0000950170-24-027998 | 10-K | XBRL Viewer

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Composition of Certain Balance Sheet Components - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization expense	$ 5,614	$ 5,172

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Private Placement	Public Offering	ATM Offering	Common Stock	Common Stock Private Placement	Common Stock Public Offering	Common Stock ATM Offering	Additional Paid-in Capital	Additional Paid-in Capital Private Placement	Additional Paid-in Capital Public Offering	Additional Paid-in Capital ATM Offering	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2021	$ 156,211				$ 6				$ 563,064				$ 0	$ (406,859)
Beginning balance, Shares at Dec. 31, 2021					62,523,596
Issuance of common stock under employee stock compensation plans	1,310								1,310
Issuance of common stock under employee stock compensation plans, Shares					440,565
Issuance of common stock, net of issuance costs			$ 75,299				$ 3				$ 75,296
Issuance of common stock, net of issuance costs, Shares							23,000,000
Stock-based compensation expense	18,926								18,926
Unrealized gain (loss) on available-for-sale securities	(149)												(149)
Net loss	(64,002)													(64,002)
Ending balance at Dec. 31, 2022	187,595				$ 9				658,596				(149)	(470,861)
Ending balance, Shares at Dec. 31, 2022					85,964,161
Issuance of common stock under employee stock compensation plans	782								782
Issuance of common stock under employee stock compensation plans, Shares					1,220,059
Issuance of common stock, net of issuance costs		$ 14,417		$ 928		$ 1				$ 14,416		$ 928
Issuance of common stock, net of issuance costs, Shares						8,333,333		119,000
Stock-based compensation expense	23,134								23,134
Unrealized gain (loss) on available-for-sale securities	275												275
Net loss	(123,430)													(123,430)
Ending balance at Dec. 31, 2023	$ 103,701				$ 10				$ 697,856				$ 126	$ (594,291)
Ending balance, Shares at Dec. 31, 2023					95,636,553

- Definition

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

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- Definition

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

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- Definition

Amount of equity (deficit) attributable to parent. Excludes temporary equity and equity attributable to noncontrolling interest.

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+ Details

Collaboration and License Agreements

12 Months Ended

Dec. 31, 2023

Collaborations And License Agreement [Line Items]

Collaboration and License Agreements

Note 8. California Institute of Regenerative Medicine Award

The Company has been awarded funding from the California Institute of Regenerative Medicine (“CIRM”) to develop certain internal programs. Under the terms of the funding, both CIRM and the Company have co-funded specified programs, under which funding is provided in developmental milestones determined as a part of the award. The Company is obligated to share potential future revenues for the related programs with CIRM. The percentage of revenues due to CIRM in the future is dependent on the amount of the award received and whether revenue is generated from product sales or through license fees. The maximum revenue sharing amount the Company may be required to pay to CIRM is equal to nine times the total amount awarded and paid to the Company. As an alternative

to revenue sharing, the Company has the option to convert any award to a loan, which such option the Company must exercise on or before ten business days after the U.S. Food and Drug Administration (“FDA”) notifies the Company that it has accepted the Company’s application for marketing authorization. In the event the Company exercises its right to convert any award to a loan, it would be obligated to repay the loan within ten business days of making such election. Repayment amounts due to CIRM vary dependent on when the award is converted to a loan, ranging from 60% of the award granted to the full amount received plus interest at the rate of the three-month LIBOR rate plus 10% per annum. Since the Company may be required to repay some or all of the amounts awarded by CIRM, the Company accounts for this award as a liability as the Company’s intention is to convert the award into a loan. Given the uncertainty in amounts due upon repayment, the Company has recorded amounts received without any discount or interest recorded, upon determination of amounts that would become due, the Company will adjust accordingly.

In September 2018, the Company was granted an award in the amount of $4.0 million from CIRM to support the Company’s preclinical studies for its P-PSMA-101 program. The Company received the full amount of the award based on achievement of specific developmental milestones. In the third quarter of 2023, the Company decided not to pursue additional clinical or other development activities of the P-PSMA-101 program, which resulted in write off of the amount previously included in the deferred CIRM grant liability as the Company no longer intends to repay the award and which amount is included in other income in the accompanying consolidated statement of operations.

Roche Ltd And Takeda Pharmaceuticals USA Inc.

Collaborations And License Agreement [Line Items]

Collaboration and License Agreements

Note 7. Collaboration and License Agreements

Roche

Terms of the Agreement

In July 2022, the Company entered into a collaboration and license agreement (the “Roche Collaboration Agreement”) with F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (collectively, “Roche”), pursuant to which the Company granted to Roche: (i) an exclusive, worldwide license under certain Company intellectual

property to develop, manufacture and commercialize allogeneic CAR-T cell therapy products from each of the Company’s existing P-BCMA-ALLO1 and P-CD19CD20-ALLO1 programs (each a “Tier 1 Program”); (ii) an exclusive option to acquire an exclusive, worldwide license under certain Company intellectual property to develop, manufacture and commercialize allogeneic CAR-T cell therapy products from each of the Company’s existing P-BCMACD19-ALLO1 and P-CD70-ALLO1 programs (each, a “Tier 2 Program”); (iii) an exclusive license under certain Company intellectual property to develop, manufacture and commercialize allogeneic CAR-T cell therapy products from the up to six Collaboration Programs (as defined below) designated by Roche; (iv) an option for a non-exclusive, commercial license under certain limited Company intellectual property to develop, manufacture and commercialize certain Roche proprietary cell therapy products for up to three solid tumor targets to be identified by Roche (“Licensed Products”); and (v) the right of first offer for two (2) early-stage existing programs within hematologic malignancies. The Roche Collaboration Agreement became effective in September 2022 upon expiration of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended.

For each Tier 1 Program, the Company will perform development activities through a Phase 1 dose escalation clinical trial, and Roche is obligated to reimburse a specified percentage of certain costs incurred by the Company in its performance of such activities, up to a specified reimbursement cap for each Tier 1 Program. For Tier 1 Program activities beyond the Phase 1 dose escalation, Roche is obligated to reimburse all costs incurred for the program. For each Tier 2 Program, the Company will perform research and development activities either through selection of a development candidate for IND-enabling studies or, subject to Roche’s election and payment of an option maintenance fee, through completion of a Phase 1 dose escalation clinical trial. In addition, for each Tier 2 Program for which Roche exercises its option for an exclusive license, Roche is obligated to pay an option exercise fee. For each Tier 1 Program and Tier 2 Program, the Company will perform manufacturing activities until the completion of a technology transfer to Roche.

The parties will conduct an initial two-year research program to explore and preclinically test a specified number of agreed-upon next generation therapeutic concepts relating to allogeneic CAR-T cell therapies. Subject to Roche’s election and payment of a specified fee, the parties would subsequently conduct a second research program of 18 months under which the parties could extend the existing work being performed under the initial term, and/or would explore and preclinically test a specified number of additional agreed-upon next generation therapeutic concepts relating to allogeneic CAR-T therapies. Roche may designate up to six heme malignancy-directed, allogeneic CAR-T programs from the two research programs, for each of which the Company will perform research and development activities through selection of a development candidate for IND-enabling activities (each, a “Collaboration Program”). Upon its designation of each Collaboration Program, Roche is obligated to pay a designation fee. After the Company’s completion of lead optimization activities for a Collaboration Program, Roche may elect to transition such program to Roche with a payment to the Company or terminate it. Alternatively, Roche may elect, for a limited number of Collaboration Programs, to have the Company conduct certain additional development and manufacturing activities through the completion of a Phase 1 dose escalation clinical trial, in which case Roche will pay certain milestones and reimburse a specified percentage of the Company’s costs incurred in connection with such development and manufacturing activities. For each Collaboration Program, the Company will perform manufacturing activities until the completion of a technology transfer to Roche.

In consideration for the rights granted to Roche under the Roche Collaboration Agreement, the Company received an upfront payment of $110.0 million. In addition, subject to Roche exercising its Tier 2 Program options, designating Collaboration Programs, and exercising its option for the Licensed Products commercial license and further contingent on, among other things, achieving specified objectives, the Company is eligible to receive up to (i) $1.5 billion in aggregate payments for Tier 1 Programs comprised of research funding, feasibility fees and $1.4 billion in development, regulatory and net sales milestones, (ii) $1.1 billion in aggregate payments for Tier 2 Programs comprised of option exercise and maintenance fees and $1.0 billion in development, regulatory and net sales milestones, (iii) $2.9 billion in aggregate payments for the Collaboration Programs comprised of certain reimbursements, fees and milestone payments; and (iv) $415.0 million in payments for the Licensed Products comprised of certain reimbursements, fees and milestone payments.

The Company is further entitled to receive, on a product-by-product basis, tiered royalty payments in the mid-single to low double digits on net sales of products from the Tier 1 Programs, optioned Tier 2 Programs and Collaboration Programs and in the low to mid-single digits for Licensed Products, in each case, subject to certain

customary reductions and offsets. Royalties will be payable, on a product-by-product and country-by-country basis, until the latest of the expiration of the licensed patents covering such product in such country or ten years from first commercial sale of such product in such country.

The Roche Collaboration Agreement will continue in effect on a product-by-product and country-to-country basis until there is no remaining royalty or other payment obligations. The Roche Collaboration Agreement includes standard termination provisions, including for material breach or insolvency and for Roche’s convenience. Certain of these termination rights can be exercised with respect to a particular product or license, as well as with respect to the entire Roche Collaboration Agreement.

Effective November 7, 2023, the Roche Collaboration Agreement was amended to, among other things: (i) reallocate certain existing manufacturing-related fees payable to us by Roche to add new manufacturing process development and implementation transfer fees for each of our existing Tier 1 Programs; and (ii) reallocate amounts in certain development milestone payments payable to us by Roche for each Tier 1 Program. The amendment also provided for the ability for the existing two-year research program to be extended for an additional 18 months with the payment of a $15.0 million milestone. All performance obligations and payment terms under the Roche Collaboration Agreement otherwise remained unchanged.

Revenue Recognition

At contract inception, the Company has identified six performance obligations under the Roche Collaboration Agreement: (i) licenses associated with the Tier 1 Programs, (ii) research and development efforts for the Tier 1 Programs, (iii) clinical drug supply for the Tier 1 Programs, (iv) manufacturing process development program for the Tier 1 Programs, (v) research and development efforts for the Tier 2 Programs, and (vi) research and development efforts for the Collaboration Programs. The Company concluded that Roche’s options within the Roche Collaboration Agreement do not represent material rights and are not considered performance obligations as they do not contain a significant and incremental discount. The licenses associated with the Tier 1 Programs were delivered at the beginning of the agreement term and deemed capable of being distinct as the Company concluded that Roche has the knowledge and capabilities to continue development work and fully utilize the licenses without the Company’s involvement.

In order to determine the transaction price, the Company evaluated all the payments to be received during the term of the Roche Collaboration Agreement. Certain milestones and additional fees were considered variable consideration, which were not included in the initial transaction price based on the most likely amount method. 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 transaction price at the inception of the Roche Collaboration Agreement was $185.0 million, which consists of the upfront payment of $110.0 million, future research funding for the Tier 1 Programs of $40.0 million and a $35.0 million milestone achieved in September 2022 for the Tier 1 Programs. As of December 31, 2023, the Company achieved a developmental milestone of $30.0 million, and in accordance with ASC 606, the Company determined that the achieved milestone represented an increase in the initial transaction price for its manufacturing process development program for the Tier 1 Programs in the form of the receipt of variable consideration that was previously constrained. The Company recognized revenue associated with the milestone in an amount equal to the proportional percentage of the actual costs incurred under the manufacturing process development programs since its inception as a percentage of the total costs expected to be incurred over the expected term of conduct of the manufacturing process development program. The remaining unrecognized revenue associated with the milestone was recorded to deferred revenue and is being recognized as revenue over the expected term of conduct of the manufacturing process development program. All other future potential milestone payments were excluded from the estimated total transaction price as they were considered constrained. All other future potential milestone payments were excluded from the estimated total transaction price as they were considered constrained.

The performance obligation associated with the licenses for the Tier 1 Programs was satisfied as of the effective date of the Roche Collaboration Agreement. All other performance obligations will be recognized on a proportional basis as the underlying services are provided based on actual costs incurred as a percentage of total estimated costs. The Company determined that the cost-based input method most faithfully depicts the pattern in which these performance obligations are satisfied. Any cumulative effect of revisions to estimated costs to complete

the Company’s performance obligation will be recorded in the period in which changes are identified and amounts can be reasonably estimated. This approach requires the Company to use significant judgment and make estimates of future expenditures. If the Company’s estimates or judgments change over the course of the collaboration, they may affect the timing and amount of revenue that it recognizes in the current and future periods.

Takeda

In October 2021, the Company entered into a collaboration and license agreement (the “Takeda Collaboration Agreement”) with Takeda Pharmaceuticals USA, Inc. (“Takeda”), pursuant to which the Company granted to Takeda a worldwide exclusive license under the Company’s certain platform technologies including piggyBac, Cas-CLOVER, biodegradable DNA and RNA nanoparticle delivery technology and other proprietary genetic engineering platforms to research, develop, manufacture and commercialize gene therapy products for certain indications. Under the Takeda Collaboration Agreement, the Company received an upfront payment of $45.0 million and R&D reimbursement payments during the term of the agreement.

On May 31, 2023, the Company received written notice from Takeda of its election to terminate the Takeda Collaboration Agreement, effective July 30, 2023 (the “Termination Date”). Until the Termination Date, the parties performed their respective obligations under the Collaboration Agreement and upon the Termination Date, the Company’s exclusivity obligations under the Collaboration Agreement terminated. In addition, the licenses granted to Takeda by the Company, and the licenses granted to the Company by Takeda to perform research activities under the Collaboration Agreement terminated. The Company recognized $8.9 million of previously deferred revenue during the year ended December 31, 2023 in acknowledgment these performance obligations are no longer required to be performed.

Deferred Revenue Reconciliation

While the Company’s entry into the Astellas Strategic Rights Letter was a strategic investment, for purposes of recognizing the remaining amount, it has been determined to be revenue, and as such, reference to remaining deferred revenue for these agreements is included in the following table. A contract asset of $30.0 million for the Roche Collaboration Agreement was netted against deferred revenue for the year ended December 31, 2023. There were no contract assets as of December 31, 2023 or 2022 related to the Takeda Collaboration Agreement or Astellas Strategic Rights Letter.

