0001789769-24-000036 | 10-K | XBRL Viewer

Income Taxes

12 Months Ended

Dec. 31, 2023

The geographical breakdown of loss before provision for income taxes is as follows (in thousands):


	Year Ended December 31,
	2023		2022
Domestic	$	(144,570)	$	(183,994)
Foreign	(11,517)		(41,256)
Loss before income taxes	$	(156,087)	$	(225,250)

The components of the provision for income taxes are as follows (in thousands):


	Year Ended December 31,
	2023		2022
Current provision for income taxes:
Domestic	$	—	$	13
Foreign	—		—
Total current	—		13
Deferred tax provision:
Domestic	—		—
Foreign	—		(2,086)
Total deferred	—		(2,086)
Total income tax expense (benefit)	$	—	$	(2,073)

The following table presents a reconciliation of the Company’s statutory federal income tax rate and effective tax rate:


	Year Ended December 31,
	2023		2022
U.S. federal taxes at statutory rate	21.0	%	21.0	%
Stock-based compensation	(1.8)	%	(2.0)	%
Permanent differences and other	0.8	%	0.2	%
Statutory tax rate differences	3.4	%	1.1	%
Change in valuation allowance	(23.4)	%	(19.4)	%
Total	—	%	0.9	%

The components of deferred tax liabilities consist of the following (in thousands):


	Year Ended December 31,
	2023		2022
Deferred tax assets:
Net operating loss carryforwards	$	88,408	$	58,259
Research and development credits	4,915		4,915
Accrued compensation and benefits	107		352
Stock-based compensation	3,570		2,781
Capitalized research and development	19,432		20,966
Other temporary differences	8,279		517
Intangible assets	97		—
Fixed assets	1,496		—
Other	335		—
Total gross deferred tax assets	126,639		87,790
Less: valuation allowance	(126,639)		(86,285)
Total deferred tax assets, net	—		1,505
Deferred tax liabilities:
Intangible assets	—		—
Fixed assets	—		(420)
Other	—		(1,085)
Total gross deferred tax liabilities	—		(1,505)
Net deferred tax liabilities	$	—	$	—

The components of unrecognized tax benefits consist of the following (in thousands):


Balance at December 31, 2022:	$	2,339
Additions in 2023	—
Balance at December 31, 2023:	$	2,339

In assessing the realizability of deferred tax assets, the Company considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Due to the uncertainty of the business in which the Company operates, projections of future

profitability are difficult and past profitability is not necessarily indicative of future profitability. The Company does not believe it is more likely than not that the deferred tax assets will be realized, and accordingly, the valuation allowance increased $40.4 million for the year ended December 31, 2023. As of December 31, 2023, the Company had net operating loss carryforwards for federal income tax purposes of $319.5 million, which will carryforward indefinitely, but may only offset 80% of the Company’s taxable income. This limitation on the net operating loss may require the Company to pay federal income taxes in future years despite generating a loss for federal income tax purposes in prior years. In addition, the Company has $173.3 million of net operating loss carryforwards available to reduce future taxable income, for California state income tax purposes for the year ended December 31, 2023. The state net operating loss carryforwards will begin to expire, if not utilized, in 2041. The Company has R&D credits of $4.1 million, and $3.7 million for federal and California, respectively, as of December 31, 2023. The federal R&D credits expire in 2041 and the California R&D credits carryforward indefinitely.

The Company files income tax returns in the U.S. federal jurisdiction, various states where the Company has employees and/or significant business activities, and the United Kingdom. As of December 31, 2023, the Company’s federal and state returns through 2020 are still open to examination. The UK returns starting from 2020 are open to examination. The Company had uncertain tax positions as of December 31, 2022 of $2.3 million and this balance remained unchanged during December 31, 2023. The Company does not anticipate that the amount of existing unrecognized tax benefits will significantly increase or decrease during the next 12 months. The Company had no accrued interest or penalties related to uncertain tax positions as of December 31, 2023.

The Company has not completed a Section 382 study to assess whether an ownership change has occurred or whether there have been multiple ownership changes since the Company’s formation. Pursuant to Internal Revenue Code Sections 382 and 383, annual use of the Company’s net operating loss and research and development tax credit carryforwards may be limited in the event a cumulative change in ownership of more than 50% occurs within a three-year period. If eliminated, the related asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance. Due to the existence of the valuation allowance, limitations created by future ownership changes, if any, will not impact the Company’s effective tax rate.

- 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.

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+ Details

Summary of Significant Accounting Policies - Useful Life (Details)	Dec. 31, 2023
Laboratory equipment
Property, Plant and Equipment [Line Items]
Useful life	5 years
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Useful life	5 years
Office and computer equipment
Property, Plant and Equipment [Line Items]
Useful life	3 years
Building
Property, Plant and Equipment [Line Items]
Useful life	35 years

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2023
Audit Information [Abstract]
Auditor Firm ID	34
Auditor Name	Deloitte & Touche LLP
Auditor Location	San Diego, California

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2021		6,451,463
Beginning balance at Dec. 31, 2021	$ 555,199	$ 0	$ 757,003	$ (87)	$ (201,717)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares of common stock issued in connection with incentive stock plan (in shares)		52,450
Shares of common stock issued in connection with incentive stock plan	1,548		1,548
Stock-based compensation	30,441		30,441
Net loss	(223,177)				(223,177)
Other comprehensive income (loss)	$ (406)			(406)
Ending balance (in shares) at Dec. 31, 2022	6,503,913	6,503,913
Ending balance at Dec. 31, 2022	$ 363,605	$ 0	788,992	(493)	(424,894)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	18,166		18,166
Net loss	(156,087)				(156,087)
Other comprehensive income (loss)	$ 145			145
Ending balance (in shares) at Dec. 31, 2023	6,503,913	6,503,913
Ending balance at Dec. 31, 2023	$ 225,829	$ 0	$ 807,158	$ (348)	$ (580,981)

