0000950170-24-056964 | 10-Q | XBRL Viewer

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Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
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	98,114,860	97,585,415
Common stock, shares outstanding	98,114,860	97,585,415

Balance Sheet Components

3 Months Ended

Mar. 31, 2024

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Components

7. Balance Sheet Components

Prepaid Expenses and Other Current Assets

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


	March 31,		December 31,
	2024		2023
Prepaid research and development-related expenses	$	2,462	$	3,904
Collaboration receivable		34		14
Prepaid insurance		620		940
Interest and other receivables		172		217
Facilities-related deposits		9		9
Deferred financing costs		440		—
Other		566		778
Total prepaid expenses and other current assets	$	4,303	$	5,862

Deposits and Other Long-Term Assets

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


	March 31,		December 31,
	2024		2023
Lease security deposits	$	924	$	924
Total deposits and other long-term assets	$	924	$	924

Stock Based Compensation - Additional Information (Detail) - USD ($)		1 Months Ended		3 Months Ended
	Feb. 02, 2023	Mar. 31, 2024	Apr. 30, 2022	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Sep. 30, 2018	Aug. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance		5,907,374		5,907,374		6,186,925
Unrecognized compensation cost related to non-vested employee and consultant options		$ 11,000,000		$ 11,000,000
Recognition period of unrecognized compensation cost related to non-vested employee and consultant				1 year 7 months 17 days
Fair value of shares vested				$ 2,240,000
Stock Based Compensation Expense				3,246,000	$ 2,891,000
Awards granted to non-employees				$ 200,000	$ 200,000
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 restricted stock unit awards have a term of up to 10 years and generally vest over a 6 month, 1 or 2-year period.
Restricted Stock Unit Awards under 2018 Equity Plan \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting period				2 years
Option granted expiration period				10 years
Restricted Stock Unit Awards under 2018 Equity Plan \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting period				6 months
Performance-Based Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Based Compensation Expense				$ 0
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%		4.00%
Maximum number of shares authorized		45,000,000		45,000,000
Minimum percentage of outstanding shares held by individual				10.00%
Minimum percentage fair market value of share price				110.00%
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 Award Incentive Plan [Member] \| Performance-Based Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Granted, Value, Share-Based Payment Arrangement, after Forfeiture, Total		$ 1,117,020
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		790,400
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Period Increase (Decrease), Total	1,300,000		700,000

Net Loss Per Common Share

3 Months Ended

Mar. 31, 2024

Earnings Per Share [Abstract]

Net Income (Loss) Per Common Share

12. Net Loss Per Common 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.

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):


	Three Months Ended March 31,
	2024			2023
Numerator:
Net loss	$	(40,385	)	$	(33,982	)
Denominator:
Weighted-average common shares outstanding, basic and diluted		118,391,224			114,423,000
Net loss per share, basic and diluted	$	(0.34	)	$	(0.30	)

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). 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 the Warrants 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:


	March 31,
	2024		2023
Options issued and outstanding and ESPP shares issuable and outstanding		10,483,282		7,120,656
Restricted stock subject to future vesting		2,582,528		3,491,659
Performance-based restricted stock subject to future vesting		1,117,020		—
Total		14,182,830		10,612,315

Net Loss Per Common Share - Additional Information (Detail) - Private Investment In Public Equity [Member] - $ / shares	Oct. 31, 2022	Dec. 31, 2020
Earnings Per Share Basic [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	13,274,923	27,480,719
Class of warrant nominal exercise price	$ 0.0001	$ 0.01

Collaboration and License Agreements and Grant Revenue - Schedule of Changes in Contract Asset and Deferred Revenue Balance (Detail)	3 Months Ended
	Mar. 31, 2024 USD ($)
Gilead Sciences Inc [Member]
Contract Asset
Balance at December 31, 2021	$ 0
Balance at March 31, 2022	0
2 Seventy [Member]
Contract Asset
Balance at December 31, 2021	0
Balance at March 31, 2022	0
Collaboration, Option and License Agreement [Member] \| Gilead Sciences Inc [Member]
Deferred Revenue
Balance at December 31, 2022	51,000
Additions	0
Deductions	(14,000)
Balance at March 31, 2023	37,000
C E P I Funding Agreement [Member] \| Coalition for Epidemic Preparedness Innovations [Member]
Deferred Revenue
Balance at December 31, 2022	2,291,000
Additions	0
Deductions	(1,057,000)
Balance at March 31, 2023	1,234,000
Gates Grant Agreement [Member] \| Gates Foundation [Member]
Deferred Revenue
Balance at December 31, 2022	8,000
Additions	281,000
Deductions	(275,000)
Balance at March 31, 2023	$ 14,000

Stock-Based Compensation - Schedule of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Number of Shares Available for Issuance
Number of options beginning balance	6,186,925
Authorized	3,903,416
Granted	(5,733,435)
Cancelled	1,550,468
Number of options ending balance	5,907,374	6,186,925
Number of Shares
Outstanding at beginning of period	7,273,461
Granted	3,971,589
Exercised	(30,797)
Cancelled	(907,736)
Outstanding at end of period	10,306,517	7,273,461
Options Outstanding, Number of Shares, Vested and exercisable	5,146,980
Options Outstanding, Number of Shares, Vested and expected to vest	9,805,788
Weighted-Average Exercise Price
Beginning Balance	$ 7.5
Granted	2.45
Exercised	1.99
Cancelled	3.16
Ending Balance	5.95	$ 7.5
Weighted-Average Exercise Price, Vested and exercisable	8.29
Weighted-Average Exercise Price, Vested and expected to vest	$ 6.08
Options Outstanding, Weighted-Average Remaining Contractual Term (in years)	7 years 10 months 28 days	7 years 3 months 3 days
Options Outstanding, Weighted-Average Remaining Contractual Term, Vested and exercisable (in years)	6 years 7 months 9 days
Options Outstanding, Weighted-Average Remaining Contractual Term, Vested and expected to vest (in years)	7 years 10 months 2 days
Options Outstanding, Aggregate Intrinsic Value	$ 998	$ 264
Options Outstanding, Aggregate Intrinsic Value, Vested and exercisable	352
Options Outstanding, Aggregate Intrinsic Value, Vested and expected to vest	$ 934

Severance and Other Costs - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended
	Feb. 29, 2024	Mar. 31, 2024
Restructuring Charges [Abstract]
Reduction in Workforce	40.00%
Severance and Other Costs		$ 3,866

Balance Sheet Components (Tables)

3 Months Ended

Mar. 31, 2024

Balance Sheet Related Disclosures [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

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


	March 31,		December 31,
	2024		2023
Prepaid research and development-related expenses	$	2,462	$	3,904
Collaboration receivable		34		14
Prepaid insurance		620		940
Interest and other receivables		172		217
Facilities-related deposits		9		9
Deferred financing costs		440		—
Other		566		778
Total prepaid expenses and other current assets	$	4,303	$	5,862

Schedule of Deposits and Other Long-Term Assets

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


	March 31,		December 31,
	2024		2023
Lease security deposits	$	924	$	924
Total deposits and other long-term assets	$	924	$	924

Stock-Based Compensation - Summary of Restricted Stock Unit Activity (Detail)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Number of Shares
Outstanding, unvested beginning balance \| shares	3,088,970
Issued \| shares	644,826
Vested \| shares	(826,642)
Canceled/Forfeited \| shares	(324,626)
Outstanding, unvested ending balance \| shares	2,582,528
Weighted Average Grant Date Fair Value
Outstanding, unvested beginning balance \| $ / shares	$ 3.29
Issued \| $ / shares	2.46
Vested \| $ / shares	3.28
Canceled/Forfeited \| $ / shares	3.09
Outstanding, unvested ending balance \| $ / shares	$ 3.11

Severance and Other Costs (Tables)

3 Months Ended

Mar. 31, 2024

Restructuring Charges [Abstract]

Summary of changes in the Company's accrued restructuring balance

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


	Beginning Balance December 31, 2023		Charges		Payments			Ending Balance March 31, 2024
Severance liability	$	—	$	2,198	$	(2,139	)	$	59

Summary of the charges related to the restructuring activities

A summary of the charges related to the severance and other activities as of March 31, 2024 is as follows (in thousands):


	Severance and Incentive Compensation		Stock Based Compensation		Asset Impairments		Total Severance and Other Costs
Research and development	$	2,010	$	185	$	1,483	$	3,678
General and administrative		188		—		—		188
Total	$	2,198	$	185	$	1,483	$	3,866

As of March 31, 2024, the Company accrued a negligible amount under accrued compensation on the condensed consolidated balance sheet related to unpaid severance liabilities which are expected to be paid within one month.

