, shares					3,195,680
Issuance of common stock under the ESPP	801						801
Issuance of common stock under the ESPP, shares				592,049
Unrealized gain (loss) on marketable securities	83									83
Issuance of common stock upon exercise of stock options	$ 5						5
Issuance of common stock upon exercise of stock options, shares	6,000			6,000
Issuance of pre-funded warrants, net of issuance costs			$ 28,200
Issuance of common stock for warrant exercises, Share				6,348,805
Issuance of common stock for warrant exercises, Value	$ 34						34
Issuance of common stock upon exercise of warrants	34						34
Issuance of common stock upon exercise of warrants, shares				6,348,805
Issuance of common stock upon restricted stock units vesting, shares				547,980
Tax payments related to shares withheld for vested restricted stock units	(946)						(946)
Stock-based compensation	11,618						11,618
Net Income (Loss)	(138,490)										(138,490)
Balance at Dec. 31, 2023	$ 51,850			$ 22			$ 711,386			$ 3	$ (659,561)
Balance, shares at Dec. 31, 2023				97,585,415

Property and Equipment, Net

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

5. Property and Equipment, Net

Property and equipment and related accumulated depreciation and amortization are as follows (in thousands):


	December 31,
	2023			2022
Computer equipment and software	$	1,704		$	1,155
Furniture and fixtures		2,723			2,285
Laboratory equipment		29,521			27,309
Leasehold improvements		15,733			18,024
		49,681			48,773
Less accumulated depreciation and amortization		(32,415	)		(28,782	)
Construction-in-progress		15			1,344
Total property and equipment, net	$	17,281		$	21,335

Depreciation and amortization expense was $7.6 million, $6.6 million, and $6.3 million for the years ended December 31, 2023, 2022, and 2021, respectively.

Debt (Tables)

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Schedule of Long term debt balance


	December 31,
	2023
Principal loan balance	$	40,000
Final fee		2,300
Unamortized debt discount and issuance costs		(2,156	)
Long term debt, net	$	40,144

Schedule of estimated future principal payments


2024		—
2025		8,457
2026		18,030
2027		13,513
Total principal payments	$	40,000

Stockholders' Equity - Additional Information (Detail) - USD ($)		1 Months Ended				12 Months Ended
	Oct. 31, 2022	Oct. 31, 2022	Mar. 31, 2022	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Subsidiary Sale Of Stock [Line Items]
Common stock, shares authorized						300,000,000	300,000,000
Preferred stock, shares authorized						10,000,000	10,000,000
Common Stock, Par or Stated Value Per Share						$ 0.0001	$ 0.0001
Preferred stock, par value						$ 0.0001	$ 0.0001
Preferred stock, shares issued						0	0
Preferred stock, shares outstanding						0	0
Common stock, shares issued						97,585,415	86,894,901
Common stock, shares outstanding						97,585,415	86,894,901
Common stock voting rights						Holders of the Company’s common stock are entitled to one vote per share.
Common stock, preferred stock, debt securities, warrants and units covered in Registration Statement			$ 250,000,000
Warrants exercised						6,359,371	3,442,567
Amended and Restated Certificate of Incorporation [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares authorized						300,000,000
Preferred stock, shares authorized						10,000,000
Common Stock, Par or Stated Value Per Share						$ 0.0001
Preferred stock, par value						$ 0.0001
ATM Equity Offering Program [Member]
Subsidiary Sale Of Stock [Line Items]
Net proceeds from issuance of stock						$ 8,092,000	$ 19,737,000	$ 36,719,000
2022 ATM Equity Offering Program [Member] \| Maximum [Member]
Subsidiary Sale Of Stock [Line Items]
Net proceeds from issuance of stock			$ 100,000,000
Private Investment in Public Equity [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued	6,637,165	6,637,165
Net proceeds from issuance of stock		$ 42,400,000
Issuance of pre-funded warrants, net of issuance costs					$ 87,700,000	$ 28,200,000	$ 28,240,000
Warrants to purchase shares of common stock	13,274,923
2022 ATM Program
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued						10,230,628	7,034,948
Net proceeds from issuance of stock						$ 27,500,000	$ 19,600,000
Cowen [Member] \| 2022 ATM Program
Subsidiary Sale Of Stock [Line Items]
Percentage of gross proceeds as underwriter compensation			3.00%
Maximum offering expense agreed to be reimbursed			$ 50,000
Cowen [Member] \| 2022 ATM Program \| Maximum [Member]
Subsidiary Sale Of Stock [Line Items]
Net proceeds from issuance of stock			$ 100,000,000
Common Stock [Member] \| ATM Equity Offering Program [Member]
Subsidiary Sale Of Stock [Line Items]
Stock Issued During Period, Shares, New Issues						3,195,680	7,034,948	3,990,869
Common Stock [Member] \| Private Investment in Public Equity [Member]
Subsidiary Sale Of Stock [Line Items]
Shares issued price per share	$ 2.26	$ 2.26		$ 11
Stock Issued During Period, Shares, New Issues				5,000,000			6,637,165	5,000,000
Net proceeds from issuance of stock				$ 52,700,000
Common Stock and Warrants [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued						6,348,805	3,442,567
Warrants exercised						6,359,371
Common Stock and Warrants [Member] \| Private Investment in Public Equity [Member]
Subsidiary Sale Of Stock [Line Items]
Shares issued price per share					$ 3.34
Proceed from issuance of stock and pre-funded warrants					$ 119,800,000
Sale of common stock					5,543,351
Warrant exercise price	0.0001	0.0001			$ 0.01
Offering price per share	2.26	2.26			3.34
Offering price per share, prepaid by purchaser	$ 2.2599	$ 2.2599			$ 3.33
Warrants to purchase shares of common stock		13,274,923			27,480,719
Maximum percentage of common stock ownership to exercise warrant					9.99%	9.99%
Common Stock and Warrants [Member] \| Private Investment in Public Equity [Member] \| Additional Shares [Member]
Subsidiary Sale Of Stock [Line Items]
Shares issued price per share					$ 3.71
Stock Issued During Period, Shares, New Issues					4,043,127

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurement Level 1 to Level 2 Transfers	$ 0	$ 0

Commitments and Contingencies - Schedule of Minimum Annual Payments Under Operating Lease Agreements (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Operating Leases
2024	$ 12,834
2025	10,749
2026	10,376
2027	10,466
2028	10,732
Thereafter	41,615
Total minimum payments	96,772
Less: Amounts representing interest expense	(32,141)
Present value of future minimum lease payments	64,631
Less: Current portion of lease liability	(6,904)	$ (5,294)
Noncurrent portion of lease liability	$ 57,727	$ 15,673

Debt - Schedule of estimated future principal payments (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Debt Disclosure [Abstract]
2024	$ 0
2025	8,457
2026	18,030
2027	13,513
Total principal payments	$ 40,000

Net Loss Per Common Share - Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net Income (Loss)	$ (138,490)	$ (119,687)	$ (75,082)
Denominator:
Weighted-average common shares outstanding, basic	115,527,546	90,918,333	78,885,186
Weighted-average common shares outstanding, diluted	115,527,546	90,918,333	78,885,186
Net loss per share, basic	$ (1.2)	$ (1.32)	$ (0.95)
Net loss per share, diluted	$ (1.2)	$ (1.32)	$ (0.95)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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+ Details

Net Loss Per Common Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Computation of Basic and Diluted Net Loss Per Share

The following table sets forth the computation of the basic and diluted net loss per share (in thousands, except for share and per share amounts):


	Year Ended December 31,
	2023			2022			2021
Numerator:
Net loss	$	(138,490	)	$	(119,687	)	$	(75,082	)
Denominator:
Weighted-average common shares outstanding, basic and diluted		115,527,546			90,918,333			78,885,186
Net loss per share, basic and diluted	$	(1.20	)	$	(1.32	)	$	(0.95	)

Computation of Potentially Anti-Dilutive Securities

Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:


	December 31,
	2023		2022		2021
Options issued and outstanding and ESPP shares issuable and outstanding		7,534,035		7,145,817		5,170,331
Restricted stock subject to future vesting		3,088,970		561,526		708,800
Total		10,623,005		7,707,343		5,879,131

Stock Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	Feb. 02, 2023	Apr. 21, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance			6,186,925	4,814,394
Weighted-average grant-date fair value granted employee stock options granted			$ 1.73	$ 3.2	$ 8.03
Stock-based compensation expense and awards granted to non-employees			$ 0.8	$ 0.6	$ 0.7
Intrinsic value of stock option awards exercised				0.5	5.8
Share based Compensation Arrangement By Sharebased Payment Award Options Exercised Cash Received				$ 0.2	$ 3.4
Total cost related to non-vested employee and consultant options expected to be recognized			$ 8.5
Total cost related to non-vested employee and consultant options unrecognized weighted average period			1 year 8 months 1 day
Fair value of shares vested			$ 7.8
Restricted Stock Unit Awards under 2018 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period			1 year
Share based compensation by shared based payment award, description			granted restricted stock unit awards under the 2018 Equity Plan. The Company's restricted stock unit awards have a term of up to 10 years and generally vest over a 6 month, 1 or 2-year period
Maximum [Member] \| Restricted Stock Unit Awards under 2018 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period			2 years
Option granted expiration period			10 years
Minimum [Member] \| Restricted Stock Unit Awards under 2018 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period			6 months
2018 Award Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance			92,815
Number of shares available for issuance						2,690,000
Increase in shares available for issuance			4.00%
Maximum number of shares authorized			45,000,000
Minimum percentage of outstanding shares held by individual			10.00%
Minimum percentage fair market value of share price			110.00%
Option vesting period			4 years
Share based compensation by shared based payment award, description			If an individual owns stock representing 10% or more of the outstanding shares, the price of each share shall be at least 110% of the fair market value, as determined by the board of directors. Options granted have a term of up to 10 years and generally vest over a 4-year period with a straight-line vesting.
2018 Award Incentive Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option granted expiration period			10 years
2018 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for issuance						282,334
Increase in shares available for issuance			1.00%
Maximum number of shares authorized			5,000,000
Maximum contribution of employee's eligible compensation			15.00%
2021 Employment Inducement Incentive Award Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance					790,400
Number of Shares increase under plan	1,300,000	700,000

Balance Sheet Components - Schedule of Deposits and Other Long-Term Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deposit Assets And Other Assets Noncurrent Disclosure [Abstract]
Lease security deposits	$ 924	$ 934
Prepaid research and development-related expenses	0	643
Prepaid rent	0	8,162
Total deposits and other long-term assets	$ 924	$ 9,739

Debt (Additional Information) (Details) - USD ($)		1 Months Ended	12 Months Ended
Debt (Additional Information) (Details) - USD ($)	Apr. 01, 2024	Jul. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 15, 2023	Mar. 31, 2023
Debt Instrument [Line Items]
Unamortized issuance costs and debt discounts			$ (2,156,000)
Loan Agreement [Member]
Debt Instrument [Line Items]
Borrowing capacity		$ 80,000,000
Description Of Interest Rate			Borrowings under the Loan Agreement bear interest (i) at an annual cash rate equal to the greater of (x) the lesser of (1) the prime rate (as customarily defined) and (2) 5.50%, in either case, plus 3.15%, and (y) 7.15% and (ii) at an annual payment-in-kind rate which may equal 2.00%.
Prime rate percent		5.50%
Prime rate percent			13.00%
Debt instrument , interest percent		7.15%
Debt instrument, facility charge		$ 150,000
Facility Charge Percentage of Borrowing		0.50%
Unamortized issuance costs and debt discounts			$ 2,200,000	$ 1,800,000
Final payment fee percentage		5.75%
Interest expense, debt			$ 4,000,000	$ 1,200,000
Loan Agreement [Member] \| Forecast [Member]
Debt Instrument [Line Items]
Minimum Liquidity Requirement Capital Description	the Company is subject to a minimum liquidity requirement equal to the then outstanding balance under the Amended Loan Agreement multiplied by 0.55 or 0.45, which multiplier depends on whether the Company achieves certain performance milestones.
Loan Agreement [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Prepayment premium rate		0.00%
Loan Agreement [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Prepayment premium rate		2.50%
Loan Agreement [Member] \| Maximum [Member] \| Forecast [Member]
Debt Instrument [Line Items]
Market capitalization	$ 400,000,000
Loan Agreement [Member] \| Prime Rate Plus [Member]
Debt Instrument [Line Items]
Debt instrument , interest percent		3.15%
Loan Agreement [Member] \| Payment-in-kind rate [Member]
Debt Instrument [Line Items]
Debt instrument , interest percent		2.00%
Loan Agreement [Member] \| Tranche One [Member]
Debt Instrument [Line Items]
Initial amount of borrowing		$ 20,000,000
Loan Agreement [Member] \| Tranche One Additional [Member]
Debt Instrument [Line Items]
Initial amount of borrowing						$ 10,000,000
Loan Agreement [Member] \| Remaining Tranche [Member]
Debt Instrument [Line Items]
Initial amount of borrowing		$ 50,000,000			$ 10,000,000

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

6. Commitments and Contingencies

Leases

The Company leases office, laboratory and storage space in facilities at several locations:

Emeryville Lease

The Company’s principal executive offices in Emeryville, California, consisting of office and laboratory space, are leased pursuant to a 120-month operating lease (the “Emeryville Lease”), which the Company entered into in January 2019, with the obligation to pay rent commencing in November 2019. In conjunction with signing the Emeryville Lease, the Company paid a cash security deposit of $0.6 million, which is recorded as a deposit on the Company’s consolidated balance sheets as of December 31, 2023 and 2022. The Emeryville Lease includes a free rent period, an escalation clause for increased rent and a renewal provision allowing the Company to extend this lease for an additional two five-year periods at the then market rental rate. The lessor provided the Company a tenant improvement allowance for a total of $4.0 million to complete the laboratory and office renovation. The Company has determined the tenant improvements to be lessee owned. The Company recorded a $7.3 million ROU Asset and a $11.6 million lease liability on the consolidated balance sheet as of December 31, 2023. The Company recorded a $8.1 million ROU Asset and a $12.8 million lease liability on the consolidated balance sheet as of December 31, 2022.

Pleasanton Leases

The Company leases office, cleanroom, and laboratory support manufacturing space in Pleasanton, California pursuant to a non-cancelable operating lease (the “Pleasanton Lease”), which the Company entered into in March 2017, with the obligation to pay rent commencing in December 2017. The Pleasanton Lease includes a free rent period, escalating rent payments and a term that expires on November 30, 2024. The Company may extend the lease term for a period of five years at the then market rental rate. The Company obtained an irrevocable letter of credit in March 2017 in the initial amount of approximately $1.0 million as a security deposit to the Pleasanton Lease, which may be drawn down by the landlord in the event the Company fails to fully and faithfully perform its obligations under the Pleasanton lease. The letter of credit may be reduced based on certain levels of cash and cash equivalents the Company holds. In October 2022, the letter of credit was reduced to a balance of $0.6 million. As of December 31, 2022, none of the irrevocable letter of credit amount had been drawn. The Pleasanton Lease further provides that the Company is obligated to pay to the landlord its proportionate share of certain basic operating costs, including taxes and operating expenses.

In connection with the Pleasanton Lease, the Company received a tenant improvement allowance of $1.2 million from the landlord for the costs associated with the design, development and construction of tenant improvements. The unamortized tenant improvement balance is recognized as a component of operating lease ROU Assets on the consolidated balance sheets as of December 31, 2023 and 2022.

In addition, in May 2019, the Company entered into a 64-month non-cancelable operating lease for additional office space in Pleasanton, California, with an obligation to pay rent commencing in August 2019. In January 2022, the Company amended the lease to add additional leased space and extend the lease expiration date to February 2027.

Cambridge Leases

The Company leases or has leased laboratory, office and storage space in several facilities in Cambridge, Massachusetts, pursuant to different lease agreements:

The Company’s facility located at 40 Erie Street in Cambridge, Massachusetts is leased pursuant to a 67-month non-cancelable operating lease (as amended, the “40 Erie Lease”), which the Company entered into in February 2016, with an obligation to pay rent commencing in October 2016. The lessor provided the Company a tenant improvement allowance for a total of $2.1 million to complete the laboratory and office renovation. In September 2021, the Company executed an amendment to the 40 Erie Lease, which extends its term through April 2025 and provides for monthly base rent amounts, subject to annual increases over the term of the lease.

In conjunction with the move to the Boston facility, the Company ceased use of the 40 Erie Street facility, which triggered an impairment assessment. In connection with the impairment assessment, the Company recorded an impairment loss of $2.0 million related to the ROU Asset from the 40 Erie Lease, which is included in operating expenses on the consolidated statement of operations and

comprehensive loss for the year ended December 31, 2023. The Company is subject to the fixed rental fee payments for the existing lease through the remaining term until May 2025.

The Company’s facility located at 21 Erie Street in Cambridge, Massachusetts was leased pursuant to a 24-month non-cancelable operating lease (as amended, the “21 Erie Lease”), which the Company entered into in September 2018. The 21 Erie Lease has since been amended five times, as a result of which the lease term extended through June 2023.

In March 2021, the Company entered into a 17-month operating lease (as amended, the “Cambridge Storage Lease”) for additional office and laboratory storage space in Cambridge, Massachusetts, which commenced on April 1, 2021. The Company also paid an insignificant cash security deposit. The Cambridge Storage Lease was amended in June 2022 to extend the lease term through June 30, 2023.

In conjunction with the 40 Erie Lease, the 21 Erie Lease and the Cambridge Storage Lease, each as amended (if applicable), the Company has paid certain cash security deposits, which in each case included amounts for the applicable last month’s rent and has been classified as part of the operating lease ROU Assets. As of December 31, 2023, the $0.3 million security deposit was recorded in deposits and other long-term assets on the Company's consolidated balance sheet and relates to the 40 Erie Lease. The security deposits for the 21 Erie Lease and the Cambridge Storage Lease were returned to the Company upon lease termination in 2023. As of December 31, 2022, of the $0.7 million security deposits, $0.4 million was recorded in prepaid expenses and other current assets and the remaining $0.3 million was recorded in deposits and other long-term assets on the Company's consolidated balance sheet.

Boston Lease

The Company occupies a newly built facility in Boston, Massachusetts, with office and laboratory space, pursuant to a 120-month operating lease (as amended, the “Boston Lease”), which the Company entered into in September 2021. The Boston Lease includes a free rent period, an escalation clause for increased rent and a renewal provision allowing the Company to extend the Boston Lease for two additional five-year periods at the then market rental rate. The landlord provided the Company with a tenant improvement allowance of up to approximately $19.1 million for costs relating to the design, permitting and construction of improvements owned by the landlord. The Company incurred tenant improvement costs relating to the initial design and construction of the improvements before the commencement date which were accounted for as lease prepayments. The Company’s obligation to pay rent commenced in July 2023, subject to free rent periods of three and nine months with respect to certain premises. The Company was provided early access to the premises to install fixtures and equipment 60 days prior to the anticipated rent commencement date. The Boston Lease expires in 2033. Under the Boston Lease, the Company is obligated to pay to the landlord its proportionate share of certain basic operating costs, including taxes and operating expenses. As a security deposit under the Boston Lease, the Company provided the landlord an irrevocable letter of credit in the amount of approximately $4.6 million, which is collateralized by a restricted cash deposit of $4.7 million, and which may be reduced in the fifth and seventh years of the Boston Lease. As of December 31, 2023, none of the irrevocable letter of credit amount had been drawn.

The Boston Lease commenced in April 2023, when the Company was provided early access to the premises and gained control over the use of the underlying assets. Upon commencement, the Company recognized an ROU Asset of $59.3 million and a lease liability of $50.9 million on the consolidated balance sheet. Upon commencement, the ROU Asset includes $8.4 million of lease prepayments made before the commencement date, which are primarily related to the lessor owned tenant improvement cost.

In September 2023, the Company amended the Boston Lease, whereby the lease term commenced on July 1, 2023 and expires on June 30, 2033.

The Company’s operating leases include various covenants, indemnities, defaults, termination rights, security deposits and other provisions customary for lease transactions of this nature.