- Definition

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

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+ Details

Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares authorized (in shares)	433,000	0	0
Shares available for future issuance (in shares)		659,608
Term to authorize additional shares		10 years
Percentage of outstanding capital stock		5.00%
Shares authorized (in shares)		642,722
Options exercised (in shares)		0	52,450
Options granted, weighted-average grant date fair value (in dollars per share)		$ 8.74	$ 103.83
Share-based payment arrangement, expense		$ (18,166)	$ (30,441)
Unrecognized compensation cost		$ 22,400	$ 55,000
Unrecognized compensation cost, recognition period		1 year 4 months 20 days	1 year 11 months 23 days
Options granted (in shares)		271,921	300,707
Minimum number of additional shares to be authorized (in shares)	123,700
Stock options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield		0.00%	0.00%
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment arrangement, expense		$ (4,200)
Unrecognized compensation cost		$ 5,100	$ 10,600
Options granted (in shares)		4,796	14,762
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of outstanding capital stock	1.00%
Shares authorized (in shares)	61,850
Weighted Average \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 months 13 days	3 years 2 months 1 day
Share-based Payment Arrangement, Tranche One \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years
Share-based Payment Arrangement, Tranche One \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		1 year
2018 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)		209,722

Corporate Restructuring

12 Months Ended

Dec. 31, 2023

Restructuring and Related Activities [Abstract]

Corporate Restructuring

In December 2022, the Company’s Board of Directors approved to implement a strategic prioritization of the Company’s preclinical and clinical development programs. The strategy was designed to reduce costs and reallocate resources to focus on advancing the Company’s CoStAR platform and other next-generation tumor infiltrating lymphocyte (TIL) technologies. As part of the strategy, the Company’s ITIL-168 development program was discontinued, and the Company reduced its U.S. workforce by approximately 60%.

In January 2023, the Company announced the consolidation of the ITIL-306 Phase 1 clinical trial and related manufacturing of CoStAR-TIL operations in Manchester, UK and stopped recruiting for the ITIL-306-201 clinical trial. The December 2022 and January 2023 events are collectively referred to as (the “Plan”).

In January 2024, the Company’s Board of Directors approved the 2024 Plan that includes closing the Company’s Manchester, UK manufacturing facility and clinical trial operations and cessation of the Company’s ITIL-306-202 clinical trial. The Company expects to record restructuring and impairment charges in 2024.

In connection with the 2024 Plan, the Company currently estimates that it will incur charges of up to $6.1 million, including employee termination costs, severance and other benefits, and contract termination costs. The charges that the Company expects to incur in connection with the 2024 Plan are subject to a number of assumptions, and actual results may differ materially. The Company may also incur additional costs not currently contemplated due to events that may occur as a result of, or that are associated with, the 2024 Plan.

Restructuring and Impairment Charges

As a result of the Plan, in the year ended December 31, 2023 and 2022, the Company recorded restructuring and impairment charges of approximately $72.0 million and $23.2 million, respectively, within the restructuring and impairment charges line item within the consolidated statements of operations and comprehensive loss. These

charges relate to asset impairments, contract terminations, severance payments and other employee-related costs incurred. The following table summarizes the restructuring and impairment charges by category (in thousands):


	Year Ended December 31,
	2023		2022
Asset impairment for goodwill and intangible assets	$	—	$	15,826
Asset impairment for leasehold improvements	2,644		1,202
Asset impairment for other fixed assets	—		705
One-time employee termination benefits	1,844		2,995
Building and construction work in progress impairment	41,542		—
Contract terminations expense	1,987		2,439
Right-of-use asset impairment	7,724		—
Impairment of long-lived assets held for sale	16,271		—
Total restructuring and impairment charges	$	72,012	$	23,167

Restructuring Liability

As a result of the Plan, the restructuring liability was recorded in the consolidated balance sheets under “Accrued expenses and other current liabilities” and were measured at the amount expected to be paid. During the year ended December 31, 2023, the Company paid $5.4 million of restructuring costs and expects to pay the remainder of the restructuring costs within the next 12 months. The following table shows the liability related to the Plan (in thousands):


	Employee Benefits		Contract terminations		Total
Restructuring liability ending December 31, 2022	$	2,995	$	2,439	$	5,434
Payments	(4,543)		(893)		(5,436)
Additions, net	1,548		1,590		3,138
Restructuring liability balance as of December 31, 2023	$	—	$	3,136	$	3,136

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Presentation

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying consolidated financial statements include but are not limited to the fair value of contingent consideration payable, assets held for sale, fair value of the Company's building, contract terminations, and the estimation of fair value of goodwill and in-process research and development (IPR&D) intangible assets and associated impairment charges. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates.

Concentration of Credit Risk

Financial Instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, restricted cash, marketable securities and long-term investments. The Company's cash and cash equivalents are held by two financial institutions in the United States (“U.S.”) and one financial institution in the United Kingdom (“UK”), which management believes to be financially sound, and accordingly, minimal credit risk exists with respect to the financial institutions. At times, the Company's deposits held in the U.S. and UK may exceed the Federal Depository Insurance Corporation and Financial Services Compensation Scheme, respectively, insured limits. During the years ended December 31, 2023 and 2022, the Company has not experienced any credit losses in such accounts or marketable securities.

Risks and Uncertainties

The Company is subject to a number of risks similar to other development-stage biopharmaceutical companies, including but not limited to, dependency on the clinical and commercial success of its product candidates, ability to obtain regulatory approval of its product candidates, uncertainty of broad adoption of its approved products, if any, by physicians and patients, manufacturing, the need to obtain adequate additional funding, significant competition, and protection of its intellectual property portfolio.

Reverse Stock Split

Effective December 7, 2023, the Company effected a 1-for-20 reverse stock split of its outstanding shares of common stock. Where applicable, all share and per share amounts in this Annual Report have been adjusted to reflect the effect of the reverse stock split.

Segments

Operating segments are identified as components of an entity for which separate discrete financial information is available and that is regularly reviewed by the chief operating decision-maker in deciding how to allocate resources to an individual segment and in assessing performance. The Company has determined it operates in a single operating segment and has one operating segment.

Cash, Cash Equivalents, Restricted Cash, Marketable Securities and Long-Term Investments

The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. Cash equivalents include amounts invested in money market accounts.

The Company did not have restricted cash on the consolidated balance sheet as of December 31, 2022. Restricted cash consists of a cash reserve which serves as collateral for the Company’s construction loan and is classified within Restricted cash on the consolidated balance sheet as of December 31, 2023.