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2024

Share-Based Payment Arrangement [Abstract]

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, 2023		6,186,925			7,273,461		$	7.50		7.26	$	264
Authorized		3,903,416			—
Granted		(5,733,435	)		3,971,589		$	2.45
Exercised		—			(30,797	)	$	1.99
Cancelled		1,550,468			(907,736	)	$	3.16
Balance at March 31, 2024		5,907,374			10,306,517		$	5.95		7.91	$	998
Vested and exercisable at March 31, 2024					5,146,980		$	8.29		6.61	$	352
Vested and expected to vest at March 31, 2024					9,805,788		$	6.08		7.84	$	934

Summary of Restricted Stock Unit Activity

The following table summarizes the Company's restricted stock unit activity during the three months ended March 31, 2024:


	Number of Shares			Weighted- Average Grant Date Fair Value
Outstanding, unvested at December 31, 2023		3,088,970		$	3.29
Issued		644,826		$	2.46
Vested		(826,642	)	$	3.28
Canceled/Forfeited		(324,626	)	$	3.09
Outstanding, unvested at March 31, 2024		2,582,528		$	3.11

Schedule of Stock Based Compensation Expense

Total stock-based compensation for all awards granted to employees, directors and non-employees and purchase rights under the Company's 2018 and 2021 Equity Plans and the 2018 Employee Stock Purchase Plan (“ESPP”), before taxes, is as follows (in thousands):


	Three Months Ended March 31,
	2024		2023
Research and development expenses	$	1,660	$	1,613
General and administrative expenses		1,586		1,278
Total	$	3,246	$	2,891

Stock-Based Compensation

3 Months Ended

Mar. 31, 2024

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 the Company or one of our subsidiaries following a bona fide period of non-employment with the Company, and for whom such awards are granted as a material inducement to commencing employment with the Company or one of its subsidiaries. Awards under the 2021 Plan may not be granted to the Company's 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. The Company's 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.

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, 2023		6,186,925			7,273,461		$	7.50		7.26	$	264
Authorized		3,903,416			—
Granted		(5,733,435	)		3,971,589		$	2.45
Exercised		—			(30,797	)	$	1.99
Cancelled		1,550,468			(907,736	)	$	3.16
Balance at March 31, 2024		5,907,374			10,306,517		$	5.95		7.91	$	998
Vested and exercisable at March 31, 2024					5,146,980		$	8.29		6.61	$	352
Vested and expected to vest at March 31, 2024					9,805,788		$	6.08		7.84	$	934

For the three months ended March 31, 2024, the total intrinsic value of stock option awards exercised was de minimis, determined at the date of option exercise, and the total cash received upon exercise of stock options was not significant for the period. For the three months ended March 31, 2023, there were no stock options exercised. 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 March 31, 2024, $11.0 million of total unrecognized compensation cost related to non-vested employee and consultant options is expected to be recognized over a weighted-average period of 1.63 years. The total fair value of shares vested during the three months ended March 31, 2024 was $2.24 million.

Stock-based compensation expense and awards granted to non-employees were $0.2 million and $0.2 million, respectively, for the three months ended March 31, 2024 and 2023.

Restricted Stock Units

The Company has granted restricted stock unit awards under the 2018 Equity Plan. The 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 three months ended March 31, 2024:


	Number of Shares			Weighted- Average Grant Date Fair Value
Outstanding, unvested at December 31, 2023		3,088,970		$	3.29
Issued		644,826		$	2.46
Vested		(826,642	)	$	3.28
Canceled/Forfeited		(324,626	)	$	3.09
Outstanding, unvested at March 31, 2024		2,582,528		$	3.11

Performance-Based Restricted Stock Units

In March 2024, the Company granted 1,117,020 performance-based restricted stock unit awards ("PSUs") to certain executives under the 2018 Equity Plan. Vesting of the PSUs is dependent upon achievement of certain performance-based metrics through December 31, 2025. Assuming achievement of each performance-based metric, the executive must also generally remain in the Company's service at the date of achievement of the performance-based metric. PSUs are converted into shares of the Company's common stock once vested. The number of shares earned at the end of the performance period will vary, based on actual performance. Upon grant of the PSUs, the Company recognizes stock-based compensation expense related to these awards based on assumptions as to what percentage of each target will be achieved. The Company evaluates these target assumptions on a quarterly basis and adjusts stock-based compensation expense related to these awards, as appropriate.

For the three months ended March 31, 2024, there was no stock-based compensation expense recorded related to the PSUs as none of the performance-based metrics were deemed probable for achievement.

Stock-Based Compensation Expense


	Three Months Ended March 31,
	2024		2023
Research and development expenses	$	1,660	$	1,613
General and administrative expenses		1,586		1,278
Total	$	3,246	$	2,891

Severance and Other Costs - Summary of changes in the Company's accrued restructuring balance (Details) - Severance liability $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 0
Charges	2,198
Payments	(2,139)
Ending Balance	$ 59

- 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

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Total revenues	$ 1,742	$ 2,443
Operating expenses:
Research and development	33,041	30,514
General and administrative	8,502	6,745
Total operating expenses	41,543	37,259
Loss from operations	(39,801)	(34,816)
Interest income	712	1,678
Interest Expense	(1,296)	(844)
Net loss	(40,385)	(33,982)
Other comprehensive loss:
Unrealized (loss) gain on marketable securities	(4)	28
Comprehensive loss	$ (40,389)	$ (33,954)
Net loss per share, basic	$ (0.34)	$ (0.3)
Net loss per share, diluted	$ (0.34)	$ (0.3)
Weighted-average number of shares used in computing net loss per share, basic	118,391,224	114,423,000
Weighted-average number of shares used in computing net loss per share, diluted	118,391,224	114,423,000
Collaboration and license revenues [Member]
Total revenues	$ 49	$ 542
Grant Revenues [Member]
Total revenues	$ 1,693	$ 1,901

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurement Level 1 to Level 2 Transfers	$ 0	$ 0

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

Debt

3 Months Ended

Mar. 31, 2024

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 March 31, 2024, 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 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 condensed 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 March 31, 2024, the Company has 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 March 31, 2024, the Company is in compliance with all covenants in the Amended Loan Agreement, as amended.

As of March 31, 2024, there were debt discounts, unamortized issuance costs and unaccreted value of the final fee of $2.0 million which were recorded as a direct deduction from the term loan on the condensed consolidated

balance sheet. Interest expense related to the Amended Loan Agreement was $1.3 million and $0.8 million, respectively, for the three months ended March 31, 2024 and 2023. 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):


	March 31,
	2024
Principal loan balance	$	40,000
Final fee		2,300
Unamortized debt discount, issuance costs, and unaccreted value of final fee		(1,970	)
Long term debt, net	$	40,330

As of March 31, 2024, the estimated future principal payments due (excluding the final payment fee) are as follows (in thousands):


2024 (remaining nine months)		—
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

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Summary Of Significant Accounting Policies [Line Items]
Income tax expense	$ 0	$ 0