The components of lease costs, which were included in our consolidated statements of operations and comprehensive loss, were as follows (in thousands):


	Year ended December 31,
	2023		2022		2021
Lease cost
Operating lease cost	$	13,561	$	8,797	$	7,973
Short-term lease cost		30		—		—
Total lease cost	$	13,591	$	8,797	$	7,973

Supplemental information related to leases was as follows:


	Year ended December 31,
	2023			2022			2021
Cash paid for amounts included in the measurement of lease liabilities (in thousands):
Operating cash flows from operating leases	$	17,290		$	8,915		$	7,925
New right-of-use assets obtained in exchange for lease obligations (in thousands):
Right-of-use assets obtained from entering new leases	$	59,604		$	553		$	6,562
Increase in right-of-use assets from lease modifications	$	706		$	1,406		-
Weighted average remaining lease term (years):
Operating leases		8.30			5.10			5.30
Weighted average discount rate:
Operating leases		10.1	%		7.7	%		7.4	%

As of December 31, 2023, minimum annual payments under the Company’s lease agreements are as follows (in thousands):


	Lease Financing Obligation
Year ending December 31,
2024		12,834
2025		10,749
2026		10,376
2027		10,466
2028		10,732
Thereafter		41,615
Total minimum payments		96,772
Less: Amounts representing interest expense		(32,141	)
Present value of future minimum lease payments		64,631
Less: Current portion of lease liability		(6,904	)
Noncurrent portion of lease liability	$	57,727

Guarantees and Indemnifications

The Company, as permitted under Delaware law and in accordance with its amended and restated certificate of incorporation, as amended, and amended and restated bylaws, and pursuant to indemnification agreements with certain of its officers and directors, indemnifies its officers and directors for certain events or occurrences, subject to certain limits, with respect to which the officer or director is or was serving in such capacity at the Company’s request. The term of the indemnification period lasts as long as an officer or director may be subject to any proceeding arising out of acts or omissions of such officer or director in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company currently holds director and officer liability insurance. This insurance limits the Company’s exposure and may enable it to recover a portion of any future amounts paid. The Company believes that the fair value of these indemnification obligations is minimal. Accordingly, the Company has not recognized any liabilities relating to these obligations for any period presented.

Net Loss Per Common Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss Per Common Share

13. Net Loss Per Common Share

The following table sets forth the computation of the basic and diluted net loss per share (in thousands, except for share and per share amounts):


	Year Ended December 31,
	2023			2022			2021
Numerator:
Net loss	$	(138,490	)	$	(119,687	)	$	(75,082	)
Denominator:
Weighted-average common shares outstanding, basic and diluted		115,527,546			90,918,333			78,885,186
Net loss per share, basic and diluted	$	(1.20	)	$	(1.32	)	$	(0.95	)

In December 2020, the Company issued and sold Warrants to purchase 27,480,719 shares of common stock at a nominal exercise price of $0.01 per share, and in October 2022 the Company issued and sold Warrants to purchase 13,274,923 shares of common stock at a nominal exercise price of $0.0001 per share (see Note 10). During the year ended December 31, 2023, there were 6,359,371 warrants exercised, resulting in the Company issuing 6,348,805 shares of common stock due to net exercise of the warrants. During the year ended December 31, 2022, 3,442,567 warrants were exercised, resulting in the Company issuing 3,442,567 shares of common stock. As of December 31, 2023 and 2022, there are 20,489,256 and 26,848,627 warrants outstanding, respectively. The shares of common stock into which the 2020 and 2022 Warrants may be exercised are considered outstanding for the purposes of computing earnings per share, because the shares may be issued for little or no consideration, they are fully vested and they are immediately exercisable upon their issuance date.

During a period of net loss, basic net loss per share is the same as diluted net loss per share, as the inclusion of all potential common shares outstanding would have been anti-dilutive. Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:


	December 31,
	2023		2022		2021
Options issued and outstanding and ESPP shares issuable and outstanding		7,534,035		7,145,817		5,170,331
Restricted stock subject to future vesting		3,088,970		561,526		708,800
Total		10,623,005		7,707,343		5,879,131

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)	$ (138,490)	$ (119,687)	$ (75,082)

- Definition

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

+ References

+ Details

Collaboration and License Agreements - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended									12 Months Ended
	Jun. 30, 2023	Apr. 30, 2022	Aug. 14, 2021	Sep. 30, 2023	Apr. 30, 2023	Dec. 31, 2021	Sep. 30, 2021	Jan. 31, 2021	Oct. 31, 2020	Oct. 31, 2018	Sep. 30, 2018	Aug. 31, 2018	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2019	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2020	Oct. 31, 2017
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock shares issued													0	0
Short-term deferred revenue													$ 2,350	$ 5,131
Short-term restricted cash													$ 2,299	$ 3,977
Common stock, shares issued													97,585,415	86,894,901
Research and development													$ 127,182	$ 111,403	$ 97,490
Deferred revenue													(2,781)	(15,198)	8,633
Operating Income (Loss)													(139,621)	(120,428)	(75,209)
Revenue recognized grant revenue													16,344	19,945	48,214
Letters of Credit Outstanding, Amount													$ 600
Gilead [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment								$ 30,000
Offering price per share								$ 25.65
Proceeds from issuance of common stock								$ 30,000
Collaboration agreement early termination notice period													90 days
Early termination reduction of future milestone and royalty payments, description													Additionally, if terminated early by Gilead for convenience or by the Company for material breach or insolvency, all of Gilead’s payment obligations for reimbursable costs or for future milestone and royalty payments remain. If terminated early by Gilead for material breach or insolvency, all of Gilead’s unaccrued payment obligations related to future milestone and royalty payments will be reduced by 50% for the remainder of the agreement term.
Revenue recognition contract start month year													2021-01
Deferred revenue													$ 100	100
Receivables														100
Contract assets													$ 0	0
Proceeds from equity investment								$ 30,000
Common stock fair value closing price per share								$ 18.1
Non-refundable option fee								$ 40,000
Maximum aggregate contingent milestone payment								685,000
Collaboration agreement termination term													Gilead may terminate the Gilead Supply Agreement without cause by giving six months prior written notice and may terminate any active orders with 60-day notice without terminating the agreement, and either party may terminate based on an uncured material breach, insolvency of the other party, or in the event that the Gilead Collaboration Agreement is terminated. Upon termination, the Company will deliver all supply products that have been produced and destroy, reimburse or deliver materials that Gilead has reimbursed, and Gilead must pay for any manufacturing costs that the Company has actually incurred or committed to pay, including any cancellation costs owed to subcontractors.
Transaction price allocated to shares of common stock at fair value								$ 21,200
Common stock, shares issued								1,169,591
Common stock purchase price in excess of fair value								$ 8,800
Deferred incremental costs																		$ 100
Coalition for Epidemic Preparedness Innovation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
First tranche of funding received							$ 11,300
Second tranche of funding received		$ 2,700
Third tranche of funding received	$ 1,200
Fourth tranche of funding received													$ 2,400
Additional funding															5,000
Total grant amount			$ 20,600
Amended total grant amount															25,600
Maximum [Member] \| Gilead [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition contract end period								4 years
Minimum [Member] \| Gilead [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition contract end period								2 years
Collaboration and license revenues [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized grant revenue													1,331	9,269	46,717
Collaboration and license revenues [Member] \| Gilead [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration and license revenue															38,600
Collaboration Revenue [Member] \| Gilead [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration and license revenue													300	1,600
Collaboration and license revenue															5,100
Grant revenues [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized grant revenue													15,013	10,676	1,497
Common Stock [Member] \| Gilead [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of common shares sold								1,169,591
Arbutus Biopharma Corporation and Protiva Biotherapeutics Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development													$ 0	0	0
Maximum milestone consideration payable																				$ 123,500
Milestone payment included in research and development expense											$ 2,500					$ 3,000
Gates Foundation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment					$ 700	$ 2,200
2 Seventy [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment												$ 20,000
Proceeds from issuance of convertible preferred stock, net of issuance costs												10,000
Maximum development, regulatory, and commercial milestones												$ 1,200,000
Collaboration agreement early termination notice period													120 days
Early termination reduction of future milestone and royalty payments, description													Additionally, all of 2seventy’s payment obligations that have not yet accrued related to future milestone and royalty payments will be reduced by 50% for the remainder of the agreement term.
Future Milestone And Royalty Payments, Reduction Percentage													50.00%
Revenue recognition contract start month year													2018-08
Collaboration and license revenue													$ 1,000	7,700	3,000
Deferred revenue														1,000
Receivables													0	0
Contract assets													0	0
Deferred revenue														6,400
Decrease in loss from operations														$ 6,400
Decrease in loss per share														$ (0.07)
2 Seventy [Member] \| Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Offering price per share										$ 15
Proceeds from issuance of common stock										$ 10,000
Number of common shares sold										666,667
2 Seventy [Member] \| Series C [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock shares issued												768,115
Proceeds from issuance of convertible preferred stock, net of issuance costs												$ 10,000
Offering price per share												$ 13.04
Issuance of convertible preferred stock, Transaction price												$ 10,000
Barda Contract [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential maximum government funding for performance of certain milestones				$ 433,000
Maximum government funding				10,000
Barda Contract [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional Funding for Two Stages				$ 423,000
Barda Contract [Member] \| Grant revenues [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized grant revenue													9,000
Contract Amount Received													9,000
Grant Agreement [Member] \| Gates Foundation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue													8	$ 1,025
Short-term deferred revenue														1,000
Short-term restricted cash														1,000
Revenue recognized grant revenue													1,700	1,200
C E P I Funding Agreement [Member] \| Coalition for Epidemic Preparedness Innovation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Short-term deferred revenue													2,300	3,000
Short-term restricted cash													2,300	3,000
Collaboration and license revenue													4,300	$ 9,500	1,500
2020 Genevant License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment									$ 2,000
2020 Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount to extend the option term									1,000
2020 Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member] \| Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment																			$ 2,000
Milestone payments																	$ 1,000
2020 Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate payment in specified development regulatory and commercial milestone									71,000
Payments for options to license for each indication									$ 1,500
2021 Genevant License Agreement [Member] \| Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payments								$ 1,500
2021 Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum aggregate contingent milestone payment								$ 191,000
2021 Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member] \| Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments						1,000							0		1,000			$ 1,000
Upfront payments						$ 1,500									$ 1,500
2023 Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum aggregate contingent milestone payment													136,000
2023 Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member] \| Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment made													$ 2,500

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Schedule of Issued and Outstanding Warrants to Purchase Shares of the Company's Common Stock

As of December 31, 2023, the following warrants to purchase shares of the Company’s common stock were issued and outstanding:


Issue Date	Expiration Date	Exercise Price		Number of Warrants Outstanding
December 28, 2020	None	$	0.01		7,214,333
October 24, 2022	None	$	0.0001		13,274,923
					20,489,256

Net Loss Per Common Share - Additional Information (Detail) - $ / shares		1 Months Ended		12 Months Ended
	Oct. 31, 2022	Oct. 31, 2022	Dec. 31, 2020	Dec. 31, 2023	Dec. 31, 2022
Earnings Per Share Basic [Line Items]
Warrants exercised				6,359,371	3,442,567
Number of Warrants Outstanding				20,489,256
Common stock, shares issued				97,585,415	86,894,901
Warrant [Member]
Earnings Per Share Basic [Line Items]
Number of Warrants Outstanding				20,489,256	26,848,627
Common Stock and Warrants [Member]
Earnings Per Share Basic [Line Items]
Warrants exercised				6,359,371
Common stock, shares issued				6,348,805	3,442,567
Private Investment in Public Equity [Member]
Earnings Per Share Basic [Line Items]
Common stock called by warrants			27,480,719
Class of warrant nominal exercise price			$ 0.01
Warrant exercise price		$ 0.0001
Warrants to purchase shares of common stock	13,274,923
Common stock, shares issued	6,637,165	6,637,165
Private Investment in Public Equity [Member] \| Common Stock and Warrants [Member]
Earnings Per Share Basic [Line Items]
Warrants to purchase shares of common stock		13,274,923	27,480,719

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

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) and the rules and regulations of the Securities and Exchange Commission (the “SEC”) for reporting. The consolidated financial statements are comprised of the consolidation of the Company and its wholly-owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation. The Company has no unconsolidated subsidiaries or investments accounted for under the equity method.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the reported amounts of assets and liabilities and disclosures of contingent liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Such estimates include, but are not limited to, determining the fair value of assets and liabilities, the fair value of right-of-use assets and lease liabilities, stock-based compensation expense, and including those related to revenue recognition, including but not limited to, transaction price and progress toward completion of performance obligation under the Company's contracts with customers. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates.

Fair Value of Financial Instruments

U.S. GAAP establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances.

Fair value is established as the exchange price, or 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 a basis for considering market participant assumptions in fair value measurements, an established three-tier fair value hierarchy distinguishes between the following:

•

Level 1 inputs are quoted prices in active markets that are accessible at the market date for identical assets or liabilities.

•

Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly.

•

Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the assets or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement.

To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value instrument.

The carrying amounts reflected on the consolidated balance sheets for cash and cash equivalents, prepaid expenses and other current assets, accounts payable, accrued compensation and accrued liabilities approximate their fair values due to their short-term nature.

Cash, Cash Equivalents and Restricted Cash

Cash equivalents, which consist primarily of highly liquid investments with original maturities of three (3) months or less when purchased, are stated at fair value. These assets include investments in money market funds that invest in U.S. Treasury obligations and certificates of deposit, which are stated at fair value.

The Company has issued letters of credit under certain lease agreements that have been collateralized by cash deposits for an equal amount and are recorded within short-term restricted cash and deposits and other long-term assets on the consolidated balance sheets based on the term of the underlying lease. Additionally, the Company’s restricted cash includes payments received under the Coalition for Epidemic Preparedness Innovations (“CEPI”) Funding Agreement, dated as of August 14, 2021 (the “CEPI Funding Agreement”) and the Gates Foundation Grant Agreement (see Note 7). The Company will utilize the CEPI and Gates Foundation funds as it incurs expenses for services performed under the agreements.

The following table provides a reconciliation of cash, cash equivalents and short-term and long-term restricted cash reported within the consolidated balance sheets that sum to the total of the same amounts shown in the consolidated statements of cash flows (in thousands):


	December 31,
	2023		2022
Cash and cash equivalents	$	62,986	$	55,498
Restricted cash		2,299		3,977
Long-term restricted cash		5,290		5,290
Total cash, cash equivalents and restricted cash	$	70,575	$	64,765

Marketable Securities

The Company invests its excess cash in investment grade short-term and long-term fixed income securities. Such investments in marketable securities are considered available for sale, and reported at fair value, with unrealized gains and losses included as a component of accumulated other comprehensive gain (loss). Marketable securities with maturities of greater than three (3) months from the date of purchase but less than one year from the consolidated balance sheet date are classified as short-term, while marketable securities with maturities in one year or beyond one year from the consolidated balance sheet date are classified as long term. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in interest income on the consolidated statements of operations and comprehensive loss. Realized gains and losses and declines in value judged to be other than temporary, if any, on available-for-sale securities are included in interest income, net. The cost of securities sold is determined using specific identification method.

The Company periodically evaluates whether declines in fair values of its marketable securities below their book value are other than temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the marketable security until a forecasted recovery occurs. Additionally, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any marketable securities before recovery of its amortized cost basis. Factors considered include quoted market prices, recent financial results and operating trends, implied values from any recent transactions or offers of investee securities, credit quality of debt instrument issuers, other publicly available information that may affect the value of the marketable security, duration and severity of the decline in value, and the Company’s strategy and intentions for holding the marketable security. To date, the Company has not recorded any impairment charges on its marketable securities related to other-than-temporary declines in market value. No significant facts or circumstances have arisen to indicate that there has been any significant deterioration in the creditworthiness of the issuers of the securities held by us, thus there has been no recognition of any other-than-temporary impairment in the year ended December 31, 2023, 2022, or 2021. Additionally, the Company has determined that it has the ability and intent to hold all marketable securities that have been in a continuous loss position until maturity or recovery, thus there has been no recognition of any other-than-temporary impairment in the year ended December 31, 2023, 2022 or 2021.

Debt Issuance Costs and Debt Discounts

Debt issuance costs include legal fees, accounting fees, and other direct costs incurred in connection with the execution of the Company’s debt financing. Debt discounts represent costs paid to the lenders. Debt issuance costs and debt discounts are deducted from the carrying amount of the debt liability and are amortized to interest expense over the term of the related debt using the effective interest method.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk consist of cash, cash equivalents and marketable securities. Cash, cash equivalents and marketable securities are invested through banks and other financial institutions in the United States. Such deposits may be in excess of federally insured limits. The Company maintains cash equivalents and marketable securities with various high-credit-quality and capitalized financial institutions. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds.

The Company’s investment policy limits investments to certain types of securities issued by the U.S. government, its agencies, and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The

Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents and marketable securities and issuers of marketable securities to the extent recorded on the consolidated balance sheets. As of December 31, 2023, the Company has no off-balance sheet concentrations of credit risk.

Other Risks and Uncertainties

The Company is subject to a number of risks similar to those faced by other clinical-stage biotechnology companies, including dependence on key individuals; the need to develop commercially viable therapeutics; competition from other companies, many of which are larger and better capitalized; and the need to obtain adequate additional financing to fund the development of its products. The Company currently depends on third-party suppliers for key materials and services used in its research and development manufacturing process and is subject to certain risks related to the loss of these third-party suppliers or their inability to supply the Company with adequate materials and services. Further, the Company is subject to broad market risks and uncertainties resulting from recent events, such as the regional conflicts around the world, inflation, rising or sustained high interest rates and recession risks, market volatility, recent instability in the global financial markets, uncertainty as to the U.S. federal budget and the related potential for government shutdowns, as well as supply chain and labor shortages.

Property and Equipment, Net

Property and equipment are stated at cost, less accumulated depreciation and amortization. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred.

Depreciation is calculated using the straight-line method over the estimated useful lives of the respective assets, which are as follows:


Asset		Estimated Useful Life
Computer equipment and software		3 to 5 years
Furniture and fixtures		5 years
Laboratory equipment		5 to 7 years
Leasehold improvements		Shorter of useful life or lease term

Long-Lived Assets

The Company evaluates long-lived assets, including property and equipment and operating lease right-of-use assets ("ROU Assets"), for impairment whenever events or changes in business circumstances indicate that the carrying amount of the asset may not be fully recoverable. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. Impairment, if any, is measured as the amount by which the carrying amount of a long-lived asset exceeds its fair value. The primary measure of fair value is discounted cash flows, which may include significant estimates primarily related to the discount rate and projected cash flows. The discount rate considers the relevant risk associated with asset-specific characteristics and the uncertainty related to the ability to achieve the projected cash flows.

In conjunction with the move to the Boston lease, the Company ceased use of the 40 Erie Street facility, which triggered an impairment assessment. In connection with the impairment assessment, the Company recorded an impairment loss of $2.0 million related to the ROU Asset and related tenant improvements from the 40 Erie Lease, which is included in operating expenses on the consolidated statement of operations and comprehensive loss for the year ended December 31, 2023 (see Note 6). There were no indicators of impairment of long-lived assets and no impairment losses have been recorded as of and for the year ended December 31, 2022 or 2021.

Revenue Recognition

The Company performs research and development under collaboration, license, grant, and clinical development agreements. The Company’s revenue primarily consists of collaboration agreements and grant funding agreements. At contract inception, the Company analyzes a revenue arrangement to determine the appropriate accounting under U.S. GAAP. Currently, the Company’s revenue arrangements represent customer contracts within the scope of ASC Topic 606, Revenue from Contracts with Customers (Topic 606) (“ASC 606”) or grant funding agreements subject to the contribution guidance in ASC Topic 958-605, Not-for-Profit Entities – Revenue Recognition (“ASC 958-605”), which applies to business entities that receive contributions within the scope of ASC 958-605.