A reconciliation of the closing balance of deferred revenue related to the agreements is as follows (in thousands):


	Roche Collaboration Agreement			Takeda Collaboration Agreement			Astellas Strategic Rights Letter		Total
Balance as of December 31, 2021	$	—		$	13,762		$	—	$	13,762
Amounts received/invoiced		153,169			4,617			—		157,786
Revenue recognized		(121,420	)		(9,072	)		—		(130,492	)
Balance as of December 31, 2022	$	31,749		$	9,307		$	—	$	41,056
Amounts received/invoiced		30,741			5,111			35,583		71,435
Revenue recognized		(50,285	)		(14,418	)		—		(64,703	)
Balance as of December 31, 2023	$	12,205		$	—		$	35,583	$	47,788

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Summary of Components of Pretax Loss from Operations

The components of the pretax loss from operations are as follows (in thousands):


	Year Ended December 31,
	2023			2022
U.S. Domestic	$	(123,323	)	$	(63,458	)
Net loss before income tax	$	(123,323	)	$	(63,458	)

Schedule of Provision for Income Taxes

The provision for income taxes consists of the following (in thousands):


	Year Ended December 31,
	2023		2022
Current:
Federal	$	51	$	456
State		56		88
Total current provision		107		544
Deferred:
Federal		—		—
State		—		—
Total deferred provision		—		—
Total provision	$	107	$	544

Schedule of (Benefit from) Provision for Income Taxes Differs from Income Tax Determined by Applicable U.S. Statutory Federal Income Tax Rate to Pretax Income

The provision for income taxes differs from the amount of income tax determined by applying the applicable U.S. statutory federal income tax rate to pretax income as a result of the following differences (in thousands):


	Year Ended December 31,
	2023			2022
Federal statutory rate	$	(25,898	)	$	(13,326	)
Adjustments for tax effects of:
Tax credits		(12,938	)		(9,026	)
State taxes, net		(6,856	)		(2,842	)
Unrecognized tax benefits		2,970			2,209
Stock-based compensation		3,279			3,106
Other, net		224			171
Change in valuation allowance		39,326			20,252
Total	$	107		$	544

Significant Components of Deferred Tax Assets and Liabilities

Significant components of the Company’s deferred tax assets and liabilities consist of the following as of (in thousands):


	December 31,
	2023			2022
Deferred tax assets:
Net operating losses	$	91,285		$	89,300
Income tax credit carryforwards		48,119			38,674
R&D capitalization		39,341			23,370
Deferred revenue		9,965			2,584
Lease liabilities		7,514			8,468
Amortization		5,136			1,252
Accrued expenses		3,436			2,910
Grant income		—			1,108
Other, net		4,910			3,612
Total deferred tax assets		209,706			171,278
Deferred tax liabilities:
Right of use assets		(6,084	)		(6,965	)
Depreciation		(2,003	)		(1,948	)
Acquired indefinite lived intangibles		(370	)		(366	)
Total deferred tax liabilities		(8,457	)		(9,279	)
Valuation allowance		(201,304	)		(162,054	)
Net deferred tax liability	$	(55	)	$	(55	)

Schedule of Unrecognized Tax Benefits

As of December 31, 2023, the Company had unrecognized tax benefits of $15.3 million, determined as follows:


	December 31,
	2023		2022
Balance at beginning of year	$	11,805	$	9,494
Increase for current year positions		3,091		2,403
Increase (decrease) for prior year positions		383		(92	)
Balance at the end of year	$	15,279	$	11,805

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Line Items]
Income tax expense	$ 107,000	$ 544,000
Valuation allowance	201,304,000	162,054,000
Unrecognized tax benefits	15,279,000	$ 11,805,000	$ 9,494,000
Impact the effective tax rate due to valuation allowance, if reversed	0
Accrued interest or penalties	$ 0
Federal
Income Taxes [Line Items]
Operating loss carryforwards, limitations on use	the Company had federal net operating loss carryforwards that do not expire but utilization is limited to 80% of taxable income for any given tax year in the amount of $285.3 million.
Operating loss carryforwards limitations on use percentage of taxable income	80.00%
Operating loss carryforwards limitations on use taxable income	$ 285,300,000
Research and development credits	$ 46,900,000
Research and development tax credit carryforward expiration year	2037
Tax cuts and jobs act capitalize and amortize research and development expenditures period	5 years
State
Income Taxes [Line Items]
Operating loss carryforwards	$ 445,500,000
Research and development credits	$ 19,700,000
Foreign
Income Taxes [Line Items]
Tax cuts and jobs act capitalize and amortize research and development expenditures period	15 years

Collaboration and License Agreements - Additional Information (Details)		1 Months Ended
	Nov. 07, 2023 USD ($)	Jul. 31, 2022 USD ($) Program PerformanceObligation	Oct. 31, 2021 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Takeda Pharmaceuticals USA, Inc.
Collaborations And License Agreement [Line Items]
Deferred revenue recognized				$ 8,900,000
Contract Assets				0	$ 0
Collaboration Agreement \| Takeda Pharmaceuticals USA, Inc.
Collaborations And License Agreement [Line Items]
Upfront cash payment from collaboration agreement			$ 45,000,000
Roche Collaboration Agreement
Collaborations And License Agreement [Line Items]
Number of collaboration programs \| Program		6
Number of early-stage existing programs \| Program		2
Research collaboration period	2 years	2 years
Research collaboration extension period	18 months	18 months
Upfront cash payment from collaboration agreement		$ 110,000,000
Number of performance obligations \| PerformanceObligation		6
Milestone payments	$ 15,000,000
Collaboration revenue receivable terms		10 years
Roche Collaboration Agreement \| Roche Ltd
Collaborations And License Agreement [Line Items]
Upfront cash payment from collaboration agreement		$ 110,000,000
Transaction price		185,000,000
Contract Assets				30,000,000
Developmental milestone				30,000,000
Roche Collaboration Agreement \| Tier 1 Programs
Collaborations And License Agreement [Line Items]
Fees and milestone payments receivable		1,500,000,000
Development, regulatory and net sales milestones		1,400,000,000
Roche Collaboration Agreement \| Tier 1 Programs \| Roche Ltd
Collaborations And License Agreement [Line Items]
Future research funding		40,000,000
Milestone payments		35,000,000
Roche Collaboration Agreement \| Tier 2 Programs
Collaborations And License Agreement [Line Items]
Fees and milestone payments receivable		1,100,000,000
Development, regulatory and net sales milestones		1,000,000,000
Roche Collaboration Agreement \| Collaboration Programs
Collaborations And License Agreement [Line Items]
Fees and milestone payments receivable		2,900,000,000
Roche Collaboration Agreement \| Licensed Products
Collaborations And License Agreement [Line Items]
Fees and milestone payments receivable		$ 415,000,000
Astellas Strategic Rights Letter Agreement
Collaborations And License Agreement [Line Items]
Contract Assets				$ 0	$ 0

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2020	Dec. 31, 2023	Dec. 31, 2022	Feb. 28, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock reserved for issuance		25,571,785
Aggregate intrinsic value of options exercised		$ 0.1	$ 0.2
Weighted-average grant date fair value of options granted		$ 3.4	$ 2.64
Cash received from options exercised		$ 0.1	$ 0.2
Unrecognized compensation cost		24.1
Fair value of shares vested		$ 22.3	$ 22.1
Expected dividend yield		0.00%
Risk-free interest rate		4.05%	2.16%
Expected term (years)		5 years 11 months 19 days	5 years 11 months 19 days
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		2 years
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		4 years
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period over which cost expected to be recognized		2 years 3 months 18 days
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		4 years
Weighted-average period over which cost expected to be recognized		2 years 9 months 18 days
Unrecognized compensation cost		$ 15.1
2020 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock reserved for issuance	11,183,476
Share-based compensation award term	10 years
Percentage increase of outstanding number of shares of common stock	5.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant		2,383,334
2020 Equity Incentive Plan \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of the fair market value per share of common stock		100.00%
Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant		1,949,646
Inducement Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock issuable		3,517,105		2,000,000
2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock reserved for issuance	615,000
Share-based compensation award term	10 years
Percentage increase of outstanding number of shares of common stock	1.00%
Share-based compensation shares issued in period	1,230,000
Offering period of common stock	six months
Percentage of the fair market value per share of common stock	85.00%
Risk-free interest rate		5.26%	2.39%
Expected term (years)		6 months	6 months
Total shares purchased by employees		536,669
Net proceeds from share purchase by employees		$ 1.1
2020 Employee Stock Purchase Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of annual compensation	15.00%
Number of shares purchased	3,000
2020 Employee Stock Purchase Plan \| Incentive Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of the fair market value per share of common stock		110.00%

Stock-Based Compensation - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 23,134	$ 18,926
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	12,303	9,566
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 10,831	$ 9,360

Composition of Certain Balance Sheet Components - Summary of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Contract research services	$ 1,556	$ 2,465
Prepaid insurance	995	1,507
Prepaid rent	506	492
Other	2,206	2,518
Total prepaid expenses and other current assets	$ 5,263	$ 6,982

Income Taxes - Summary of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Current:
Federal	$ 51	$ 456
State	56	88
Current Income Tax Expense (Benefit), Total	107	544
Deferred:
Total	$ 107	$ 544

- Definition

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

+ References + Details

Commitments and Contingencies - Summary of Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
2024	$ 6,188
2025	6,374
2026	5,107
2027	5,260
2028	5,418
Thereafter	5,581
Total future lease payments	33,928
Imputed interest	(7,095)
Total lease liability balance	26,833
Less current portion of lease liability	5,951	$ 5,866
Lease liability, net of current portion	$ 20,882	$ 24,636

Stock-Based Compensation - Summary of Restricted Stock Unit (RSU) Activity (Details) - Restricted Stock Units (RSUs)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Balance, Shares \| shares	2,614,402
Granted, Shares \| shares	2,944,792
Vested, Shares \| shares	(725,082)
Forfeited/Cancelled, Shares \| shares	(279,013)
Balance, Shares \| shares	4,555,099
Balance, Weighted Average Grant Date Fair Value \| $ / shares	$ 3.69
Granted, Weighted Average Grant Date Fair Value \| $ / shares	4.76
Vested, Weighted Average Grant Date Fair Value \| $ / shares	3.58
Forfeited/Cancelled, Weighted Average Grant Date Fair Value \| $ / shares	4.46
Balance, Weighted Average Grant Date Fair Value \| $ / shares	$ 4.35

California Institute of Regenerative Medicine Award

12 Months Ended

Dec. 31, 2023

Collaborative Arrangement [Abstract]

Collaboration and License Agreements

Note 8. California Institute of Regenerative Medicine Award

Strategic Investment - Additional Information (Details) - USD ($)		1 Months Ended	12 Months Ended
	Aug. 04, 2023	Aug. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Strategic Investment [Line Items]
Common stock, par value			$ 0.0001	$ 0.0001
Aggregate gross proceeds			$ 928,000
Non-refundable upfront payment	$ 35,600,000
Revenue recognized			(64,703,000)	$ (130,492,000)
Common Stock
Strategic Investment [Line Items]
Sale of stock, number of shares issued		23,000,000
Sale of stock, price per share		$ 3.5
Aggregate gross proceeds		$ 75,300,000
Astellas
Strategic Investment [Line Items]
Revenue recognized			0
Deferred revenue recognized			$ 35,600,000
Securities Purchase Agreement \| Astellas \| Common Stock
Strategic Investment [Line Items]
Discount for lack of marketability of shares, at fair value on date of issuance	$ 14,400,000
Securities Purchase Agreement \| Astellas \| Private Placement \| Common Stock
Strategic Investment [Line Items]
Sale of stock, number of shares issued	8,333,333
Common stock, par value	$ 0.0001
Sale of stock, price per share	$ 3
Aggregate gross proceeds	$ 25,000,000
Astellas Strategic Rights Letter Agreement \| Astellas
Strategic Investment [Line Items]
Proceeds from rights granted	$ 25,000,000
Maximum number of shares owned at time of termination	8,000,000
Discount for lack of marketability of shares, at fair value on date of issuance	$ 14,400,000
Proceeds from shares allocated to non-refundable upfront payment	$ 10,600,000

Net Loss Per Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss Per Share

Note 15. Net Loss Per Share

Basic net loss (income) per share is computed by dividing net loss (income) attributable to common stockholders for the period by the weighted average number of common shares outstanding during the period. Diluted net loss (income) per share reflects the additional dilution from potential issuances of common stock, such as stock issuable pursuant to the exercise of stock options and from purchases under the ESPP, as well as from the possible exercise of the outstanding warrants.

The Company’s potentially dilutive securities, which include warrants to purchase common stock, common stock options and common stock from the ESPP, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of shares of common stock outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same.

The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:


	Year Ended December 31,
	2023		2022
Outstanding stock options and RSUs		19,465,011		14,476,283
Warrants to purchase common stock		121,122		121,122
ESPP Shares		243,906		45,285
		19,830,039		14,642,690

Nature of Business and Basis of Presentation

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of Business and Basis of Presentation

Note 1. Nature of Business and Basis of Presentation

Nature of Operations

Poseida Therapeutics, Inc. (the “Company” or “Poseida”) is a clinical-stage cell and gene therapy company advancing a new class of treatments for patients with cancer and rare diseases. The Company has discovered and is developing a broad portfolio of product candidates in a variety of indications based on its core proprietary platforms, including its non-viral piggyBac DNA Delivery System, Cas-CLOVER Site-specific Gene Editing System and nanoparticle- and AAV-based gene delivery technologies.

The Company is subject to risks and uncertainties common to development-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s therapeutic development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

Liquidity and Capital Resources

The Company has experienced net losses and negative cash flows from operations since its inception and has relied on its ability to fund its operations primarily through equity and debt financings and strategic collaborations. For the years ended December 31, 2023 and 2022, the Company has incurred net losses of $123.4 million and $64.0 million respectively, and negative cash flows from operations for these same periods of $92.2 million and $26.8 million, respectively. The Company expects it will continue to incur net losses and negative cash flows from operations for at least the next several years. As of December 31, 2023, the Company had an accumulated deficit of $594.3 million.