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating activities
Net loss	$ (40,385)	$ (33,982)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,742	1,799
Net accretion of premiums and discounts on marketable securities	(70)	(973)
Amortization of debt discount and issuance costs	384	342
Stock-based compensation	3,246	2,891
Non-cash operating lease expense	3,308	2,243
Impairment of property, plant and equipment	1,483	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,559	134
Deposits and other long-term assets	0	(4,177)
Accounts payable	3,548	327
Accrued compensation	(5,017)	(3,518)
Accrued and other non-current liabilities	494	(869)
Accrued research and development expenses	349	105
Lease liability	(3,143)	(2,082)
Deferred revenue	(1,065)	(2,330)
Net cash used in operating activities	(33,567)	(40,090)
Investing activities
Purchase of marketable securities	(382)	(15,874)
Maturities of marketable securities	12,691	38,614
Purchase of property and equipment	(143)	(1,567)
Sales of marketable securities	137	0
Net cash provided by investing activities	12,303	21,173
Financing activities
Proceeds from long-term debt, net of debt discount and issuance costs	0	9,977
Deferred (payments of) financing costs	426	(2,489)
Payments of financing lease	(62)	(59)
Tax payments related to shares withheld for vested restricted stock units	(788)	(742)
Net cash (used in) provided by financing activities	(379)	8,647
Net decrease in cash, cash equivalents and restricted cash	(21,643)	(10,270)
Cash, cash equivalents and restricted cash at beginning of period	70,575	64,765
Cash, cash equivalents and restricted cash at end of period	48,932	54,495
Supplemental disclosures of non-cash investing and financing information
Property and equipment purchases accrued but not yet paid	22	407
Cash paid for interest on debt	858	436
Financing costs included in accrued liabilities and accounts payable	440	0
ATM Offering Program [Member]
Financing activities
Proceeds from issuance of common stock	0	1,960
Stock Options, Warrants and Other [Member]
Financing activities
Proceeds from issuance of common stock	$ 45	$ 0

Commitments and Contingencies - Schedule of Minimum Annual Rental Payments Under Operating Lease Agreements (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Operating Leases
2024 (remaining three months)	$ 9,627
2025	10,749
2026	10,376
2027	10,466
2028	10,732
Thereafter	41,615
Total minimum payments	93,565
Less: Amounts representing interest expense	(30,613)
Present value of future minimum lease payments	62,952
Less: Current portion of lease liability	(6,811)	$ (6,904)
Noncurrent portion of lease liability	$ 56,141	$ 57,727

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Basis of Presentation

The accompanying interim condensed consolidated financial statements are unaudited and 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.

The accompanying interim condensed 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 interim reporting.

The interim condensed consolidated financial statements are unaudited and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, necessary for the fair presentation for interim reporting. The results of operations for any interim period are not necessarily indicative of results of operations for any future period.

Certain information and footnote disclosures typically included in annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements as of and for the year ended December 31, 2023, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023, as filed with the SEC on March 5, 2024.

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 condensed 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.

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 condensed consolidated balance sheets. As of March 31, 2024, 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 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.

Cash, Cash Equivalents, and Restricted Cash

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, 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 condensed 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 9). 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 condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows (in thousands):


	March 31,		December 31,
	2024		2023
Cash and cash equivalents	$	42,395	$	62,986
Restricted cash		1,247		2,299
Long-term restricted cash		5,290		5,290
Total cash, cash equivalents and restricted cash	$	48,932	$	70,575

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 right-of-use ("ROU Assets"), lease liabilities, current portion, and lease liabilities, net of current portion in the Company’s condensed consolidated balance sheets as of March 31, 2024 and December 31, 2023. The Company has elected not to recognize on the condensed 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 the Company determines 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 condensed consolidated balance sheets and amortized as lease expense on a straight-line basis over the lease term.

Revenue Recognition

The Company performs research and development under collaboration, license, grant, and clinical development agreements. The Company’s revenue primarily consists of collaboration and license 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 and license 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 condensed 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 condensed 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 9).

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 condensed 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 9).

Income Taxes

The Company did not record income tax expense for the three months ended March 31, 2024 and 2023, respectively, as the Company expected to be in a cumulative taxable loss position in 2024 and 2023, and the net deferred tax assets are fully offset by a valuation allowance as it is not more likely than not that the benefit will be realized. As of March 31, 2024, the Company remains in a cumulative book loss position and does not have sufficient positive evidence to realize its net deferred tax assets. As such, the Company continues to maintain a full valuation allowance against its net deferred tax assets.

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 condensed consolidated financial statements.

Severance and Other Costs

Severance and other costs are comprised of employee separation costs and asset impairments. Employee separation costs principally consist of severance and stock-based compensation expense for the acceleration of stock awards.

The Company records severance charges based on whether the termination benefits are provided under an on-going benefit arrangement or under a one-time benefit arrangement. The Company accounts for on-going benefit arrangements, such as those documented by employment agreements, in accordance with ASC 712, Nonretirement Postemployment Benefits. Under ASC 712, liabilities for post employment benefits are recorded at the time the obligations are probable of being incurred and can be reasonably estimated. The Company accounts for one-time employment benefit arrangements in accordance with ASC 420 Exit or Disposal Cost Obligations. One-time

termination benefits are expensed at the date the entity notifies the employee. The Company recognized losses on disposal of property and equipment, which was accounted in accordance with ASC 360, Impairment of Long-Lived Assets.

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. The adoption of ASU 2020-06 on January 1, 2024 did not have a material impact on the Company's condensed 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 condensed 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.

Collaboration and License Agreements and Grant Revenue (Tables)

3 Months Ended

Mar. 31, 2024

Gilead Sciences Inc [Member]

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Schedule of Changes in Contract Asset and Deferred Revenue Balance

Changes in the deferred revenue balance during the three months ended March 31, 2024 for the Gilead Collaboration Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2023	$	51
Additions		—
Deductions		(14	)
Balance at March 31, 2024	$	37

Grant Agreement [Member] | Gates Foundation [Member]

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Schedule of Changes in Contract Asset and Deferred Revenue Balance

Changes in the deferred revenue balance during the three months ended March 31, 2024 for the Gates Grant Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2023	$	8
Additions		281
Deductions		(275	)
Balance at March 31, 2024	$	14

Funding Agreement [Member] | CEPI [Member]

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Schedule of Changes in Contract Asset and Deferred Revenue Balance

Changes in the deferred revenue balance during the three months ended March 31, 2024 for the CEPI Funding Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2023	$	2,291
Additions		—
Deductions		(1,057	)
Balance at March 31, 2024	$	1,234

Severance and Other Costs

3 Months Ended

Mar. 31, 2024

Restructuring Charges [Abstract]

Severance and Other Costs

On February 29, 2024, the Company announced a reduction in its workforce by approximately 40 percent, which was intended to reduce costs and preserve capital. In connection with the workforce reduction, the Company recognized severance and other charges of $3.9 million in the three months ended March 31, 2024, consisting of costs associated with employee severance and asset impairments. The severance and other charges were recorded to the respective research and development and general and administrative operating expense categories on the condensed consolidated statement of operations and comprehensive loss.

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


	Beginning Balance December 31, 2023		Charges		Payments			Ending Balance March 31, 2024
Severance liability	$	—	$	2,198	$	(2,139	)	$	59

A summary of the charges related to the severance and other activities as of March 31, 2024 is as follows (in thousands):


	Severance and Incentive Compensation		Stock Based Compensation		Asset Impairments		Total Severance and Other Costs
Research and development	$	2,010	$	185	$	1,483	$	3,678
General and administrative		188		—		—		188
Total	$	2,198	$	185	$	1,483	$	3,866

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

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.

•

Debt Issuance Costs and Debt Discounts

Concentrations of Credit Risk

Other Risks and Uncertainties

Cash, Cash Equivalents and Restricted Cash

Agreement (see Note 9). The Company will utilize the CEPI and Gates Foundation funds as it incurs expenses for services performed under the agreements.


	March 31,		December 31,
	2024		2023
Cash and cash equivalents	$	42,395	$	62,986
Restricted cash		1,247		2,299
Long-term restricted cash		5,290		5,290
Total cash, cash equivalents and restricted cash	$	48,932	$	70,575

Leases

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

Revenue Recognition

Government Contract

Income Taxes

Severance and Other Costs

Recently Issued Accounting Pronouncements Not Yet Adopted

Collaboration and License Agreements and Grant Revenue

3 Months Ended

Mar. 31, 2024

Collaborative And License Agreements [Abstract]

Collaboration and License Agreements

9. Collaboration and License Agreements and Grant Revenue

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 March 31, 2024, 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.