For collaboration agreements, the Company analyzes 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. This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. For collaboration arrangements that are considered to be in the scope of the collaboration guidance and that contain multiple elements, the Company first determines which elements of the collaboration are deemed to be within the scope of the collaboration guidance and those that are more reflective of a vendor-customer relationship and, therefore, within the scope of the revenue with contracts with customers guidance. Elements of collaboration arrangements that are reflective of a vendor-customer relationship are accounted for pursuant to the revenue from contracts with customers guidance. The terms of the licensing and collaboration agreements entered into typically include payment of one or more of the following: non-refundable, up-front fees; development, regulatory, and commercial milestone payments; payments for manufacturing supply services; and royalties on net sales of licensed products. Each of these payments results in license, collaboration and other revenues, except for revenues from royalties on net sales of licensed products, which are classified as royalty revenues. The core principle of the accounting for revenue from contracts with customers guidance is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received in exchange for those goods or services.

In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies 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 (12) 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 (12) months, this will be classified in current assets. A net contract asset or liability is presented for each contract with a customer.

At contract inception, the Company assesses the goods or services promised in a contract with a customer and identifies those distinct goods and services that represent a performance obligation. A promised good or service may not be identified as a performance obligation if it is immaterial in the context of the contract with the customer, if it is not separately identifiable from other promises in the contract (either because it is not capable of being separated or because it is not separable in the context of the contract), or if the performance obligation does not provide the customer with a material right.

The Company considers the terms of the contract and its customary business practices to determine the transaction price. 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. Variable consideration will only be included in the transaction price when it is not considered constrained, which is when it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur.

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. The relative selling price for each performance obligation is estimated using objective evidence if it is available. If objective evidence is not available, the Company uses its best estimate of the selling price for the performance obligation.

Revenue is recognized when, or as, the Company satisfies a performance obligation by transferring a promised good or service to a customer. An asset is transferred when, or as, the customer obtains control of that asset, which for a service is considered to be as the services are received and used. The Company recognizes revenue over time by measuring the progress toward complete satisfaction of the relevant performance obligation, using an appropriate input or output 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. Any change in the transaction price is allocated to the performance obligations on the same basis as at contract inception.

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, estimating the stand-alone selling prices of identified performance obligations (which may include forecasted revenue, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success) and estimating the progress towards satisfaction of performance obligations.

For grant funding agreements, grant revenue is recognized during the period that the research and development services occur, as qualifying expenses are incurred. The Company concluded that payments received under these grants represent nonreciprocal contributions, as described in ASC 958, Not-for-Profit Entities, and that the grants are not within the scope of ASC 606 as the organization providing the grant does not meet the definition of a customer. Grant revenue relates primarily to the CEPI Funding Agreement and the Gates Grant Agreement (see Note 7).

Government Contract

Contracts with government agencies, including cost reimbursement agreements, are assessed to determine if the contract should be accounted for as an exchange transaction or a contribution. A government contract is accounted for as a contribution if the government agency does not receive commensurate value in return for the assets transferred. Contributions are recognized as grant revenue when there is reasonable assurance that the contribution will be received, and all attaching conditions have been complied with.

The Company receives reimbursement under its U.S. government contract that support research and development of defined projects. The contract generally provides for reimbursement of approved costs incurred under the terms of the contracts. Revenue related to the cost reimbursement provisions under the Company’s U.S. government contract is recognized as the qualified direct and indirect costs on the projects are incurred. The Company invoices under its U.S. government contract using the provisional rates in the government contract and thus is subject to future audits at the discretion of the government. The Company believes that government contract revenue for periods not yet audited has been recorded in amounts that are expected to be realized upon final audit and settlement. However, these audits could result in an adjustment to government contract revenue previously reported, which adjustments could be potentially significant. Costs incurred related to services performed under the contract are included as a component of research and development or selling, general and administrative expenses in the Company’s consolidated statements of operations. The Company’s use of estimates in recording accrued liabilities for government contract activities (see “Use of Estimates” above) affects the revenue recorded from development funding and under the government contracts. Grant revenue related to the U.S. government contract relates to the BARDA Contract (see Note 7).

Stock-Based Compensation

The Company measures and recognizes compensation expense for all stock-based awards made to employees, directors, and non-employees based on the grant date estimated fair value of each award. Such expense is recognized on a straight-line basis over the requisite service period which is generally the vesting period for the entire award. Expense is adjusted for estimated forfeitures. Forfeitures of awards are estimated based on historical forfeiture experience and the experience of other companies in the same industry. The estimate of forfeitures will be adjusted over the service period to the extent that actual forfeitures differ, or are expected to differ, from prior estimates.

The Company estimates the fair value of stock option grants and employee stock purchase plan (ESPP) purchase rights using the Black-Scholes option-pricing model (“the Black-Scholes model”). The Black-Scholes model requires management to make assumptions and judgments about the variables used in the calculation, including the expected term (weighted-average period of time that the options granted are expected to be outstanding), the expected volatility of common stock, an assumed risk-free interest rate, and expected dividends the Company may pay. Management uses the simplified calculation (based on the mid-point between the vesting date and the end of the contractual term) of the expected term for its stock options as the Company has concluded that its stock option history does not provide a reasonable basis upon which to estimate expected term. Volatility is based on an average of the historical volatilities of the common stock of entities with characteristics similar to the Company’s. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected life of the option. The Company uses an assumed dividend yield of zero as the Company has never paid dividends and has no current plans to pay any dividends on its common stock.

Research and Development Expenses

All research and development costs, including work performed by third parties, are expensed as incurred. Research and development costs consist of salaries and other personnel-related expenses, including associated non-cash stock-based compensation, consulting fees, laboratory supplies, and facility costs, as well as external research and development expenses incurred under arrangements with third parties, fees paid to other entities that conduct certain research and development activities on behalf of the Company, and costs incurred related to our collaboration agreements. Costs to develop the Company’s technologies are recorded as research and development expense unless certain costs which meet the criteria to be capitalized as internal-use software costs is met. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods are received or services are realized or consumed. Such payments are evaluated for current or long-term classification based on when they will be realized.

Clinical and pre-clinical costs are a component of research and development expense. The Company accrues and expenses clinical and pre-clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with its service providers. The Company determines the actual costs through discussions with internal personnel and external service providers as to the progress or stage of completion of services and the agreed-upon fee to be paid for such services.

Leases

The Company determines whether the arrangement is or contains a lease at the inception of the arrangement and if such a lease is classified as a financing lease or operating lease. The majority of the Company’s leases are classified as operating leases. Leases with a term greater than one year are included in operating lease ROU Assets, lease liabilities, current portion, and lease liabilities, net of current portion in the Company’s consolidated balance sheets at December 31, 2023 and 2022. The Company has elected not to recognize on the consolidated balance sheets leases with terms of one year or less. Lease liabilities and their corresponding ROU Assets are recorded based on the present value of lease payments over the expected lease term. In determining the net present value of lease payments, the interest rate implicit in lease contracts is typically not readily determinable. As such, the Company estimates the appropriate incremental borrowing rate, which is the rate that would be incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. Certain adjustments to the ROU Assets may be required for items such as initial direct costs paid or incentives received and impairment charges if we determine the ROU Asset is impaired.

The Company considers a lease term to be the non-cancelable period that it has the right to use the underlying asset, including any periods where it is reasonably assured the Company will exercise the option to extend the contract. Periods covered by an option to extend are included in the lease term if the lessor controls the exercise of that option.

The Company recognizes lease expense on a straight-line basis over the expected lease term.

The Company has elected not to separate lease and non-lease components for its leased assets and accounts for all lease and non-lease components of its agreements as a single lease component. The lease components resulting in a ROU Asset have been recorded on the consolidated balance sheets and amortized as lease expense on a straight-line basis over the lease term.

Income Taxes

The Company accounts for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates that will be in effect when the differences are expected to reverse. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized.

The Company recognizes and measures uncertain tax positions using a two—step approach set forth in authoritative guidance. The first step is to evaluate the tax position taken or expected to be taken by determining whether the weight of available evidence indicates that it is more likely than not that the tax position will be sustained in an audit, including resolution of any related appeals or litigation processes. The second step is to measure the tax benefit as the largest amount that is more than 50% likely to be realized upon ultimate settlement. Significant judgment is required to evaluate uncertain tax positions. The Company evaluates uncertain tax positions on a regular basis. The evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, correspondence with tax authorities during the course of the audit, and effective settlement of audit issues. The provision for income taxes includes the effects of any accruals that the Company believes are appropriate. It is the Company’s policy to recognize interest and penalties related to income tax matters in income tax expense. Through December 31, 2023, the Company had not accrued interest or penalties related to uncertain tax positions.

On March 18, 2020, the Families First Coronavirus Response Act (the “FFCR Act”), and on March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) were each enacted in response to the COVID-19 pandemic. The FFCR Act and the CARES Act contain numerous income tax provisions relating to refundable payroll tax credits, deferment of employer side social security payments, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property.

On June 29, 2020, Assembly Bill 85 (“A.B. 85”) was signed into California law. A.B. 85 provides for a three-year suspension of the use of net operating losses for medium and large businesses and a three-year cap on the use of business incentive tax credits to offset no more than $5.0 million of tax per year. A.B. 85 suspends the use of net operating losses for taxable years 2020 and 2021 for certain taxpayers with taxable income of $1.0 million or more. The carryover period for any net operating losses that are suspended under this provision will be extended. A.B. 85 also requires that business incentive tax credits, including carryovers, may not reduce the applicable tax by more than $5.0 million for taxable years 2020 and 2021.

The FFCR Act, CARES Act and A.B. 85 did not have a material impact on the Company’s consolidated financial statements as of December 31, 2023.

Effective January 1, 2022, a provision of the Tax Cuts and Jobs Act (TCJA) took effect creating a significant change to the treatment of research and experimental expenditures under Section 174 of the Internal Revenue Code (Sec. 174 expenses). Historically, businesses have had the option of deducting Sec. 174 expenses in the year incurred or capitalizing and amortizing the costs over five years. The new TCJA provision, however, eliminates this option and will require Sec. 174 expenses associated with research conducted in the United States to be capitalized and amortized over a five-year period. For expenses associated with research outside of the United States, Sec. 174 expenses will be capitalized and amortized over a 15-year period. This provision did not have a material impact on the Company's consolidated financial statements as of December 31, 2023.

Comprehensive Loss

Comprehensive loss includes net loss and certain changes in stockholders’ equity that are excluded from net loss, primarily unrealized gains and losses on the Company’s marketable 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 outstanding during the period, without consideration for common stock equivalents. 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.

Recently Issued Accounting Pronouncements Not Yet Adopted

In August 2020, the FASB issued ASU No. 2020-06, Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (“ASU 2020-06”). The standard eliminates the beneficial conversion and cash conversion accounting models for convertible instruments. It also amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions. In addition, the standard modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted EPS computation. The amendments in ASU 2020-06 are effective for the Company for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted, but not earlier than fiscal years beginning after December 15, 2020. The

Company does not expect the adoption of ASU 2020-06 to have a material impact on its consolidated financial statements and related disclosures.

In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures (“ASU 2023-07”). The standard improves reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. In addition, the guidance enhances interim disclosure requirements, clarifies circumstances in which an entity can disclose multiple segment measures of profit or loss, provides new segment disclosure requirements for entities with a single reportable segment and contains other disclosure requirements. The purpose of the guidance is to enable investors to better understand an entity’s overall performance and assess potential future cash flows. The amendments in ASU 2023-07 are effective for the Company for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. The Company does not expect the adoption of ASU 2023-07 to have a material impact on its consolidated financial statements and related disclosures.

In December 2023, the FASB issued ASU No. 2023-09, Income Taxes-Improvements to Income Tax Disclosures, which requires greater disaggregation of income tax disclosures related to the income tax rate reconciliation and income taxes paid ("ASU 2023-09"). ASU 2023-09 is effective for the Company for the year ending December 31, 2025, although early adoption is permitted. The Company is currently evaluating the impact of the provisions of ASU 2023-09.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Cash, Cash Equivalents, and Restricted Cash


	December 31,
	2023		2022
Cash and cash equivalents	$	62,986	$	55,498
Restricted cash		2,299		3,977
Long-term restricted cash		5,290		5,290
Total cash, cash equivalents and restricted cash	$	70,575	$	64,765

Estimated Useful Lives of Assets

Depreciation is calculated using the straight-line method over the estimated useful lives of the respective assets, which are as follows:


Asset		Estimated Useful Life
Computer equipment and software		3 to 5 years
Furniture and fixtures		5 years
Laboratory equipment		5 to 7 years
Leasehold improvements		Shorter of useful life or lease term

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):


	December 31,
	2023		2022
Prepaid research and development-related expenses	$	3,904	$	4,241
Collaboration receivable		14		135
Prepaid insurance		940		1,158
Interest and other receivables		217		529
Facilities-related deposits		9		384
Other		778		567
Total prepaid expenses and other current assets	$	5,862	$	7,014

Schedule of Deposits and Other Long-Term Assets

Deposits and other long-term assets consist of the following (in thousands):


	December 31,
	2023		2022
Lease security deposits	$	924	$	934
Prepaid research and development-related expenses		—		643
Prepaid rent		—		8,162
Total deposits and other long-term assets	$	924	$	9,739

Cash Equivalents and Marketable Securities - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Security	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Cash equivalents and marketable securities [Line Items]
Cash and cash equivalents and marketable securities	$ 79,300	$ 175,900
Cash and cash equivalents	62,986	55,498
Marketable securities	$ 16,300	120,400
Number of individual securities in an unrealized loss position for 12 months or greater \| Security	0
Marketable securities recognition of other-than-temporary impairment	$ 0	$ 0	$ 0
Realized gains or losses on marketable securities, description	no material realized gains or losses	no material realized gains or losses
Maximum [Member]
Cash equivalents and marketable securities [Line Items]
Marketable securities contractual maturities period	1 year

Debt

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Debt

8. Debt

In July 2022, the Company entered into a loan and security agreement (as amended, the “Loan Agreement”) with Hercules Capital, Inc. (“Hercules”) and Silicon Valley Bank (“SVB”), which provides the Company a 60-month term loan facility for up to $80.0 million in borrowing capacity across five potential tranches. At the closing of the Loan Agreement, the Company drew $20.0 million from the first tranche and drew an additional $10.0 million in March 2023. The remaining tranches provide up to $50.0 million borrowing capacity and become available upon the Company meeting certain milestones set forth in the Loan Agreement. In the fourth quarter of 2022, one milestone had been achieved, and the Company drew the available $10.0 million on December 15, 2023. As of December 31, 2023, no additional milestones had been met. The term loan is secured by substantially all of the Company’s assets, other than intellectual property. There are no warrants associated with the Loan Agreement.

Borrowings under the Loan Agreement bear interest (i) at an annual cash rate equal to the greater of (x) the lesser of (1) the prime rate (as customarily defined) and (2) 5.50%, in either case, plus 3.15%, and (y) 7.15% and (ii) at an annual payment-in-kind rate

which may equal 2.00%. The Company is required to make monthly interest-only payments prior to the amortization date of January 1, 2025, subject to a potential six-month and one-year extension upon satisfaction of certain conditions. The interest-only payment date has been extended an additional six months based on our achievement of one of the milestones as set forth in the Loan Agreement. In addition, the Company paid a $150,000 facility charge upon closing, and must pay a facility charge equal to 0.50% of the principal amount of any borrowings made pursuant to the amounts under the last four tranches.

All unpaid principal and accrued and unpaid interest with respect to each term loan is due and payable in full on July 19, 2027. At the Company’s option, the Company may prepay all or any portion of the outstanding borrowings, plus accrued and unpaid interest thereon and fees and expenses, subject to a prepayment premium ranging from zero to 2.5%, during the first three years after closing, depending on the year of such prepayment. Upon repayment of the term loan, the Company is required to make a final payment fee to the lenders equal to 5.75% of the aggregate original principal amount of the loan. Debt issuance costs have been treated as debt discounts on the Company’s consolidated balance sheet and together with the final payment are being amortized to interest expense throughout the life of the term loan using the effective interest rate method.

In March 2023, the Company entered into the First Amendment to Loan and Security Agreement, dated as of March 31, 2023, with SVB, Hercules, Hercules Capital Funding Trust 2002-1 (the “First Amendment” and the Loan Agreement as amended by the First Amendment, the “Amended Loan Agreement”), to amend the minimum liquidity requirements under the Loan Agreement, beginning on the earliest occurrence of certain milestones or April 1, 2024, and at all times thereafter, so long as the Company’s market capitalization is no greater than $400.0 million, the Company is subject to a minimum liquidity requirement equal to the then outstanding balance under the Amended Loan Agreement multiplied by 0.55 or 0.45, which multiplier depends on whether the Company achieves certain performance milestones. As of December 31, 2023, we have not achieved the performance milestones to be subject to the lower 0.45 multiplier.

The Company’s obligations under the Amended Loan Agreement are subject to acceleration upon the occurrence of customary events of default, including payment default, insolvency and the occurrence of certain events having a material adverse effect on the Company, including (but not limited to) material adverse effects upon the business, operations, properties, assets or financial condition of the Company and its subsidiaries, taken as a whole. As of December 31, 2023, the Company is in compliance with all covenants in the Amended Loan Agreement, as amended.

As of December 31, 2023 and 2022, there were debt discounts, unamortized issuance costs and unaccreted value of the final fee of $2.2 million and $1.8 million, respectively, which were recorded as a direct deduction from the term loan on the consolidated balance sheet. Interest expense related to the Loan Agreement was $4.0 million and $1.2 million, respectively, for the years ended December 31, 2023 and 2022. The effective interest rate on the term loan, including the amortization of the debt discount and issuance costs, and accretion of the final payment, was 13%. The components of the long-term debt balance are as follows (in thousands):


	December 31,
	2023
Principal loan balance	$	40,000
Final fee		2,300
Unamortized debt discount and issuance costs		(2,156	)
Long term debt, net	$	40,144

As of December 31, 2023, the estimated future principal payments due (excluding the final payment fee) were as follows (in thousands):


2024		—
2025		8,457
2026		18,030
2027		13,513
Total principal payments	$	40,000

- Definition

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

+ References

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

Reference 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(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//470/tableOfContent

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

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

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

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

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

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

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

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

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

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

+ Details

Cash Equivalents and Marketable Securities - Schedule of Amortized Cost, Unrealized Gains and Losses and Fair Value of Cash Equivalent and Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Cash equivalents and marketable securities [Line Items]
Cash and Cash Equivalents, at Carrying Value, Total	$ 62,986	$ 55,498
Amortized Cost	62,262	158,691
Unrealized Gains	5	55
Unrealized Losses	(2)	(135)
Fair Value	62,265	158,611
Cash Equivalents [Member]
Cash equivalents and marketable securities [Line Items]
Cash and Cash Equivalents, at Carrying Value, Total	45,977	38,191
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	45,977	38,191
Cash Equivalents [Member] \| Money Market Funds [Member]
Cash equivalents and marketable securities [Line Items]
Cash and Cash Equivalents, at Carrying Value, Total	39,243	38,191
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	39,243	38,191
Cash Equivalents [Member] \| Commercial Paper [Member]
Cash equivalents and marketable securities [Line Items]
Cash and Cash Equivalents, at Carrying Value, Total	4,484
Unrealized Gains	0
Unrealized Losses	0
Fair Value	4,484
Cash Equivalents [Member] \| U.S. Government Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Cash and Cash Equivalents, at Carrying Value, Total	2,250
Unrealized Gains	0
Unrealized Losses	0
Fair Value	2,250
Short-Term Marketable Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	16,285	116,464
Unrealized Gains	5	55
Unrealized Losses	(2)	(130)
Fair Value	16,288	116,389
Short-Term Marketable Securities [Member] \| U.S. Treasuries [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	9,861	35,608
Unrealized Gains	5	3
Unrealized Losses	(1)	(71)
Fair Value	9,865	35,540
Short-Term Marketable Securities [Member] \| Commercial Paper [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	3,485	33,318
Unrealized Gains	0	23
Unrealized Losses	0	(13)
Fair Value	3,485	33,328
Short-Term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	939	21,887
Unrealized Gains	0	6
Unrealized Losses	0	(40)
Fair Value	939	21,853
Short-Term Marketable Securities [Member] \| Certificates of Deposit [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost		948
Unrealized Gains		1
Unrealized Losses		0
Fair Value		949
Short-Term Marketable Securities [Member] \| U.S. Government Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	2,000	24,703
Unrealized Gains	0	22
Unrealized Losses	(1)	(6)
Fair Value	$ 1,999	24,719
Long-term Marketable Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost		4,036
Unrealized Gains		0
Unrealized Losses		(5)
Fair Value		4,031
Long-term Marketable Securities [Member] \| U.S. Treasuries [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost		3,103
Unrealized Gains		0
Unrealized Losses		(4)
Fair Value		3,099
Long-term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost		933
Unrealized Gains		0
Unrealized Losses		(1)
Fair Value		$ 932