The Company expects that its cash, cash equivalents and short-term investments as of December 31, 2023 of $212.2 million will be sufficient to fund its operations for at least the next twelve months from the date of issuance of these consolidated financial statements. In the long term, the Company will need additional financing to support its continuing operations and pursue its business strategy. Until such time as the Company can generate significant revenue from product sales, if ever, it expects to finance its operations through a combination of equity offerings, debt financings, collaborations, strategic alliances, and licensing arrangements. The Company may be unable to raise additional funds or enter into such other agreements when needed on favorable terms or at all. The inability to raise capital as and when needed would have a negative impact on the Company’s financial condition and its ability to pursue its business strategy. The Company will need to generate significant revenue to achieve profitability, and it may never do so.

Basis of Presentation and Consolidation

The accompanying consolidated financial statements reflect the Company’s financial position, results of operations and cash flows, in conformity with generally accepted accounting principles in the United States of America (“GAAP”) and include the accounts of Poseida Therapeutics, Inc. and its wholly owned subsidiary. All intercompany transactions and balances have been eliminated.

Risk and Uncertainties

Global events such as the conflict in the Middle East, Russia’s invasion of Ukraine and the retaliatory measures that have been taken, or could be taken in the future, by the United States, NATO, and other countries have created global security concerns that could result in a regional conflict and otherwise have a lasting impact on

regional and global economies, any or all of which could disrupt the Company’s supply chain and adversely affect its ability to conduct ongoing and future clinical trials of the Company’s product candidates. The extent to which any such ongoing or future conflict ultimately impacts the Company’s business is highly uncertain and cannot be predicted with confidence at this time.

Stock-Based Compensation - Summary of the Company's Stock Option Activity (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
Share-Based Payment Arrangement [Abstract]
Balance, Shares \| shares	11,861,881
Granted, Shares \| shares	4,054,949
Exercised, Shares \| shares	(37,166)
Forfeited/Cancelled, Shares \| shares	(969,752)
Balance, Shares \| shares	14,909,912
Options vested and expected to vest as of December 31, 2023 \| shares	14,909,912
Options vested and exercisable as of December 31, 2023 \| shares	8,003,272
Balance, Weighted Average Exercise Price \| $ / shares	$ 7.61
Options Granted, Weighted Average Exercise Price \| $ / shares	4.69
Exercised, Weighted Average Exercise Price \| $ / shares	3.65
Forfeited/Cancelled, Weighted Average Exercise Price \| $ / shares	7.41
Balance, Weighted Average Exercise Price \| $ / shares	6.84
Options vested and expected to vest as of December 31, 2023 \| $ / shares	6.84
Options vested and exercisable as of December 31, 2023 \| $ / shares	$ 8.01
Balance, Weighted Average Remaining Contractual Term (Years)	7 years 8 months 19 days
Options vested and expected to vest as of December 31, 2023	7 years 8 months 19 days
Options vested and exercisable as of December 31, 2023	7 years 1 month 2 days
Balance,Aggregate Intrinsic Value \| $	$ 1,680
Options vested and expected to vest as of December 31, 2023 \| $	1,680
Options vested and exercisable as of December 31, 2023 \| $	$ 840

Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss	$ 123,430	$ 64,002
Net cash used in operating activities	92,167	26,772
Accumulated deficit	594,291	$ 470,861
Cash, cash equivalents and short-term investments	$ 212,200

- Definition

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

+ References

+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 2. Summary of Significant Accounting Policies

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, the Company evaluates its estimates, which include, but are not limited to, estimates related to revenue, accrued expenses, research and development expenses, stock-based compensation expense and deferred tax valuation allowances. The Company bases its estimates on historical experience and other market-specific or relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.

Segment Information

The Company’s sole operations consist of developing therapeutics for patients with high unmet medical need. Accordingly, the Company has determined that it operates in one operating and reportable business segment. Operating segments are defined as components of an enterprise about which separate financial information is evaluated regularly by the Company’s chief operating decision maker, who is its Chief Executive Officer, in deciding how to allocate resources and assess performance. The Company’s chief operating decision maker allocates resources and assesses performance based upon discrete financial information at the consolidated level. All of the Company’s tangible assets are held in the United States.

Fair Value Measurements

Certain financial instruments are required to be recorded at fair value. Other financial instruments, like cash are recorded at cost, which approximates fair value. Cash equivalents and short-term investments are comprised of available-for-sale securities, which are carried at fair value. Additionally, carrying amounts of accounts receivable, accounts payable and accrued liabilities approximate fair value because of the short maturity of those instruments. The carrying value of the Company’s term debt approximates its fair value due to its variable interest rate, which approximates a market interest rate.

Concentration of Business Risk

The Company relies, and expects to continue to rely, on a small number of vendors to manufacture supplies and materials for its development programs. These programs could be adversely affected by a significant interruption in these manufacturing services. The Company’s revenue has been derived from collaboration and license agreements with two customers.

Leases

The Company accounts for leases in accordance with Accounting Standards Codification Topic 842, Leases, (“ASC 842”). The Company determines if an arrangement is a lease at contract inception. A lease exists when a contract conveys the right to control the use of identified property, plant, or equipment for a period of time in exchange for consideration. The definition of a lease embodies two conditions: (1) there is an identified asset in the contract that is land or a depreciable asset (i.e., property, plant, and equipment), and (2) the Company has the right to control the use of the identified asset.

Operating leases where the Company is the lessee are included in operating lease right-of-use (“ROU”) assets, operating lease liabilities, current and operating lease liabilities, non-current on its consolidated balance sheets. The lease liabilities are initially and subsequently measured at the present value of the unpaid lease payments at the lease commencement date.

ASC 842 requires a lessee to discount its unpaid lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. The rates implicit in the Company’s leases are not known, therefore, the incremental borrowing rate is used based on the information available at commencement date in determining the present value of lease payments. The Company’s incremental borrowing rate for a lease is the rate of interest it would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms.

The term for all of the Company’s leases includes the noncancelable period of the lease. Where the Company’s lease term is impacted by options to extend or terminate the lease, when it is reasonably certain that it will exercise such option, then the lease payments are included in the measurement of the lease asset or liability.

The Company has elected not to recognize ROU assets and lease liabilities for all short-term leases that have a lease term of 12 months or less. The Company recognizes the lease payments associated with its short-term leases as an expense on a straight-line basis over the lease term. There are no variable lease payments associated with these leases. Additionally, the Company has elected to account for the lease and non-lease components together as a single lease component for its real estate asset class.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to a significant concentration of credit risk consist primarily of cash, cash equivalents, and short-term investments. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits and investments are held.

Cash and Cash Equivalents

The Company considers all highly liquid investments purchased with original final maturities of 90 days or less from the date of purchase to be cash equivalents. Cash and cash equivalents consist of deposits with financial institutions and marketable securities. Cash equivalents are reported at fair value.

Short-Term Investments

Investments with a remaining maturity when purchased of greater than three months are classified as short-term investments in the consolidated balance sheet and consist primarily of U.S. Treasury and other government agency obligations. As the Company’s entire investment portfolio is considered available for use in current operations, the Company classifies all investment as available-for-sale and as current assets, even though the stated maturity date may be one year or more beyond the current consolidated balance sheet date, which reflects management’s intention to use the proceeds from sales of these securities to fund its operations, as necessary. Debt securities are carried at fair value with the unrealized gains and losses included in other comprehensive income (loss) as a component of stockholders’ equity until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the instrument. If any adjustment to fair value reflects a decline in the value of the investment that the Company considers to be “other than temporary,” the Company reduces the investment to fair value through a charge to the statement of operations and comprehensive loss. No such adjustments were necessary during the periods presented.

Goodwill and Other Intangible Assets

Intangible assets were acquired as part of a business combination and have been capitalized at their acquisition date fair value. Indefinite-lived in process research and development (“IPR&D”) is not subject to amortization but is tested annually for impairment or more frequently if there are indicators of impairment. The Company tests its indefinite-lived IPR&D annually for impairment during the fourth quarter. In testing indefinite-lived IPR&D for impairment, the Company has the option to first assess qualitative factors to determine whether the existence of events or circumstances would indicate that it is more likely than not that its fair value is less than its carrying amount, or the Company can perform a quantitative impairment analysis to determine the fair value of the indefinite-lived IPR&D without performing a qualitative assessment. Qualitative factors that the Company considers

include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If the Company chooses to first assess qualitative factors and it determines that it is more likely than not that the fair value of the indefinite-lived IPR&D is less than its carrying amount, the Company would then determine the fair value of the indefinite-lived IPR&D. Under either approach, if the fair value of the indefinite-lived IPR&D is less than its carrying amount, an impairment charge would be recognized for the difference between the fair value and the carrying amount. There was no impairment of IPR&D for the years ended December 31, 2023 and 2022.

The Company additionally tests its goodwill for impairment annually during the fourth quarter, or whenever events or changes in circumstances indicate an impairment may have occurred. Should an impairment exist, the impairment loss would be measured based on the excess of the carrying amount of the asset or asset group over the estimated asset’s fair value. Impairment may result from, among other things, deterioration in the performance of the acquired business, adverse results from developmental work, adverse changes in applicable laws or regulations and a variety of other circumstances. In evaluating the recoverability of the carrying value of goodwill, the Company must make assumptions regarding estimated future cash flows and other factors to determine the fair value of the acquired assets. Changes in strategy or market conditions could significantly impact those judgments in the future and require an adjustment to the recorded balances. There were no impairments of goodwill for the years ended December 31, 2023 and 2022.

Property and Equipment

Property and equipment are stated at cost and depreciated or amortized using the straight-line method, based on their estimated useful lives as follows:


Asset Classification	Estimated Useful Life (years)
Laboratory equipment		5
Leasehold improvements	Lesser of useful life or lease-term
Computer equipment and software		3
Furniture and fixtures		7

Maintenance and repair costs are charged to expense as incurred. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the Company’s consolidated balance sheet and any resulting gain or loss is reflected in the Company’s consolidated statement of operations and comprehensive loss.

Property and equipment are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparison of the carrying amount to the future net undiscounted cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the projected discounted future net cash flows arising from the asset. There has been no impairment of long-lived assets during the years ended December 31, 2023 and 2022.

Revenue Recognition

The Company’s revenues to date have been generated primarily through collaboration and license agreements. The Company’s collaboration and license agreements may contain multiple elements including intellectual property licenses and research, and development services. Consideration the Company receives under these arrangements may include upfront payments, research and development funding, cost reimbursements, research, development, regulatory and commercial milestone payments, and royalty payments.

The Company applies Accounting Standard Codification Topic 606, Revenue from Contracts with Customers (“ASC 606”), issued by the Financial Accounting Standards Board (“FASB”) to account for its contracts with customers. Under ASC 606, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration that the Company expects to be entitled to receive in

exchange for these services. The Company analyzes the nature of these performance obligations in the context of individual collaboration and license agreements in order to assess the distinct performance obligations. The Company evaluates its contracts with customers for proper classification in the consolidated statements of operations based on the nature of the underlying activity. Transactions with customers recorded in the Company’s consolidated statements of operations are recorded on either a gross or net basis, depending on the characteristics of the collaborative relationship.

To determine revenue recognition for arrangements within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that it will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer.

The Company uses judgment in determining the customer's ability and intent to pay, which is based upon factors including the customer's historical payment experience or, for new customers, credit and financial information pertaining to the customers. Determining whether a promised goods or service is a separate performance obligation requires the use of significant judgment. A change in such judgment could result in a significant change in the period in which revenue is recognized. The Company determines standalone selling price based on its overall pricing and discounting objectives, taking into consideration the type of services, estimates of hourly market rates, and stage of the research, development or clinical trials. The process for determining the transaction price involves significant judgment and includes consideration of multiple factors such as estimated revenues, market size, and development risk, among other factors contemplated in negotiating the arrangement with the customer. The Company determines the transaction price based on the consideration to which it expects to be entitled in exchange for transferring goods and services to the customer. In determining the transaction price, any variable consideration would be considered, to the extent applicable, if, in the Company’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. In accordance with the royalty exception under ASC 606 for licenses of intellectual property, the transaction price excludes future royalty payments to be received from our customers. The Company’s collaboration and license agreement contain no consideration payable to our customer or a significant financing component.

Performance Obligations

The following is a description of principal goods and services from which the Company generates revenue.

Intellectual property licenses

The Company generates revenue from licensing its intellectual property including know-how and development and commercialization rights. These licenses provide customers with a term-based license to further research, develop and commercialize the Company’s internally-discovered platform technologies for specified therapeutic indications. The consideration the Company receives in the form of nonrefundable upfront consideration allocated to the functional intellectual property licenses is recognized at a point in time for licenses determined to be distinct from other performance obligations in the contract when the Company transfers such license to the customer. If the license is combined with other goods or services into one performance obligation, the revenue is recognized over a period of time based on the Company’s method of measuring progress in which it satisfies the combined performance obligation. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company’s licensing agreements are generally cancelable. Customers have the right to terminate their contracts upon notice. The Company has the right to terminate the contracts generally only if the customer is in breach of the contract and fails to remedy the breach in accordance with the contractual terms.

Material Rights

Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options. The Company assesses if these options provide a material right (i.e., an optional good or service offered for free or at a discount) to the customer and if so, whether they are considered performance obligations. The identification of material rights requires judgments related to the determination of the value of the

underlying license relative to the option exercise price, including assumptions about the amount of the discount and likelihood that the option will be exercised. The exercise of a material right is accounted for as a contract modification for accounting purposes. Amounts allocated to any material right are recognized as revenue when or as the related future goods or services are transferred or when the option expires.

Research and development services

The Company generates revenue from research and development services it provides to its customers in connection with the licensed intellectual property. The services the Company provides to its customers primarily include scientific research activities. Revenue associated with these services is recognized over time using the cost-to-cost input method, based on the total estimated costs to fulfill the obligations.

Contracts with Multiple Performance Obligations

The Company’s collaboration and license agreements with customers may contain multiple promised goods or services. Based on the characteristics of the promised goods and services the Company analyzes whether they are separate or combined performance obligations. The transaction price is allocated to the separate performance obligations on a relative standalone selling price basis. The Company determines standalone selling price based on its overall pricing and discounting objectives, taking into consideration the type of services, estimates of hourly market rates, and stage of the development and clinical trials.