Revenue was recognized when, or as, the Company satisfied its performance obligation by transferring the promised services to 2seventy. Revenue was 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 was thought to best reflect the transfer of services to 2seventy. In applying a cost-based input method of revenue recognition, we used 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 were recorded in the period in which changes are identified and amounts can be reasonably estimated.

There is no deferred revenue recorded on the condensed consolidated balance sheets in current liabilities as of March 31, 2024 and December 31, 2023 as collaboration revenue was fully recognized for the 2seventy Agreement during the year ended December 31, 2023. During the three months ended March 31, 2023, the Company recognized $0.4 million in collaboration revenue under the 2seventy Agreement.

There were no receivables or net contract assets recorded as of March 31, 2024 and December 31, 2023 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 March 31, 2024 and no royalties were due from the sale of licensed products.

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 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 March 31, 2024 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.

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 three months ended March 31, 2024 and 2023, the Company did not record any license revenue and recorded de minimis and $0.1 million, respectively, as collaboration revenue as a result of satisfying its performance obligations by transferring the promised goods and services for the Gilead Collaboration Agreement. There was no contract asset recorded on the condensed consolidated balance sheets as of March 31, 2024 or December 31, 2023. There was a de minimis amount recorded as deferred revenue as of March 31, 2024 and December 31, 2023 associated with the Gilead Collaboration Agreement.

Changes in the deferred revenue balance during the three months ended March 31, 2024 for the Gilead Collaboration Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2023	$	51
Additions		—
Deductions		(14	)
Balance at March 31, 2024	$	37

There was de minimis of receivables recorded on the condensed consolidated balance sheets as a current asset in the prepaid expenses and other current assets balance as of March 31, 2024 and December 31, 2023, associated with the Gilead Collaboration Agreement.

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 three months ended March 31, 2024 and 2023, 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 March 31, 2024, 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 March 31, 2024 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 March 31, 2024.

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 March 31, 2024.

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 March 31, 2024.

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 support 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 three months ended March 31, 2024 and 2023, the Company recognized grant revenue of $1.0 million and $1.5 million, respectively, under the CEPI Funding Agreement. As of March 31, 2024 and December 31, 2023, short-term restricted cash and short-term deferred revenue of $1.2 million and $2.3 million, respectively, were recorded on the condensed 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 first quarter of 2025.

Changes in the deferred revenue balance during the three months ended March 31, 2024 for the CEPI Funding Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2023	$	2,291
Additions		—
Deductions		(1,057	)
Balance at March 31, 2024	$	1,234

Gates Foundation

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 the Gates Foundation 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 three months ended March 31, 2024 and 2023, the Company recognized $0.3 million and $0.4 million, respectively, in revenue under the Gates Grant Agreement. As of March 31, 2024 and December 31, 2023, short-term restricted cash and short-term deferred revenue of an insignificant amount were recorded on the condensed 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 deferred revenue balance during the three months ended March 31, 2024 for the Gates Grant Agreement are as follows (in thousands):


	Deferred Revenue
Balance at December 31, 2023	$	8
Additions		281
Deductions		(275	)
Balance at March 31, 2024	$	14

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 second 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. 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 March 31, 2024, BARDA and Gritstone have amended the base period to extend to June 30, 2024. Also, as of March 31, 2024, BARDA had not yet made the decision to proceed with either of the two stages nor has the Company been awarded a new award by or entered into a new agreement with the RRPV Consortium, terms and financials of which may be different from the original BARDA Contract. 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 and conditions are expected under a potential agreement with the RRPV Consortium.

The Company recognized $0.4 million of grant revenue under the BARDA Contract for the three months ended March 31, 2024 and $0.4 million was received under the BARDA Contract during the three months ended March 31, 2024.

Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Schedule of Cash and Cash Equivalents


	March 31,		December 31,
	2024		2023
Cash and cash equivalents	$	42,395	$	62,986
Restricted cash		1,247		2,299
Long-term restricted cash		5,290		5,290
Total cash, cash equivalents and restricted cash	$	48,932	$	70,575

Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended				3 Months Ended		12 Months Ended
	Oct. 31, 2022	Mar. 31, 2022	Sep. 30, 2021	Dec. 31, 2020	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Subsidiary Sale Of Stock [Line Items]
Common stock, shares authorized					300,000,000		300,000,000
Common stock, par value					$ 0.0001		$ 0.0001
Preferred stock, shares authorized					10,000,000		10,000,000
Preferred stock, par value					$ 0.0001		$ 0.0001
Preferred stock, shares issued					0		0
Preferred stock, shares outstanding					0		0
Common stock, shares issued					98,114,860		97,585,415
Common stock, shares outstanding					98,114,860		97,585,415
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					0	0
Amended and Restated Certificate of Incorporation [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares authorized					300,000,000
Common stock, par value					$ 0.0001
Preferred stock, shares authorized					10,000,000
Preferred stock, par value					$ 0.0001
ATM Equity Offering Program [Member] \| Common Stock [Member]
Subsidiary Sale Of Stock [Line Items]
Stock Issued During Period, Shares, New Issues						607,853
2022 At The Market Equity Offering Program [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued					10,230,628		10,230,628
Net proceeds from issuance of stock					$ 27,500,000		$ 27,500,000
2022 At The Market Equity Offering Program [Member] \| Cowen [Member]
Subsidiary Sale Of Stock [Line Items]
Percentage of gross proceeds as underwriter compensation		3.00%
Maximum offering expense agreed to be reimbursed		$ 50,000
2022 At The Market Equity Offering Program [Member] \| Maximum [Member]
Subsidiary Sale Of Stock [Line Items]
Net proceeds from issuance of stock		100,000,000
2022 At The Market Equity Offering Program [Member] \| Maximum [Member] \| Cowen [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
Net proceeds from issuance of stock	$ 42,400,000
Shares issued price per share	$ 2.26
Issuance of pre-funded warrants, net of issuance costs	$ 28,200,000			$ 87,700,000
Private Investment In Public Equity [Member] \| Common Stock and Warrants [Member]
Subsidiary Sale Of Stock [Line Items]
Sale of common stock				5,543,351
Shares issued price per share				$ 3.34
Proceed from issuance of stock and pre-funded warrants				$ 119,800,000
Sale Of Stock, Price Per Share Prepaid By Purchaser	$ 2.2599			$ 3.33
Warrant exercise price	0.0001			0.01
Offering price per share	$ 2.26			$ 3.34
Pre-funded 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%
Private Investment In Public Equity [Member] \| Common Stock and Warrants [Member] \| Additional Shares [Member]
Subsidiary Sale Of Stock [Line Items]
Stock Issued During Period, Shares, New Issues				4,043,127
Shares issued price per share				$ 3.71
Private Investment In Public Equity [Member] \| Common Stock [Member]
Subsidiary Sale Of Stock [Line Items]
Net proceeds from issuance of stock			$ 52,700,000
Stock Issued During Period, Shares, New Issues			5,000,000
Shares issued price per share			$ 11

Severance and Other Costs - Summary of the charges related to the restructuring activities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Restructuring Cost and Reserve [Line Items]
Severance and Incentive Compensation	$ 2,198
Employee Benefits and Share-Based Compensation	185
Asset impairment charges	1,483
Total Severance and Other Costs	3,866
Research and Development Expense [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Incentive Compensation	2,010
Employee Benefits and Share-Based Compensation	185
Asset impairment charges	1,483
Total Severance and Other Costs	3,678
General and Administrative Expense [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Incentive Compensation	188
Employee Benefits and Share-Based Compensation	0
Asset impairment charges	0
Total Severance and Other Costs	$ 188

- 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

3 Months Ended

Mar. 31, 2024

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):


	March 31,			December 31,
	2024			2023
Computer equipment and software	$	1,704		$	1,704
Furniture and fixtures		2,723			2,723
Laboratory equipment		27,659			29,521
Leasehold improvements		15,452			15,733
		47,538			49,681
Less accumulated depreciation and amortization		(33,465	)		(32,415	)
Construction-in-progress		15			15
Total property and equipment, net	$	14,088		$	17,281

Depreciation and amortization expense was $1.7 million and $1.8 million for the three months ended March 31, 2024 and 2023, respectively.