Stockholders' Equity - Schedule of Issued and Outstanding Warrants to Purchase Shares of the Company's Common Stock (Detail)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Subsidiary, Sale of Stock [Line Items]
Number of Warrants Outstanding	20,489,256
Common Stock Warrants One [Member]
Subsidiary, Sale of Stock [Line Items]
Issue Date	Dec. 28, 2020
Expiration Date	None
Warrant exercise price \| $ / shares	$ 0.01
Number of Warrants Outstanding	7,214,333
Common Stock Warrants Two [Member]
Subsidiary, Sale of Stock [Line Items]
Issue Date	Oct. 24, 2022
Expiration Date	None
Warrant exercise price \| $ / shares	$ 0.0001
Number of Warrants Outstanding	13,274,923

Net Loss Per Common Share - Computation of Potentially Anti-dilutive Securities (Detail) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities that were not included in the diluted per share calculations	10,623,005	7,707,343	5,879,131
Options Issued and Outstanding and ESPP Shares Issuable and Outstanding [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities that were not included in the diluted per share calculations	7,534,035	7,145,817	5,170,331
Restricted Stock Subject to Future Vesting [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities that were not included in the diluted per share calculations	3,088,970	561,526	708,800

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 62,986	$ 55,498
Marketable securities	16,288	116,389
Restricted cash	2,299	3,977
Prepaid expenses and other current assets	5,862	7,014
Total current assets	87,435	182,878
Long-term restricted cash	5,290	5,290
Property and equipment, net	17,281	21,335
Lease right-of-use assets	66,839	17,481
Deposits and other long-term assets	924	9,739
Long-term marketable securities	0	4,031
Total assets	177,769	240,754
Current liabilities:
Accounts payable	3,819	8,694
Accrued compensation	9,357	8,215
Accrued liabilities	1,213	4,124
Accrued research and development expenses	3,696	3,343
Lease liabilities, current portion	6,904	5,294
Deferred revenue, current portion	2,350	5,131
Total current liabilities	27,339	34,801
Other liabilities, noncurrent	709	150
Lease liabilities, net of current portion	57,727	15,673
Debt, noncurrent	40,144	19,349
Total liabilities	125,919	69,973
Commitments and contingencies (Notes 6, 7 and 8)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding at December 31, 2023 and 2022	0	0
Common stock, $0.0001 par value; 300,000,000 shares authorized at December 31, 2023 and 2022; 97,585,415 and 86,894,901 shares issued and outstanding at December 31, 2023 and 2022, respectively	22	22
Additional paid-in capital	711,386	691,910
Accumulated other comprehensive gain (loss)	3	(80)
Accumulated deficit	(659,561)	(521,071)
Total stockholders’ equity	51,850	170,781
Total liabilities and stockholders’ equity	$ 177,769	$ 240,754

Balance Sheet Components

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Balance Sheet Components

9. Balance Sheet Components

Prepaid Expenses and Other Assets

Prepaid expenses and other current assets consist of the following (in thousands):


	December 31,
	2023		2022
Prepaid research and development-related expenses	$	3,904	$	4,241
Collaboration receivable		14		135
Prepaid insurance		940		1,158
Interest and other receivables		217		529
Facilities-related deposits		9		384
Other		778		567
Total prepaid expenses and other current assets	$	5,862	$	7,014

Deposits and Other Long-Term Assets

Deposits and other long-term assets consist of the following (in thousands):


	December 31,
	2023		2022
Lease security deposits	$	924	$	934
Prepaid research and development-related expenses		—		643
Prepaid rent		—		8,162
Total deposits and other long-term assets	$	924	$	9,739

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Detail) - 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]
Stock Based Compensation Expense	$ 11,618	$ 12,557	$ 10,552
Research and Development Expense [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock Based Compensation Expense	6,266	6,730	6,626
General and Administrative Expense [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock Based Compensation Expense	$ 5,352	$ 5,827	$ 3,926

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Fair Value of Financial Instruments

•

Level 1 inputs are quoted prices in active markets that are accessible at the market date for identical assets or liabilities.

•

Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly.

•

Cash, Cash Equivalents, and Restricted Cash

Cash, Cash Equivalents and Restricted Cash


	December 31,
	2023		2022
Cash and cash equivalents	$	62,986	$	55,498
Restricted cash		2,299		3,977
Long-term restricted cash		5,290		5,290
Total cash, cash equivalents and restricted cash	$	70,575	$	64,765

Marketable Securities

Debt Issuance Costs and Debt Discounts

Concentrations of Credit Risk

Other Risks and Uncertainties

Property and Equipment, Net

Depreciation is calculated using the straight-line method over the estimated useful lives of the respective assets, which are as follows:


Asset		Estimated Useful Life
Computer equipment and software		3 to 5 years
Furniture and fixtures		5 years
Laboratory equipment		5 to 7 years
Leasehold improvements		Shorter of useful life or lease term

Long-Lived Assets

Revenue Recognition

Government Contract

Share-Based Compensation

Stock-Based Compensation

Research and Development Expenses

Leases

The Company recognizes lease expense on a straight-line basis over the expected lease term.

Income Taxes

The FFCR Act, CARES Act and A.B. 85 did not have a material impact on the Company’s consolidated financial statements as of December 31, 2023.

Comprehensive Loss

Comprehensive loss includes net loss and certain changes in stockholders’ equity that are excluded from net loss, primarily unrealized gains and losses on the Company’s marketable securities.

Net Loss per Share

Net Loss Per Share

Recently Issued Accounting Pronouncements Not Yet Adopted

Company does not expect the adoption of ASU 2020-06 to have a material impact on its consolidated financial statements and related disclosures.

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Common Stock [Member] \| Sales Purchase Agreement [Member]
Payment for issuance cost			$ 339
Common Stock [Member] \| ATM Equity Offering Program [Member]
Payment for issuance cost	$ 128	$ 146	124
Common Stock [Member] \| Private Investment in Public Equity [Member]
Payment for issuance cost		880	$ 2,348
Warrant [Member] \| Private Investment in Public Equity [Member]
Payment for issuance cost		$ 1,759

Income Taxes - Schedule of Reconciliation of the Statutory Federal Income Tax Rate to the Company's Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	21.00%	21.00%	21.00%
State tax, net of federal benefit	1.30%	(7.60%)	10.20%
Permanent differences	(0.70%)	(0.40%)	(0.10%)
Research and development tax credits	1.50%	1.20%	1.90%
Impact of changes in state tax rate on deferred taxes	(2.90%)	0.00%	0.00%
Other	(0.20%)	(1.10%)	(1.80%)
Non-taxable stock premium	0.00%	0.00%	2.50%
Change in valuation allowance	(20.00%)	(28.30%)	(33.70%)
Total provision for income taxes	0.00%	0.00%	0.00%

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue recognized grant revenue	$ 16,344	$ 19,945	$ 48,214
Operating expenses:
Research and development	127,182	111,403	97,490
General and administrative	28,783	28,970	25,933
Total operating expenses	155,965	140,373	123,423
Loss from operations	(139,621)	(120,428)	(75,209)
Interest income	5,199	1,976	164
Interest expense	(4,036)	(1,235)	(37)
Other expense	(32)	0	0
Net loss	(138,490)	(119,687)	(75,082)
Other comprehensive loss:
Unrealized loss on marketable securities	83	(7)	(73)
Comprehensive loss	$ (138,407)	$ (119,694)	$ (75,155)
Net loss per share, basic	$ (1.2)	$ (1.32)	$ (0.95)
Net loss per share, diluted	$ (1.2)	$ (1.32)	$ (0.95)
Weighted-average number of shares used in computing net loss per share, basic	115,527,546	90,918,333	78,885,186
Weighted-average number of shares used in computing net loss per share, diluted	115,527,546	90,918,333	78,885,186
Collaboration and license revenues [Member]
Revenue recognized grant revenue	$ 1,331	$ 9,269	$ 46,717
Grant revenues [Member]
Revenue recognized grant revenue	$ 15,013	$ 10,676	$ 1,497

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of Assumptions Used for Estimating the Fair Value of Stock Purchase Rights Granted Under 2018 Employee Stock Purchase Plan

The estimated fair value of stock purchase rights granted under the 2018 ESPP were calculated using the Black-Scholes option-pricing model using the following assumptions:


	Year ended December 31,
	2023			2022			2021
Expected dividend yield		—	%		—	%		—	%
Expected term	0.50 years			0.50 years			0.57 years
Risk-free interest rate		5.1	%		1.3	%		0.1	%
Expected volatility		90.1	%		94.9	%		88.0	%

Schedule of Weighted-Average Assumptions Used in Black-Scholes Option-Pricing Model to Estimate Fair Value of Employee Stock Options at Grant Date

The fair value of each stock option granted to an employee or a director was estimated as of the date of grant using the Black-Scholes model with the following weighted-average assumptions:


	Year Ended December 31,
	2023			2022			2021
Expected dividend yield		—	%		—	%		—	%
Expected term	5.77 years			5.98 years			6.01 years
Risk-free interest rate		4.0	%		2.1	%		1.1	%
Expected volatility		98.9	%		77.9	%		79.0	%

Schedule of Stock Options Activity

A summary of the 2018 Plan and 2021 Plan activity is as follows:


				Options Outstanding
	Number of Shares Available for Issuance			Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2022		4,814,394			6,951,620		$	7.92		8.08	$	1,089
Authorized		4,775,796			—
Granted		(4,227,353	)		712,566		$	2.20
Exercised					(6,000	)	$	0.76
Cancelled		824,088			(384,725	)	$	5.35
Balance at December 31, 2023		6,186,925			7,273,461		$	7.50		7.26	$	264
Vested and exercisable – December 31, 2023					4,647,325		$	8.53		6.67	$	200
Vested and expected to vest – December 31, 2023					6,997,158		$	7.60		7.22	$	254

Summary of Restricted Stock Unit Activity

The following table summarizes the Company's restricted stock unit activity during the year ended December 31, 2023:


	Number of Shares			Weighted Average Grant Date Fair Value
Outstanding, unvested as December 31, 2022		561,526		$	5.38
Issued		3,514,787		$	3.29
Vested		(871,385	)	$	4.64
Canceled/Forfeited		(115,958	)	$	3.29
Outstanding, unvested as December 31, 2023		3,088,970		$	3.29

Schedule of Stock Based Compensation Expense

Total stock-based compensation for all awards granted to employees, consultants and the Company's 2018 ESPP, before taxes, is as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Research and development expenses	$	6,266	$	6,730	$	6,626
General and administrative expenses		5,352		5,827		3,926
Total	$	11,618	$	12,557	$	10,552

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

12. Income Taxes

The effective tax rate for the years ended December 31, 2023, 2022, and 2021 is different from the federal statutory rate primarily due to the valuation allowance against deferred tax assets as a result of insufficient sources of income. The effective tax rate of the Company’s provision for income taxes differs from the federal statutory rate as follows:


	Year Ended December 31,
	2023			2022			2021
Statutory federal income tax rate		21.0	%		21.0	%		21.0	%
State tax, net of federal benefit		1.3			7.6			10.2
Permanent differences		(0.7	)		(0.4	)		(0.1	)
Research and development tax credits		1.5			1.2			1.9
Impact of changes in state tax rate on deferred taxes		(2.9	)		—			—
Other		(0.2	)		(1.1	)		(1.8	)
Non-taxable stock premium		—			—			2.5
Change in valuation allowance		(20.0	)		(28.3	)		(33.7	)
Total provision for income taxes		—	%		—	%		—	%

The Company uses the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and the 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 assesses the likelihood that the resulting deferred tax assets will be realized. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized.

In assessing the realizability of deferred tax assets, the Company considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which the temporary differences representing net future deductible amounts become deductible. Due to the Company’s history of losses, and lack of other positive evidence, the Company has determined that it is more likely than not that its net deferred tax assets will not be realized, and therefore, the net deferred tax assets are fully offset by a valuation allowance at December 31, 2023 and 2022. The deferred tax assets were primarily comprised of federal and state tax net operating losses and tax credit carryforwards. The increase in valuation allowance of $27.7 million and $33.9 million during 2023 and 2022, respectively, was primarily attributable to the Company’s current year taxable loss and increase in the effective state tax rate due to changes in the Company’s state apportionment factors.

The components of the net deferred tax assets/liabilities are as follows (in thousands):


	December 31,
	2023			2022
Deferred tax assets:
Federal and state net operating loss carryforwards	$	112,904		$	109,191
Research and development tax credits		18,038			14,877
Lease liabilities		18,506			6,031
Accruals and other		4,685			3,786
Amortization		9,344			9,437
Deferred revenue		—			700
Other depreciation		593			449
Section 174 Capitalized Expense		41,571			21,434
Gross deferred tax assets		205,641			165,905
Valuation allowance		(188,663	)		(160,877	)
Net deferred tax assets		16,978			5,028
Deferred tax liabilities:
Other depreciation		—			—
Operating lease right-of-use assets		(16,978	)		(5,028	)
Deferred tax assets, net of allowance	$	—		$	—

Beginning January 1, 2022, the Tax Cuts and Jobs Act (the “Tax Act”) eliminated the option to deduct research and development expenditures in the current year and requires taxpayers to capitalize such expenses pursuant to Internal Revenue Code (“IRC”) Section 174. The capitalized expenses are amortized over a 5-year period for domestic expenses and a 15-year period for foreign expenses. As a result of this provision of the Tax Act, deferred tax assets related to capitalized research expenses increased by $20.1 million.

At December 31, 2023, the Company’s federal and state income tax net operating loss carryforwards were approximately $406.3 million and $485.8 million, respectively, which may be subject to limitations as described below. If not utilized, the federal tax loss carryforwards will begin to expire in 2035 and the state tax loss carryforwards will begin to expire in 2035. Under the Tax Act, federal net operating losses generated after 2017 and in future years may be carried forward indefinitely, but the deductibility of such federal net operating losses is limited. The federal net operating losses generated after December 31, 2017 of $355.7 million are carried forward indefinitely. In addition, the Company has certain federal, California and Massachusetts research and development income tax credit carryforwards of $17.1 million, $8.6 million and $1.9 million, respectively. If not utilized, the federal research and development income tax credit carryforwards will begin to expire in 2035. The California research and development income tax credit carryforwards do not expire and can be carried forward indefinitely. The Massachusetts research and development income tax credit carryforwards will begin to expire in 2035.

Net operating loss and tax credit carryforwards as of December 31, 2023 are as follows (in thousands):


	Amount		Expiration Years
Net operating losses, federal (post December 31, 2017)	$	355,720	Do not expire
Net operating losses, federal (pre January 1, 2018)		50,587	2035 - 2037
Net operating loss, state		485,794	2035 - 2043
Tax credits, federal		17,131	2035 - 2043
Tax credits, state		10,489	CA: credits do not expire MA: 2035 - 2043

The net operating loss and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities and may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%, as defined under IRC Sections 382 and 383. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. Subsequent ownership changes may further affect the limitation in future years. In connection with the Company’s IPO, which closed in October 2018, the Company did experience an ownership change pursuant to Section 382. There was no reduction in federal or California net operating loss carryforwards or research and development income tax credits as a result of this ownership change. The Company has not performed an analysis through December 31, 2023 under IRC Sections 382 and 383 to determine if the Company’s net operating loss carryforwards

and research and development credits are limited due to a change in ownership and may have an ownership change pursuant to Section 382.

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


	December 31,
	2023			2022		2021
Beginning of year—unrecognized tax benefits	$	6,715		$	5,481	$	4,025
Decrease for tax positions taken during prior periods		(77	)		—		—
Increases for tax positions taken during current period		8,213			1,234		1,456
End of year—unrecognized tax benefits	$	14,851		$	6,715	$	5,481

If recognized, none of the unrecognized tax benefits as of December 31, 2023, 2022, and 2021 would impact the annual effective tax rate, primarily due to corresponding adjustments to the valuation allowance. The Company does not expect any material changes to the estimated amount of liability associated with its uncertain tax positions within the next twelve (12) months.

During the years ended December 31, 2023, 2022, and 2021, the Company did not recognize accrued interest and penalties related to unrecognized tax benefits.

The Company files income tax returns in the U.S. federal jurisdiction and various state jurisdictions. The Company is not currently under audit by the Internal Revenue Service or other similar state or local authorities. Due to the net operating loss carryforwards, all years remain open for income tax examination by tax authorities in the United States and various state tax jurisdictions in which the Company files tax returns.

- Definition

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

+ References

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

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

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

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

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

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

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

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

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

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

+ Details

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Jan. 01, 2022	Dec. 31, 2021	Jan. 01, 2018
Income Taxes [Line Items]
Increase in valuation allowance	$ 27,700	$ 33,900
Changes in ownership over period	3 years
Unrecognized tax benefits that would impact effective tax rate	$ 0	0		$ 0
Accrued interest and penalties related to unrecognized tax benefits	0	0		$ 0
Deferred tax assets, capitalized research expense	$ 41,571	$ 21,434
Increased in deferred tax assets capitalized expense			$ 20,100
Minimum [Member]
Income Taxes [Line Items]
Cumulative changes in ownership interest of shareholders	50.00%
Research and Development \| California
Income Taxes [Line Items]
Business incentive tax credits to offset against taxes	$ 8,600
Research and Development \| Massachusetts
Income Taxes [Line Items]
Business incentive tax credits to offset against taxes	$ 1,900
Tax credits, Expiration year	2035
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	$ 406,300				$ 355,700
Net operating losses, Expiration year	2035
Business incentive tax credits to offset against taxes	$ 17,131
Tax credits, Expiration year	2035 - 2043
Federal \| Research and Development
Income Taxes [Line Items]
Business incentive tax credits to offset against taxes	$ 17,100
Tax credits, Expiration year	2035
State
Income Taxes [Line Items]
Net operating loss carryforwards	$ 485,794
Net operating losses, Expiration year	2035 - 2043
Net operating losses, Expiration year	2035
Business incentive tax credits to offset against taxes	$ 10,489
Tax credits, Expiration year	CA: credits do not expireMA: 2035 - 2043

Organization

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization

1. Organization

Description of Business

Gritstone bio, Inc. (“Gritstone” or “the Company”) is a clinical stage biotechnology company that aims to develop the world's most potent vaccines. The Company was incorporated in the state of Delaware in August 2015, and is based in Emeryville, California and Boston, Massachusetts, with a manufacturing facility in Pleasanton, California. The Company operates in one segment.

Liquidity

The Company has incurred operating losses and has an accumulated deficit as a result of ongoing efforts to develop drug product candidates, including conducting preclinical and clinical trials and providing general and administrative support for these operations. The Company had net losses of $138.5 million, $119.7 million, and $75.1 million for the years ended December 31, 2023, 2022, and 2021, respectively. The Company used net cash of $121.6 million, $115.9 million, and $50.7 million through its operating activities for the years ended December 31, 2023, 2022, and 2021, respectively. The Company had an accumulated deficit of $659.6 million and $521.1 million as of December 31, 2023 and 2022, respectively. To date, none of the Company’s product candidates have been approved for sale and therefore the Company has not generated any revenue from sales of commercial products. Management expects operating losses to continue for the foreseeable future. The Company has funded its operations to date primarily through private placements of its convertible preferred stock, the sale of common stock in public offerings, under an “at the market offering” (the “ATM Offering Program”), the private placement of common stock and pre-funded warrants, and through proceeds received from its collaboration arrangements. As of December 31, 2023, the Company had cash, cash equivalents and marketable securities of $79.3 million. The Company’s cash, cash equivalents and marketable securities are not sufficient to fund the Company’s planned operations for a period of 12 months from the date these consolidated financial statements are issued. To fund the Company's planned operations, the Company will need to raise additional capital. The Company intends to raise additional capital through private and public equity offerings, including its “at-the-market” offering program, debt financings, and potential future collaboration, license and development agreements. However, there can be no assurance that the Company will be successful in acquiring additional funding at levels sufficient to fund its operations or on terms acceptable to the Company or at all. If the Company is unsuccessful in its efforts to raise additional capital or if sufficient funds on acceptable terms are not available when needed, the Company could be required to significantly reduce operating expenses and delay, reduce the scope of or eliminate one or more of its development programs or its future commercialization efforts, out-license intellectual property rights to its product candidates and sell unsecured assets, or a combination of the above, any of which may have a material adverse effect on the Company’s business, results of operations, financial condition and/or its ability to fund its scheduled obligations on a timely basis or at all. Failure to manage discretionary spending or raise additional capital, as needed, may adversely impact the Company’s ability to achieve its intended business objectives. These conditions raise substantial doubt about the Company’s ability to continue as a going concern for a period of one year from the date of the issuance of these consolidated financial statements. If we are unable to raise additional funds, secure a waiver or renegotiate the terms of our Loan Agreement, we expect to be in default of the minimum liquidity requirement in the second quarter of 2024. Upon such a default, our existing cash, cash equivalents and investments will only be sufficient to fund our operations into the second quarter of 2024. The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The consolidated financial statements do not reflect any adjustments relating to the recoverability and classification of assets or the amounts and classification of liabilities that might be necessary if the Company is unable to continue as a going concern.