ASC 606 requires the Company to allocate the arrangement consideration on a relative standalone selling price basis for each performance obligation after determining the transaction price of the contract and identifying the performance obligations to which that amount should be allocated. The relative standalone selling price is defined in ASC 606 as the price at which an entity would sell a promised good or service separately to a customer. If other observable transactions in which the Company has sold the same performance obligation separately are not available, the Company estimates the standalone selling price of each performance obligation. When standalone selling prices for the Company’s products or services are not directly observable, the Company determines the standalone selling prices using relevant information available and applies suitable estimation methods considering market conditions and entity-specific factors including, but not limited to, features and functionality of the underlying intellectual property licenses and the economic potential associated with ongoing research activities. Key assumptions to determine the standalone selling price may also include development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success.

Variable Consideration

The Company’s contracts with customers generally include two types of variable consideration: (i) research, development and regulatory milestone payments, which the Company is entitled to upon achievement of such specific milestones and (ii) one-time sales-based payments and sales-based royalties associated with licensed intellectual property.

If an arrangement includes research, development or regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal will not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control are generally not considered probable of being achieved until those approvals are received.

Product sales-based royalties under licensed intellectual property are accounted for under the royalty exception. The Company recognizes revenue for sales-based royalties under licensed intellectual property and one-time payments at the later of when the sales occur or the performance obligation is satisfied or partially satisfied.

Under the royalty exception in ASC 606 for licensed intellectual property the Company does not recognize any revenue for the variable amounts related to sales-based royalties and milestones until the later of when the sales occur, or the performance obligation is satisfied or partially satisfied. Accordingly, the revenue related to future

sales-based royalties and milestones are excluded from the estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied.

Disaggregation of Revenue

The Company operates in one reportable business segment and has two customers.

Contract Assets and Contract Liabilities

The Company receives payments from customers based on contractual terms. Accounts receivable are recorded when the right to consideration becomes unconditional. For research and development services, the Company generally bills its customers monthly or quarterly as the services are performed. Payment terms on invoiced amounts are typically 30 - 60 days. Contract assets include amounts related to the Company’s contractual right to consideration for both completed and partially completed performance obligations that have not been invoiced and for which the Company does not yet have the right to payment. The current portion of contract asset is included within current assets on the consolidated balance sheet. Contract liabilities consist of deferred revenue and include payments received in advance of performance under the contract.

Cost to Obtain and Fulfill a Contract

The Company generally does not incur costs to obtain new contracts. Costs to fulfill contracts are expensed as incurred.

Accounts Receivable and Allowance for Credit Losses

Accounts receivable primarily consist of amounts due from customers for services and payments due based on contractual terms. Accounts receivable are recorded when the right to consideration becomes unconditional. For research and development services, the Company generally bills its customers monthly or quarterly as the services are performed. Payment terms on invoiced amounts are typically 30 - 60 days. The Company recognizes estimated allowance for credit losses based on an assessment of a customer’s ability to pay, credit quality of the customer, age of receivable balances and current economic conditions. As of December 31, 2023 and 2022, the Company recorded no allowance for credit losses.

Research and Development

Research and development expense consists of labor, material, equipment, and allocated facilities costs of the Company’s scientific staff who are working on research and development projects. Research and development costs are charged to operations as incurred.

Upfront payments and milestone payments made for the licensing of technology are expensed as research and development in the period in which they are incurred. Advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses or other long-term assets. The advanced payments are expensed as the related goods are delivered or the services are performed.

Research and Manufacturing Contract Costs and Accruals

The Company has entered into various research and development and manufacturing agreements. These agreements are generally cancelable, and related payments are recorded as the corresponding expenses are incurred. The Company records accruals for estimated costs incurred to date. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the research studies or clinical trials and manufacturing activities, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent Costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.

Stock-Based Compensation

Stock-based compensation related to stock options and restricted stock units (“RSUs”) granted to the Company’s employees and consultants and the 2020 Employee Stock Purchase Plan (“ESPP”) awards is measured at the grant date based on the fair value of the award. The fair value is recognized as stock-based compensation expense in the consolidated financial statements over the requisite service period, which is generally the vesting period of the respective awards. Compensation related to service-based awards is recognized starting on the grant date on a straight-line basis over the vesting period, which is typically two to four years. The Company recognizes the fair value of stock options and RSUs granted to non-employees as stock-based compensation expense over the period in which the related services are received. Stock-based compensation expense related to stock options granted to non-employees is recognized based on the grant date fair value of awards as the stock options are earned. The Company believes that the estimated fair value of stock options is more readily measurable than the fair value of the services rendered. All option grants require continued service to continue vesting. For the ESPP, the requisite service period is generally the period of time from the offering date to the purchase date. The Company accounts for the forfeitures in the period in which they occur.

The Company uses the Black-Scholes valuation model to estimate the grant date fair value of the stock option awards and shares purchasable under the ESPP. The determination of the fair value of each stock award using the option-pricing model is affected by the Company’s assumptions regarding a number of variables including the fair value of the common stock at the date of grant, the expected term of the awards, the expected stock price volatility over the term of the awards, risk-free interest rate, and dividend rate.

Comprehensive Income (Loss)

Comprehensive income (loss) is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources, including unrealized gains and losses on short-term investments. Comprehensive gains (losses) have been reflected in the consolidated statements of operations and comprehensive income (loss) for all periods presented.

Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period without consideration for common stock equivalents. Diluted net loss per share is the same as basic net loss per common share, since the effects of potentially dilutive securities are anti-dilutive due to the net loss position of all periods presented.

Income Taxes

Deferred tax assets and liabilities are determined based on the difference between the financial statement carrying amounts of assets and liabilities and their respective tax bases, as well as net operating losses and credit carry forwards applied by the enacted tax rates expected to be in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies.

The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be

evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

Emerging Growth Company Status

The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it (i) is no longer an emerging growth company or (ii) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these consolidated financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates.

Recently Adopted Accounting Pronouncements

In June 2016, the FASB issued Accounting Standard Update (“ASU”) 2016-13, Measurement of Credit Losses on Financial Instruments, which established ASC 326, Financial Instruments - Credit Losses. This ASU, along with subsequent amendments, improves financial reporting by requiring timely recording of credit losses on loans and other financial instruments held by financial institutions and other organizations. ASU 2016-13 requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions and reasonable and supportable forecasts. The Company adopted ASU 2016-13 on January 1, 2023. The adoption of this standard had no impact on the Company’s consolidated financial statements and disclosures.

Recently Issued Accounting Pronouncements

In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting, and in January 2021, issued ASU 2021-01, Reference Rate Reform: Scope. These updates provide optional expedients and exceptions for applying US GAAP to contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. The optional guidance is provided to ease the potential burden of accounting for reference rate reform. The guidance is effective and could be adopted no later than December 31, 2022. In December 2022, the FASB issued ASU 2022-06, Reference Rate Reform (Topic 848): Deferral of the Sunset Date of Topic 848, to extend the temporary accounting rules under Topic 848 from December 31, 2022 to December 31, 2024. The Company is currently evaluating the impact adopting the new accounting guidance may have on the Company’s financial position and results of operations, but do not expect it to have a material impact on the Company’s consolidated financial statements and disclosures.

In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. This standard improves disclosures about a public entity's reportable segments, primarily through enhanced disclosures about significant segment expenses. ASU 2023-07 is effective for fiscal years beginning after December 15, 2023 and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the impact adopting the new accounting guidance may have on the Company’s financial position and results of operations, but do not expect it to have a material impact on the Company’s consolidated financial statements and disclosures.

In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. ASU 2023-09 requires disaggregated information about a reporting entity’s effective tax rate reconciliation as well as information on income taxes paid. ASU 2023-09 is effective for public entities with annual

periods beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements and disclosures.

Financial Instruments

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Financial Instruments

Note 4. Financial Instruments

The following table summarizes the amortized cost and fair value of available-for-sale securities (in thousands):


	Maturity	Amortized Cost/Cost		Unrealized Gains		Unrealized Losses			Fair Value
At December 31, 2023:
Money market funds	1 year or less	$	37,590	$	—	$	—		$	37,590
U.S. government agency securities and treasuries	1 year or less		167,604		158		(32	)		167,730
Total		$	205,194	$	158	$	(32	)	$	205,320

At December 31, 2022:
Money market funds	1 year or less	$	57,799	$	—	$	—		$	57,799
U.S. government agency securities and treasuries	1 year or less		206,520		13		(162	)		206,371
Total		$	264,319	$	13	$	(162	)	$	264,170

The Company has classified all of its short-term investments as available-for-sale as the sale of such securities may be required prior to maturity to implement management strategies, and therefore, they are carried at fair value. No available-for-sale debt securities held as of December 31, 2023 and 2022 had remaining maturities greater than one year. Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. As of December 31, 2023, none of the Company’s securities were in material unrealized loss positions.

The Company reviews its investment holdings at the end of each reporting period and evaluates any unrealized losses using the expected credit loss model to determine if the unrealized loss is a result of a credit loss or other factors. The Company also evaluates its investment holdings for impairment using a variety of factors including the Company’s intent to sell the underlying securities prior to maturity and whether it is more likely than not that the Company would be required to sell the securities before the recovery of their amortized basis. During the year ended December 31, 2023 and 2022, the Company did not recognize any impairment or realized gains or losses on sales of investments, and the Company did not record an allowance for, or recognize, any expected credit losses.

Financial Instruments - (Tables)

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Summary of Amortized Cost and Fair Value of Available-for-Sale Securities

The following table summarizes the amortized cost and fair value of available-for-sale securities (in thousands):


	Maturity	Amortized Cost/Cost		Unrealized Gains		Unrealized Losses			Fair Value
At December 31, 2023:
Money market funds	1 year or less	$	37,590	$	—	$	—		$	37,590
U.S. government agency securities and treasuries	1 year or less		167,604		158		(32	)		167,730
Total		$	205,194	$	158	$	(32	)	$	205,320

At December 31, 2022:
Money market funds	1 year or less	$	57,799	$	—	$	—		$	57,799
U.S. government agency securities and treasuries	1 year or less		206,520		13		(162	)		206,371
Total		$	264,319	$	13	$	(162	)	$	264,170

- 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
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Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
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-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

+ Details

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Schedule of Anti-Dilutive Securities Excluded From Computation of Diluted Net Loss per Share Attributable to Common Stockholders


	Year Ended December 31,
	2023		2022
Outstanding stock options and RSUs		19,465,011		14,476,283
Warrants to purchase common stock		121,122		121,122
ESPP Shares		243,906		45,285
		19,830,039		14,642,690

Fair Value Measurement - Schedule of Company's Valuation Hierarchy of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Assets
Cash and cash equivalents	$ 44,472	$ 81,378
Recurring Basis \| Level 1
Assets
Total	205,320	264,170
Recurring Basis \| Level 1 \| Money Market Funds
Assets
Cash and cash equivalents	37,590
Recurring Basis \| Level 1 \| Money market funds and U.S. government agency treasuries
Assets
Cash and cash equivalents		63,055
Recurring Basis \| Level 1 \| U.S. government agency securities and treasuries
Assets
Total	$ 167,730	$ 201,115

Stockholders' Equity

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Stockholders' Equity

Note 10. Stockholders’ Equity

Authorized Shares

In connection with the completion of the Company’s initial public offering in July 2020, the Company amended its certificate of incorporation to authorize 250,000,000 shares of common stock, par value $0.0001 per share, and 10,000,000 shares of undesignated preferred stock, par value $0.0001 per share, that may be issued from time to time by the Company’s board of directors in one or more series. Each share of common stock is entitled to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the Company’s board of directors. Since the Company’s inception, there have been no dividends declared.

Warrants

Pursuant to the Amended Loan Agreement, the Company issued Oxford (i) in 2017, a warrant to purchase 93,518 shares of common stock at an exercise price of $4.28 per share, which will expire in 2027 unless earlier exercised and (ii) in 2018 and 2019, warrants to purchase an aggregate of 27,604 shares of common stock at an exercise price of $7.25 per share, which will expire in 2028 and 2029, respectively, unless earlier exercised.

Sale of Common Stock

In August 2022, the Company completed the sale of an aggregate of 23,000,000 shares of its common stock in an underwritten public offering, at a price of $3.50 per share, including 3,000,000 shares sold pursuant to the full exercise of the underwriters' option to purchase additional shares. The net proceeds to the Company from the offering were $75.3 million after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company.

On August 4, 2023, the Company entered into a securities purchase agreement with Astellas, pursuant to which the Company agreed to issue and sell to Astellas in the Private Placement an aggregate of 8,333,333 shares of common stock at a purchase price of $3.00 per Share, for aggregate gross proceeds of $25.0 million. The Private Placement closed on August 7, 2023. The Company recorded the issuance of common stock at its estimated fair value on the date of issuance of $14.4 million, which reflects a DLOM of the shares. The DLOM was applied due to the inability to trade the shares until they are registered. The issuance of the equity shares was recorded upon the delivery of the underlying shares, with the associated fair value recorded within equity on the Company’s consolidated balance sheet.

At the Market Facility

In August 2021, the Company entered into a Controlled Equity OfferingSM Sales Agreement (the “Sales Agreement”) with Cantor Fitzgerald & Co. (“Cantor”) to sell shares of common stock, from time to time, through an “at the market offering” program having an aggregate offering price of up to $85.0 million through which Cantor would act as sales agent. During the year ended December 31, 2023, the Company issued and sold an aggregate of 119,000 shares of common stock at a weighted average price of $8.04 per share for net proceeds of approximately $0.9 million.

Common Stock

Each share of common stock is entitled to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the Company’s board of directors. Since the Company’s inception, there have been no dividends declared.

Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following at December 31, 2023:


Stock options issued and outstanding			14,909,912
Restricted stock units issued and outstanding			4,555,099
Authorized for future options and award grants			4,332,980
Authorized for future issuance under Employee Stock Purchase Plan			1,773,794
Total			25,571,785

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//505/tableOfContent

Reference 11: 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

Financial Instruments - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Gain (loss) on sale of investments	$ 0	$ 0
Allowance for credit loss	0	$ 0
Debt securities, available-for-sale, unrealized loss position	$ 0

Income Taxes - Summary of Components of Pretax Loss from Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest1 [Line Items]
U.S. Domestic	$ (123,323)	$ (63,458)
Net loss before income tax	$ (123,323)	$ (63,458)

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
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+ Details

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 44,472	$ 81,378
Short-term investments	167,730	201,115
Accounts receivable	9,010	9,088
Prepaid expenses and other current assets	5,263	6,982
Total current assets	226,475	298,563
Property and equipment, net	19,055	21,586
Operating lease right-of-use assets	21,726	25,085
Intangible assets, net	1,320	1,320
Goodwill	4,228	4,228
Other long-term assets	1,081	1,055
Total assets	273,885	351,837
Current liabilities:
Accounts payable	3,267	2,228
Accrued expenses and other liabilities	31,092	26,068
Operating lease liabilities, current	5,951	5,866
Deferred revenue, current	31,008	19,723
Total current liabilities	71,318	53,885
Term debt	58,590	58,250
Deferred CIRM grant liability		3,992
Deferred revenue, non-current	16,780	21,333
Operating lease liabilities, non-current	20,882	24,636
Other long-term liabilities	2,614	2,146
Total liabilities	170,184	164,242
Commitments and Contingencies (Note 12)
Stockholders’ equity:
Common stock, $0.0001 par value: 250,000,000 shares authorized at December 31, 2023 and December 31, 2022; 95,636,553 and 85,964,161 shares issued and outstanding at December 31, 2023 and December 31, 2022, respectively	10	9
Additional paid-in capital	697,856	658,596
Accumulated other comprehensive income (loss)	126	(149)
Accumulated deficit	(594,291)	(470,861)
Total stockholders’ equity	103,701	187,595
Total liabilities and stockholders’ equity	$ 273,885	$ 351,837

Stock-Based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

Note 11. Stock-Based Compensation

Equity Incentive Plan

In July 2020, the Company’s board of directors and stockholders approved and adopted the 2020 Equity Incentive Plan (the “2020 Plan”). Under the 2020 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units and other stock or cash-based awards to individuals who are current employees, officers, directors or consultants of the Company. A total of 11,183,476 shares of common stock were approved to be initially reserved for issuance under the 2020 Plan. The number of shares that remained available for issuance under the Company’s previous equity incentive plan as of the effective date of the 2020 Plan and shares subject to outstanding awards under the Company’s previous equity incentive plan as of the effective date of the 2020 Plan that are subsequently canceled, forfeited or repurchased by the Company are added to the shares reserved under the 2020 Plan. The number of shares of common stock available for issuance under the 2020 Plan is automatically increased on the first day of each calendar year during the ten-year term of the 2020 Plan, beginning with January 1, 2021 and ending with January 1, 2030, by an amount equal to 5% of the outstanding number of shares of the Company’s common stock on December 31 of the preceding calendar year or such lesser amount as determined by the Company’s board of directors.

As of December 31, 2023, there were 2,383,334 shares available to be granted under the 2020 Plan. Through December 31, 2023, the Company has exclusively granted stock options and restricted stock units under the 2020 Plan. Shares issued under the 2020 Plan are newly issued shares and the Company has no intention to repurchase previously issued shares. The exercise price of stock options granted under the 2020 Plan cannot be less than 100% of the fair value of the common stock on the grant date. The term and vesting period of each option shall be stated in the underlying agreements. However, the term shall be no more than ten years from the date of grant. The stock options generally vest over a four-year period. If stock options are granted to an optionee who, at the grant date, owns the Company common stock representing more than ten percent of the voting power of all classes of stock of the Company, then the term of the stock option shall be five years from the date of grant and the stock option exercise price is equal to 110% of the fair value at the date of grant.

In February 2022, the Company’s board of directors approved and adopted the 2022 Inducement Plan (the “Inducement Plan”). Under the Inducement Plan, the Company may grant nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance awards and other awards to individuals not previously employees or non-employee directors of the Company, as an inducement toward entering into employment with the Company. Under the Inducement Plan approved in February 2022, the maximum number of shares of common stock initially approved to be issued was 2,000,000 shares. In December 2023, the Compensation Committee of the Company’s board of directors approved an amendment to the Inducement Plan which increased the pool to a maximum of 3,517,105 shares. As of December 31, 2023, there were 1,949,646 shares available to be granted under the Inducement Plan.

Stock Options

The following is a summary of the Company’s stock option activity for the year ended December 31, 2023:


	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (thousands)
Balance at January 1, 2023		11,861,881		$	7.61
Granted		4,054,949			4.69
Exercised		(37,166	)		3.65
Forfeited/Cancelled		(969,752	)		7.41
Balance at December 31, 2023		14,909,912		$	6.84		7.72	$	1,680
Options vested and expected to vest as of December 31, 2023		14,909,912		$	6.84		7.72	$	1,680
Options vested and exercisable as of December 31, 2023		8,003,272		$	8.01		7.09	$	840

The weighted-average grant date fair value of options granted for the years ended December 31, 2023 and 2022 was $3.40 and $2.64, respectively. The aggregate intrinsic value of options exercised was $0.1 million and $0.2 million for the years ended December 31, 2023 and 2022, respectively, determined as of the date of exercise. The Company received $0.1 million and $0.2 million in cash from options exercised for the years ended December 31, 2023 and 2022, respectively. The total fair value of options vested was $22.3 million and $22.1 million during the years ended December 31, 2023 and 2022, respectively.

As of December 31, 2023, total unrecognized compensation cost related to stock options was $24.1 million, and the weighted-average period over which this cost is expected to be recognized was approximately 2.3 years.

The fair value of options granted is estimated at the date of grant using the Black-Scholes option pricing model. Forfeitures are accounted for as incurred as a reversal of any share-based compensation expense related to options that will not vest. The assumptions that the Company used to determine the fair value of options granted to employees, non-employees and directors were as follows:


	Year Ended December 31,
	2023	2022
Risk-free interest rate	4.05%	2.16%
Expected volatility	82.59%	84.94%
Expected term (years)	5.97	5.97
Dividend yield	—	—

Risk-free interest rate—The risk-free interest rate is based on the U.S. Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term of option.

Expected volatility—The expected volatility is estimated based on the average volatility for comparable publicly traded biotechnology companies over a period equal to the expected term of the stock option grants. The comparable companies were chosen based on their similar size, stage in the life cycle or area of specialty.

Expected term—The expected term represents the period that stock-based awards are expected to be outstanding. The expected term for option grants is determined using the simplified method which is used when there is insufficient historical data about exercise patterns and post-vesting employment termination behavior. The simplified method deems the expected term to be the midpoint between the vesting date and the contractual life of the stock-based awards.

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

Restricted Stock Units

The following is a summary of the Company’s restricted stock unit (“RSU”) activity for the year ended December 31, 2023:


	Shares			Weighted Average Grant Date Fair Value
Balance at January 1, 2023		2,614,402		$	3.69
Granted		2,944,792			4.76
Vested		(725,082	)		3.58
Forfeited/Cancelled		(279,013	)		4.46
Balance at December 31, 2023		4,555,099		$	4.35

RSU awards are share awards that, upon vesting, will deliver to the holder shares of the Company’s common stock. The RSUs granted to employees and non-employee directors vest up to four years from the grant date. The grant-date fair value is recognized as compensation expense over the vesting period. As of December 31, 2023, total unrecognized compensation cost related to RSUs was $15.1 million, and the weighted-average period over which this cost is expected to be recognized was approximately 2.8 years.

2020 Employee Stock Purchase Plan

In July 2020, the Company’s board of directors and stockholders approved and adopted the 2020 Employee Stock Purchase Plan (the “ESPP”), which became effective as of the pricing of the Company’s initial public offering. A total of 615,000 shares of common stock were approved to be initially reserved for issuance under the ESPP. The number of shares of common stock available for issuance under the ESPP is automatically increased on the first day of each calendar year during the first ten-years of the term of the ESPP, beginning with January 1, 2021 and ending with January 1, 2030, by an amount equal to the lessor of (i) 1% of the outstanding number of shares of the Company’s common stock on December 31 of the preceding calendar year, (ii) 1,230,000 shares of common stock or (iii) such lesser amount as determined by the Company’s board of directors. Under the 2020 ESPP, substantially all employees can elect to have up to 15% of their annual compensation withheld to purchase up to 3,000 shares of common stock per purchase period, subject to certain limitations. The shares of common stock can be purchased over an offering period of six months and at a price of 85% of the fair market value per share of common stock on the first trading day of the applicable offering period or on the exercise date of the applicable offering period, whichever is less. Under applicable accounting guidance, the 2020 ESPP is classified as a compensatory plan. During the year ended December 31, 2023, a total of 536,669 shares were purchased by the Company’s employees under the 2020 ESPP resulting in net proceeds of $1.1 million.

The Company uses the Black-Scholes pricing model to estimate the fair value of the purchase rights issued under the ESPP on each offering date. The assumptions that the Company used to determine the fair value of the purchase rights issued to employees were as follows:


	Year Ended December 31,
	2023	2022
Risk-free interest rate	5.26%	2.39%
Expected volatility	87.07%	93.68%
Expected term (years)	0.5	0.5
Dividend yield	—	—

The Company recorded total stock-based compensation expense related to stock options, RSUs, and the ESPP in the following expense categories of the accompanying consolidated statements of operations and comprehensive income (loss) (in thousands):


	Year Ended December 31,
	2023		2022
Research and development	$	12,303	$	9,566
General and administrative		10,831		9,360
Total stock-based compensation expense	$	23,134	$	18,926

Net Loss Per Share - Schedule of Anti-Dilutive Securities Excluded From Computation of Diluted Net Loss per Share Attributable to Common Stockholders (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	19,830,039	14,642,690
Outstanding stock options and RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	19,465,011	14,476,283
Warrants to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	121,122	121,122
ESPP Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	243,906	45,285

Composition of Certain Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2023

Balance Sheet Related Disclosures [Abstract]

Summary of Prepaid Expenses and Other Current Assets

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


	December 31,
	2023		2022
Contract research services	$	1,556	$	2,465
Prepaid insurance		995		1,507
Prepaid rent		506		492
Other		2,206		2,518
Total prepaid expenses and other current assets	$	5,263	$	6,982

Summary of Property and Equipment Net

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


	December 31,
	2023			2022
Laboratory equipment	$	21,271		$	18,551
Leasehold improvements		14,113			14,006
Computer equipment and software		1,355			1,504
Furniture and fixtures		1,125			1,001
Total property and equipment		37,864			35,062
Less: Accumulated depreciation and amortization		(18,809	)		(13,476	)
Total property and equipment, net	$	19,055		$	21,586

Summary of Accrued Expenses and Other Liabilities

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


	December 31,
	2023		2022
Contract research services	$	14,621	$	10,908
Payroll and related expense		13,076		11,271
Other		3,395		3,889
Total accrued expenses and other liabilities	$	31,092	$	26,068

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Public Offering
Net of issuance costs	$ 5,223

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenues:
Collaboration revenue	$ 64,703	$ 130,492
Operating expenses:
Research and development	156,772	152,899
General and administrative	37,435	37,539
Total operating expenses	194,207	190,438
Loss from operations	(129,504)	(59,946)
Other income (expense):
Interest expense	(8,671)	(6,370)
Other income, net	14,852	2,858
Net loss before income tax	(123,323)	(63,458)
Income tax expense	(107)	(544)
Net loss	(123,430)	(64,002)
Other comprehensive income (expense):
Unrealized gain (loss) on short-term investments	275	(149)
Comprehensive loss	$ (123,155)	$ (64,151)
Net loss per share attributable to common stockholders, basic	$ (1.37)	$ (0.89)
Net loss per share attributable to common stockholders, diluted	$ (1.37)	$ (0.89)
Weighted-average number of shares outstanding, basic	90,185,096	71,953,703
Weighted-average number of shares outstanding, diluted	90,185,096	71,953,703
Collaboration Revenue
Revenues:
Collaboration revenue	$ 64,703	$ 130,492

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) Customer Segment Contract PerformanceObligation	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Recent Accounting Guidance [Line Items]
Number of operating segment \| Segment	1
Variable lease, payments		$ 0
Impairment of goodwill		0	$ 0
Impairment of long-lived assets	$ 0	0
Consideration payable to customer	$ 47,788,000	41,056,000	13,762,000
Number of revenue performance obligation \| PerformanceObligation	1
Number of reportable segment \| Segment	1
Number of customer \| Customer	2
Description of payment terms	Payment terms on invoiced amounts are typically 30 - 60 days.
Costs incurred to obtain contracts \| Contract	0
Allowance for credit loss	$ 0	0
Minimum
Recent Accounting Guidance [Line Items]
Stock based compensation, vesting period	2 years
Maximum
Recent Accounting Guidance [Line Items]
Stock based compensation, vesting period	4 years
IPR&D
Recent Accounting Guidance [Line Items]
Impairment of intangible assets, indefinite-lived		$ 0	$ 0
Collaboration and License Agreements
Recent Accounting Guidance [Line Items]
Consideration payable to customer	$ 0

Employee Benefit Plan

12 Months Ended

Dec. 31, 2023

Retirement Benefits [Abstract]

Employee Benefit Plan

Note 14. Employee Benefit Plan

The Company has a defined contribution retirement savings plan under Section 401(k) of the Internal Revenue Code. This plan covers all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. Company contributions to the plan may be made at the discretion of the Board of Directors. Total contributions by the Company during the years ended December 31, 2023 and 2022 were $1.9 million and $1.5 million, respectively.

Composition of Certain Balance Sheet Components

12 Months Ended

Dec. 31, 2023

Balance Sheet Related Disclosures [Abstract]

Composition of Certain Balance Sheet Components

Note 3. Composition of Certain Balance Sheet Components

Prepaid expenses and other current assets

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


	December 31,
	2023		2022
Contract research services	$	1,556	$	2,465
Prepaid insurance		995		1,507
Prepaid rent		506		492
Other		2,206		2,518
Total prepaid expenses and other current assets	$	5,263	$	6,982

Property and equipment, net

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


	December 31,
	2023			2022
Laboratory equipment	$	21,271		$	18,551
Leasehold improvements		14,113			14,006
Computer equipment and software		1,355			1,504
Furniture and fixtures		1,125			1,001
Total property and equipment		37,864			35,062
Less: Accumulated depreciation and amortization		(18,809	)		(13,476	)
Total property and equipment, net	$	19,055		$	21,586

Depreciation and amortization expense associated with property and equipment was $5.6 million and $5.2 million for the years ended December 31, 2023 and 2022, respectively.