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	1 Months Ended				3 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2021 USD ($)	Jan. 31, 2019 USD ($) RenewalTerm	Mar. 31, 2017 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Apr. 01, 2023 USD ($)	Oct. 31, 2022 USD ($)	May 31, 2019	Feb. 28, 2016 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Operating lease cash security deposit					$ 924		$ 924
Lease right-of-use assets					65,057		66,839
Lease liability					62,952
Asset impairment charges					1,483
Research and Development Expense					33,041	$ 30,514
40 Erie Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Asset impairment charges							2,000
Emeryville lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term			120 months
Operating lease cash security deposit					600
Operating leases number of renewal terms \| RenewalTerm			2
Operating leasing renewal option to extend lease			5 years
Tenant improvement allowance			$ 4,000
Lease right-of-use assets					7,100		7,300
Lease liability					11,200		11,600
Pleasanton Lease [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					$ 600
Withdrawal from irrevocable letters of credit					0
Pleasanton Lease [Member] \| Additional Office Space [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term										64 months
Cambridge Lease [Member] \| Deposits and Other Long-Term Assets [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating lease cash security deposit					300		$ 300
Cambridge Lease [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
Boston Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term		120 months
Lease right-of-use assets								$ 59,300
Lease liability								50,900
Lease expiration date	Jun. 30, 2033
Letters of credit outstanding, amount					4,600
Withdrawal from irrevocable letters of credit					0	$ 0
Restricted cash deposit used as collateral for letter of credit					$ 4,700
Lease prepayment included in the ROU asset								$ 8,400
Lease operations commenced date	Jul. 01, 2023
Boston Lease [Member] \| Maximum [Member]
Commitments and Contingencies Disclosure [Line Items]
Tenant improvement allowance		$ 19,100

Stockholders' Equity - Schedule of Issued and Outstanding Warrants to Purchase Shares of the Company's Common Stock (Detail)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Number of warrants outstanding	20,489,256
Common Stock Warrants One [Member]
Number of warrants outstanding	7,214,333
Warrant exercise price \| $ / shares	$ 0.01
Expiration Date	None
Issue Date	Dec. 28, 2020
Common Stock Warrants Two [Member]
Number of warrants outstanding	13,274,923
Warrant exercise price \| $ / shares	$ 0.0001
Expiration Date	None
Issue Date	Oct. 24, 2022

Subsequent Event - Additional Information (Details) - Subsequent Event [Member] - Underwritten Public Offering [Member] $ / shares in Units, $ in Millions	Apr. 04, 2024 USD ($) $ / shares shares
Subsequent Event [Line Items]
Gross proceeds from the offering \| $	$ 32.5
Common Warrants [Member]
Subsequent Event [Line Items]
Warrant exercise price \| $ / shares	$ 1.65
Initial Pre-Funded Warrants [Member]
Subsequent Event [Line Items]
Warrant exercise price \| $ / shares	$ 0.0001
Common Stock [Member]
Subsequent Event [Line Items]
Number of common shares sold	8,333,333
Common Stock [Member] \| Common Warrants [Member]
Subsequent Event [Line Items]
Warrants to purchase shares of common stock	8,333,333
Common Stock [Member] \| Initial Pre-Funded Warrants [Member]
Subsequent Event [Line Items]
Warrants to purchase shares of common stock	13,334,222
Warrants [Member]
Subsequent Event [Line Items]
Warrants to purchase shares of common stock	13,334,222
Warrant exercise price \| $ / shares	$ 1.4999

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	Mar. 31, 2024	Dec. 31, 2023
Cash equivalents and marketable securities [Line Items]
Cash and cash equivalents	$ 42,395	$ 62,986
Amortized Cost	41,995	62,262
Unrealized Gains	0	5
Unrealized Losses	(1)	(2)
Fair Value	41,994	62,265
Cash Equivalents [Member]
Cash equivalents and marketable securities [Line Items]
Cash and cash equivalents	38,086	45,977
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	38,086	45,977
Cash Equivalents [Member] \| Money Market Funds [Member]
Cash equivalents and marketable securities [Line Items]
Cash and cash equivalents	38,086	39,243
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	38,086	39,243
Cash Equivalents [Member] \| Commercial Paper [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost		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]
Amortized Cost		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	3,909	16,285
Unrealized Gains	0	5
Unrealized Losses	(1)	(2)
Fair Value	3,908	16,288
Short-Term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost		939
Unrealized Gains		0
Unrealized Losses		0
Fair Value		939
Short-Term Marketable Securities [Member] \| Commercial Paper [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	246	3,485
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	246	3,485
Short-Term Marketable Securities [Member] \| U.S. Government Treasuries [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	3,663	9,861
Unrealized Gains	0	5
Unrealized Losses	(1)	(1)
Fair Value	$ 3,662	9,865
Short-Term Marketable Securities [Member] \| U.S. Government Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost		2,000
Unrealized Gains		0
Unrealized Losses		(1)
Fair Value		$ 1,999

Commitments and Contingencies - Schedule of Supplemental Information Related to Leases (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash paid for amounts included in the measurement of lease liabilities (in thousands):
Operating cash flows from operating leases	$ 3,143	$ 2,094
Weighted-average remaining lease term (years):
Operating leases	8 months 6 days	5 months 3 days
Weighted-average discount rate:
Operating leases	10.10%	7.90%

Debt (Tables)

3 Months Ended

Mar. 31, 2024

Debt Disclosure [Abstract]

Schedule of Components of Long Term Debt Balance

The components of the long-term debt balance are as follows (in thousands):


	March 31,
	2024
Principal loan balance	$	40,000
Final fee		2,300
Unamortized debt discount, issuance costs, and unaccreted value of final fee		(1,970	)
Long term debt, net	$	40,330

Schedule of the Estimated Future Principal Payments Due

As of March 31, 2024, the estimated future principal payments due (excluding the final payment fee) are as follows (in thousands):


2024 (remaining nine months)		—
2025		8,457
2026		18,030
2027		13,513
Total principal payments	$	40,000

Cash Equivalents and Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2024

Cash and Cash Equivalents [Abstract]

Cash Equivalents and Marketable Securities

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


	March 31, 2024
Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	38,086	$	—	$	—		$	38,086
Total cash equivalents		38,086		—		—			38,086
Short-term marketable securities:
U.S. government treasuries		3,663		—		(1	)		3,662
Commercial paper		246		—		—			246
Total short-term marketable securities		3,909		—		(1	)		3,908
Total	$	41,995	$	—	$	(1	)	$	41,994


	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

- 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

Subsequent Event

3 Months Ended

Mar. 31, 2024

Subsequent Events [Abstract]

Subsequent Event

14. Subsequent Event

On April 4, 2024 the Company completed an underwritten public offering transaction in which it issued and sold 8,333,333 shares of common stock and accompanying common warrants to purchase up to 8,333,333 shares of common stock at a per share exercise price of $1.65 and to a certain investor in lieu of common stock, pre-funded warrants to purchase up to 13,334,222 shares of common stock at a per share exercise price of $0.0001 (the “Initial Pre-Funded Warrants”) and accompanying common warrants to purchase up to 13,334,222 shares of common stock at a combined purchase price of $1.4999 per Initial Pre-Funded Warrant and Accompanying Warrant. The Company received gross proceeds from the offering in the amount of $32.5 million, before deducting underwriting discounts and commissions and estimated expenses.

Net Loss Per Common Share - Computation of Potentially Anti-dilutive Securities (Detail) - shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities that were not included in the diluted per share calculations	14,182,830	10,612,315
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	10,483,282	7,120,656
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	2,582,528	3,491,659
Performance-based 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	1,117,020	0

Commitments and Contingencies

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

6. Commitments and Contingencies

Leases

The Company leases office and laboratory 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 condensed consolidated balance sheet as of March 31, 2024. 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 two additional 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 and therefore has recorded a $7.1 million ROU Asset and a $11.2 million lease liability on the condensed consolidated balance sheet as of March 31, 2024. 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.