Stock-Based Compensation - Schedule of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Number of options beginning balance	4,814,394
Authorized	4,775,796
Granted	(4,227,353)
Cancelled	824,088
Number of options ending balance	6,186,925	4,814,394
Number of Shares
Outstanding at beginning of period	6,951,620
Granted	712,566
Exercised	(6,000)
Cancelled	(384,725)
Outstanding at end of period	7,273,461	6,951,620
Options Outstanding, Number of Shares, Vested and exercisable	4,647,325
Options Outstanding, Number of Shares, Vested and expected to vest	6,997,158
Weighted-Average Exercise Price
Beginning Balance	$ 7.92
Granted	2.2
Exercised	0.76
Cancelled	5.35
Ending Balance	7.5	$ 7.92
Weighted-Average Exercise Price, Vested and exercisable	8.53
Weighted-Average Exercise Price, Vested and expected to vest	$ 7.6
Options Outstanding, Weighted-Average Remaining Contractual Term (in years)	7 years 3 months 3 days	8 years 29 days
Options Outstanding, Weighted-Average Remaining Contractual Term, Vested and exercisable (in years)	6 years 8 months 1 day
Options Outstanding, Weighted-Average Remaining Contractual Term, Vested and expected to vest (in years)	7 years 2 months 19 days
Options Outstanding, Aggregate Intrinsic Value	$ 264	$ 1,089
Options Outstanding, Aggregate Intrinsic Value, Vested and exercisable	200
Options Outstanding, Aggregate Intrinsic Value, Vested and expected to vest	$ 254

Stockholders' Equity

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Stockholders' Equity

10. Stockholders’ Equity

The Company’s amended and restated certificate of incorporation, as amended, provides for 300,000,000 shares of common stock and 10,000,000 shares of preferred stock authorized for issuance, each with a par value of $0.0001 per share.

As of December 31, 2023 and 2022, no shares of preferred stock were issued and outstanding.

As of December 31, 2023 and 2022, there were 97,585,415 and 86,894,901 shares of common stock issued and outstanding, respectively. Holders of the Company’s common stock are entitled to one vote per share.

Sale of Common Stock and Pre-Funded Warrants

In December 2020, the Company entered into two private placement financing transactions (collectively, the “First PIPE Financing”), as follows: (i) to sell 5,543,351 shares of its common stock at a price of $3.34 per share and pre-funded warrants (the “Warrants”) to purchase 27,480,719 shares of common stock at a price of $3.34 per share (of which $3.33 per share was prepaid by each purchaser), and (ii) to sell an additional 4,043,127 shares of its common stock at a price per share of $3.71. In connection with the First PIPE Financing, the Company received aggregate net proceeds of approximately $119.8 million. The Warrants are exercisable upon issuance at an exercise price of $0.01 per share.

The outstanding Warrants generally may not be exercised if the holder’s aggregate beneficial ownership would be more than 9.99% of the total issued and outstanding shares of the Company’s common stock following such exercise. The exercise price and number of shares of common stock issuable upon the exercise of the Warrants (the “Warrant Shares”) are subject to adjustment in the event of any stock dividends and splits, reverse stock split, recapitalization, reorganization or similar transaction, as described in the Warrant agreements. Under certain circumstances, the Warrants may be exercisable on a “cashless” basis. In connection with the issuance and sale of the common stock and Warrants, the Company granted the purchasers certain registration rights with respect to the Warrants and the Warrant Shares.

The Warrants were classified as a component of permanent stockholders’ equity within additional paid-in-capital and were recorded at the issuance date using a relative fair value allocation method. The Warrants are equity classified because they are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, are immediately exercisable, do not embody an obligation for the Company to repurchase its shares, permit the holders to receive a fixed number of common shares upon exercise, are indexed to the Company’s common stock and meet the equity classification criteria. In addition, such Warrants do not provide any guarantee of value or return. The Company valued the Warrants at issuance, concluding their sales price approximated their fair value, and allocated net proceeds from the sale proportionately to the common stock and Warrants, of which $87.7 million, net of issuance costs, was allocated to the Warrants and recorded as a component of additional paid-in-capital.

In September 2021, the Company completed a PIPE financing transaction, in which it sold 5,000,000 shares of its common stock at a price of $11.00 per share pursuant to a securities purchase agreement entered into on September 16, 2021 (the “Second PIPE Financing”). The Company received aggregate net proceeds of approximately $52.7 million after deducting placement agent commissions and offering expenses payable by the Company. In connection with the issuance and sale of the common stock, the Company agreed to file a registration statement with the SEC registering the resale of the shares of common stock issued in the Second PIPE Financing.

In March 2022, the Company filed a Registration Statement on Form S-3 with the SEC (the “2022 Shelf Registration Statement”), covering the offering of up to $250.0 million of common stock, preferred stock, debt securities, warrants and units. The 2022 Shelf Registration Statement included a prospectus supplement covering the issuance and sale of up to $100.0 million of the Company’s common stock, from time to time, through an “at-the-market” offering program (the “2022 ATM Offering Program”) under the Securities Act. The SEC declared the 2022 Shelf Registration Statement effective as of May 6, 2022.

In connection with the 2022 ATM Offering Program, in March 2022, the Company also entered into a sales agreement (the “2022 Sales Agreement”) with Cowen, pursuant to which Cowen and Company, LLC. ("Cowen") will act as the Company’s sales agent and, from time to time, offer and sell shares of the Company’s common stock having an aggregate offering price of up to $100.0 million. Cowen is entitled to compensation for its services equal to up to 3.0% of the gross proceeds of any shares of common stock sold under the 2022 Sales Agreement. In addition, the Company agreed to reimburse a portion of Cowen’s expenses in connection with the 2022 ATM Offering Program up to $50,000. As of December 31, 2023, the Company has received aggregate proceeds from its 2022 ATM Offering Program of $27.5 million, net of commissions and offering costs, pursuant to the issuance of 10,230,628 shares of its common stock. As of December 31, 2022, the Company has received aggregate proceeds from its 2022 ATM Offering Program of $19.6 million, net of commissions and offering costs, pursuant to the issuance of 7,034,948 shares of its common stock.

In October 2022, the Company completed a PIPE financing transaction, in which it sold 6,637,165 shares of its common stock at a price of $2.26 per share pursuant to a securities purchase agreement entered into on October 24, 2022 and pre-funded warrants (the “Warrants”) to purchase 13,274,923 shares of common stock at a price of $2.26 per share (of which $2.2599 per share was prepaid by each purchaser) (the “Third PIPE Financing”). The Company received aggregate net proceeds of approximately $42.4 million after deducting placement agent commissions and offering expenses payable by the Company. In connection with the issuance and sale of the common stock, the Company agreed to file a registration statement with the SEC registering the resale of the shares of common stock issued in the Third PIPE Financing. The Warrants are exercisable upon issuance at an exercise price of $0.0001 per share.

The Warrants were classified as a component of permanent stockholders’ equity within additional paid-in-capital and were recorded at the issuance date using a relative fair value allocation method. The Warrants are equity classified because they are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, are immediately exercisable, do not embody an obligation for the Company to repurchase its shares, permit the holders to receive a fixed number of common shares upon exercise, are indexed to the Company’s common stock and meet the equity classification criteria. In addition, such Warrants do not provide any guarantee of value or return. The Company valued the Warrants at issuance, concluding their sales price approximated their fair value, and allocated net proceeds from the sale proportionately to the common stock and Warrants, of which $28.2 million, net of issuance costs, was allocated to the Warrants and recorded as a component of additional paid-in-capital.

Common Stock Warrants

As of December 31, 2023, the following warrants to purchase shares of the Company’s common stock were issued and outstanding:


Issue Date	Expiration Date	Exercise Price		Number of Warrants Outstanding
December 28, 2020	None	$	0.01		7,214,333
October 24, 2022	None	$	0.0001		13,274,923
					20,489,256

During the year ended December 31, 2023, there were 6,359,371 warrants exercised, resulting in the Company issuing 6,348,805 shares of common stock due to net exercise of the warrants. During the year ended December 31, 2022, there were 3,442,567 warrants exercised, resulting in the Company issuing 3,442,567 shares of common stock.

- Definition

The entire disclosure for equity.

+ References

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+ Details

Subsequent Events

12 Months Ended

Dec. 31, 2023

Subsequent Events [Abstract]

Subsequent Events

15. Subsequent Events

In February 2024, we implemented a reduction in workforce of approximately 40% of our workforce intended to reduce costs and preserve capital. We are currently evaluating the accounting impact on our consolidated financial statements.

Property and Equipment, Net - Summary of Property and Equipment and Related Accumulated Depreciation and Amortization (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 49,681	$ 48,773
Less accumulated depreciation and amortization	(32,415)	(28,782)
Total property and equipment, net	17,281	21,335
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,704	1,155
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,723	2,285
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	29,521	27,309
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	15,733	18,024
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, net	$ 15	$ 1,344

Stock-Based Compensation - Schedule of Fair Value of Stock Purchase Rights Granted Under 2018 Employee Stock Purchase Plan (Detail) - 2018 Employee Stock Purchase Plan [Member]	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%
Expected term	6 months	6 months	6 months 25 days
Risk-free interest rate	5.10%	1.30%	0.10%
Expected volatility	90.10%	94.90%	88.00%

- 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.

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-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

+ Details

Collaboration and License Agreements

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Collaboration and License Agreements

7. Collaboration and License Agreements

2seventy bio, Inc.

In August 2018, the Company entered into a Research Collaboration and License Agreement with bluebird bio, Inc. (“bluebird”). In November 2021, bluebird assigned the Research Collaboration and License Agreement (the “2seventy Agreement”), to its affiliate, 2seventy bio, Inc. (“2seventy”), in connection with an internal restructuring and subsequent spin-out of 2seventy. Under the terms of the 2seventy Agreement, the Company provides to 2seventy tumor-specific targets across several tumor types and, in certain cases, T cell receptors (TCR) directed to those targets. The Company received a non-refundable upfront payment of $20.0 million, and 2seventy also concurrently acquired 768,115 shares of the Company’s Series C convertible preferred stock for $10.0 million at $13.04 per share. Per the 2seventy Agreement, 2seventy was also provided an option to acquire shares of the Company’s common stock at the same price as all other investors in connection with the Company’s initial public offering (“IPO”). In October 2018, 2seventy purchased 666,667 shares of the Company’s common stock at the price to the public of $15.00 per share for a total of $10.0 million. Under the terms of the 2seventy Agreement, the Company is eligible to earn development, regulatory, and sales-based milestones in an amount of up to $1.2 billion, and single-digit royalties on sales of products that utilize the technology subject to the 2seventy Agreement. None of these events had occurred as of December 31, 2023, and no royalties were due from the sale of licensed products.

In August 2019, the Company entered into a First Amendment to the 2seventy Agreement, which extended the timeline for the Company and 2seventy to execute a Patient Selection Services Agreement from within one year to within two years after the Effective Date of the 2seventy Agreement. In August 2020, the Company entered into a Second Amendment, which extended the timeline of the Patient Selection Services Agreement to within three years and also extended the Tissue Analysis Period from February 28, 2021 to June 30, 2021. In April 2021, the Company entered into a Third Amendment, which removed the Patient Selection Services Agreement in its entirety and extended the Tissue Analysis Period from June 30, 2021 to December 31, 2021. In November 2023, the Company entered into a Fourth Amendment, which extended the timeline of the Target Designation Period for a final TCR discovery campaign to January 31, 2024. The amendments were entered into for administrative purposes, and the Company determined the amendments were not a modification of contract under the contract with customers guidance.

2seventy may terminate the 2seventy Agreement by giving a 120-day prior written notice to the Company at any time after the effective date of the agreement. Unless terminated early, the agreement has a term that ends upon the last payment owed by the Company on a licensed product. The 2seventy Agreement may be terminated for cause by either party based on an uncured material breach by the other party or bankruptcy of the other party. Upon early termination, all ongoing activities under the agreement and all mutual collaboration, development and commercialization licenses and sublicenses will terminate. The licenses granted by the Company to 2seventy under the licensed intellectual property will remain in effect in accordance with their respective terms. Additionally, all of 2seventy’s payment obligations that have not yet accrued related to future milestone and royalty payments will be reduced by 50% for the remainder of the agreement term.

The Company concluded that 2seventy is a customer, and the contract is not subject to guidance on collaborative arrangements. This is because the Company granted 2seventy a license to the Company’s intellectual property and provided research and development services, all of which are outputs of the Company’s ongoing activities, in exchange for consideration.

The Company identified the following three material promises under the 2seventy Agreement: (i) transfer of a license to intellectual property and related technology know-how (“License and Know-How”); (ii) the obligation to perform target selection and TCR generation services (“Research and Development Services”); and (iii) participation on the Joint Steering Committee (the “JSC”). The Company provided to 2seventy standard indemnification and protection of licensed intellectual property, which is part of assurance that the license meets the contract’s specifications and is not an obligation to provide goods or services.

The Company considered that the License and Know-How has standalone functionality, was considered to be functional intellectual property, and is capable of being distinct. However, the Company determined that the License and Know-How is not distinct from the Research and Development Services or participation on the JSC within the context of the 2seventy Agreement, because 2seventy is dependent on the Company to execute the Research and Development Services and participate on the JSC in order for 2seventy to benefit from the License and Know-How. As such, the License and Know-How is combined with the Research and Development Services and participation on the JSC into a single performance obligation, and the transaction price under this arrangement will be allocated to this single performance obligation.

The Company has also determined that all other goods or services that are contingent upon 2seventy reaching various milestones are not considered performance obligations at the inception of the arrangement.

The transaction price at the inception of the 2seventy Agreement consisted of the upfront payment of $20.0 million and the $10.0 million received from 2seventy for the purchase of the Company’s Series C convertible preferred stock. The sale of the Series C convertible preferred stock was not considered to be a performance obligation, as it was a separate financing component of the transaction. Accordingly, $10.0 million of the transaction price was allocated to the issuance of 768,115 shares of Series C convertible preferred stock at fair value of $13.04 per share and recorded in stockholders’ equity.

The variable consideration related to the remaining development, regulatory, and sales-based milestones payments has not been included in the initial transaction price and continues to be fully constrained as of December 31, 2023. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon initiation of clinical trials for early-stage targets and 2seventy’s development efforts. Any variable consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur, as they were determined to relate predominantly to the License and Know-How granted to 2seventy. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur.

For revenue recognition purposes, the Company determined that the duration of the 2seventy Agreement began on the effective date in August 2018 and ends upon completion of the Research and Development Services, which is also when the participation on the JSC is no longer an obligation. The contract duration is defined as the period in which parties to the contract have present enforceable rights and obligations. The Company also analyzed the impact of 2seventy terminating the agreement prior to August 2023 and determined, considering both quantitative and qualitative factors, that there were substantive non-monetary penalties to 2seventy for doing so.

Revenue is recognized when, or as, the Company satisfies its performance obligation by transferring the promised services to 2seventy. Revenue is being recognized over time using a cost-based input method, based on internal labor cost effort to perform the research services, since the internal labor cost incurred over time is thought to best reflect the transfer of services to 2seventy. In applying a cost-based input method of revenue recognition, we use actual costs incurred relative to budgeted costs to fulfill the combined performance obligation. A cost-based input method of revenue recognition requires us to make estimates of costs to complete the performance obligation. The cumulative effect of any revisions to estimated costs to complete the performance obligation will be recorded in the period in which changes are identified and amounts can be reasonably estimated. A significant change in these assumptions and estimates could have a material impact on the timing and amount of revenue recognized in future periods.

For the years ended December 31, 2023, 2022, and 2021, the Company recognized $1.0 million, $7.7 million, and $3.0 million, respectively, in collaboration revenue under the 2seventy Agreement. The amount of collaboration revenue recognized during the year ended December 31, 2022 included cumulative catch-up adjustments increasing collaboration revenue by $6.4 million due to revisions to estimated costs to complete the remaining performance obligation. The adjustments resulted in a decrease in the Company’s loss from operations of $6.4 million and a decrease in loss per share of $0.07 for the year ended December 31, 2022. No deferred revenue was recorded on the consolidated balance sheet as of December 31, 2023. Deferred revenue of $1.0 million was recorded on the consolidated balance sheet in current liabilities as of December 31, 2022. Deferred revenue related to the performance obligations identified under the 2seventy Agreement that was recognized over the period the performance obligations were satisfied.

Changes in the deferred revenue balance during the year ended December 31, 2023 are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2022	$	1,047
Additions		—
Deductions		(1,047	)
Balance at December 31, 2023	$	—

There were no receivables or net contract assets recorded as of December 31, 2023 or 2022 associated with the 2seventy Agreement.

Gilead Sciences, Inc.

In January 2021, the Company entered into a Collaboration, Option and License Agreement (the “Gilead Collaboration Agreement”) with Gilead Sciences, Inc. (“Gilead”) to research and develop a vaccine-based immunotherapy as part of Gilead’s efforts to find a curative treatment for HIV infection. Under the terms of the Gilead Collaboration Agreement, the Company granted to Gilead an exclusive, worldwide license to develop and commercialize a HIV-specific therapeutic vaccine utilizing the Company’s technology. Gilead is responsible for conducting all development and commercialization activities beginning with a Phase 1 clinical trial, and the Company is responsible for contributing to preclinical research studies and participation in a joint steering committee (collectively, “research and development activities”). Concurrently with the execution of the Gilead Collaboration Agreement, the Company and Gilead entered into a Supply Agreement (the “Gilead Supply Agreement”) under which the Company will supply research product and GMP product (“Product Supply”) that may be required under the Gilead Collaboration Agreement until Gilead completes its first GMP product batch, and the Company will participate in a joint manufacturing team (collectively, “product supply activities”). In addition, the Company also concurrently entered into a Stock Purchase Agreement (the “Gilead Stock Purchase Agreement”) under which Gilead acquired, in a private placement transaction, 1,169,591 shares of the Company’s common stock. The common shares were issued to Gilead with certain registration rights and certain standstill and market stand-off provisions. The Company determined that these concurrent contracts represent a combined arrangement (the “Gilead Arrangement”).

Under the Gilead Collaboration Agreement, the Company received a non-refundable upfront payment of $30.0 million. Under the Gilead Collaboration Agreement and the Gilead Supply Agreement, the Company will receive additional reimbursement payments for expenses incurred in the research and development activities and product supply activities. Under the Gilead Stock Purchase Agreement, the common shares were sold at a price of $25.65 per share for a total of $30.0 million. The Company’s common stock at fair value on closing was $18.10 per share. If Gilead decides to move forward with development beyond the initial Phase 1 clinical trial (the “Option”), the Company will receive a $40.0 million non-refundable option fee and will be eligible to receive up to an aggregate of $685.0 million if certain clinical, regulatory and commercial milestones are achieved, as well as tiered royalties ranging from the mid-single digits to low double-digits on net sales of a therapeutic product utilizing its technology. None of these events had occurred as of December 31, 2023 and no royalties were due from the sale of licensed products.