The Company’s investments in marketable securities and long-term investments have been classified and accounted for as available-for-sale. The Company classifies its maturities as either short-term or long-term based on each instrument's underlying contractual maturity date, which are carried at their fair values based on the quoted market prices of the securities. Unrealized gains and losses are reported as accumulated other comprehensive income (loss). Realized gains and losses on available-for-sale securities are included in net loss in the period earned or incurred. As of December 31, 2023 and 2022, marketable securities consisted of U.S. Treasury bills.

Short-term and long-term marketable securities are recorded at their estimated fair value. The Company periodically reviews whether its securities may be other-than-temporarily impaired, including whether or not (i) the Company has the intent to sell the security or (ii) it is more likely than not that the Company will be required to sell the security before its anticipated recovery. If one of these factors is met, the Company will record an impairment loss associated with its impaired investment. The impairment loss will be recorded as a write-down of investments in the consolidated balance sheets and a realized loss within other expense in the consolidated statements of operations

and comprehensive loss. For the year ended December 31, 2023 and 2022, there were no impairment losses for the investments.

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


	December 31,
	2023		2022
Cash and cash equivalents	$	9,195	$	43,716
Restricted cash	1,501		—
Cash, cash equivalents and restricted cash	$	10,696	$	43,716

Fair Value Measurement

Assets and liabilities recorded at fair value on a recurring basis in the balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value maximize the use of observable inputs and minimize the use of unobservable inputs. The Company measures fair value based on a three-tier hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows:

Level 1 —Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 2 —Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable for the assets or liabilities. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active.

Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

In determining fair value, the Company utilize quoted market prices, or valuation techniques that maximize the use of unobservable inputs to the extent possible as well as considers counterparty credit risk in its assessment of fair value.

Property, Plant and Equipment, Net

Property, plant and equipment, with the exception of land, is stated at cost less accumulated depreciation. Depreciation is computed on a straight-line basis over the estimated useful lives of the related assets. Maintenance and repairs are charged to operations as incurred. Upon sale or retirement of assets, the cost and related accumulated depreciation are removed from the balance sheets and the resulting gain or loss is reflected in the consolidated statement of operations and comprehensive loss. The estimated useful lives of the Company’s property, plant and equipment are as follows:


Laboratory equipment			5 years
Manufacturing equipment			5 years
Office and computer equipment			3 years
Building			35 years
Leasehold improvements			Shorter of remaining lease term or estimated useful life

The Company owns land and buildings and as described in Note 3, the clinical and commercial manufacturing building has been completed and is ready for its intended use. A variety of costs were incurred in the development of a property. After determination is made to capitalize a cost, it is allocated to the specific component of a project that is benefited. The capitalized costs include pre-construction costs essential to the development of the property, development costs, and construction costs. When the Tarzana development project was completed and available for occupancy, the Company ceased capitalization of costs other than costs to improve the functionality or extend the useful lives of property, plant and equipment included as part of the project. During the year ended December 31, 2023, the Company recorded a building impairment of $41.5 million recognized in the consolidated statements of operations and comprehensive loss in the line item “restructuring and impairment charges.” See Note 3 for more information.

Assets Held for Sale

The Company classifies long-lived assets or disposal groups to be sold as held for sale in the period in which all of the following criteria are met: management, having the authority to approve the action, commits to a plan to sell the asset or disposal group; the asset or disposal group is available for immediate sale in its present condition subject only to terms that are usual and customary for sales of such assets or disposal group; the sale of the asset or disposal group is probable, and transfer of the asset or disposal group is expected to qualify for recognition as a completed sale within one year, except if events or circumstances beyond the Company’s control extend the period of time required to sell the asset or disposal group beyond one year; the asset or disposal group is being actively marketed for sale at a price that is reasonable in relation to its current fair value; and actions required to complete the plan to sell have been initiated.

The Company initially measures a long-lived asset or disposal group that is held for sale at the lower of its carrying value or fair value less any costs to sell. Fair value is estimated by the Company through evaluations of quoted market prices received for other comparable held for sale assets sold by the Company. Any loss resulting from this measurement is recognized in the period in which the held for sale criteria are met. Conversely, gains are not recognized on the sale of a long-lived asset or disposal group until the date of sale. The Company assesses the fair value of a long-lived asset or disposal group less any costs to sell each reporting period it remains classified as held for sale and reports any subsequent changes as an adjustment to the carrying value of the asset or disposal group, as long as the new carrying value does not exceed the carrying value of the asset at the time it was initially classified as held for sale. Upon determining that a long-lived asset or disposal group meets the criteria to be classified as held for sale, the Company ceases depreciation and reports long-lived assets in the line item “assets held for sale” in its consolidated balance sheet. To date, the Company has recorded impairment losses on assets held for sale associated with the Plan. During the year ended December 31, 2023, the Company recognized a non-cash impairment charge of $16.3 million and sold remaining assets held for sale for $1.6 million. The non-cash impairment charge was recorded in the consolidated statements of operations and comprehensive loss in the line item “restructuring and impairment charges.” See Note 12 for more information.

Impairment of Long-Lived Assets

The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable or that the useful life is shorter than originally estimated. Recoverability of assets is measured by comparing the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset over its remaining useful life. If such assets are impaired, the impairment recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. If the useful life is shorter than originally estimated, the Company depreciates or amortizes the remaining carrying value over the revised shorter useful life. Assets to be disposed of by sale are reflected at the lower of their carrying amount or fair value less costs to sell. To date, the Company has recorded impairment losses on long-lived assets associated with a sustained decrease in the Company’s stock price and implementation of the Plan. The Company recognized a non-cash impairment charge of $68.2 million during the year ended December 31, 2023 and $1.9 million during the year ended December 31, 2022. The impairment charge was recorded in the consolidated statements of operations and comprehensive loss in the line item “restructuring and impairment charges.” See Note 12 for more information.

Business Combinations

The Company evaluates acquisitions of assets and related liabilities and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen to determine if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If the screen is met, the transaction is accounted for as an asset acquisition. If the screen is not met, further determination is required as to whether or not the Company has acquired inputs and processes that have the ability to create outputs which would meet the requirements of a business.