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 March 31, 2024, 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 Asset on the condensed consolidated balance sheets as of March 31, 2024 and December 31, 2023.

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 Lease

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 condensed 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.

In conjunction with the 40 Erie Lease, as amended, the Company has paid a cash security deposit, which included amounts for the applicable last month’s rent and has been classified as part of the operating lease ROU Assets. As of March 31, 2024 and December 31, 2023, the $0.3 million security deposit for the 40 Erie lease was recorded in deposits and other long-term assets on the Company's condensed 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 March 31, 2024 and 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 condensed 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 the Company's condensed consolidated statements of operations and comprehensive loss, were as follows (in thousands):


	Three Months Ended March 31,
	2024		2023
Lease cost
Operating lease cost	$	3,221	$	2,164
Short-term lease cost		18		—
Total lease cost	$	3,239	$	2,164

Supplemental information related to leases was as follows:


	Three Months Ended March 31,
	2024			2023
Cash paid for amounts included in the measurement of lease liabilities (in thousands):
Operating cash flows from operating leases	$	3,143		$	2,094
Weighted-average remaining lease term (years):
Operating leases		8.2			5.1
Weighted-average discount rate:
Operating leases		10.1	%		7.9	%

As of March 31, 2024, minimum annual rental payments under the Company’s lease agreements are as follows (in thousands):


	Lease Financing Obligation
Year ending December 31,
2024 (remaining nine months)	$	9,627
2025		10,749
2026		10,376
2027		10,466
2028		10,732
Thereafter		41,615
Total minimum payments		93,565
Less: Amounts representing interest expense		(30,613	)
Present value of future minimum lease payments		62,952
Less: Current portion of lease liability		(6,811	)
Noncurrent portion of lease liability	$	56,141

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.

Property and Equipment, Net - Summary of Property and Equipment and Related Accumulated Depreciation and Amortization (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 47,538	$ 49,681
Less accumulated depreciation and amortization	(33,465)	(32,415)
Total property and equipment, net	14,088	17,281
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,704	1,704
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,723	2,723
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	27,659	29,521
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	15,452	15,733
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, net	$ 15	$ 15

Net Loss Per Common Share (Tables)

3 Months Ended

Mar. 31, 2024

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):


	Three Months Ended March 31,
	2024			2023
Numerator:
Net loss	$	(40,385	)	$	(33,982	)
Denominator:
Weighted-average common shares outstanding, basic and diluted		118,391,224			114,423,000
Net loss per share, basic and diluted	$	(0.34	)	$	(0.30	)

Computation of Potentially Anti-Dilutive Securities


	March 31,
	2024		2023
Options issued and outstanding and ESPP shares issuable and outstanding		10,483,282		7,120,656
Restricted stock subject to future vesting		2,582,528		3,491,659
Performance-based restricted stock subject to future vesting		1,117,020		—
Total		14,182,830		10,612,315

Organization

3 Months Ended

Mar. 31, 2024

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 $40.4 million and $34.0 million for the three months ended March 31, 2024 and 2023, respectively. Cash used by operating activities was $33.6 million and $40.1 million during the three months ended March 31, 2024 and 2023, respectively. The Company had an accumulated deficit of $699.9 million and $659.6 million as of March 31, 2024 and December 31, 2023, 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, common stocks and warrants, public offerings of its common stock, common warrants and pre-funded warrants, the sale of common stock under an “at the market offering,” proceeds from the Loan Agreement, proceeds received from its collaboration arrangement, and non-dilutive grants from various nonprofit and governmental organizations. As of March 31, 2024, the Company had cash, cash equivalents and marketable securities of $46.3 million. As discussed in Note 14, in April 2024 the Company completed a public offering of common stock and accompanying common warrants for which the Company received gross proceeds of $32.5 million, before deducting underwriting discounts and commissions and estimated expenses. After giving consideration to this public offering, 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 condensed 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 condensed consolidated financial statements.

If the Company is unable to raise additional funds, secure a waiver or renegotiate the terms of its Loan Agreement, it expects to be in default of the minimum liquidity requirement in the third quarter of 2024. Upon such a default, the Company's existing cash, cash equivalents and marketable securities will only be sufficient to fund its operations into the third quarter of 2024. The accompanying condensed 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 condensed 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.

Fair Value Measurements

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

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


	March 31, 2024
Description	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	38,086	$	38,086	$	—	$	—
Total cash equivalents		38,086		38,086		—		—
Short-term marketable securities:
U.S. government treasuries		3,662		3,662		—		—
Commercial paper		246		—		246		—
Total short-term marketable securities		3,908		3,662		246		—
Total	$	41,994	$	41,748	$	246	$	—


	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	$	—

The Company measures the fair value of money market funds and U.S. government treasuries based on quoted prices in active markets for identical securities. Commercial paper, corporate debt securities, U.S. government treasuries, 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 the Company’s 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

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($)
Common Stock [Member] \| ATM Equity Offering Program [Member]
Payment for issuance cost	$ 58

Property and Equipment, Net (Tables)

3 Months Ended

Mar. 31, 2024

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):


	March 31,			December 31,
	2024			2023
Computer equipment and software	$	1,704		$	1,704
Furniture and fixtures		2,723			2,723
Laboratory equipment		27,659			29,521
Leasehold improvements		15,452			15,733
		47,538			49,681
Less accumulated depreciation and amortization		(33,465	)		(32,415	)
Construction-in-progress		15			15
Total property and equipment, net	$	14,088		$	17,281

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

Schedule of Components of Lease Costs

The components of lease costs, which were included in the Company's condensed consolidated statements of operations and comprehensive loss, were as follows (in thousands):


	Three Months Ended March 31,
	2024		2023
Lease cost
Operating lease cost	$	3,221	$	2,164
Short-term lease cost		18		—
Total lease cost	$	3,239	$	2,164

Schedule of Supplemental Information Related to Leases

Supplemental information related to leases was as follows:


	Three Months Ended March 31,
	2024			2023
Cash paid for amounts included in the measurement of lease liabilities (in thousands):
Operating cash flows from operating leases	$	3,143		$	2,094
Weighted-average remaining lease term (years):
Operating leases		8.2			5.1
Weighted-average discount rate:
Operating leases		10.1	%		7.9	%

Schedule of Minimum Annual Rental Payments Under Operating Lease Agreements

As of March 31, 2024, minimum annual rental payments under the Company’s lease agreements are as follows (in thousands):


	Lease Financing Obligation
Year ending December 31,
2024 (remaining nine months)	$	9,627
2025		10,749
2026		10,376
2027		10,466
2028		10,732
Thereafter		41,615
Total minimum payments		93,565
Less: Amounts representing interest expense		(30,613	)
Present value of future minimum lease payments		62,952
Less: Current portion of lease liability		(6,811	)
Noncurrent portion of lease liability	$	56,141

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 42,395	$ 62,986
Restricted cash	1,247	2,299
Long-term restricted cash	5,290	5,290
Total cash, cash equivalents and restricted cash	48,932	70,575	$ 54,495	$ 64,765
Total cash, cash equivalents and restricted cash	$ 48,932	$ 70,575

Cash Equivalents and Marketable Securities - Additional Information (Detail) - Security	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Cash equivalents and marketable securities [Line Items]
Realized gains or losses on marketable securities	no material realized gains or losses	no material realized gains or losses
Number of individual securities in an unrealized loss position for 12 months or greater	0
Period of unrealized loss position	12 months or greater
Maximum [Member]
Cash equivalents and marketable securities [Line Items]
Marketable securities contractual maturities period	1 year