Gilead may terminate the Gilead Collaboration Agreement for convenience by giving a 90-day prior written notice to the Company at any time after the effective date of the agreement. Unless terminated early, the agreement has a term that ends upon the expiration of the royalty term, or, if the Option is not exercised, by the end of the Option term. The Gilead Collaboration Agreement may be terminated for cause by either party based on an uncured material breach by the other party, insolvency of the other party, or patent challenge. Upon early termination, all ongoing activities under the agreement and all mutual collaboration, development and commercialization licenses and sublicenses will terminate. The licenses granted by the Company to Gilead under the licensed intellectual property will remain in effect in accordance with their respective terms. Additionally, if terminated early by Gilead for convenience or by the Company for material breach or insolvency, all of Gilead’s payment obligations for reimbursable costs or for future milestone and royalty payments remain. If terminated early by Gilead for material breach or insolvency, all of Gilead’s unaccrued payment obligations related to future milestone and royalty payments will be reduced by 50% for the remainder of the agreement term. Furthermore, Gilead may terminate the Gilead Supply Agreement without cause by giving six months prior written notice and may terminate any active orders with 60-day notice without terminating the agreement, and either party may terminate based on an uncured material breach, insolvency of the other party, or in the event that the Gilead Collaboration Agreement is terminated. Upon termination, the Company will deliver all supply products that have been produced and destroy, reimburse or deliver materials that Gilead has reimbursed, and Gilead must pay for any manufacturing costs that the Company has actually incurred or committed to pay, including any cancellation costs owed to subcontractors.

The Company concluded that Gilead is a customer and therefore revenue recognition should be accounted for in accordance with ASC 606, because the Company granted to Gilead licenses to its intellectual property and will provide research and development services and Product Supply, all of which are outputs of the Company’s ongoing activities, in exchange for consideration. The Option, if exercised by Gilead, will be considered a modification that increases the scope of the arrangement beyond the Option term.

The Company identified the following performance obligations under the Gilead Collaboration Agreement: (i) licenses including an exclusive (in the HIV field), royalty-free, worldwide collaboration license and transfer of know-how and an exclusive (in the HIV field) worldwide, royalty-bearing development and commercialization license subject to restrictions on its use during the Option term and an exclusive option to release such restrictions; (ii) preclinical research and development activities, manufacturing-related activities, and participation on a Joint Steering Committee; and (iii) product supply, including research and GMP product, until Gilead completes its first GMP batch, and participation on a Joint Manufacturing Team.

The Company considered that the licenses and know-how have standalone functionality, are considered to be functional intellectual property and are capable of being distinct. The Company also determined that the research and development activities and product supply by Gritstone could be provided by resources otherwise available to Gilead and thus are capable of being distinct.

The Company has also determined that the pricing for optional goods and services and release of license restrictions upon exercise of the Option do not constitute material rights and are not a potential performance obligation. The Company evaluated whether there is an interdependence between the promises and determined that the licenses are a combined solution and the predominant performance obligation, while the other promises are separately identifiable in the context of the contract; however, the research and development activities are dependent on the research product supply, which is accounted for as a combined performance obligation. As a result, the Company identified three performance obligations in the Gilead Arrangement: (i) exclusive licenses and know-how, (ii) research and development activities and product supply, and (iii) GMP product supply.

The transaction price at the inception of the Gilead Collaboration Agreement consisted of the upfront payment of $30.0 million and the $30.0 million received for the sale of the Company’s common stock. The sale of the common stock was not considered to be a performance obligation, as it was a separate financing component of the transaction. Accordingly, $21.2 million of the transaction price was allocated to the issuance of 1,169,591 shares of the Company’s common stock at fair value on closing of $18.10 per share and recorded in stockholders’ equity. The remaining $8.8 million of the common stock purchase price in excess of the fair value of the shares received is added to the transaction price for the Gilead Collaboration Agreement. In addition, the initial transaction price includes estimated variable consideration for budgeted reimbursement of research and development costs and product supply. The variable consideration related to reimbursable costs and product supply has been constrained as of December 31, 2023 based on the current research and development plan forecast. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur.

The Company determined that the variable consideration for the $40.0 million option exercise fee and for the development, regulatory, and sales-based milestones payments were probable of significant revenue reversal as their achievement was highly dependent on factors outside the Company’s control. As a result, these payments were fully constrained and were not included in the transaction price. Any variable consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur, as they were determined to relate predominantly to the exclusive licenses and know-how granted to Gilead.

The transaction price is allocated to the performance obligation based upon relative standalone selling prices, which were determined for the exclusive licenses and know-how using an adjusted market approach and for the research and development activities and product supply using a cost plus reasonable margin approach. Variable consideration is allocated to the specific performance obligations to which it relates.

For revenue recognition purposes, the Company determined that the duration of the contract began on the effective date in January 2021 and ends upon (i) the completion of the Option term, which is expected to end two to four years after the effective date, if the Option is not exercised or (ii) the expiration of the royalty-term on a product-by-product and country-by-country basis. The Company also analyzed the impact of Gilead terminating the agreement prior to the end of the Option term and determined, considering both quantitative and qualitative factors, that there were substantive non-monetary penalties to Gilead for doing so.

Revenue for the exclusive licenses and know-how was recognized on the effective date of the Gilead Collaboration Agreement at the point in time that the licenses are effective. The research and development activities and product combined performance obligation and the GMP product supply performance obligation are recognized over time when, or as, the Company transfers the promised goods and services to Gilead. Research and development service and product supply revenues will be recognized over time using a cost-based input method, based on internal and external labor cost effort to perform the services, costs to acquire research materials, and costs of product supply, since the costs incurred over time are thought to best reflect the transfer of goods and services to Gilead. In applying a cost-based input method of revenue recognition, we use actual costs incurred relative to estimated total costs to fulfill each performance obligation. A cost-based input method of revenue recognition requires us to make estimates of costs to complete the performance obligation. The cumulative effect of any revisions to estimated costs to complete the performance obligation and associated variable consideration will be recorded in the period in which changes are identified and amounts can be reasonably estimated. A significant change in these assumptions and estimates could have a material impact on the timing and amount of revenue recognized in future periods.

For the years ended December 31, 2023 and 2022, the Company did not record any license revenue. For the years ended December 31, 2023 and 2022, the Company recorded $0.3 million and $1.6 million, respectively, as collaboration revenue as a result of

satisfying its performance obligations by transferring the promised goods and services estimated by the costs incurred for the Gilead Collaboration Agreement. For the year ended December 31, 2021, the Company recognized $38.6 million as license revenue, and $5.1 million as collaboration revenue as a result of satisfying its performance obligations by transferring the promised goods and services estimated by the costs incurred for the Gilead Collaboration Agreement. There was no contract asset recorded on the consolidated balance sheet as of December 31, 2023 or 2022. There was $0.1 million and $0.1 million recorded as deferred revenue as of December 31, 2023 and 2022, respectively, associated with the Gilead Collaboration Agreement.

Changes in the short-term deferred revenue balance during the year ended December 31, 2023 for the Gilead Collaboration Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2022	$	107
Additions		—
Deductions		(56	)
Balance at December 31, 2023	$	51

There was de minimis and $0.1 million of receivables recorded on the consolidated balance sheet as a current asset in the prepaid expenses and other current assets balance as of December 31, 2023 and 2022, respectively.

The Company deferred $0.1 million in incremental costs to acquire the Gilead Collaboration Agreement in the first quarter of 2021 allocated to performance obligations recognized over time, which will be recognized over time in each period proportionate to revenue recognition. There were no deferred contract acquisition costs amortized during the year ended December 31, 2023 as they were fully amortized during the year ended December 31, 2022. Deferred contract acquisition costs amortized during the year ended December 31, 2022 and 2021 were negligible.

Arbutus Biopharma Corporation

In October 2017, the Company entered into an Exclusive License Agreement with Arbutus and its wholly-owned subsidiary, Protiva Biotherapeutics Inc. Certain terms of the agreement were modified by amendment in July 2018. Under the license agreement, the Company has an exclusive license to utilize certain Arbutus intellectual property, including patents and know-how relating to immunotherapy. During the years ended December 31, 2023, 2022, and 2021, the Company had no research and development expense under the agreement. The Company is obligated to pay Arbutus certain milestone payments up to $123.5 million on achievement of specified events, and royalties on sales of its licensed products. Following the acceptance of our investigational new drug application for GRANITE by the FDA, the Company made a $2.5 million development milestone payment to Arbutus in September 2018 that was recorded as research and development expense. In August 2019, a milestone was met following the initial patient treatment of SLATE in the Company’s GO-005 clinical trial. In 2019, the Company recorded $3.0 million as research and development expense in connection with the milestone. None of the other events had occurred as of December 31, 2023, and no royalties were due from the sale of licensed products.

Non-Profit Hospital Cancer Center

In January 2016, the Company entered into an Exclusive License Agreement with a non-profit hospital cancer center. Under the license agreement, the Company has an exclusive license to utilize certain patents and know-how relating to immunotherapy for an insignificant upfront payment, cash milestone payments on achievement of specified events, and a low single digit royalty on sales of licensed products. The achievement of the milestones and payment of royalties is dependent upon obtaining regulatory approval. Upon achievement of a milestone related to the Company’s Phase 1 clinical trial for GRANITE, GO-004, in December 2018 the Company recorded an insignificant amount to research and development expense for amounts owed to the Hospital Cancer Center, which was paid to the hospital in February 2019. None of the other milestone events had occurred as of December 31, 2023, and no royalties were due from the sales of licensed products.

Genevant Sciences GmbH

In October 2020, the Company entered into an Option and License and Development Agreement (as amended, the “2020 Genevant License Agreement”) with Genevant Sciences GmbH (“Genevant”), pursuant to which Genevant granted the Company exclusive license rights under certain intellectual property related to Genevant’s LNP technology for a single therapeutic indication, and

the Company agreed to pay Genevant an initial payment of $2.0 million, up to an aggregate of $71.0 million in specified development, regulatory, and commercial milestones, and low to mid-single digit royalties on net sales of licensed products. The upfront payment of $2.0 million was included in research and development expense for the year ended December 31, 2020. Genevant is a spin-off of Arbutus, and the 2020 Genevant License Agreement expands Gritstone’s intellectual property rights to such LNP technology originally obtained pursuant to the Company’s license agreement with Arbutus. Prior to the 2020 Genevant License Agreement, the Company licensed Arbutus’ LNP technology for indications in the oncology space. The remainder of Arbutus’ IP portfolio was transferred to Genevant in the spin-off. In March 2022, a milestone in the amount of $1.0 million was met, which was included in research and development expense for the year ended December 31, 2022. None of the other milestone events under the 2020 Genevant License Agreement had occurred as of December 31, 2023.

Pursuant to the 2020 Genevant License Agreement, Genevant also granted the Company certain options to license the LNP technology for additional therapeutic indications of up to $1.5 million for each indication and $1.0 million to extend the option term. The 2020 Genevant License Agreement continues in effect until the last to expire royalty term or early termination. It is terminable by the Company for convenience with 90 days prior written notice or immediately if based on certain product safety or efficacy or regulatory criteria. Either party may terminate the agreement for material breach, subject to a cure period, and Genevant may terminate the agreement if the Company challenges a licensed patent. In August 2023, the 2020 Genevant License Agreement was amended to terminate the options to license the LNP technology for additional indications.

In January 2021, the Company entered into a Non-Exclusive License and Development Agreement (the “2021 Genevant License Agreement”) with Genevant. Pursuant to the 2021 Genevant License Agreement, the Company obtained a nonexclusive license to Genevant’s LNP technology to develop and commercialize self-amplifying RNA (“samRNA”) vaccines against SARS-CoV-2, the virus that causes COVID-19. Under the 2021 Genevant License Agreement, the Company made a $1.5 million upfront payment to Genevant, and Genevant is eligible to receive from the Company up to an aggregate of $191.0 million in contingent milestone payments per product, plus certain tiered royalties, upon achievement of development and commercial milestones. In certain scenarios, in lieu of milestones and royalties, Genevant will be entitled to a percentage of amounts that the Company receives from sublicenses under the 2021 Genevant License Agreement, subject to certain conditions. In March 2021, a milestone in the amount of $1.0 million was met following the initial patient treatment in the Phase 1 clinical trial conducted through the NIAID-supported Infectious Diseases Clinical Research Consortium (“IDCRC”). Both the $1.5 million upfront and $1.0 million milestone payments were recorded as research and development expense for the year ended December 31, 2021. None of the other milestone events under the 2021 Genevant License Agreement had occurred as of December 31, 2023.

In August 2023, the Company entered into an Option and Non-Exclusive License and Development Agreement (the “2023 Genevant License Agreement”) with Genevant. Pursuant to the 2023 Genevant License Agreement, the Company obtained a multi-year option for a non-exclusive license under Genevant’s LNP technology on a pathogen-by-pathogen basis to develop and commercialize samRNA vaccines against infectious disease. Under the 2023 Genevant License Agreement, (i) the Company made a $2.5 million upfront payment to Genevant, recorded as research and development expense for the year ended December 31, 2023, and (ii) Genevant is eligible to receive from the Company option maintenance and exercise fees in the single digit millions and up to an aggregate of $136.0 million in contingent milestone payments per product, subject to increase for multi-pathogen products and in other specified circumstances, and royalties ranging from the mid to high single digits on future product sales. If Gritstone outlicenses an applicable infectious disease program, in lieu of certain of these payments, Genevant may be entitled to a percentage of amounts that Gritstone receives from its sublicensee. None of the milestone events under the 2023 Genevant License Agreement had occurred as of December 31, 2023.

Coalition for Epidemic Preparedness Innovations

In August 2021, the Company entered into the CEPI Funding Agreement with CEPI, under which CEPI agreed to provide funding of up to $20.6 million to the Company to advance the Company’s CORAL program, a second-generation COVID-19 vaccine program, with an initial clinical trial in South Africa. Under the terms of the agreement, CEPI is funding a multi-arm Phase 1 clinical trial evaluating the CORAL program’s samRNA vaccine in naïve, convalescent, and HIV+ patients. The study is evaluating three different samRNA vaccine constructs that each target both the spike protein and other SARS-CoV-2 targets and are designed to drive both robust B and T cell immune responses. The funding will also supporting pre-clinical studies, scale-up and formulation development to enable manufacturing of large quantities of stable vaccine product.

Under the terms of the CEPI Funding Agreement, among other things, the Company and CEPI agreed on the importance of global equitable access to the vaccine produced pursuant to the CEPI Funding Agreement. The vaccine, if approved, is expected to be

made available to the COVAX Facility for procurement and allocation. The COVAX Facility aims to deliver equitable access to COVID-19 vaccines for all countries, at all levels of development, that wish to participate.

The scope and continuation of the CEPI Funding Agreement may be amended depending on ongoing developments of the COVID-19 outbreak and the success of the Company’s COVID-19 vaccine candidate developed under the CEPI Funding Agreement relative to other third-party COVID-19 vaccine candidates or treatments. If the World Health Organization (“WHO”), CEPI or a regulatory authority having jurisdiction over a clinical trial performed under the CEPI Funding Agreement determines that a third-party product candidate has substantially greater potential than the Company’s COVID-19 vaccine candidate developed under the CEPI Funding Agreement and should be prioritized instead for a particular trial, the Company must consider in good faith any written request of CEPI not to proceed with a clinical trial of such COVID-19 vaccine candidate; however the determination of whether or not to proceed with such trial shall be made by the Company in its sole discretion. In addition, CEPI has the right to unilaterally terminate the CEPI Funding Agreement upon prior written notice if CEPI determines that (i) there are material safety, regulatory, scientific misconduct or ethical issues with the project undertaken by the Company under the CEPI Funding Agreement, (ii) the project undertaken by the Company under the CEPI Funding Agreement should be terminated, (iii) the Company becomes unable to discharge its obligations under the CEPI Funding Agreement, (iv) the Company fails to meet certain criteria set forth in the CEPI Funding Agreement, or (v) the Company commits fraud or a financial irregularity, as such terms are defined in the CEPI Funding Agreement.

In December 2021, the Company and CEPI entered into an amendment to the CEPI Funding Agreement, under which CEPI agreed to provide additional funding up to $5.0 million, for a total of up to $25.6 million, to the Company to conduct a Phase 1 clinical trial of the Company’s Omicron vaccine candidate in South Africa. In January 2024, the Company and CEPI entered into a second amendment to the CEPI Funding Agreement, which repurposed certain unspent funds for preclinical immunogenicity studies for use for preclinical challenge studies.

CEPI advances grant funds upon request by the Company consistent with the agreed upon amounts and schedules as provided in the CEPI Funding Agreement. The first tranche of funding of $11.3 million was received in September 2021, the second tranche of funding of $2.7 million was received in April 2022, the third tranche of funding of $1.2 million was received in June 2023, and the fourth tranche of funding of $2.4 million was received in December 2023.

Payments received in advance that are related to future performance are deferred and recognized as grant revenue when the research and development activities are performed. Cash payments received under the CEPI Funding Agreement are restricted as to their use until expenditures contemplated in the agreement are incurred. During the years ended December 31, 2023, 2022 and 2021, the Company recognized grant revenue of $4.3 million, $9.5 million, and $1.5 million, respectively, under the CEPI Funding Agreement. As of December 31, 2023 and 2022, short-term restricted cash and short-term deferred revenue of $2.3 million and $3.0 million, respectively, were recorded on the consolidated balance sheets. Deferred revenue will be recognized over the period in which the CEPI Funding Agreement activities related to the tranches of funding are expected to take place, which is currently estimated to be through the third quarter of 2024.

Changes in the short-term deferred revenue balance during the year ended December 31, 2023 for the CEPI Funding Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2022	$	2,952
Additions		3,634
Deductions		(4,295	)
Balance at December 31, 2023	$	2,291

Gates

In November 2021, the Company entered into a Grant Agreement with the Gates Foundation (the “Gates Grant Agreement”), which provides funding for the Company’s development of an optimal immunogen in the context of a therapeutic human papillomavirus (“HPV”) vaccine. In consideration for the work to be performed, the Gates Foundation provided the Company with an upfront payment of $2.2 million in December 2021, and an additional $0.7 million was received in April 2023. In November 2023, the Company and Gates entered into an amendment to the Gates Grant Agreement, which extended the end date to March 31, 2024.

Payments received in advance that are related to future performance are deferred and recognized as grant revenue when the research and development activities are performed. Cash payments received under the Gates Grant Agreement are restricted as to their use until expenditures contemplated in the funding agreement are incurred. During the year ended December 31, 2023 and 2022, the Company recognized $1.7 million and $1.2 million, respectively, in revenue under the Gates Grant Agreement. The Company did not recognize any grant revenue under the Gates Grant Agreement in 2021. As of December 31, 2023 and 2022, short-term restricted cash and short-term deferred revenue of an insignificant amount and $1.0 million were recorded on the consolidated balance sheet. Deferred revenue will be recognized over the period in which the funding agreement activities related to the tranches of funding are expected to take place, which is currently estimated to be through the first quarter of 2024.

Changes in the short-term deferred revenue balance during the year ended December 31, 2023 for the Grant Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2022	$	1,025
Additions		700
Deductions		(1,717	)
Balance at December 31, 2023	$	8

Biomedical Advanced Research and Development Authority

In September 2023, the Company entered into a contract (the “BARDA Contract”) with the Biomedical Advanced Research and Development Authority ("BARDA"), part of the Administration for Strategic Preparedness and Response in the U.S. Department of Health and Human Services. Under the BARDA Contract, the Company may be eligible to receive funding of up to an estimated $433.0 million to conduct a 10,000-participant randomized Phase 2b comparative clinical trial evaluating the Company’s next-generation samRNA vaccine candidate containing Spike plus other viral targets to protect against COVID-19. The BARDA Contract could result in payments to the Company of up to approximately $433.0 million. The BARDA Contract consists of a base period (ending on or before the first quarter of 2024, though this period may be extended) and a total contract period-of-performance (base period plus two stages gated at BARDA’s discretion) of up to approximately four years. The base period for the BARDA Contract includes government funding of up to approximately $10.0 million for performance of certain milestones such as preparation of protocol synopsis and submission of an investigational new drug application. Following successful completion of the base period, the BARDA Contract provides for up to approximately $423.0 million of additional BARDA funding for two stages gated at BARDA’s discretion in support of the clinical trial execution and additional analyses for the clinical trial. However, BARDA instructed the Company to apply for funding for these two stages under a new award administered by the Rapid Response Partnership Vehicle ("RRPV Consortium"), which would be awarded at BARDA's discretion with BARDA funds. As of December 31, 2023, BARDA has not executed either of the two stages nor has the Company been awarded a new agreement under the RRPV Consortium. The BARDA Contract contains terms and conditions that are customary for contracts with BARDA of this nature, including provisions giving the government the right to terminate the contract at any time for its convenience, and similar terms are expected under a potential agreement with the RRPV Consortium.