The Company accounts for its business combinations using the acquisition method of accounting which requires recognition and measurement of all identifiable assets acquired and liabilities assumed at their full fair value as of the date it obtains control. The Company has determined the fair value of assets acquired and liabilities assumed based upon management's estimates of the fair values of assets acquired and liabilities assumed in the acquisitions. Goodwill represents the excess of the purchase price over the fair value of the net tangible and identifiable assets acquired. The Company accounts for contingent considerations at the acquisition-date fair value as part of the consideration transferred in the transaction and remeasures at fair value for each reporting period.

While management has used its best estimates and assumptions to measure the fair value of the identifiable assets acquired and liabilities assumed at the acquisition date, these estimates are inherently uncertain and subject to refinement. As a result, during the measurement period, not to exceed one year from the date of acquisition, any changes in the estimated fair values of the net assets recorded for the acquisition will result in an adjustment to goodwill. Upon the conclusion of the measurement period of final determination of the values of assets acquired or liabilities assumed, whichever comes first, the Company records any subsequent adjustments to the consolidated statements of operations and comprehensive loss. Acquisition-related costs, such as legal and consulting fees, are expensed as incurred.

The Company accounts for an asset acquisition by recognizing net assets based on the cost to the acquiring entity on a relative fair value basis, which includes transaction costs in addition to consideration given. Goodwill is not recognized in an asset acquisition; any excess consideration transferred over the fair value of the net assets acquired is allocated to the non-monetary identifiable assets and liabilities assumed based on relative fair values. Acquired IPR&D is expensed as incurred provided there is no alternative future use.

Goodwill and other Indefinite Lived Intangible Assets

Indefinite-lived intangible assets consist of goodwill and IPR&D acquired in a business combination.

Goodwill represents the excess of the purchase price over the fair value of the net tangible and intangible assets acquired in a business combination. Goodwill is not amortized but is tested for impairment at least annually or more frequently if a triggering event occurs. The Company’s impairment tests are based on a single operating segment and reporting unit structure. If the carrying value of the reporting unit exceeds its fair value, an impairment charge is recognized for the excess of the carrying value of the reporting unit over its fair value (see Note 12).

IPR&D assets represent the fair value of incomplete research and development projects that had not reached technological feasibility as of the date of acquisition; initially, these are classified as IPR&D and are not subject to amortization. Once these research and development projects are completed, the asset balances are transferred from IPR&D to acquisition-related developed technology and are subject to amortization from this point forward. The Company reviews IPR&D for possible impairment annually or more frequently if events or changes in circumstances indicate that carrying amount may not be recoverable. Significant assumptions inherent in the evaluation and measurement of impairment include, but are not limited to, external factors such as industry and economic trends, and internal factors such as changes in the Company’s business strategy and the Company’s forecasts for specific projects (see Note 12). During the year ended December 31, 2022, there was $15.8 million in impairment of Goodwill & IPR&D recognized in the consolidated statement of operations and comprehensive loss in the line item “restructuring and impairment charges”.

Grant Proceeds

The Company receives government grants in the UK for the furtherance of certain research and development projects. Grant proceeds are recognized when all conditions of such grants are fulfilled or there is a reasonable assurance that they will be fulfilled. Grant proceeds are classified as a reduction of research and development expenses. For the years ended December 31, 2023 and 2022, $0.1 million and $1.6 million, of grant proceeds were recognized in research and development expenses on the Company’s consolidated statements of operations and comprehensive loss, respectively.

Research and Development Expenses

Research and development (“R&D”) costs are expensed as incurred. Advance payments for research and development activities are deferred as prepaid expenses, classified as current or noncurrent on the Company’s consolidated balance sheets based on the estimated timing the related services will be performed and are expensed as the related services are performed. Costs incurred by third parties pursuant to contracts with research institutions and clinical research organizations are expensed as the contracted work is performed. The Company accrues for costs incurred as the services are being provided by monitoring the status of the trial or project and the invoices received from the external service providers. The Company adjusts its accrual as actual costs become known. If the actual timing of the performance of services or the level of effort varies significantly from the estimate, the Company will adjust the accrual accordingly. The Company has not experienced any material differences between accrued costs and actual costs incurred since its inception.

Research and development expenses are presented net of government grants, as described above, and R&D tax and expenditure credits from the UK government, which are recognized over the period necessary to match the reimbursement with the related costs when it is probable that the Company has complied with any conditions attached and will receive the reimbursement. Reimbursable R&D tax and expenditure credits were $3.1 million in the years ended December 31, 2023 and 2022, respectively.

Stock-Based Compensation

The Company measures its stock-based awards granted to employees, non-employee directors, consultants and independent advisors based on the estimated grant date fair value of the awards. For stock-based awards with only service conditions, compensation expense is recognized over the requisite service period using the straight-line method. For stock-based awards that include performance conditions, compensation expense is not recognized until the performance condition is probable to occur. The Company uses the Black-Scholes option pricing model to estimate the fair value of its stock-based awards. The Black-Scholes option pricing model requires the Company to make assumptions and judgements about the variables used in the calculations, including the fair value of common stock, expected term, expected volatility of the Company’s common stock, risk-free interest rate and expected dividend yield. The Company accounts for forfeitures of stock-based awards as they occur.

Income Taxes

Income taxes are accounted for using the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts or existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period of enactment. The Company records a valuation allowance to reduce deferred tax assets to an amount expected to be realized.

The Company recognizes the tax benefit from an uncertain tax position if it is more likely than not that the tax position will be sustained upon examination by the tax authorities, based on the merits of the position. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits.

Foreign Currency

The Company’s reporting currency is the U.S. dollar. The functional currency of the Company’s subsidiary located in the United Kingdom is the British pound sterling. Balance sheets prepared in the functional currency are translated to the reporting currency at exchange rates in effect at the end of the accounting period, except for stockholders’ deficit accounts, which are translated at rates in effect when these balances were originally recorded. Revenue and expense accounts are translated using an average exchange rate in effect during the period. The resulting foreign currency translation adjustments are recorded as a separate component of accumulated other comprehensive loss in the accompanying consolidated balance sheets.

Gains and losses resulting from exchange rate changes on intercompany transactions denominated in a currency other than the local currency are included in earnings as incurred as the related amounts are expected to be repaid in the foreseeable future.

Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of the Company’s common stock outstanding for the period, without consideration for potential dilutive shares of common stock. For purposes of the diluted net loss per share calculation, convertible preferred stock and common stock options are considered to be potentially dilutive securities. Diluted net loss per share is the same as basic net loss per share for each period presented since the effects of potentially dilutive securities are antidilutive given the net loss of the Company.

Comprehensive Loss

Comprehensive loss is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. For the year ended December 31, 2023 and 2022, comprehensive loss consists of foreign currency translation adjustments and unrealized loss on available-for-sale securities net of tax.

Leases

The Company adopted as its new standard Accounting Standards Updated (“ASU”) No. 2016-2, Leases effective January 1, 2022 using the modified retrospective transition approach. For its long-term operating leases, the Company recognizes a right-of-use asset and a lease liability on its consolidated balance sheets.

The Company determines if an arrangement is or contains a lease at contract inception by assessing whether the arrangement contains an identified asset and whether the lessee has the right to control such asset. Lessees are required to classify leases as either finance or operating leases and to record a right-of-use (“ROU”) asset and a lease liability for all leases with a term greater than 12 months regardless of the lease classification. The lease classification will determine whether the lease expense is recognized based on an effective interest rate method or on a straight-line basis over the term of the lease. The Company determines the initial classification and measurement of its ROU assets and lease liabilities at the lease commencement date and thereafter if modified. For leases with a term greater than 12 months, the Company records the lease liability at the present value of lease payments over the term. The term of the Company’s leases equals the non-cancellable period of the lease, including any rent-free periods provided by the lessor, and also includes options to extend or terminate the lease that the Company is reasonably certain to exercise. The ROU asset equals the carrying amount of the related lease liability, adjusted for any lease payments made prior to lease commencement, any deferred rent upon adoption, and lease incentives provided by the lessor.

The Company has elected, for all classes of underlying assets, not to recognize ROU assets and lease liabilities for leases with a term of 12 months or less. Lease cost for short-term leases is recognized on a straight-line basis over the lease term. The Company estimates its incremental borrowing rate based on the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment.

Variable lease payments are expensed as incurred and do not factor into the measurement of the applicable ROU asset or lease liability. Lease payments may be fixed or variable; however, only fixed payments are included in the Company’s lease liability calculation. Lease costs for the Company’s operating leases are recognized on a straight-line basis within operating expenses over the lease term. The Company’s lease agreements may contain non-lease components such as common area maintenance, operating expenses or other costs, which are expensed as incurred for all classes of assets. The Company’s leases do not contain any residual value guarantees.

See Note 7, Commitments and Contingencies, regarding the Company’s leases, below.

Recent Accounting Pronouncements Adopted

In February 2016, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2016-02, Leases (Topic 842) which supersedes FASB ASC Topic 840, Leases (Topic 840) and provides principles for the recognition, measurement, presentation, and disclosure of leases for both lessees and lessors. Leases with a term of twelve months or less will be accounted for similar to existing guidance for operating leases. The Company adopted the new standard effective January 1, 2022 using the modified retrospective transition approach. Upon adoption on January 1, 2022, the Company recognized ROU assets and lease liabilities totaling $12.5 million and $7.6 million, respectively, to reflect the present value of remaining lease payments under existing lease arrangements. The Company applied the modified retrospective transition approach and did not recast prior periods. As permitted by the standard, the Company elected the transition practical expedient package, which among other things, allows the carryforward of historical lease classifications. The Company’s new accounting policies around leases are described in Leases, above, and in Note 7, Commitments and Contingencies.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Additionally, the FASB issued ASU No. 2019-04, Codification Improvements to Topic 326, in April 2019 and ASU 2019-05, Financial Instruments — Credit Losses (Topic 326) — Targeted Transition Relief, in May 2019. The amendments affect loans, debt securities, trade receivables, net investments in leases, off-balance-sheet credit exposures, reinsurance receivables, and any other financial assets not excluded from the scope that have the contractual right to receive cash. The Company adopted this standard on January 1, 2022. The adoption of this standard did not have a material impact on the Company's consolidated financial statements and disclosures.

In December 2019, the FASB issued ASU No. 2019-12. Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. The standard simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740 and also improves consistent application by clarifying and amending existing guidance. The Company adopted this standard on January 1, 2022. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements and disclosures.

Recent Accounting Pronouncements Not Yet Adopted

In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures which requires public entities to disclose information about their reportable segments’ significant expenses on an interim and annual basis. ASU 2023-07 is effective for annual periods 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 of this ASU 2023-07 on its consolidated financial statements and related disclosures.

In December 2023, the FASB issued ASU 2023-09 "Income Taxes (Topics 740): Improvements to Income Tax Disclosures" to expand the disclosure requirements for income taxes, specifically related to the rate reconciliation and income taxes paid. ASU 2023-09 is effective for annual periods beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the impact of this ASU 2023-09 on its consolidated financial statements and related disclosures.

Stock-Based Compensation - Valuation Assumption (Details) - Stock option - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum	76.19%	72.08%
Expected volatility, maximum	77.56%	74.30%
Risk-free interest rate, minimum	3.54%	1.61%
Risk-free interest rate, maximum	4.01%	4.21%
Expected dividend yield	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 3 months 10 days	6 years 1 month 6 days
Fair Value of Common Stock (in dollars per share)	$ 11.18	$ 26.60
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 29 days	6 years 3 months 3 days
Fair Value of Common Stock (in dollars per share)	$ 15.20	$ 268.20

Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
U.S. federal taxes at statutory rate	21.00%	21.00%
Stock-based compensation	(1.80%)	(2.00%)
Permanent differences and other	0.80%	0.20%
Statutory tax rate differences	3.40%	1.10%
Change in valuation allowance	(23.40%)	(19.40%)
Total	0.00%	0.90%

Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Mar. 31, 2020
Goodwill [Line Items]
Impairment of goodwill and intangible assets	$ 0	$ 15,826
Immetacyte
Goodwill [Line Items]
Percentage of share capital acquired			100.00%
Impairment of goodwill and intangible assets		5,700
Impairment of intangibles		$ 10,100

- 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 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 24
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482548/350-20-55-24

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1A

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
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-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-2

+ Details

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share

The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share for the periods presented due to their anti-dilutive effect:


	December 31,
	2023	2022
Stock options to purchase common stock	799,622	1,053,997
Total	799,622	1,053,997

Commitments and Contingencies - Lease Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Short-term lease cost	$ 375	$ 1,155
Operating lease cost	2,185	4,852
Variable lease cost	1,170	1,096
Total lease cost	3,730	7,103
Cash paid for operating lease liabilities	2,308	3,258
Operating lease right-of-use assets	2,387	12,457
Current operating lease liabilities	1,750	2,381
Non-current operating lease liabilities	$ 2,877	$ 5,171
Weighted-average remaining lease term (in years)	2 years 7 months 6 days	3 years 3 months 14 days
Weighted-average discount rate	6.75%	6.75%

Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Schedule of Marketable Securities and Long-Term Investments

Marketable securities classified as available-for-sale at December 31, 2023 and 2022 consisted of the following (in thousands):


	December 31, 2023
	Maturity	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. Treasury bills	Less than one year	$	141,075	$	86	$	—	$	141,161
U.S. Treasury bills	Between one and two years	23,134		27		—		23,161
		$	164,209	$	113	$	—	$	164,322


	December 31, 2022
	Maturity	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. Treasury bills	Less than one year	$	217,669	$	—	$	(465)	$	217,204

- 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
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-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
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-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
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-SubTopic 10
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-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
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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
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-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-Subparagraph (aaa)
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Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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

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

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

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

+ Details

Balance Sheet Components

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Balance Sheet Components

Property, Plant and Equipment, Net

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


	December 31,
	2023		2022
Land	$	31,243	$	31,243
Laboratory equipment	8,291		19,050
Buildings	102,433		32,778
Office and computer equipment	831		4,969
Leasehold improvements	1,424		4,340
Manufacturing equipment	2,017		8,803
Vehicles	—		64
Construction work-in-progress	—		104,117
Total property, plant and equipment, gross	146,239		205,364
Less: accumulated depreciation	(7,555)		(8,484)
Total property, plant and equipment, net	$	138,684	$	196,880

For the years ended December 31, 2023 and 2022 the Company recognized depreciation expense of $4.8 million and $6.0 million, respectively, in the consolidated statements of operations and comprehensive loss.

The Company’s contractual commitments for its Tarzana development project are limited to unreimbursed spend by the general contractor and as such, as of December 31, 2023 and 2022, $0.2 million and $4.0 million, respectively, was contractually committed to the development of this project.

During the year ended December 31, 2023 and 2022, the Company capitalized interest of $2.4 million and $1.2 million, respectively, related to qualifying expenditures for construction work-in-progress for its Tarzana manufacturing facility.

During the year ended December 31, 2023, the Company determined there were indicators of impairment on its buildings and construction work-in-progress asset groups. As a result, the Company performed recoverability tests on these groups and concluded these assets’ undiscounted cash flows did not exceed their carrying values. The Company estimates the fair value of its buildings through a combination of an income-based approach and a market-based approach. The income-based approach is dependent on specific assumptions such as market rental rates, capitalization rates and discount rates which are Level 3 inputs. The market-based approach utilizes observable data, such as comparable building sales and occupancy rates which are Level 2 inputs. The fair value of its buildings were determined to be $132.1 million, below the carrying value of $173.7 million. This led to an impairment of $41.5 million recognized in the consolidated statements of operations and comprehensive loss in the line item “restructuring and impairment charges.”

Accrued Expenses and Other Current Liabilities

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


	December 31,
	2023		2022
Accrued construction costs	$	—	$	12,359
Accrued compensation and benefits	1,026		3,273
Accrued operational expenses	1,412		2,203
Accrued restructuring costs	3,136		5,434
Accrued research, development and clinical trial expenses	1,833		3,827
Operating lease liabilities, current	1,750		2,381
Other current liabilities	190		592
Total accrued expenses and other current liabilities	$	9,347	$	30,069

Financial Instruments - Schedule of Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Amortized Cost [Abstract]
Amortized Cost	$ 164,209
Unrealized Gains [Abstract]
Unrealized Gains	113
Unrealized Losses [Abstract]
Unrealized Losses	0
Fair Value [Abstract]
Fair Value	164,322
U.S. Treasury bills
Amortized Cost [Abstract]
Less than one year	141,075	$ 217,669
Between one and two years	23,134
Unrealized Gains [Abstract]
Less than one year	86	0
Between one and two years	27
Unrealized Losses [Abstract]
Less than one year	0	(465)
Between one and two years	0
Fair Value [Abstract]
Less than one year	141,161	$ 217,204
Between one and two years	$ 23,161

Income Taxes - Current and Deferred Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Current provision for income taxes:
Domestic	$ 0	$ 13
Foreign	0	0
Total current	0	13
Deferred tax provision:
Domestic	0	0
Foreign	0	(2,086)
Total deferred	0	(2,086)
Total income tax expense (benefit)	$ 0	$ (2,073)

- Definition

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

+ References + Details

Commitments and Contingencies - Interest Expense Related to the Loan (Details) - Secured Mortgage Loan - Loans Payable - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Interest Expense Related to the Loan [Line Items]
Contractual interest expense	$ 4,214	$ 1,302
Amortization of debt issuance cost	995	581
Total interest expense related to the Loan	$ 5,209	$ 1,883

Income Taxes - Loss before Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Domestic	$ (144,570)	$ (183,994)
Foreign	(11,517)	(41,256)
Loss before income tax benefit	$ (156,087)	$ (225,250)

- Definition

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

+ References

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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 32
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
-Paragraph 32
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

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

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 940
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481913/940-20-25-1

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

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

+ Details

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following tables provide information by level for assets and liabilities that are measured at fair value on a recurring and nonrecurring basis:


	As of December 31, 2023
	Level 1		Level 2		Level 3		Total
	(In thousands)
Financial Assets
Money market funds	$	5,684	$	—	$	—	$	5,684
U.S. Treasury bills	—		164,322		—		164,322
Derivative financial instrument	—		1,055		—		1,055
Total	$	5,684	$	165,377	$	—	$	171,061
Financial Liabilities
Contingent consideration	$	—	$	—	$	4,858	$	4,858