Accrued expenses and other liabilities

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


	December 31,
	2023		2022
Contract research services	$	14,621	$	10,908
Payroll and related expense		13,076		11,271
Other		3,395		3,889
Total accrued expenses and other liabilities	$	31,092	$	26,068

Income Taxes - Schedule of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 11,805	$ 9,494
Increase for current year positions	3,091	2,403
Increase (decrease) for prior year positions	383	(92)
Balance at the end of year	$ 15,279	$ 11,805

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 12. Commitments and Contingencies

Operating Leases

In October 2018, the Company entered into a lease agreement for a facility in San Diego, California to be used for research and development and administrative activities. The lease term commenced on April 1, 2019 and will expire on December 31, 2029. In October 2019, the Company entered into a lease amendment to expand the existing premises. The lease term for the additional premises commenced on July 29, 2020 and will expire on December 31, 2029. Both the original lease and amendment provides for rent abatements and scheduled increases in base rent. In connection with the lease and its amendment, the Company made cash security deposits in the amount of $0.3 million, included in other long-term assets in the Company’s consolidated balance sheets as of December 31, 2023 and 2022.

In July 2019, the Company entered into a lease agreement for a facility in San Diego, California that was retrofitted to Good Manufacturing Practice standards and is used for manufacturing in its early-stage clinical trials. The lease term commenced on June 26, 2020 and will expire on December 31, 2029. The lease provides for rent abatements and scheduled increases in base rent. In connection with the lease, the Company made a one-time cash security deposit in the amount of $0.1 million, included in other long-term assets in the Company’s consolidated balance sheets as of December 31, 2023 and 2022.

As of December 31, 2023, the Company had operating leases consisting of approximately 110,000 square feet of manufacturing, laboratory and office space in San Diego, California, including 87,000 square feet under a lease that expires on December 31, 2029, which contains a clinical manufacturing facility adjacent to office and laboratory space. The lease agreements include two options to extend the term for a period of 5 years each.

In October 2021, the Company entered into a sublease agreement for a facility in San Diego, California consisting of approximately 23,000 square feet to be used for research and administrative activities. The lease term commenced in March 2022 and will expire on December 31, 2025. During the year ended December 31, 2022, the Company recorded an ROU asset of $4.4 million and a corresponding lease liability related to this sublease.

During the years ended December 31, 2023 and 2022, the Company recognized $5.8 million and $7.0 million, respectively, of operating lease expense, including a $0.6 million impairment of an ROU asset during the year ended December 31, 2022. During the year ended December 31, 2023, the Company paid $6.3 million for its operating

leases. As of December 31, 2023, the weighted-average remaining lease term and weighted-average discount rate for operating leases were 5.6 years and 8.92%, respectively.

As of December 31, 2023, maturities of lease liabilities were as follows (in thousands):


Year ending December 31,
2024	$	6,188
2025		6,374
2026		5,107
2027		5,260
2028		5,418
Thereafter		5,581
Total future lease payments		33,928
Imputed interest		(7,095	)
Total lease liability balance		26,833
Less current portion of lease liability		5,951
Lease liability, net of current portion	$	20,882

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, contract research organizations, business partners and other parties with respect to certain matters including, but not limited to, losses arising from breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and certain of its executive officers that require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The Company has not incurred any material costs as a result of such indemnifications and is not currently aware of any indemnification claims.

April 2017 Commercial License Agreement with TeneoBio, Inc. (a subsidiary of Amgen Inc.)

In April 2017, the Company entered into a commercial license agreement (the “2017 TeneoBio Agreement”) with TeneoBio, Inc. (“TeneoBio”) pursuant to which the Company obtained exclusive worldwide rights to use and develop pharmaceutical products comprising allogeneic T-cells expressing a CAR molecule containing certain heavy chain sequences provided by TeneoBio for treatment of human disease.

August 2018 Commercial License Agreement with TeneoBio, Inc. (a subsidiary of Amgen Inc.)

In August 2018, the Company entered into a commercial license agreement (the “2018 TeneoBio Agreement”) with TeneoBio pursuant to which the Company obtained exclusive rights to research, develop and commercialize up to a certain number of targets from TeneoBio, for the development and use of TeneoBio's human heavy-chain-only antibodies in CAR-T cell therapies.

October 2019 License Agreement with Xyone Therapeutics, Inc (a successor-in-interest to Genus Oncology, LLC)

In October 2019, the Company entered into a license agreement (the “Xyone Agreement”) with Xyone, pursuant to which the Company obtained an exclusive worldwide license under certain patents and a non-exclusive worldwide license under certain know-how controlled by Xyone to research, develop and commercialize pharmaceutical products incorporating CAR cells expressing antibodies and derivatives thereof targeting MUC1, or a Xyone licensed product, and a non-exclusive worldwide license under certain patents and know-how controlled by Xyone to research, develop and commercialize companion diagnostics for the treatment, prevention and palliation of human diseases and conditions.

Legal Contingencies

In the ordinary course of business, the Company may face claims brought by third parties against the Company. The Company believes that there are currently no lawsuits, threats of litigation, or asserted or unasserted claims pending that could, individually or in the aggregate, have a material adverse effect on the Company’s results of operations or financial condition.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Schedule of Estimated Useful Lives of Property and Equipment

Property and equipment are stated at cost and depreciated or amortized using the straight-line method, based on their estimated useful lives as follows:


Asset Classification	Estimated Useful Life (years)
Laboratory equipment		5
Leasehold improvements	Lesser of useful life or lease-term
Computer equipment and software		3
Furniture and fixtures		7

Collaboration and License Agreements - Summary of Reconciliation of Closing Balance of Deferred Revenue Related to agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Collaborations And License Agreement [Line Items]
Beginning balance	$ 41,056	$ 13,762
Amounts received/invoiced	71,435	157,786
Revenue recognized	(64,703)	(130,492)
Ending balance	47,788	41,056
Roche Collaboration Agreement
Collaborations And License Agreement [Line Items]
Beginning balance	31,749
Amounts received/invoiced	30,741	153,169
Revenue recognized	(50,285)	(121,420)
Ending balance	12,205	31,749
Takeda Collaboration Agreement
Collaborations And License Agreement [Line Items]
Beginning balance	9,307	13,762
Amounts received/invoiced	5,111	4,617
Revenue recognized	(14,418)	(9,072)
Ending balance		$ 9,307
Astellas Strategic Rights Letter Agreement
Collaborations And License Agreement [Line Items]
Amounts received/invoiced	35,583
Ending balance	$ 35,583

Income Taxes - Schedule of (Benefit from) Provision for Income Taxes Differs from Income Tax Determined by Applicable U.S. Statutory Federal Income Tax Rate to Pretax Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Federal statutory rate	$ (25,898)	$ (13,326)
Adjustments for tax effects of:
Tax credits	(12,938)	(9,026)
State taxes, net	(6,856)	(2,842)
Unrecognized tax benefits	2,970	2,209
Stock-based compensation	3,279	3,106
Other, net	224	171
Change in valuation allowance	39,326	20,252
Total	$ 107	$ 544

Term Debt

12 Months Ended

Dec. 31, 2023

Debt Instruments [Abstract]

Term Debt

Note 9. Term Debt

In 2017, the Company entered into a loan and security agreement with Oxford Finance LLC (“Oxford”), which was subsequently amended (“Amended Loan Agreement”), pursuant to which the Company borrowed a total amount of $30.0 million.

In February 2022, the Company entered into a new Loan and Security Agreement (“2022 Loan Agreement”) with Oxford. Pursuant to the terms of the 2022 Loan Agreement, the Company borrowed $60.0 million in term loans (the “Term Loans”), of which $31.6 million was used to repay the balance outstanding under the Amended Loan Agreement, including $0.2 million of accrued interest. Under the 2022 Loan Agreement the initial interest-only period was through April 1, 2025, followed by 23 equal monthly payments of principal and applicable interest. In September 2022, a qualifying equity event, as defined in the 2022 Loan Agreement, was achieved which extended the interest-only period through April 1, 2026, followed by 11 equal monthly payments of principal and applicable interest. As a result, all amounts outstanding under the 2022 Loan Agreement will mature on February 1, 2027 (the “Maturity Date”). In connection with the repayment of the balance outstanding under the Amended Loan Agreement, the Company incurred amendment and final payment fees of $1.5 million previously due on the earlier of (i) the maturity date, (ii) acceleration of any Amended Loan Agreement loans, or (iii) the prepayment of any Amended Loan Agreement loans.

The Company accounted for this amendment as debt modification in accordance with ASC Topic 470, Debt because the modification was not considered substantial.

The balance outstanding under the 2022 Loan Agreement initially bore interest at a floating per annum rate equal to 7.83% plus the greater of (a) the 30-day U.S. Dollar (USD) LIBOR rate and (b) 0.11%. The interest rate applicable to the Term Loans as of December 31, 2023 was 13.27% per annum. The 2022 Loan Agreement included a provision addressing replacement of LIBOR with an alternate benchmark rate, when LIBOR was phased out in June 2023. Effective July 1, 2023, the balance outstanding under the 2022 Loan Agreement bears interest at a floating per annum rate equal to the greater of (a) 7.94% and (b) the sum of (i) the 1-Month CME Term Secured Overnight Financing Rate (“SOFR”) on the last business day of the month that immediately precedes the month in which the interest will accrue, (ii) 0.10% and (iii) 7.83%. The Company is required to make a final payment fee of 7.5% of the principal balance outstanding, payable on the earlier of (i) the Maturity Date, (ii) acceleration of any Term Loan, or (iii) the prepayment of the Term Loan. As of December 31, 2023, there was $60.0 million outstanding under the Term Loans. In connection with the Amended Loan Agreement, the Company previously incurred debt issuance costs of $1.5 million, which have been recorded as a debt discount and are being accreted to interest expense over the term of the Term Loans. Interest on the Term Loans, consisting of the stated interest rate, final payment fee and amortization of the discount, is being recognized under the effective interest method using a

rate of 14.76%. As of December 31, 2023, the balance of the unamortized debt discount was $1.4 million. The balance of the accrued final payment fee was $2.6 million as of December 31, 2023 and is presented as other long-term liability in the accompanying consolidated balance sheet.

The Company has an option to repay the outstanding debt under the 2022 Loan Agreement at any time in increments of $5.0 million, with no prepayment penalty.

The Company may use the proceeds from the Term Loans solely for its working capital requirements and to fund its general business operations. The Company’s obligations under the 2022 Loan Agreement are secured by a first priority security interest in substantially all of its current and future assets, other than its intellectual property. In addition, the Company has also agreed not to encumber its intellectual property assets, except as permitted by the 2022 Loan Agreement. While any amounts are outstanding under the 2022 Loan Agreement, the Company is subject to a number of affirmative and restrictive covenants, including covenants regarding dispositions of property, business combinations or acquisitions, among other customary covenants. The Company is also restricted from declaring dividends or making other distributions or payments on its capital stock in excess of $0.3 million per calendar year, subject to limited exceptions. As of December 31, 2023, the Company was in compliance with all covenants under the 2022 Loan Agreement.

- 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
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-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

Commitments and Contingencies - Additional Information (Details) $ in Thousands	1 Months Ended			12 Months Ended
	Oct. 31, 2019	Jul. 31, 2019	Oct. 31, 2018	Dec. 31, 2023 USD ($) ft² Option	Dec. 31, 2022 USD ($)	Oct. 31, 2021 ft²
Commitments And Contingencies [Line Items]
Operating leases, number of square feet \| ft²				110,000
ROU asset				$ 21,726	$ 25,085
Lease liability				$ 26,833
Operating lease, number of options to extend term \| Option				2
Operating lease, extended term				5 years
Operating lease, option to extend				true
Operating lease, option to extend, description				The lease agreements include two options to extend the term for a period of 5 years each.
Operating lease, commencement date	Jul. 29, 2020	Jun. 26, 2020	Apr. 01, 2019
Operating lease, expiration date	Dec. 31, 2029	Dec. 31, 2029	Dec. 31, 2029
Security deposit				$ 300	300
One time cash security deposit				100	100
Operating lease expense				5,800	7,000
Impairment of ROU asset					600
Operating lease, payments				$ 6,300
Operating lease, weighted-average remaining lease term				5 years 7 months 6 days
Operating lease, weighted -average discount rate				8.92%
Research and Administrative Activities
Commitments And Contingencies [Line Items]
Operating leases, number of square feet \| ft²						23,000
Lease Expires on December 31, 2029
Commitments And Contingencies [Line Items]
Operating leases, number of square feet \| ft²				87,000
Laboratory and Office Space Facility
Commitments And Contingencies [Line Items]
ROU asset					4,400
Lease liability					$ 4,400

Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Property and Equipment (Details)	Dec. 31, 2023
Laboratory Equipment
Property Plant And Equipment [Line Items]
Estimated useful life of property and equipment	5 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, Plant, and Equipment, Useful Life, Term, Description [Extensible Enumeration]	us-gaap:UsefulLifeShorterOfTermOfLeaseOrAssetUtilityMember
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Estimated useful life of property and equipment	3 years
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Estimated useful life of property and equipment	7 years

Stock-Based Compensation - Schedule of Assumptions Used to Determine the Fair Value of Purchase Rights Issued Under ESPP (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	4.05%	2.16%
Expected volatility	82.59%	84.94%
Expected term (years)	5 years 11 months 19 days	5 years 11 months 19 days
Dividend yield	0.00%
2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	5.26%	2.39%
Expected volatility	87.07%	93.68%
Expected term (years)	6 months	6 months

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480483/718-10-35-1D

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-Paragraph 2
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-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-Name Accounting Standards Codification
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-Paragraph 2
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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+ Details

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Nature of Operations

Basis of Presentation and Consolidation

Risk and Uncertainties

Use of Estimates

Segment Information

Fair Value Measurements

Concentration Of Business Risk

Concentration of Business Risk

Leases

Concentration of Credit Risk

Cash and Cash Equivalents

Short Term Investments

Short-Term Investments

Goodwill and Other Intangible Assets

Property and Equipment

Property and equipment are stated at cost and depreciated or amortized using the straight-line method, based on their estimated useful lives as follows:


Asset Classification	Estimated Useful Life (years)
Laboratory equipment		5
Leasehold improvements	Lesser of useful life or lease-term
Computer equipment and software		3
Furniture and fixtures		7

Revenue Recognition

Performance Obligations

The following is a description of principal goods and services from which the Company generates revenue.

Intellectual property licenses

Material Rights

Research and development services

Contracts with Multiple Performance Obligations

Variable Consideration

sales-based royalties and milestones are excluded from the estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied.

Disaggregation of Revenue

The Company operates in one reportable business segment and has two customers.