The Company recognized $9.0 million in revenue under the BARDA Contract for base period activities for the year ended December 31, 2023. The Company received $9.0 million under the BARDA Contract as of December 31, 2023.

Subsequent Events (Additional Information) (Details)	1 Months Ended
Subsequent Events (Additional Information) (Details)	Feb. 29, 2024
Subsequent Event [Member]
Subsequent Event [Line Items]
Reduction in Workforce Rate	40.00%

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid research and development-related expenses	$ 3,904	$ 4,241
Collaboration receivable	14	135
Prepaid insurance	940	1,158
Interest and other receivables	217	529
Faclities-related deposits	9	384
Other	778	567
Total prepaid expenses and other current assets	$ 5,862	$ 7,014

Income Taxes - Components of the Net Deferred Tax Assets/Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Federal and state net operating loss carryforwards	$ 112,904	$ 109,191
Research and development tax credits	18,038	14,877
Lease liabilities	18,506	6,031
Accruals and other	4,685	3,786
Amortization	9,344	9,437
Deferred revenue	0	700
Other depreciation	593	449
Section 174 Capitalized Expense	41,571	21,434
Gross deferred tax assets	205,641	165,905
Valuation allowance	(188,663)	(160,877)
Net deferred tax assets	16,978	5,028
Deferred tax liabilities:
Other depreciation	0	0
Operating lease right-of-use assets	(16,978)	(5,028)
Deferred tax assets, net of allowance	$ 0	$ 0

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of Statutory Federal Income Tax Rate to Company's Effective Tax Rate

The effective tax rate of the Company’s provision for income taxes differs from the federal statutory rate as follows:


	Year Ended December 31,
	2023			2022			2021
Statutory federal income tax rate		21.0	%		21.0	%		21.0	%
State tax, net of federal benefit		1.3			7.6			10.2
Permanent differences		(0.7	)		(0.4	)		(0.1	)
Research and development tax credits		1.5			1.2			1.9
Impact of changes in state tax rate on deferred taxes		(2.9	)		—			—
Other		(0.2	)		(1.1	)		(1.8	)
Non-taxable stock premium		—			—			2.5
Change in valuation allowance		(20.0	)		(28.3	)		(33.7	)
Total provision for income taxes		—	%		—	%		—	%

Schedule of Components of Net Deferred Tax Assets/Liabilities

The components of the net deferred tax assets/liabilities are as follows (in thousands):


	December 31,
	2023			2022
Deferred tax assets:
Federal and state net operating loss carryforwards	$	112,904		$	109,191
Research and development tax credits		18,038			14,877
Lease liabilities		18,506			6,031
Accruals and other		4,685			3,786
Amortization		9,344			9,437
Deferred revenue		—			700
Other depreciation		593			449
Section 174 Capitalized Expense		41,571			21,434
Gross deferred tax assets		205,641			165,905
Valuation allowance		(188,663	)		(160,877	)
Net deferred tax assets		16,978			5,028
Deferred tax liabilities:
Other depreciation		—			—
Operating lease right-of-use assets		(16,978	)		(5,028	)
Deferred tax assets, net of allowance	$	—		$	—

Schedule of Net Operating Loss and Tax Credit Carryforwards

Net operating loss and tax credit carryforwards as of December 31, 2023 are as follows (in thousands):


	Amount		Expiration Years
Net operating losses, federal (post December 31, 2017)	$	355,720	Do not expire
Net operating losses, federal (pre January 1, 2018)		50,587	2035 - 2037
Net operating loss, state		485,794	2035 - 2043
Tax credits, federal		17,131	2035 - 2043
Tax credits, state		10,489	CA: credits do not expire MA: 2035 - 2043

Schedule of Unrecognized Tax Benefits

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


	December 31,
	2023			2022		2021
Beginning of year—unrecognized tax benefits	$	6,715		$	5,481	$	4,025
Decrease for tax positions taken during prior periods		(77	)		—		—
Increases for tax positions taken during current period		8,213			1,234		1,456
End of year—unrecognized tax benefits	$	14,851		$	6,715	$	5,481

Debt - Schedule of Long term debt balance (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Debt Disclosure [Abstract]
Principal loan balance	$ 40,000
Final Fee	2,300
Unamortized issuance costs and debt discounts	(2,156)
Long-Term Debt, Total	$ 40,144

- Definition

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

+ References + Details

Defined Contribution Plan

12 Months Ended

Dec. 31, 2023

Retirement Benefits [Abstract]

Defined Contribution Plan

14. Defined Contribution Plan

The Company began sponsoring a 401(k) Plan in 2017, which provides that eligible employees can elect to contribute to the 401(k) Plan, subject to certain limitations, on a pretax basis. The Company matches up to 50% of the first 4% of each employee’s contribution. During the years ended December 31, 2023, 2022 and 2021, expenses recognized for the 401(k) Plan were $1.3 million, $0.5 million and $0.4 million, respectively.

- Definition

The entire disclosure for retirement benefits.

+ References

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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147480126/715-20-S99-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 3
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480266/715-60-50-3

+ Details

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	97,585,415	86,894,901
Common stock, shares outstanding	97,585,415	86,894,901

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
Cover [Abstract]
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	Gritstone bio, Inc.
Entity Central Index Key	0001656634
Current Fiscal Year End Date	--12-31
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	GRTS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
ICFR Auditor Attestation Flag	false
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		98,065,594
Entity Small Business	true
Document Financial Statement Error Correction	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 173.7
Entity File Number	001-38663
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-4859534
Entity Address, Address Line One	5959 Horton Street
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	Emeryville
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94608
City Area Code	510
Local Phone Number	871-6100
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement relating to the 2024 Annual Meeting of Shareholders are incorporated by reference into Part III of this Annual Report on Form 10-K where so indicated herein. Such definitive Proxy Statement will be filed with the Securities and Exchange Commission within 120 days after the fiscal year to which this report relates. Except with respect to information specifically incorporated by reference in this Annual Report on Form 10-K, the Proxy Statement shall not be deemed to be filed as part hereof.
Auditor Name	Ernst & Young LLP
Auditor Location	San Mateo, California
Auditor Firm ID	42

Organization - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments \| Segment	1
Net losses	$ 138,490	$ 119,687	$ 75,082
Net cash used in operating activities	121,648	115,946	$ 50,678
Accumulated deficit	659,561	$ 521,071
Cash, cash equivalents and marketable securities	$ 79,300
Period not covered by company's available cash.	12 months

- Definition

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

+ References

+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Fair Value Measurements

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

The Company’s financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands):


	December 31, 2023
Description	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	39,243	$	39,243	$	—	$	—
Commercial paper		4,484		—		4,484		—
U.S. government debt securities		2,250		—		2,250		—
Total cash equivalents		45,977		39,243		6,734		—
Short-term marketable securities:
Commercial paper		3,485		—		3,485		—
Corporate debt securities		939		—		939		—
U.S. government treasuries		9,865		9,865		—		—
U.S. government debt securities		1,999		—		1,999		—
Total short-term marketable securities		16,288		9,865		6,423		—
Total	$	62,265	$	49,108	$	13,157	$	—


	December 31, 2022
Description	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	38,191	$	38,191	$	—	$	—
Total cash equivalents		38,191		38,191		—		—
Short-term marketable securities:
Certificates of deposit		949		—		949		—
Commercial paper		33,328		—		33,328		—
Corporate debt securities		21,853		—		21,853		—
U.S. government treasuries		35,540		35,540		—		—
U.S. government debt securities		24,719		—		24,719		—
Total short-term marketable securities		116,389		35,540		80,849		—
Long-term marketable securities:
Corporate debt securities		932		—		932		—
U.S. government treasuries		3,099		3,099		—		—
Total long-term marketable securities		4,031		3,099		932		—
Total	$	158,611	$	76,830	$	81,781	$	—

The Company measures the fair value of money market funds and U.S. treasuries based on quoted prices in active markets for identical securities. Commercial paper, corporate debt securities, certificates of deposits, asset backed securities, and U.S. government debt securities are valued taking into consideration valuations obtained from third-party pricing services. These pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of, and broker/dealer quotes on, the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs.

There were no transfers between Level 1 and Level 2 during the periods presented. See Note 3 for further information regarding the amortized cost of our financial instruments.

- 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

Collaboration and License Agreements - Schedule of Changes in Deferred Revenue Balance (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Gilead [Member]
Deferred Revenue
Balance at December 31, 2022	$ 100
Balance at December 31, 2023	100
2 Seventy [Member]
Deferred Revenue
Balance at December 31, 2022	1,000
Research Collaboration and License Agreement [Member] \| 2 Seventy [Member]
Deferred Revenue
Balance at December 31, 2022	1,047
Additions	0
Deductions	(1,047)
Balance at December 31, 2023	0
Collaboration, Option and License Agreement [Member] \| Gilead [Member]
Deferred Revenue
Balance at December 31, 2022	107
Additions	0
Deductions	(56)
Balance at December 31, 2023	51
Funding Agreement [Member] \| CEPI [Member]
Deferred Revenue
Balance at December 31, 2022	2,952
Additions	3,634
Deductions	(4,295)
Balance at December 31, 2023	2,291
Grant Agreement [Member] \| Gates Foundation [Member]
Deferred Revenue
Balance at December 31, 2022	1,025
Additions	700
Deductions	(1,717)
Balance at December 31, 2023	$ 8

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured at Fair Value

The Company’s financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands):


	December 31, 2023
Description	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	39,243	$	39,243	$	—	$	—
Commercial paper		4,484		—		4,484		—
U.S. government debt securities		2,250		—		2,250		—
Total cash equivalents		45,977		39,243		6,734		—
Short-term marketable securities:
Commercial paper		3,485		—		3,485		—
Corporate debt securities		939		—		939		—
U.S. government treasuries		9,865		9,865		—		—
U.S. government debt securities		1,999		—		1,999		—
Total short-term marketable securities		16,288		9,865		6,423		—
Total	$	62,265	$	49,108	$	13,157	$	—


	December 31, 2022
Description	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	38,191	$	38,191	$	—	$	—
Total cash equivalents		38,191		38,191		—		—
Short-term marketable securities:
Certificates of deposit		949		—		949		—
Commercial paper		33,328		—		33,328		—
Corporate debt securities		21,853		—		21,853		—
U.S. government treasuries		35,540		35,540		—		—
U.S. government debt securities		24,719		—		24,719		—
Total short-term marketable securities		116,389		35,540		80,849		—
Long-term marketable securities:
Corporate debt securities		932		—		932		—
U.S. government treasuries		3,099		3,099		—		—
Total long-term marketable securities		4,031		3,099		932		—
Total	$	158,611	$	76,830	$	81,781	$	—

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net Income (Loss)	$ (138,490)	$ (119,687)	$ (75,082)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	7,591	6,560	6,347
Net amortization (accretion) of premiums and discounts on marketable securities	(2,698)	(372)	817
Amortization of debt discount and issuance costs	1,412	392	0
Stock-based compensation	11,618	12,557	10,552
Impairment of right-of-use assets	1,969	0	0
Non-cash operating lease expense	14,063	9,131	8,052
Loss on disposition of property and equipment	22	0	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,152	658	(3,426)
Deposits and other long-term assets	4,619	(7,387)	(614)
Accounts payable	(1,968)	1,879	(419)
Accrued compensation	1,142	1,290	593
Accrued and other non-current liabilities	(2,362)	3,509	(859)
Accrued research and development expenses	353	(363)	2,653
Lease liability	(17,290)	(8,915)	(7,925)
Deferred revenue	(2,781)	(15,198)	8,633
Net cash used in operating activities	(121,648)	(115,946)	(50,678)
Investing activities
Purchase of marketable securities	(26,295)	(141,908)	(199,905)
Maturities of marketable securities	133,208	134,816	87,053
Purchase of property and equipment	(4,572)	(5,872)	(5,463)
Prepayments on financing lease	0	0	(238)
Net cash provided by (used in) investing activities	102,341	(12,964)	(118,553)
Financing activities
Proceeds from long-term debt, net of debt discount and issuance costs	19,919	19,130	0
Payments of financing costs	(2,548)	(420)	(8,394)
Payments of financing lease	(240)	(228)	(56)
Tax payments related to shares withheld for vested restricted stock units	(946)	(890)	0
Net cash provided by financing activities	25,117	83,098	108,760
Net increase (decrease) in cash, cash equivalents and restricted cash	5,810	(45,812)	(60,471)
Cash, cash equivalents and restricted cash at beginning of period	64,765	110,577	171,048
Cash, cash equivalents and restricted cash at end of period	70,575	64,765	110,577
Supplemental disclosures of non-cash investing and financing information
Property and equipment purchases accrued but not yet paid	133	1,146	738
Financing costs included in accrued liabilities and accounts payable	14	2,433	69
Remeasurement of operating lease right-of-use asset for lease modification	706	1,406	6,452
Lease liabilities arising from obtaining right -of-use asset from new leases	0	553	109
Assets acquired under leasing obligations	59,604	0	0
Cash paid for interest on debt	2,415	647	0
Public Offering [Member]
Financing activities
Proceeds from issuance of common stock	0	0	21,169
PIPE Financing [Member]
Financing activities
Proceeds from issuance of common stock	0	45,000	55,000
Stock Options, Warrants and Other [Member]
Financing activities
Proceeds from issuance of common stock	39	220	3,408
ATM Equity Offering Program [Member]
Financing activities
Proceeds from issuance of common stock	8,092	19,737	36,719
ESPP Employee Stock Purchase Plan [Member]
Financing activities
Proceeds from issuance of common stock	$ 801	$ 549	$ 914

Cash Equivalents and Marketable Securities

12 Months Ended

Dec. 31, 2023

Cash and Cash Equivalents [Abstract]

Cash Equivalents and Marketable Securities

3. Cash Equivalents and Marketable Securities

The amortized cost, unrealized gains and losses and fair values of cash equivalents and marketable securities were as follows (in thousands):


	December 31, 2023
Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	39,243	$	—	$	—		$	39,243
Commercial paper		4,484		—		—			4,484
U.S. government debt securities		2,250		—		—			2,250
Total cash equivalents		45,977		—		—			45,977
Short-term marketable securities:
Commercial paper		3,485		—		—			3,485
Corporate debt securities		939		—		—			939
U.S. government treasuries		9,861		5		(1	)		9,865
U.S. government debt securities		2,000		—		(1	)		1,999
Total short-term marketable securities		16,285		5		(2	)		16,288
Total	$	62,262	$	5	$	(2	)	$	62,265


	December 31, 2022
Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	38,191	$	—	$	—		$	38,191
Total cash equivalents		38,191		—		—			38,191
Short-term marketable securities:
Certificates of deposit		948		1		—			949
Commercial paper		33,318		23		(13	)		33,328
Corporate debt securities		21,887		6		(40	)		21,853
U.S. government treasuries		35,608		3		(71	)		35,540
U.S. government debt securities		24,703		22		(6	)		24,719
Total short-term marketable securities		116,464		55		(130	)		116,389
Long-term marketable securities:
Corporate debt securities		933		—		(1	)		932
U.S. government treasuries		3,103		—		(4	)		3,099
Total long-term marketable securities		4,036		—		(5	)		4,031
Total	$	158,691	$	55	$	(135	)	$	158,611

As of December 31, 2023 and 2022, the Company had a total of $79.3 million and $175.9 million in cash, cash equivalents and marketable securities, which includes $63.0 million and $55.5 million in cash and cash equivalents and $16.3 million and $120.4 million in marketable securities, respectively.

All marketable securities held as of December 31, 2023, had contractual effective maturities of less than one year. There have been no material realized gains or losses on marketable securities for the periods presented. As of December 31, 2023, the Company did not hold any individual securities in an unrealized loss position for 12 months or greater. The Company has the ability and intent to hold all marketable securities that have been in a continuous loss position until maturity or recovery. No significant facts or circumstances have arisen to indicate that there has been any significant deterioration in the creditworthiness of the issuers of the securities held by us, thus there has been no recognition of any other-than-temporary impairment in the year ended December 31, 2023, 2022 or 2021. The Company has not recorded an allowance for credit losses as of December 31, 2023 or 2022.

See Note 4 for further information regarding the fair value of the Company’s consolidated financial instruments.

Cash Equivalents and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2023

Cash and Cash Equivalents [Abstract]

Cash Equivalents and Marketable Securities

The amortized cost, unrealized gains and losses and fair values of cash equivalents and marketable securities were as follows (in thousands):


	December 31, 2023
Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	39,243	$	—	$	—		$	39,243
Commercial paper		4,484		—		—			4,484
U.S. government debt securities		2,250		—		—			2,250
Total cash equivalents		45,977		—		—			45,977
Short-term marketable securities:
Commercial paper		3,485		—		—			3,485
Corporate debt securities		939		—		—			939
U.S. government treasuries		9,861		5		(1	)		9,865
U.S. government debt securities		2,000		—		(1	)		1,999
Total short-term marketable securities		16,285		5		(2	)		16,288
Total	$	62,262	$	5	$	(2	)	$	62,265


	December 31, 2022
Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	38,191	$	—	$	—		$	38,191
Total cash equivalents		38,191		—		—			38,191
Short-term marketable securities:
Certificates of deposit		948		1		—			949
Commercial paper		33,318		23		(13	)		33,328
Corporate debt securities		21,887		6		(40	)		21,853
U.S. government treasuries		35,608		3		(71	)		35,540
U.S. government debt securities		24,703		22		(6	)		24,719
Total short-term marketable securities		116,464		55		(130	)		116,389
Long-term marketable securities:
Corporate debt securities		933		—		(1	)		932
U.S. government treasuries		3,103		—		(4	)		3,099
Total long-term marketable securities		4,036		—		(5	)		4,031
Total	$	158,691	$	55	$	(135	)	$	158,611

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

+ Details

Income Taxes - Schedule of Net Operating Loss and Tax Credit Carryforwards (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Jan. 01, 2018
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 406,300	$ 355,700
Business incentive tax credits to offset against taxes	$ 17,131
Net operating losses, Expiration year	2035
Tax credits, Expiration year	2035 - 2043
Federal \| Post December 31, 2017
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 355,720
Net operating losses, Expiration year	Do not expire
Federal \| Pre January 1, 2018
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 50,587
Net operating losses, Expiration year	2035 - 2037
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 485,794
Business incentive tax credits to offset against taxes	$ 10,489
Net operating losses, Expiration year	2035 - 2043
Tax credits, Expiration year	CA: credits do not expireMA: 2035 - 2043

Stock-Based Compensation - Schedule of Weighted-Average Assumptions Used in Black-Scholes Option-Pricing Model to Estimate Fair Value of Employee Stock Options at Grant Date (Detail) - Employee or Director [Member]	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%
Expected term	5 years 9 months 7 days	5 years 11 months 23 days	6 years 3 days
Risk-free interest rate	4.00%	2.10%	1.10%
Expected volatility	98.90%	77.90%	79.00%

- 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

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 7,591	$ 6,560	$ 6,347

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment, Net

Property and equipment and related accumulated depreciation and amortization are as follows (in thousands):


	December 31,
	2023			2022
Computer equipment and software	$	1,704		$	1,155
Furniture and fixtures		2,723			2,285
Laboratory equipment		29,521			27,309
Leasehold improvements		15,733			18,024
		49,681			48,773
Less accumulated depreciation and amortization		(32,415	)		(28,782	)
Construction-in-progress		15			1,344
Total property and equipment, net	$	17,281		$	21,335

Stock-Based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

11. Stock-Based Compensation

Award Incentive Plans

In August 2015, the Company’s board of directors approved the 2015 Equity Incentive Plan (“2015 Plan”). In connection with the Company’s IPO and the effectiveness of the 2018 Award Incentive Plan (“2018 Plan”), discussed below, the 2015 Plan terminated. The 92,815 shares of common stock that were then unissued and available for future issuance under the 2015 Plan became available under the 2018 Plan.