	As of December 31, 2022
	Level 1		Level 2		Level 3		Total
	(In thousands)
Financial Assets
Money market funds	$	22,830	$	—	$	—	$	22,830
U.S. Treasury bills	—		217,204		—		217,204
Derivative financial instrument	—		2,202		—		2,202
Total	$	22,830	$	219,406	$	—	$	242,236
Financial Liabilities
Contingent consideration	$	—	$	—	$	8,242	$	8,242

Schedule of Reconciliation of Level 3 Financial Liabilities

The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands):


	Year Ended December 31, 2023
Fair value, beginning balance	$	8,242
Change in fair value	(3,384)
Development milestone achieved	—
Fair value, ending balance	$	4,858


	Year Ended December 31, 2022
Fair value, beginning balance	$	12,321
Change in fair value	(2,879)
Development milestone achieved	(1,200)
Fair value, ending balance	$	8,242

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net loss	$ (156,087)	$ (223,177)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	18,166	30,441
Non-cash lease expense	640	1,765
Foreign exchange remeasurement (gain) loss	(680)	1,391
Impairment of goodwill and intangible assets	0	15,826
Impairment of fixed assets	60,088	1,741
Impairment of right-of-use assets	7,724	166
Change in fair value of contingent consideration	(3,384)	(2,879)
Depreciation	4,756	5,987
Accretion on invested securities	(6,775)	(1,027)
Non-cash interest expense	1,015	(198)
Change in fair value of derivative instrument	1,147	(1,414)
Loss on disposals of property and equipment	377	0
Other, net	0	780
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(241)	(430)
Other long-term assets	1,543	354
Accounts payable	(1,129)	(1,806)
Operating lease liabilities	(1,404)	(335)
Long-term liabilities	(12)	1,628
Accrued restructuring costs	(2,298)	5,434
Accrued expenses and other current liabilities	(5,475)	(14,411)
Net cash used in operating activities	(82,029)	(180,164)
Cash flows from investing activities:
Purchase of marketable securities	(301,466)	(665,046)
Maturities of marketable securities	361,700	865,350
Purchases of property, plant and equipment	(20,663)	(84,589)
Purchase of derivative financial instrument	0	(1,174)
Cash received from held for sale assets	1,557	0
Net cash provided by investing activities	41,128	114,541
Cash flows from financing activities:
Principal payments on loan	(587)	0
Proceeds from exercise of stock options	0	1,548
Proceeds from note payable	8,669	70,338
Net cash provided by financing activities	8,082	71,886
Net (decrease) increase in cash, cash equivalents, and restricted cash	(32,819)	6,263
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(201)	(637)
Cash, cash equivalents and restricted cash—beginning of period	43,716	38,090
Cash, cash equivalents and restricted cash—end of period	10,696	43,716
Supplemental disclosure of cash flow information:
Cash paid for interest, net of amounts capitalized	6,639	1,068
Supplemental disclosure of noncash information:
Purchases of property, plant and equipment in accounts payable and accrued expenses and other current liabilities	$ 0	$ 12,433

Commitments and Contingencies - Net Carrying Amount of the Liability Component of the Loan (Details) - Secured Mortgage Loan - Loans Payable - USD ($)	Dec. 31, 2023	Dec. 31, 2022	Jun. 30, 2022
Debt Instrument [Line Items]
Principal amount	$ 82,837,000	$ 74,755,000	$ 52,100,000
Unamortized debt issuance cost	(1,410,000)	(2,405,000)
Net carrying amount	$ 81,427,000	$ 72,350,000

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482900/835-30-50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
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-Paragraph 1
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Subparagraph (SX 210.12-04(a))
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
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Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
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-Name Accounting Standards Codification
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Reference 6: http://www.xbrl.org/2003/role/exampleRef
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+ Details

- Definition

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

+ References + Details

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Operating Loss Carryforwards [Line Items]
Increase in valuation allowance	$ 40,400
Uncertain tax positions	2,339	$ 2,339
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	319,500
Federal \| Research & Development credits
Operating Loss Carryforwards [Line Items]
Tax credits carryforward	4,100
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	173,300
State \| Research & Development credits
Operating Loss Carryforwards [Line Items]
Tax credits carryforward	$ 3,700

Income Taxes - Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 88,408	$ 58,259
Research and development credits	4,915	4,915
Accrued compensation and benefits	107	352
Stock-based compensation	3,570	2,781
Capitalized research and development	19,432	20,966
Other temporary differences	8,279	517
Intangible assets	97	0
Fixed assets	1,496	0
Other	335	0
Total gross deferred tax assets	126,639	87,790
Less: valuation allowance	(126,639)	(86,285)
Total deferred tax assets, net	0	1,505
Deferred tax liabilities:
Intangible assets	0	0
Fixed assets	0	(420)
Other	0	(1,085)
Total gross deferred tax liabilities	0	(1,505)
Net deferred tax liabilities	$ 0	$ 0

Goodwill and Intangible Assets	12 Months Ended
Goodwill and Intangible Assets	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets In March 2020, the Company acquired 100% of the share capital of Immetacyte. The acquisition was accounted for as a business combination and, accordingly, the total fair value of purchase consideration was allocated to the tangible and intangible assets acquired and liabilities assumed based on their fair values on the acquisition date. Due to the Company’s pre-commercialization stage, many of the processes and methods used in the production of TILs were still in experimental development and pre-clinical stages. As a result of the 2022 Plan, the Company determined that the carrying amount of its goodwill and intangible assets exceeded its fair value. The fair value was determined based on a discounted cash flow analysis, which took into account multiple factors including future cash flows, discount rates, and market conditions. As a result of this analysis, the Company recognized a non-cash impairment charge of $5.7 million for goodwill and $10.1 million for intangible assets during the year ended December 31, 2022. The impairment charge was recorded in the consolidated statements of operations and comprehensive loss in the line item “restructuring and impairment charges.”