Contract Assets and Contract Liabilities

Cost to Obtain and Fulfill a Contract

The Company generally does not incur costs to obtain new contracts. Costs to fulfill contracts are expensed as incurred.

Accounts Receivable and Allowance for Credit Losses

Research and Development

Research and Manufacturing Contract Costs and Accruals

Patent Costs

Stock-Based Compensation

Comprehensive Income (Loss)

Net Income (Loss) Per Share

Net Loss Per Share

Income Taxes

Emerging Growth Company Status

Recently Adopted Accounting Pronouncements

Recently Issued Accounting Pronouncements

periods beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements and disclosures.

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	95,636,553	85,964,161
Common stock, shares outstanding	95,636,553	85,964,161

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Mar. 04, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	PSTX
Entity Registrant Name	POSEIDA THERAPEUTICS, INC.
Entity Central Index Key	0001661460
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Security12b Title	Common stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity File Number	001-39376
Entity Incorporation State Country Code	DE
Entity Tax Identification Number	47-2846548
Entity Address, Address Line One	9390 Towne Centre Drive
Entity Address City Or Town	San Diego
Entity Address State Or Province	CA
Entity Address Postal Zip Code	92121
City Area Code	858
Local Phone Number	779-3100
Document Annual Report	true
Document Transition Report	false
ICFR Auditor Attestation Flag	false
Entity Common Stock, Shares Outstanding			96,489,127
Entity Public Float				$ 122.8
Auditor Firm ID	42	238
Auditor Name	Ernst & Young LLP	PricewaterhouseCoopers LLP
Auditor Location	San Diego, California	Irvine, California
Documents Incorporated by Reference	Certain information required to be disclosed in Part III of this report is incorporated by reference from the registrant’s definitive Proxy Statement for the 2024 Annual Meeting of Stockholders, which proxy statement will be filed not later than 120 days after the end of the fiscal year covered by this report.
Document Financial Statement Error Correction [Flag]	false

Composition of Certain Balance Sheet Components - Summary of Property and Equipment Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Total property and equipment	$ 37,864	$ 35,062
Less: Accumulated depreciation and amortization	(18,809)	(13,476)
Total property and equipment, net	19,055	21,586
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	21,271	18,551
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	14,113	14,006
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Total property and equipment	1,355	1,504
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	$ 1,125	$ 1,001

Strategic Investment

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Strategic Investment

Note 6. Strategic Investment

Astellas

Terms of the Agreement

On August 4, 2023 (the “Signing Date”), the Company entered into a series of agreements (collectively, the “Astellas Agreements”) with Astellas US, LLC (“Astellas”) as described below.

Securities Purchase and Registration Rights Agreement

Pursuant to a securities purchase agreement (the “Securities Purchase Agreement”), the Company agreed to issue and sell to Astellas in a private placement (the “Private Placement”) an aggregate of 8,333,333 shares (the “Shares”) of common stock, par value $0.0001 per share, of the Company, at a purchase price of $3.00 per Share, for aggregate gross proceeds of $25.0 million. The Private Placement closed on August 7, 2023 (the “Closing Date”).

The Company also entered into a registration rights agreement with Astellas (the “Registration Rights Agreement”), pursuant to which the Company agreed to register the resale by Astellas of the Shares no later than the 250th day after the Closing Date.

Strategic Rights Letter Agreement

On the Signing Date, the Company also entered into a strategic rights letter agreement (the “Astellas Strategic Rights Letter”) with Astellas, pursuant to which, the Company agreed to the following: (i) grant Astellas the right to an observer seat on the Company’s board of directors, any committee of the Company’s board of directors, and the Company’s scientific advisory board; (ii) for a period of 18 months, grant Astellas a right of notification with respect to a Change in Control (as defined in the Astellas Strategic Rights Letter); (iii) during the period beginning on the Closing Date and ending on the 12-month anniversary of the Closing Date (the “Exclusivity Period”), not to (1) solicit, knowingly encourage, negotiate or otherwise enter into bona fide discussions about a Program Transaction (as defined below) with any third party, (2) provide access to any confidential information of the Company relating to P-MUC1C-ALLO1, the Company’s fully allogeneic CAR-T product candidate for multiple solid tumor indications (the “Program”), for purposes of knowingly facilitating a Program Transaction, or (3) enter into any letter of intent, contract or other commitment for a Program Transaction (a “Program Transaction” being an exclusive or co-exclusive license or co-promote or co-marketing arrangement or granting of commercial rights to sell, promote or market one or more products of the Program for any indication in the world); (iv) provide notice to

Astellas (1) if the Company receives a bona fide proposal for a Change in Control transaction from a third party, unless such proposal is rejected by the Company’s board of directors, or (2) of the commencement of a process approved by the Company’s board of directors for a Change in Control, (3) if the Company receives a bona fide proposal for a Program Transaction from a third party unless the proposal is rejected by the Company’s board of directors (a “Program Transaction Proposal”) or, (4) following the Exclusivity Period, the commencement of substantive discussions for a Program Transaction with a third party in connection with a process approved by the Company’s board of directors for a Program Transaction (a “Program Process”). In connection with a notice related to (x) a Program Transaction Proposal, Astellas shall have a right of first refusal to provide a competing proposal that is in aggregate more favorable to the Company than the Program Transaction Proposal, and thereby have a right to negotiate exclusively a possible Program Transaction for a specified period and (y) a Program Process, Astellas shall have a right of first offer to negotiate a Program Transaction for a specified period before the Company engages with any third party in meaningful substantive discussions, in each case, in accordance with the procedures and subject to the conditions set forth in the Astellas Strategic Rights Letter.

As partial consideration for the rights granted to Astellas under the Astellas Strategic Rights Letter, Astellas paid the Company a one-time payment in the amount of $25.0 million (the “Upfront Payment”). In connection with a Change in Control transaction or Program Transaction between the Company and Astellas, some, all or none of the Upfront Payment may be offset against payments owed by Astellas in a tiered basis to the Company dependent on certain factors set forth in the Astellas Strategic Rights Letter.

The Astellas Strategic Rights Letter shall terminate upon the earliest to occur of (i) the 18-month anniversary of the Closing Date, (ii) such time that Astellas owns fewer than 8,000,000 shares of common stock (subject to adjustment for any stock splits, stock dividends or recapitalizations) and (iii) the consummation of a Change in Control.

Revenue Recognition

The Securities Purchase Agreement and the Registration Rights Agreement are not within the scope of ASC 606 and were accounted for as an equity issuance with the deemed fair value of the shares issued scoped out of the transaction price. See Note 10 for further detail of the equity issuance. The rights granted under the Astellas Strategic Rights Letter were assessed under ASC 606, as the agreement represents a contract with a customer. The rights were deemed to not transfer any control to Astellas but give Astellas a right in the future, as all or a portion of the Upfront Payment of $25.0 million is creditable to Astellas towards a future potential transaction within the restrictions and time frames specified in the letter. Therefore, the full amount allocated to the rights is treated as a non-refundable payment.

The Company recorded the issuance of common stock at its estimated fair value on the date of issuance of $14.4 million, which reflects a discount for the lack of marketability (“DLOM”) of the shares. The DLOM was applied due to the inability to trade the shares until they are registered. The $10.6 million difference between the $25.0 million paid by Astellas for the Securities Purchase Agreement and the fair market value of shares issued was allocated to the rights granted under the Astellas Strategic Rights Letter for a total amount allocable of $35.6 million. The amount will be recognized when the likelihood of Astellas exercising its remaining rights becomes remote, or when the proportionate amount of the tiered creditable amounts expire.

The Company did not recognize any revenue from the Astellas Agreements for the year ended December 31, 2023. The Company has $35.6 million of deferred revenue on its consolidated balance sheet as of December 31, 2023, expected to be recognized in tiered amounts by February 2025.

Stock-Based Compensation - Schedule of Assumptions Used to Determine the Fair Value of Options Granted (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	4.05%	2.16%
Expected volatility	82.59%	84.94%
Expected term (years)	5 years 11 months 19 days	5 years 11 months 19 days
Dividend yield	0.00%

- Definition

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

+ References

+ Details

Collaboration and License Agreements (Tables)

12 Months Ended

Dec. 31, 2023

Collaborations And License Agreement [Abstract]

Summary of Reconciliation of Closing Balance of Deferred Revenue Related to agreements

A reconciliation of the closing balance of deferred revenue related to the agreements is as follows (in thousands):


	Roche Collaboration Agreement			Takeda Collaboration Agreement			Astellas Strategic Rights Letter		Total
Balance as of December 31, 2021	$	—		$	13,762		$	—	$	13,762
Amounts received/invoiced		153,169			4,617			—		157,786
Revenue recognized		(121,420	)		(9,072	)		—		(130,492	)
Balance as of December 31, 2022	$	31,749		$	9,307		$	—	$	41,056
Amounts received/invoiced		30,741			5,111			35,583		71,435
Revenue recognized		(50,285	)		(14,418	)		—		(64,703	)
Balance as of December 31, 2023	$	12,205		$	—		$	35,583	$	47,788

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating Activities:
Net loss	$ (123,430)	$ (64,002)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	5,614	5,172
Loss on disposal of property and equipment	3	348
Stock-based compensation	23,134	18,926
Write off of deferred CIRM grant liability	(3,992)
Accretion of discount on issued term debt	808	844
Accretion on investment securities, net	(8,385)	(1,775)
Changes in operating assets and liabilities:
Accounts receivable	77	(9,088)
Prepaid expenses and other current assets	1,565	499
Operating lease right-of-use assets	3,359	4,605
Other long-term assets	(25)	605
Accounts payable	1,038	(6,748)
Accrued expenses and other liabilities	5,004	1,399
Operating lease liabilities	(3,669)	(4,852)
Deferred revenue	6,732	27,295
Net cash used in operating activities	(92,167)	(26,772)
Investing Activities:
Purchases of property and equipment	(3,066)	(3,924)
Proceeds from sale of property and equipment		12
Purchases of short-term investments	(237,800)	(294,422)
Proceeds from maturities of short-term investments	280,000	95,000
Net cash provided by (used in) investing activities	39,134	(203,334)
Financing Activities:
Proceeds from issuance of common stock under employee stock compensation plans	1,276	1,310
Payment of taxes related to net share settlement of equity awards	(494)
Proceeds from issuance of common stock through ATM offering, net of issuance costs	928
Proceeds from private placement of common stock	14,417
Proceeds from public offering of common stock, net of issuance costs		75,299
Proceeds from term debt		30,000
Payment of debt issuance costs		(1,450)
Net cash provided by financing activities	16,127	105,159
Net decrease in cash and cash equivalents	(36,906)	(124,947)
Cash and cash equivalents at beginning of period	81,378	206,325
Cash and cash equivalents at end of period	44,472	81,378
Non-cash operating, investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued liabilities	20	1,144
Right-of-use assets obtained in exchange for operating lease liabilities		4,425
Supplemental disclosure of cash flow information:
Interest paid	$ 7,796	$ 5,138

Fair Value Measurement

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurement

Note 5. Fair Value Measurement

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants as of the measurement date. Applicable accounting guidance provides an established hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs that market participants would use in valuing the asset or liability and are developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors that market participants would use in valuing the asset or liability. There are three levels of inputs that may be used to measure fair value:

•

Level 1 — Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities

•

Level 2 — Significant other observable inputs other than Level 1 prices such as quoted prices in markets that are not active, or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability

•

Level 3 — Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity)

The Company classifies its money market funds and U.S. treasury securities, which are valued based on quoted market prices in active markets with no valuation adjustment, as Level 1 assets within the fair value hierarchy.

The following table summarizes the Company’s valuation hierarchy for its financial assets and liabilities measured at fair value on a recurring basis (in thousands):


	Level 1		Level 2		Level 3
At December 31, 2023:
Assets:
Money market funds	$	37,590	$	—	$	—
U.S. government agency securities and treasuries		167,730		—		—
Total	$	205,320	$	—	$	—

At December 31, 2022:
Assets:
Money market funds and U.S. government agency treasuries	$	63,055	$	—	$	—
U.S. government agency securities and treasuries		201,115		—		—
Total	$	264,170	$	—	$	—

- 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

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Schedule of Company's Valuation Hierarchy of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table summarizes the Company’s valuation hierarchy for its financial assets and liabilities measured at fair value on a recurring basis (in thousands):


	Level 1		Level 2		Level 3
At December 31, 2023:
Assets:
Money market funds	$	37,590	$	—	$	—
U.S. government agency securities and treasuries		167,730		—		—
Total	$	205,320	$	—	$	—

At December 31, 2022:
Assets:
Money market funds and U.S. government agency treasuries	$	63,055	$	—	$	—
U.S. government agency securities and treasuries		201,115		—		—
Total	$	264,170	$	—	$	—

Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating losses	$ 91,285	$ 89,300
Income tax credit carryforwards	48,119	38,674
R&D capitalization	39,341	23,370
Deferred revenue	9,965	2,584
Lease liabilities	7,514	8,468
Amortization	5,136	1,252
Accrued expenses	3,436	2,910
Grant income		1,108
Other, net	4,910	3,612
Total deferred tax assets	209,706	171,278
Deferred tax liabilities:
Right of use assets	(6,084)	(6,965)
Depreciation	(2,003)	(1,948)
Acquired indefinite lived intangibles	(370)	(366)
Total deferred tax liabilities	(8,457)	(9,279)
Valuation allowance	(201,304)	(162,054)
Net deferred tax liability	$ (55)	$ (55)

California Institute of Regenerative Medicine Award - Additional Information (Details) - CIRM $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($)	Dec. 31, 2023 Time	Dec. 31, 2022
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue sharing multiple \| Time		9
Period to exercise loan option upon food and drug administration authorization		10 days
Repayment period		10 days
Repayment of awards percentage		60.00%
P-PSMA-101 program
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Award received \| $	$ 4.0
LIBOR
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Debt instrument basis spread on variable rate			10.00%

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Schedule of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following at December 31, 2023:


Stock options issued and outstanding			14,909,912
Restricted stock units issued and outstanding			4,555,099
Authorized for future options and award grants			4,332,980
Authorized for future issuance under Employee Stock Purchase Plan			1,773,794
Total			25,571,785

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

Note 13. Income Taxes

The components of the pretax loss from operations are as follows (in thousands):


	Year Ended December 31,
	2023			2022
U.S. Domestic	$	(123,323	)	$	(63,458	)
Net loss before income tax	$	(123,323	)	$	(63,458	)

The provision for income taxes consists of the following (in thousands):


	Year Ended December 31,
	2023		2022
Current:
Federal	$	51	$	456
State		56		88
Total current provision		107		544
Deferred:
Federal		—		—
State		—		—
Total deferred provision		—		—
Total provision	$	107	$	544

Beginning in 2022, the Tax Cuts and Jobs Act of 2017 requires taxpayers to capitalize and amortize research and development expenditures over five years for domestic research and 15 years for foreign research pursuant to Section 174 of the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”). Although the U.S. Congress is considering legislation that would defer or eliminate the capitalization and amortization requirement to later years, the Company has no assurance that the provision will be repealed or otherwise modified. As a result, the Company recorded income tax expense of $0.1 million for the year ended December 31, 2023.