In September 2018, the Company’s board of directors approved the 2018 Plan. Under the 2018 Plan, a total of 2,690,000 shares of common stock were initially reserved for issuance under the 2018 Plan, plus the number of shares remaining available for future awards under the 2015 Plan, as of the effective date of the 2018 Plan. The number of shares of common stock reserved for issuance under the 2018 Plan automatically increases on January 1 of each year, beginning on January 1, 2019 and continuing through and including January 1, 2028, by 4% of the total number of shares of the Company’s outstanding stock on December 31 of the preceding calendar year, or a lesser number of shares determined by the Company’s board of directors. The 2018 Plan provides, among other things, for the grant of options, stock appreciation rights, restricted stock awards, restricted stock unit awards and performance bonus awards.

The maximum number of shares that may be issued upon the exercise of stock options under the 2018 Plan is 45,000,000.

The Company’s board of directors has the authority to determine to whom options will be granted, the number of shares, the term, and the exercise price. If an individual owns stock representing 10% or more of the outstanding shares, the price of each share shall be at least 110% of the fair market value, as determined by the board of directors. Options granted have a term of up to 10 years and generally vest over a 4-year period with a straight-line vesting.

Material Features of the 2021 Employment Inducement Incentive Award Plan

In April 2021, the Company’s board of directors adopted the 2021 Employment Inducement Incentive Award Plan (the “2021 Plan”), pursuant to Nasdaq Listing Rule 5635(c)(4). The principal purpose of the 2021 Plan is to promote the success and enhance the value of the Company by inducing new employees to commence employment with us, and by aligning the individual interests of new employees with the interests of our stockholders. Awards granted under the 2021 Plan are intended to constitute “employment inducement awards” under Nasdaq Listing Rule 5635(c)(4), and, therefore, the 2021 Plan is intended to be exempt from the Nasdaq Listing Rules regarding shareholder approval of stock option and stock purchase plans. A total of 790,400 shares of our common stock were initially reserved for issuance under the 2021 Plan. The 2021 Plan provides for the grant of non-qualified stock options, restricted stock units, restricted stock awards, stock appreciation rights, and other stock-based and cash-based awards. The 2021 Plan does not provide for the grant of incentive stock options. Awards under the 2021 Plan may be granted to eligible employees who are either new employees or who are commencing employment with us or one of our subsidiaries following a bona fide period of non-employment with us, and for whom such awards are granted as a material inducement to commencing employment with us or one of our subsidiaries. Awards under the 2021 Plan may not be granted to our consultants or non-employee directors.

The 2021 Plan is administered by our board of directors and, to the extent our board of directors delegates its authority to it, our compensation committee. In the event of a change in control in which the successor corporation refuses to assume or substitute any outstanding award under the 2021 Plan, the vesting of such award will accelerate in full. Our board of directors may terminate, amend, or modify the 2021 Plan at any time, provided that no termination or amendment may materially impair any rights under any outstanding award under the 2021 Plan without the consent of the holder.

On April 21, 2022, the Company’s board of directors increased the number of shares available under the 2021 Plan by 700,000 shares. On February 2, 2023, the Company’s board of directors increased the number of shares available under the 2021 Plan by 1,300,000 shares.

2018 Employee Stock Purchase Plan

In September 2018, the Company’s Board of Directors approved the 2018 Employee Stock Purchase Plan (“2018 ESPP”). The 2018 ESPP also became effective in September 2018. A total of 282,334 shares were initially reserved for issuance under the 2018 ESPP. Additionally, the number of shares of common stock reserved for issuance under the 2018 ESPP will increase automatically each year, beginning on January 1, 2019 and continuing through and including January 1, 2028, by the lesser of (1) 1% of the shares of common stock outstanding on December 31 of the preceding calendar year or (2) such lesser number of shares determined by the Company’s Board of Directors. The maximum number of shares that may be issued under the 2018 ESPP is 5,000,000. The offering periods are scheduled to start on the first trading day on or after June 1 or December 1 of each year. Contributions under the 2018 ESPP are limited to a maximum of 15% of an employee’s eligible compensation.

The estimated fair value of stock purchase rights granted under the 2018 ESPP were calculated using the Black-Scholes option-pricing model using the following assumptions:


	Year ended December 31,
	2023			2022			2021
Expected dividend yield		—	%		—	%		—	%
Expected term	0.50 years			0.50 years			0.57 years
Risk-free interest rate		5.1	%		1.3	%		0.1	%
Expected volatility		90.1	%		94.9	%		88.0	%

Valuation of Stock Options

The fair value of each stock option granted to an employee or a director was estimated as of the date of grant using the Black-Scholes model with the following weighted-average assumptions:


	Year Ended December 31,
	2023			2022			2021
Expected dividend yield		—	%		—	%		—	%
Expected term	5.77 years			5.98 years			6.01 years
Risk-free interest rate		4.0	%		2.1	%		1.1	%
Expected volatility		98.9	%		77.9	%		79.0	%

Management’s calculations are based on a grant date valuation approach. Using the Black-Scholes model, the weighted-average grant-date fair value of employee stock options granted was $1.73, $3.20, and $8.03 per share during the years ended December 31, 2023, 2022, and 2021, respectively.

Stock Option Activity

A summary of the 2018 Plan and 2021 Plan activity is as follows:


				Options Outstanding
	Number of Shares Available for Issuance			Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2022		4,814,394			6,951,620		$	7.92		8.08	$	1,089
Authorized		4,775,796			—
Granted		(4,227,353	)		712,566		$	2.20
Exercised					(6,000	)	$	0.76
Cancelled		824,088			(384,725	)	$	5.35
Balance at December 31, 2023		6,186,925			7,273,461		$	7.50		7.26	$	264
Vested and exercisable – December 31, 2023					4,647,325		$	8.53		6.67	$	200
Vested and expected to vest – December 31, 2023					6,997,158		$	7.60		7.22	$	254

For the years ended December 31, 2023, 2022, and 2021, the total intrinsic value of stock option awards exercised was de minimis, $0.5 million, and $5.8 million, respectively, determined at the date of option exercise, and the total cash received upon exercise of stock options was de minimis for 2023, $0.2 million in 2022, and $3.4 million in 2021. The aggregate intrinsic value was calculated as the difference between the exercise prices of the underlying stock option awards and the estimated fair value of the common stock on the date of exercise.

As of December 31, 2023, $8.5 million of total cost related to non-vested employee and consultant options is expected to be recognized over a weighted-average period of 1.67 years. The total fair value of shares vested during the year ended December 31, 2023 was $7.8 million.

Stock-based compensation expense and awards granted to non-employees was $0.8 million, $0.6 million, and $0.7 million for the years ended December 31, 2023, 2022, and 2021, respectively.

Restricted Stock Units

The Company has granted restricted stock unit awards under the 2018 Equity Plan. The Company's restricted stock unit awards have a term of up to 10 years and generally vest over a 6 month, 1 or 2-year period. The following table summarizes the Company's restricted stock unit activity during the year ended December 31, 2023:


	Number of Shares			Weighted Average Grant Date Fair Value
Outstanding, unvested as December 31, 2022		561,526		$	5.38
Issued		3,514,787		$	3.29
Vested		(871,385	)	$	4.64
Canceled/Forfeited		(115,958	)	$	3.29
Outstanding, unvested as December 31, 2023		3,088,970		$	3.29

Stock-Based Compensation Expense

Total stock-based compensation for all awards granted to employees, consultants and the Company's 2018 ESPP, before taxes, is as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Research and development expenses	$	6,266	$	6,730	$	6,626
General and administrative expenses		5,352		5,827		3,926
Total	$	11,618	$	12,557	$	10,552

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	1 Months Ended						12 Months Ended
	Sep. 30, 2023	Sep. 30, 2021 USD ($)	Mar. 31, 2021	Jan. 31, 2019 USD ($) RenewalTerm	Sep. 30, 2018	Mar. 31, 2017 USD ($)	Dec. 31, 2023 USD ($)	Apr. 01, 2023 USD ($)	Dec. 31, 2022 USD ($)	May 31, 2019	Feb. 28, 2016 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Lease right-of-use assets							$ 66,839		$ 17,481
Lease liability							64,631
Storage space commenced			Apr. 01, 2021
Letters of credit outstanding, amount							600
Operating lease cash security deposit							924		934
40 Erie Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Asset Impairment Charges							2,000
Cambridge Storage Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Lease expiration date			Jun. 30, 2023
Emeryville California [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term				120 months
Operating leasing renewal option to extend lease				5 years
Operating leases number of renewal terms \| RenewalTerm				2
Tenant Improvement Allowance				$ 4,000
Lease right-of-use assets							7,300		8,100
Lease liability							11,600		12,800
Operating lease cash security deposit							600		600
Cambridge Massachusetts [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating lease cash security deposit									700
Cambridge Massachusetts [Member] \| Warehouse Member
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term			17 months
Cambridge Massachusetts [Member] \| Prepaid Expenses And Other Current Assets Member
Commitments and Contingencies Disclosure [Line Items]
Operating lease cash security deposit									400
Cambridge Massachusetts [Member] \| Other Noncurrent Assets Member
Commitments and Contingencies Disclosure [Line Items]
Operating lease cash security deposit							300		$ 300
Cambridge Massachusetts [Member] \| 21 Erie Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term					24 months
Operating lease termination date					2023-06
Cambridge Massachusetts [Member] \| 40 Erie Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term											67 months
Tenant Improvement Allowance											$ 2,100
Operating lease termination date		2025-04
Pleasanton [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing renewal option to extend lease						5 years
Tenant Improvement Allowance						$ 1,200
Lease expiration date						Nov. 30, 2024
Letters of credit outstanding, amount						$ 1,000
Withdrawal from irrevocable letters of credit							0
Pleasanton [Member] \| Additional Office Space [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term										64 months
Boston Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term		120 months
Lease Prepayment included in the ROU Asset								$ 8,400
Lease operations commenced date	Jul. 01, 2023
Lease right-of-use assets								59,300
Lease liability								$ 50,900
Lease expiration date	Jun. 30, 2033
Letters of credit outstanding, amount							4,600
Restricted cash deposit used as collateral for letter of credit							$ 4,700
Boston Lease [Member] \| Maximum [Member]
Commitments and Contingencies Disclosure [Line Items]
Tenant Improvement Allowance		$ 19,100

Commitments and Contingencies - Schedule of Supplemental Information Related to Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Operating cash flows from operating leases	$ 17,290	$ 8,915	$ 7,925
New right-of-use assets obtained in exchange for lease obligations (in thousands):
Right-of-use assets obtained from entering new leases	59,604	553	6,562
Increase in right-of-use assets from lease modifications	$ 706	$ 1,406	$ 0
Weighted average remaining lease term (years):
Operating leases	8 years 3 months 18 days	5 years 1 month 6 days	5 years 3 months 18 days
Weighted average discount rate:
Operating leases	10.10%	7.70%	7.40%

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Schedule of Components of Lease Costs

The components of lease costs, which were included in our consolidated statements of operations and comprehensive loss, were as follows (in thousands):


	Year ended December 31,
	2023		2022		2021
Lease cost
Operating lease cost	$	13,561	$	8,797	$	7,973
Short-term lease cost		30		—		—
Total lease cost	$	13,591	$	8,797	$	7,973

Schedule of Supplemental Information Related to Leases

Supplemental information related to leases was as follows:


	Year ended December 31,
	2023			2022			2021
Cash paid for amounts included in the measurement of lease liabilities (in thousands):
Operating cash flows from operating leases	$	17,290		$	8,915		$	7,925
New right-of-use assets obtained in exchange for lease obligations (in thousands):
Right-of-use assets obtained from entering new leases	$	59,604		$	553		$	6,562
Increase in right-of-use assets from lease modifications	$	706		$	1,406		-
Weighted average remaining lease term (years):
Operating leases		8.30			5.10			5.30
Weighted average discount rate:
Operating leases		10.1	%		7.7	%		7.4	%

Schedule of Minimum Annual Payments Under Lease Agreements

As of December 31, 2023, minimum annual payments under the Company’s lease agreements are as follows (in thousands):


	Lease Financing Obligation
Year ending December 31,
2024		12,834
2025		10,749
2026		10,376
2027		10,466
2028		10,732
Thereafter		41,615
Total minimum payments		96,772
Less: Amounts representing interest expense		(32,141	)
Present value of future minimum lease payments		64,631
Less: Current portion of lease liability		(6,904	)
Noncurrent portion of lease liability	$	57,727

Summary of Significant Accounting Policies - Schedule of Straight Line Method Over Estimated Useful Lives of Respective Assets (Detail)	12 Months Ended
	Dec. 31, 2023
Computer Equipment and Software [Member] \| Minimum [Member]
Property Plant And Equipment [Line Items]
Property, and equipment, estimated useful life	3 years
Computer Equipment and Software [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Property, and equipment, estimated useful life	5 years
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Property, and equipment, estimated useful life	5 years
Laboratory Equipment [Member] \| Minimum [Member]
Property Plant And Equipment [Line Items]
Property, and equipment, estimated useful life	5 years
Laboratory Equipment [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Property, and equipment, estimated useful life	7 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Lives	Shorter of useful life or lease term

Collaboration and License Agreements (Tables)

12 Months Ended

Dec. 31, 2023

Collaboration Agreement [Member] | 2 Seventy [Member]

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Schedule of Changes in Deferred Revenue Balance

Changes in the deferred revenue balance during the year ended December 31, 2023 are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2022	$	1,047
Additions		—
Deductions		(1,047	)
Balance at December 31, 2023	$	—

Grant Agreement [Member] | Gates Foundation [Member]

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Schedule of Changes in Deferred Revenue Balance

Changes in the short-term deferred revenue balance during the year ended December 31, 2023 for the Grant Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2022	$	1,025
Additions		700
Deductions		(1,717	)
Balance at December 31, 2023	$	8

Gilead [Member] | Collaboration, Option and License Agreement [Member]

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Schedule of Changes in Deferred Revenue Balance

Changes in the short-term deferred revenue balance during the year ended December 31, 2023 for the Gilead Collaboration Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2022	$	107
Additions		—
Deductions		(56	)
Balance at December 31, 2023	$	51

CEPI [Member] | Funding Agreement [Member]

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Schedule of Changes in Deferred Revenue Balance

Changes in the short-term deferred revenue balance during the year ended December 31, 2023 for the CEPI Funding Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2022	$	2,952
Additions		3,634
Deductions		(4,295	)
Balance at December 31, 2023	$	2,291

Commitments and Contingencies - Schedule of Components of Lease Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lease cost
Operating lease cost	$ 13,561	$ 8,797	$ 7,973
Short-term lease cost	30	0	0
Total lease cost	$ 13,591	$ 8,797	$ 7,973

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 62,986	$ 55,498
Restricted cash	2,299	3,977
Long-term restricted cash	5,290	5,290
Total cash, cash equivalents and restricted cash	$ 70,575	$ 64,765

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, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding, unvested Beginning balance \| shares \| shares	561,526
Issued \| shares	3,514,787
Vested \| shares \| shares	(871,385)
Canceled/Forfeited \| shares \| shares	(115,958)
Outstanding, unvested ending balance \| shares \| shares	3,088,970
Weighted Average Grant Date Fair Value
Outstanding, unvested beginning balance \| $ / shares \| $ / shares	$ 5.38
Issued \| $ / shares \| $ / shares	3.29
Vested \| $ / shares \| $ / shares	4.64
Canceled/Forfeited \| $ / shares \| $ / shares	3.29
Outstanding, unvested ending balance \| $ / shares \| $ / shares	$ 3.29

Defined Contribution Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent of employees' gross pay	4.00%
Defined contribution plan cost	$ 1.3	$ 0.5	$ 0.4
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer's matching contribution percentage	50.00%

Fair Value Measurements - Financial Assets and Liabilities Subject To Fair Value Measurements on a Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	$ 62,265	$ 158,611
Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	45,977	38,191
Cash Equivalents [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	39,243	38,191
Cash Equivalents [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	4,484
Cash Equivalents [Member] \| U.S. government debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	2,250
Short-Term Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	16,288	116,389
Short-Term Marketable Securities [Member] \| U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	9,865	35,540
Short-Term Marketable Securities [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	3,485	33,328
Short-Term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	939	21,853
Short-Term Marketable Securities [Member] \| Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		949
Short-Term Marketable Securities [Member] \| U.S. government debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	1,999	24,719
Long-term Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		4,031
Long-term Marketable Securities [Member] \| U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		3,099
Long-term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		932
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	49,108	76,830
Fair Value, Inputs, Level 1 [Member] \| Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	39,243	38,191
Fair Value, Inputs, Level 1 [Member] \| Cash Equivalents [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	39,243	38,191
Fair Value, Inputs, Level 1 [Member] \| Short-Term Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	9,865	35,540
Fair Value, Inputs, Level 1 [Member] \| Short-Term Marketable Securities [Member] \| U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	9,865	35,540
Fair Value, Inputs, Level 1 [Member] \| Short-Term Marketable Securities [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Fair Value, Inputs, Level 1 [Member] \| Short-Term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Fair Value, Inputs, Level 1 [Member] \| Short-Term Marketable Securities [Member] \| Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Fair Value, Inputs, Level 1 [Member] \| Short-Term Marketable Securities [Member] \| U.S. government debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Fair Value, Inputs, Level 1 [Member] \| Long-term Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		3,099
Fair Value, Inputs, Level 1 [Member] \| Long-term Marketable Securities [Member] \| U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		3,099
Fair Value, Inputs, Level 1 [Member] \| Long-term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	13,157	81,781
Fair Value, Inputs, Level 2 [Member] \| Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	6,734	0
Fair Value, Inputs, Level 2 [Member] \| Cash Equivalents [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Fair Value, Inputs, Level 2 [Member] \| Cash Equivalents [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	4,484
Fair Value, Inputs, Level 2 [Member] \| Cash Equivalents [Member] \| U.S. government debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	2,250
Fair Value, Inputs, Level 2 [Member] \| Short-Term Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	6,423	80,849
Fair Value, Inputs, Level 2 [Member] \| Short-Term Marketable Securities [Member] \| U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Fair Value, Inputs, Level 2 [Member] \| Short-Term Marketable Securities [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	3,485	33,328
Fair Value, Inputs, Level 2 [Member] \| Short-Term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	939	21,853
Fair Value, Inputs, Level 2 [Member] \| Short-Term Marketable Securities [Member] \| Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		949
Fair Value, Inputs, Level 2 [Member] \| Short-Term Marketable Securities [Member] \| U.S. government debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	1,999	24,719
Fair Value, Inputs, Level 2 [Member] \| Long-term Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		932
Fair Value, Inputs, Level 2 [Member] \| Long-term Marketable Securities [Member] \| U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Fair Value, Inputs, Level 2 [Member] \| Long-term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		932
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Fair Value, Inputs, Level 3 [Member] \| Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0
Fair Value, Inputs, Level 3 [Member] \| Cash Equivalents [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Fair Value, Inputs, Level 3 [Member] \| Short-Term Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Fair Value, Inputs, Level 3 [Member] \| Short-Term Marketable Securities [Member] \| U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Fair Value, Inputs, Level 3 [Member] \| Short-Term Marketable Securities [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Fair Value, Inputs, Level 3 [Member] \| Short-Term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Fair Value, Inputs, Level 3 [Member] \| Short-Term Marketable Securities [Member] \| Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Fair Value, Inputs, Level 3 [Member] \| Short-Term Marketable Securities [Member] \| U.S. government debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	$ 0	0
Fair Value, Inputs, Level 3 [Member] \| Long-term Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Fair Value, Inputs, Level 3 [Member] \| Long-term Marketable Securities [Member] \| U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Fair Value, Inputs, Level 3 [Member] \| Long-term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		$ 0