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	ATM Equity Offering Program [Member]	Common Stock [Member]	Common Stock [Member] ATM Equity Offering Program [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] ATM Equity Offering Program [Member]	Accumulated Other Comprehensive Gain (Loss) [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2022	$ 170,781		$ 22		$ 691,910		$ (80)	$ (521,071)
Balance, shares at Dec. 31, 2022			86,894,901
Unrealized gain (loss) on marketable securities	28						28
Issuance of common stock upon restricted stock units vestings, Shares			345,663
Tax payments related to shares withheld for vested restricted stock units	(742)				(742)
Issuance of stock, net of issuance costs		$ 1,902				$ 1,902
Issuance of stock, net of issuance costs, shares				607,853
Stock-based compensation	2,891				2,891
Net loss	(33,982)							(33,982)
Balance at Mar. 31, 2023	140,878		$ 22		695,961		(52)	(555,053)
Balance, shares at Mar. 31, 2023			87,848,417
Balance at Dec. 31, 2023	51,850		$ 22		711,386		3	(659,561)
Balance, shares at Dec. 31, 2023			97,585,415
Unrealized gain (loss) on marketable securities	(4)						(4)
Issuance of common stock upon restricted stock units vestings, Shares			508,536
Tax payments related to shares withheld for vested restricted stock units	(788)				(788)
Issuance of common stock upon exercise of stock options	$ 45				45
Issuance of common stock upon exercise of stock options, shares	30,797		20,909
Stock-based compensation	$ 3,246				3,246
Net loss	(40,385)							(40,385)
Balance at Mar. 31, 2024	$ 13,964		$ 22		$ 713,889		$ (1)	$ (699,946)
Balance, shares at Mar. 31, 2024			98,114,860

Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2024

Equity [Abstract]

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

As of March 31, 2024, 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

Stockholders' Equity

3 Months Ended

Mar. 31, 2024

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 March 31, 2024 and December 31, 2023, no shares of preferred stock were issued and outstanding.

As of March 31, 2024 and December 31, 2023, there were 98,114,860 and 97,585,415 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 and Company, LLC ("Cowen"), pursuant to which 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 March 31, 2024, 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.

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, the 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 March 31, 2024, 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

There were no warrants exercised during the three months ended March 31, 2024 and 2023, respectively.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Paragraph 1
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Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Net Loss Per Common Share - Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Numerator:
Net loss	$ (40,385)	$ (33,982)
Denominator:
Weighted-average common shares outstanding, basic	118,391,224	114,423,000
Weighted-average common shares outstanding, diluted	118,391,224	114,423,000
Net loss per share, basic	$ (0.34)	$ (0.3)
Net loss per share, diluted	$ (0.34)	$ (0.3)

- Definition

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

+ References

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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+ Details

- Definition

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

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+ Details

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock Based Compensation Expense	$ 3,246	$ 2,891
Research and Development Expense [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock Based Compensation Expense	1,660	1,613
General and Administrative Expense [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock Based Compensation Expense	$ 1,586	$ 1,278

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 1,742	$ 1,799

Cash Equivalents and Marketable Securities

3 Months Ended

Mar. 31, 2024

Cash and Cash Equivalents [Abstract]

Cash Equivalents and Marketable Securities

3. Cash Equivalents and Marketable Securities

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


	March 31, 2024
Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	38,086	$	—	$	—		$	38,086
Total cash equivalents		38,086		—		—			38,086
Short-term marketable securities:
U.S. government treasuries		3,663		—		(1	)		3,662
Commercial paper		246		—		—			246
Total short-term marketable securities		3,909		—		(1	)		3,908
Total	$	41,995	$	—	$	(1	)	$	41,994


	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

All marketable securities held as of March 31, 2024 had contractual maturities of less than one year. There have been no material realized gains or losses on marketable securities for the periods presented. As of March 31, 2024, 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 for the periods presented. The Company has not recorded an allowance for credit losses as of March 31, 2024 and December 31, 2023.

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

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured at Fair Value

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


	March 31, 2024
Description	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	38,086	$	38,086	$	—	$	—
Total cash equivalents		38,086		38,086		—		—
Short-term marketable securities:
U.S. government treasuries		3,662		3,662		—		—
Commercial paper		246		—		246		—
Total short-term marketable securities		3,908		3,662		246		—
Total	$	41,994	$	41,748	$	246	$	—


	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	$	—

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2024	May 06, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Document Quarterly Report	true
Document Transition Report	false
Entity Registrant Name	Gritstone bio, Inc.
Entity Central Index Key	0001656634
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Securities Act 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
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	GRTS
Security Exchange Name	NASDAQ
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		108,569,374

Balance Sheet Components - Schedule of Deposits and Other Long-Term Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Deposit Assets And Other Assets Noncurrent Disclosure [Abstract]
Lease security deposits	$ 924	$ 924
Total deposits and other long-term assets	$ 924	$ 924

Debt - Additional Information (Details) - USD ($)		1 Months Ended	3 Months Ended
Debt - Additional Information (Details) - USD ($)	Apr. 01, 2024	Jul. 31, 2022	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2022
Short-Term Debt [Line Items]
Unamortized debt discount and issuance costs			$ (1,970,000)
Loan Agreement [Member]
Short-Term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 80,000,000
Line of credit available for drawing			$ 0		$ 10,000,000
Debt Instrument, Description of Variable Rate Basis			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%
Debt Instrument, Interest Rate, Stated Percentage		5.50%
Debt Instrument, Basis Spread on Variable Rate		7.15%
Debt Instrument, Fee Amount		$ 150,000
Facility Charge Percentage of Borrowing		0.50%
Final Payment Fee Percentage		5.75%
Unamortized debt discount and issuance costs			$ 2,000,000
Interest Expense, Debt			$ 1,300,000	$ 800,000
Debt Instrument, Interest Rate, Effective Percentage			13.00%
Loan Agreement [Member] \| Prime Rate Plus [Member]
Short-Term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate		3.15%
Loan Agreement [Member] \| Payment-in-kind rate [Member]
Short-Term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.00%
Loan Agreement [Member] \| Forecast [Member]
Short-Term Debt [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]
Short-Term Debt [Line Items]
Prepayment Premium Rate		0.00%
Loan Agreement [Member] \| Maximum [Member]
Short-Term Debt [Line Items]
Prepayment Premium Rate		2.50%
Capitalization, Long-Term Debt and Equity	$ 400,000,000
Loan Agreement [Member] \| Tranche One [Member]
Short-Term Debt [Line Items]
Long-Term Line of Credit		$ 20,000,000
Loan Agreement [Member] \| Tranche One Additional [Member]
Short-Term Debt [Line Items]
Long-Term Line of Credit				$ 10,000,000
Loan Agreement [Member] \| Remaining Tranche [Member]
Short-Term Debt [Line Items]
Long-Term Line of Credit			$ 50,000