	Year Ended December 31,
	2023			2022
Federal statutory rate	$	(25,898	)	$	(13,326	)
Adjustments for tax effects of:
Tax credits		(12,938	)		(9,026	)
State taxes, net		(6,856	)		(2,842	)
Unrecognized tax benefits		2,970			2,209
Stock-based compensation		3,279			3,106
Other, net		224			171
Change in valuation allowance		39,326			20,252
Total	$	107		$	544

Significant components of the Company’s deferred tax assets and liabilities consist of the following as of (in thousands):


	December 31,
	2023			2022
Deferred tax assets:
Net operating losses	$	91,285		$	89,300
Income tax credit carryforwards		48,119			38,674
R&D capitalization		39,341			23,370
Deferred revenue		9,965			2,584
Lease liabilities		7,514			8,468
Amortization		5,136			1,252
Accrued expenses		3,436			2,910
Grant income		—			1,108
Other, net		4,910			3,612
Total deferred tax assets		209,706			171,278
Deferred tax liabilities:
Right of use assets		(6,084	)		(6,965	)
Depreciation		(2,003	)		(1,948	)
Acquired indefinite lived intangibles		(370	)		(366	)
Total deferred tax liabilities		(8,457	)		(9,279	)
Valuation allowance		(201,304	)		(162,054	)
Net deferred tax liability	$	(55	)	$	(55	)

The realization of deferred tax assets may be dependent on the Company’s ability to generate sufficient income in future years in the associated jurisdiction to which the deferred tax assets relate. The Company considers all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax planning strategies, and recent financial performance. A valuation allowance of $201.3 million has been recorded as of December 31, 2023, as compared to $162.1 million as of December 31, 2022. The valuation allowance is based on management’s assessment that it is more likely than not that the Company will not realize its net deferred tax asset in the foreseeable future.

Deferred tax liabilities associated with indefinite-life intangibles cannot be considered a source of income to support the realization of deferred tax assets because the reversal of these deferred tax liabilities is considered indefinite. However, as the Company has an indefinite-life asset with an unlimited loss carryforward period within the same jurisdiction, and of appropriate character, the deferred tax liability associated with the indefinite-life intangible constitutes a source of taxable income to support the realization of the deferred tax asset, since both have indefinite reversal or expiration periods.

As of December 31, 2023, the Company had state net operating loss carryforwards of $445.5 million, which begin to expire in 2035 and the Company had federal net operating loss carryforwards that do not expire but utilization is limited to 80% of taxable income for any given tax year in the amount of $285.3 million.

As of December 31, 2023, the Company had federal orphan drug credits and research and development credits and state research and development tax credits of $46.9 million and $19.7 million, respectively. The federal research and development tax credits will begin to expire in 2037, while the state credits do not expire.

Additionally, the utilization of the net operating loss and research and development tax credit carryforwards is subject to an annual limitation under Section 382 of the Internal Revenue Code. Future ownership changes as determined under Section 382 could further limit the utilization of net operating loss carryforwards. Due to the existence of the valuation allowance, future changes in the deferred tax assets related to these tax attributes will not impact the Company’s effective tax rate.

The Company is subject to taxation in the U.S. and state jurisdictions. As of December 31, 2023, the Company’s tax years beginning 2012 to date are subject to examination by federal and other state taxing authorities

due to the carry forward of unutilized net operating losses and research and development tax credits. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service or state tax authorities to the extent utilized in a future period. The Company is not currently under examination by the IRS or state and local tax authorities.

As of December 31, 2023, the Company had unrecognized tax benefits of $15.3 million, determined as follows:


	December 31,
	2023		2022
Balance at beginning of year	$	11,805	$	9,494
Increase for current year positions		3,091		2,403
Increase (decrease) for prior year positions		383		(92	)
Balance at the end of year	$	15,279	$	11,805

These unrecognized tax benefits are not expected to change within the next twelve months. Of the $15.3 million of unrecognized tax benefits, zero would impact the effective tax rate due to the valuation allowance, if reversed. The Company recognizes interest and penalties related to uncertain tax positions as a component of income tax expense. As of December 31, 2023, there are no accrued interest or penalties.

- Definition

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

+ References

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

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

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

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

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

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

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

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

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

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

+ Details

Term Debt - Additional Information (Details) $ in Millions		1 Months Ended	12 Months Ended
Term Debt - Additional Information (Details) $ in Millions	Jul. 01, 2023	Feb. 28, 2022 USD ($) Months	Dec. 31, 2023 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Debt issuance costs			$ 1.4
Debt instrument final payment fee accrued			2.6
Capital stock in excess		$ 0.3
2022 Loan Agreement
Debt Instrument [Line Items]
Debt instrument maturity date		Feb. 01, 2027
Debt instrument basis spread on variable rate	7.83%
Debt instrument interest rate during period	0.10%
2022 Loan Agreement \| Oxford
Debt Instrument [Line Items]
Long-term debt		$ 60.0
Long-term debt		In February 2022, the Company entered into a new Loan and Security Agreement (“2022 Loan Agreement”) with Oxford. Pursuant to the terms of the 2022 Loan Agreement, the Company borrowed $60.0 million in term loans (the “Term Loans”), of which $31.6 million was used to repay the balance outstanding under the Amended Loan Agreement, including $0.2 million of accrued interest. Under the 2022 Loan Agreement the initial interest-only period was through April 1, 2025, followed by 23 equal monthly payments of principal and applicable interest. In September 2022, a qualifying equity event, as defined in the 2022 Loan Agreement, was achieved which extended the interest-only period through April 1, 2026, followed by 11 equal monthly payments of principal and applicable interest. As a result, all amounts outstanding under the 2022 Loan Agreement will mature on February 1, 2027 (the “Maturity Date”).
Debt instrument repayment number of month \| Months		23
Debt instrument repayment additional number of monthly payments due period extension \| Months		11
Amended Loan Agreement
Debt Instrument [Line Items]
Long-term debt				$ 30.0
Amount used to repay outstanding debt		$ 31.6
Payment of accrued interest		0.2
Debt instrument, fee amount		$ 1.5
Debt issuance costs			1.5
Term Loans
Debt Instrument [Line Items]
Long-term debt			$ 60.0
Debt instrument basis spread on variable rate			13.27%
Interest rate recognized under effective interest method			14.76%
Term Loans \| 2022 Loan Agreement
Debt Instrument [Line Items]
Debt instrument basis spread on variable rate	7.94%	7.83%
Debt instrument floating per annum rate	1-Month CME Term Secured Overnight Financing Rate (“SOFR”)	30-day U.S. Dollar (USD) LIBOR
Debt instrument interest rate during period		0.11%
Debt instrument, final payment fee percentage		7.50%
Repayment of outstanding debt		$ 5.0

Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance (Details)	Dec. 31, 2023 shares
Equity [Abstract]
Stock options issued and outstanding	14,909,912
Restricted stock units issued and outstanding	4,555,099
Authorized for future options and award grants	4,332,980
Authorized for future issuance under Employee Stock Purchase Plan	1,773,794
Total	25,571,785

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of the Company's Stock Option Activity

The following is a summary of the Company’s stock option activity for the year ended December 31, 2023:


	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (thousands)
Balance at January 1, 2023		11,861,881		$	7.61
Granted		4,054,949			4.69
Exercised		(37,166	)		3.65
Forfeited/Cancelled		(969,752	)		7.41
Balance at December 31, 2023		14,909,912		$	6.84		7.72	$	1,680
Options vested and expected to vest as of December 31, 2023		14,909,912		$	6.84		7.72	$	1,680
Options vested and exercisable as of December 31, 2023		8,003,272		$	8.01		7.09	$	840

Schedule of Assumptions Used to Determine the Fair Value of Options Granted


	Year Ended December 31,
	2023	2022
Risk-free interest rate	4.05%	2.16%
Expected volatility	82.59%	84.94%
Expected term (years)	5.97	5.97
Dividend yield	—	—

Summary of Restricted Stock Unit (RSU) Activity

The following is a summary of the Company’s restricted stock unit (“RSU”) activity for the year ended December 31, 2023:


	Shares			Weighted Average Grant Date Fair Value
Balance at January 1, 2023		2,614,402		$	3.69
Granted		2,944,792			4.76
Vested		(725,082	)		3.58
Forfeited/Cancelled		(279,013	)		4.46
Balance at December 31, 2023		4,555,099		$	4.35

Schedule of Assumptions Used to Determine the Fair Value of Purchase Rights Issued Under ESPP

The assumptions that the Company used to determine the fair value of the purchase rights issued to employees were as follows:


	Year Ended December 31,
	2023	2022
Risk-free interest rate	5.26%	2.39%
Expected volatility	87.07%	93.68%
Expected term (years)	0.5	0.5
Dividend yield	—	—

Schedule of Stock-Based Compensation Expense


	Year Ended December 31,
	2023		2022
Research and development	$	12,303	$	9,566
General and administrative		10,831		9,360
Total stock-based compensation expense	$	23,134	$	18,926

Financial Instruments - Summary of Amortized Cost and Fair Value of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost/Cost	$ 205,194	$ 264,319
Available-for-Sale Securities, Unrealized Gains	158	13
Available-for-Sale Securities , Unrealized Losses	(32)	(162)
Available-for-Sale Securities, Fair Value	$ 205,320	$ 264,170
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less	1 year or less
Available-for-Sale Securities, Amortized Cost/Cost	$ 37,590	$ 57,799
Available-for-Sale Securities, Fair Value	$ 37,590	$ 57,799
U.S. Government Agency Securities and Treasuries
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year or less	1 year or less
Available-for-Sale Securities, Amortized Cost/Cost	$ 167,604	$ 206,520
Available-for-Sale Securities, Unrealized Gains	158	13
Available-for-Sale Securities , Unrealized Losses	(32)	(162)
Available-for-Sale Securities, Fair Value	$ 167,730	$ 206,371

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-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 3: http://www.xbrl.org/2003/role/disclosureRef
-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 4: http://www.xbrl.org/2003/role/disclosureRef
-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 5: http://www.xbrl.org/2003/role/disclosureRef
-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 6: http://www.xbrl.org/2003/role/disclosureRef
-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 7: http://www.xbrl.org/2003/role/disclosureRef
-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 8: http://www.xbrl.org/2003/role/disclosureRef
-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 9: http://www.xbrl.org/2003/role/disclosureRef
-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/2003/role/disclosureRef
-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/2003/role/disclosureRef
-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/2003/role/disclosureRef
-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

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Summary of Maturities of Lease Liabilities

As of December 31, 2023, maturities of lease liabilities were as follows (in thousands):


Year ending December 31,
2024	$	6,188
2025		6,374
2026		5,107
2027		5,260
2028		5,418
Thereafter		5,581
Total future lease payments		33,928
Imputed interest		(7,095	)
Total lease liability balance		26,833
Less current portion of lease liability		5,951
Lease liability, net of current portion	$	20,882

Stockholders' Equity - Additional Information (Details) - USD ($)		1 Months Ended		12 Months Ended
	Aug. 04, 2023	Aug. 31, 2022	Aug. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Jul. 31, 2020
Class Of Stock [Line Items]
Common stock, shares authorized				250,000,000	250,000,000
Common stock, par value				$ 0.0001	$ 0.0001
Common stock, voting rights				Each share of common stock is entitled to one vote.
Dividends declared				$ 0
Proceeds from issuance of common stock through ATM offering, net of issuance costs				$ 928,000
Common stock issued and sold				95,636,553	85,964,161
Common Stock
Class Of Stock [Line Items]
Sale of stock, price per share		$ 3.5
Warrants to purchase stock				93,518
Warrants to purchase stock				$ 4.28
Sale of common stock under an underwritten public offering		23,000,000
Shares sold pursuant to full exercise of underwriters' option to purchase additional shares		3,000,000
Proceeds from issuance of common stock through ATM offering, net of issuance costs		$ 75,300,000
Common Stock \| Astellas \| Securities Purchase Agreement
Class Of Stock [Line Items]
Discount for lack of marketability of shares, at fair value on date of issuance	$ 14,400,000
Common Stock \| 2018 and 2019 Warrants
Class Of Stock [Line Items]
Warrants to purchase stock				27,604
Warrants to purchase stock				$ 7.25
IPO
Class Of Stock [Line Items]
Common stock, shares authorized						250,000,000
Common stock, par value						$ 0.0001
Undesignated preferred stock, shares authorized						10,000,000
Undesignated preferred stock, par value						$ 0.0001
At the Market Facility \| Common Stock \| Sales Agreement \| Cantor Fitzgerald & Co.
Class Of Stock [Line Items]
Proceeds from issuance of common stock through ATM offering, net of issuance costs				$ 900,000
Aggregate offering price			$ 85,000,000
Common stock issued and sold				119,000
Weighted average price per share				$ 8.04
Private Placement \| Common Stock \| Astellas \| Securities Purchase Agreement
Class Of Stock [Line Items]
Common stock, par value	$ 0.0001
Sale of stock, price per share	$ 3
Sale of common stock under an underwritten public offering	8,333,333
Proceeds from issuance of common stock through ATM offering, net of issuance costs	$ 25,000,000

Composition of Certain Balance Sheet Components - Summary of Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Contract research services	$ 14,621	$ 10,908
Payroll and related expense	13,076	11,271
Other	3,395	3,889
Total accrued expenses and other liabilities	$ 31,092	$ 26,068

Employee Benefit Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Retirement Benefits [Abstract]
Defined contributions, total	$ 1.9	$ 1.5
Defined Contribution Plan, Tax Status [Extensible List]	us-gaap:QualifiedPlanMember	us-gaap:QualifiedPlanMember