Collaboration and License Agreements and Grant Revenue - Additional Information (Detail) - USD ($)			1 Months Ended										3 Months Ended		12 Months Ended
	Sep. 30, 2023	Aug. 14, 2021	Jun. 30, 2023	Apr. 30, 2023	Apr. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Jan. 31, 2021	Oct. 31, 2020	Oct. 31, 2018	Sep. 30, 2018	Aug. 31, 2018	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2021	Dec. 31, 2019	Dec. 31, 2023	Aug. 31, 2023	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
Contract with Customer, Liability, Current													$ 1,285,000				$ 2,350,000
Increase in contribution revenue													(1,065,000)	$ (2,330,000)
Loss from operations													(39,801,000)	(34,816,000)
Revenue													$ 1,742,000	2,443,000
Common stock, shares issued													98,114,860				97,585,415
Research and development													$ 33,041,000	30,514,000
Research and Development Expense													33,041,000	30,514,000
Restricted cash													1,247,000				$ 2,299,000
Restricted Cash													1,247,000				2,299,000
License Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue													49,000	542,000
Grant Revenues [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue													$ 1,693,000	1,901,000
Gilead Sciences Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment								$ 30,000,000
Offering price per share								$ 25.65
Proceeds from Issuance of Common Stock								$ 30,000,000
Revenue recognition contract start month year													2021-01
Contract assets													$ 0				0
Maximum aggregate contingent milestone payment								685,000,000
Proceeds from equity investment								$ 30,000,000
Common stock fair value closing price per share								$ 18.1
Non-refundable option fee								$ 40,000,000
Transaction price allocated to shares of common stock at fair value								$ 21,200,000
Common stock, shares issued								1,169,591
Common stock purchase price in excess of fair value								$ 8,800,000
Gilead Sciences Inc [Member] \| Collaboration Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration and license revenue														100,000
Contract with Customer, Liability, Revenue Recognized														100,000
Gilead Sciences Inc [Member] \| Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition contract end period													2 years
Gilead Sciences Inc [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition contract end period													4 years
Coalition for Epidemic Preparedness Innovations [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Agreement Total Funding															$ 25,600,000
Additional Funding															5,000,000
Total Grant Amount		$ 20,600,000
First tranche of funding received							$ 11,300,000
Second Tranche Of Funding Received					$ 2,700,000
ThirdTrancheOfFundingReceived			$ 1,200,000
Fourth Tranche Of Funding Received						$ 2,400,000
Common Stock [Member] \| Gilead Sciences Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of common shares sold								1,169,591
2 Seventy [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment												$ 20,000,000
Proceeds from issuance of convertible preferred stock, net of issuance costs												10,000,000
Maximum development, regulatory, and commercial milestones												$ 1,200,000,000
Collaboration and license revenue														400,000
Deferred Revenue													$ 0				0
Contract assets													0				0
Receivables													0				0
Contract with Customer, Liability, Revenue Recognized														400,000
2 Seventy [Member] \| Series C [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock shares issued												768,115
Offering price per share												$ 13.04
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										$ 10,000,000
Number of common shares sold										666,667
Arbutus Biopharma Corporation and Protiva Biotherapeutics Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum milestone consideration payable																						$ 123,500,000
Milestone payment included in research and development expense											$ 2,500,000					$ 3,000,000
Research and development													0	0
Research and Development Expense													0	0
Genevant Sciences GmbH [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment									$ 2,000,000
Gates Foundation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment				$ 700,000		2,200,000
Twenty Twenty Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount to extend the option term									1,000,000
Twenty Twenty Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member] \| Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment																					$ 2,000,000
Milestone payments																			$ 1,000,000
Twenty Twenty 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									71,000,000
Payments for options to license for each indication									$ 1,500,000
Twenty Twenty One Genevant License Agreement [Member] \| Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payments								$ 1,500,000
Twenty Twenty One Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum aggregate contingent milestone payment								$ 191,000,000
Milestone payments													0
Twenty Twenty One Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member] \| Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payments						1,500,000									1,500,000
Milestone payments						$ 1,000,000									$ 1,000,000					$ 1,000,000
Twenty Twenty Three Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum aggregate contingent milestone payment																		$ 136,000,000
Twenty Twenty Three Genevant License Agreement [Member] \| Genevant Sciences GmbH [Member] \| Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payments																	2,500,000
C E P I Funding Agreement [Member] \| Coalition for Epidemic Preparedness Innovations [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue													1,234,000				2,291,000
Collaboration and license revenue													1,000,000	1,500,000
Restricted cash													1,200,000				2,300,000
Short-term deferred revenue													1,200,000				2,300,000
Gates Grant Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue													300,000	$ 400,000
Gates Grant Agreement [Member] \| Gates Foundation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue													14,000				$ 8,000
BARDA Contract [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum Government Funding for Base Period	$ 10,000,000
Potential maximum government funding for performance of certain milestones	433,000,000
BARDA Contract [Member] \| Grant Revenues [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contract Amount Received													400,000
Revenue													$ 400,000
BARDA Contract [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional Funding for Two Stages	$ 423,000,000

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid research and development-related expenses	$ 2,462	$ 3,904
Collaboration receivable	34	14
Prepaid insurance	620	940
Interest and other receivables	172	217
Facilities-related deposits	9	9
Deferred financing costs	440	0
Other	566	778
Total prepaid expenses and other current assets	$ 4,303	$ 5,862

Commitments and Contingencies - Schedule of Components of Lease Costs (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Lease cost
Operating lease cost	$ 3,221	$ 2,164
Short-term lease cost	18	0
Total lease cost	$ 3,239	$ 2,164

Organization - Additional Information (Detail) $ in Thousands	1 Months Ended	3 Months Ended
	Apr. 30, 2024 USD ($)	Mar. 31, 2024 USD ($) Segment	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Subsidiary, Sale of Stock [Line Items]
Number of operating segments \| Segment		1
Net losses		$ 40,385	$ 33,982
Net cash used in operating activities		(33,567)	$ (40,090)
Accumulated deficit		$ (699,946)		$ (659,561)
Company planned Operation		12 months
Cash, cash equivalents and marketable securities		$ 46,300
Underwritten Public Offering [Member] \| Subsequent Event [Member]
Subsidiary, Sale of Stock [Line Items]
Gross Proceeds from the Offerings	$ 32,500

Debt - Schedule of Long term debt (Details) $ in Thousands	Mar. 31, 2024 USD ($)
Debt Disclosure [Abstract]
Principal loan balance	$ 40,000
Final Fee	2,300
Unamortized debt discount and issuance costs	(1,970)
Long-Term Debt, net	$ 40,330

- Definition

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

+ References + Details

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 42,395	$ 62,986
Marketable securities	3,908	16,288
Restricted cash	1,247	2,299
Prepaid expenses and other current assets	4,303	5,862
Total current assets	51,853	87,435
Long-term restricted cash	5,290	5,290
Property and equipment, net	14,088	17,281
Lease right-of-use assets	65,057	66,839
Deposits and other long-term assets	924	924
Total assets	137,212	177,769
Current liabilities:
Accounts payable	7,248	3,819
Accrued compensation	4,340	9,357
Accrued liabilities	2,141	1,213
Accrued research and development expenses	4,045	3,696
Lease liabilities, current portion	6,811	6,904
Deferred revenue, current portion	1,285	2,350
Total current liabilities	25,870	27,339
Other liabilities, noncurrent	907	709
Lease liabilities, net of current portion	56,141	57,727
Debt, noncurrent	40,330	40,144
Total liabilities	123,248	125,919
Commitments and contingencies (Notes 6, 8 and 9)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding at March 31, 2024 and December 31, 2023	0	0
Common stock, $0.0001 par value; 300,000,000 shares authorized at March 31, 2024 and December 31, 2023; 98,114,860 and 97,585,415 shares issued and outstanding at March 31, 2024 and December 31, 2023, respectively	22	22
Additional paid-in capital	713,889	711,386
Accumulated other comprehensive (loss) gain	(1)	3
Accumulated deficit	(699,946)	(659,561)
Total stockholders’ equity	13,964	51,850
Total liabilities and stockholders’ equity	$ 137,212	$ 177,769

Fair Value Measurements - Financial Assets Subject To Fair Value Measurements on a Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	$ 41,994	$ 62,265
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	41,748	49,108
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	246	13,157
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	38,086	45,977
Cash Equivalents [Member] \| U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		2,250
Cash Equivalents [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	38,086	39,243
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] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	38,086	39,243
Cash Equivalents [Member] \| Fair Value, Inputs, Level 1 [Member] \| U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Cash Equivalents [Member] \| Fair Value, Inputs, Level 1 [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	38,086	39,243
Cash Equivalents [Member] \| Fair Value, Inputs, Level 1 [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Cash Equivalents [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	6,734
Cash Equivalents [Member] \| Fair Value, Inputs, Level 2 [Member] \| U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		2,250
Cash Equivalents [Member] \| Fair Value, Inputs, Level 2 [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Cash Equivalents [Member] \| Fair Value, Inputs, Level 2 [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		4,484
Cash Equivalents [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Cash Equivalents [Member] \| Fair Value, Inputs, Level 3 [Member] \| U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Cash Equivalents [Member] \| Fair Value, Inputs, Level 3 [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Cash Equivalents [Member] \| Fair Value, Inputs, Level 3 [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Short-Term Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	3,908	16,288
Short-Term Marketable Securities [Member] \| U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		1,999
Short-Term Marketable Securities [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	246	3,485
Short-Term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		939
Short-Term Marketable Securities [Member] \| U.S. Government Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	3,662	9,865
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	3,662	9,865
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| U.S. Government Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	3,662	9,865
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	246	6,423
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		1,999
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	246	3,485
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		939
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| U.S. Government Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| U.S. Government Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	$ 0
Long-term Marketable Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| U.S. Government Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		$ 0