Balance Sheet Components - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 4,800	$ 6,000
Carrying value	146,239	205,364
Impairment recognized	$ (60,088)	(1,741)
Impairment, Long-Lived Asset, Held-for-Use, Statement of Income or Comprehensive Income [Extensible Enumeration]	Total restructuring and impairment charges
Construction work-in-progress
Property, Plant and Equipment [Line Items]
Interest related to qualifying expenditures	$ 2,400	1,200
Carrying value	0	104,117
Buildings and Construction in Progress
Property, Plant and Equipment [Line Items]
Fair value of long lived assets, held for use	132,100
Carrying value	173,700
Buildings and Construction in Progress \| Level 3
Property, Plant and Equipment [Line Items]
Impairment recognized	(41,500)
Tarzana Land and Building Acquired
Property, Plant and Equipment [Line Items]
Contractual commitment	$ 200	$ 4,000

Summary of Significant Accounting Policies - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Cash and cash equivalents	$ 9,195	$ 43,716
Restricted cash	1,501	0
Cash, cash equivalents and restricted cash	$ 10,696	$ 43,716	$ 38,090

Equity (Details)	Dec. 31, 2023 vote $ / shares shares	Dec. 31, 2022 $ / shares shares	Mar. 24, 2021 $ / shares shares
Equity [Abstract]
Common stock, votes per share \| vote	1
Common stock, shares outstanding (in shares)	6,503,913	6,503,913
Preferred stock authorized (in shares)	10,000,000	10,000,000	10,000,000
Common stock, par value (in dollars per share) \| $ / shares	$ 0.000001	$ 0.000001	$ 0.000001
Convertible preferred stock issued (in shares)	0	0

Balance Sheet Components - Property, Plant and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 146,239	$ 205,364
Less: accumulated depreciation	(7,555)	(8,484)
Total property, plant and equipment, net	138,684	196,880
Land
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	31,243	31,243
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	8,291	19,050
Buildings
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	102,433	32,778
Office and computer equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	831	4,969
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	1,424	4,340
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	2,017	8,803
Vehicles
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	0	64
Construction work-in-progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 0	$ 104,117

Net Loss Per Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss Per Share

The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share for the periods presented due to their anti-dilutive effect:


	December 31,
	2023	2022
Stock options to purchase common stock	799,622	1,053,997
Total	799,622	1,053,997

All outstanding shares of convertible preferred stock were converted on a 1.2-for-1 conversion ratio of shares of common stock on March 23, 2021, the date of the Company’s IPO.

Corporate Restructuring - Restructuring costs by category (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Restructuring Cost and Reserve [Line Items]
Asset impairment for goodwill and intangible assets	$ 15,800
Impairment of right-of-use assets	7,724	$ 166
Total restructuring and impairment charges	72,012	23,167
Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Asset impairment for goodwill and intangible assets	0	15,826
Restructuring charges	(5,400)
Impairment of right-of-use assets	7,724	0
Impairment of Long-Lived Assets to be Disposed of	16,271	0
Total restructuring and impairment charges	72,012	23,167
Restructuring Plan \| One-time employee termination benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,844	2,995
Restructuring Plan \| Contract terminations expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,987	2,439
Restructuring Plan \| Asset impairment for leasehold improvements
Restructuring Cost and Reserve [Line Items]
Asset impairment charges	2,644	1,202
Restructuring Plan \| Asset impairment for other fixed assets
Restructuring Cost and Reserve [Line Items]
Asset impairment charges	0	705
Restructuring Plan \| Building and construction work in progress impairment
Restructuring Cost and Reserve [Line Items]
Asset impairment charges	$ 41,542	$ 0

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating expenses:
Research and development	$ 39,604	$ 141,056
General and administrative	47,553	62,235
Restructuring and impairment charges	72,012	23,167
Total operating expenses	159,169	226,458
Loss from operations	(159,169)	(226,458)
Interest income	8,866	3,655
Interest expense	(5,209)	(1,883)
Other expense, net	(575)	(564)
Loss before income tax benefit	(156,087)	(225,250)
Income tax benefit	0	2,073
Net loss	(156,087)	(223,177)
Other comprehensive income (loss):
Foreign currency translation	(433)	9
Unrealized gain (loss) on available-for-sale securities, net	578	(415)
Net comprehensive loss	$ (155,942)	$ (223,583)
Net loss per share, basic (in dollars per share)	$ (24.00)	$ (34.46)
Net loss per share, diluted (in dollars per share)	$ (24.00)	$ (34.46)
Weighted-average shares used in computing net loss per share, basic (in shares)	6,503,913	6,475,631
Weighted-average shares used in computing net loss per share, diluted (in shares)	6,503,913	6,475,631

Corporate Restructuring - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Restructuring Cost and Reserve [Line Items]
Total restructuring and impairment charges	$ 72,012	$ 23,167
Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Expected restructuring costs remaining	6,100
Total restructuring and impairment charges	72,012	$ 23,167
Restructuring charges	$ (5,400)
UNITED STATES \| Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Workforce reduction percentage		60.00%

- 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

Commitments and Contingencies - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Jun. 30, 2022	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Lessee, Lease, Description [Line Items]
Impairment (gain) loss			$ 7,200,000	$ 0
Loss on termination			500,000	0
Lease termination agreement, amount			400,000
Milestone paid			300,000
Subsequent Event
Lessee, Lease, Description [Line Items]
Additional milestone payments		$ 2,600,000
Future milestones		$ 3,400,000
Restructuring Plan
Lessee, Lease, Description [Line Items]
Restructuring charges			(5,400,000)
One-time employee termination benefits \| Restructuring Plan
Lessee, Lease, Description [Line Items]
Restructuring charges			1,844,000	2,995,000
Contract terminations expense \| Restructuring Plan
Lessee, Lease, Description [Line Items]
Restructuring charges			1,987,000	2,439,000
Non Cancelable Purchase Commitments with Contract Research Organizations \| One-time employee termination benefits \| Restructuring Plan
Lessee, Lease, Description [Line Items]
Restructuring charges				3,000,000
Non Cancelable Purchase Commitments with Contract Research Organizations \| Contract terminations expense \| Restructuring Plan
Lessee, Lease, Description [Line Items]
Restructuring charges			3,100,000	2,400,000
Secured Mortgage Loan
Lessee, Lease, Description [Line Items]
Repayments of debt			(600,000)
Secured Mortgage Loan \| Loans Payable
Lessee, Lease, Description [Line Items]
Initial principal amount	$ 52,100,000		82,837,000	74,755,000
Unamortized debt issuance cost			(1,410,000)	(2,405,000)
Covenant, minimum net worth			85,000,000	85,000,000
Secured Mortgage Loan \| Loans Payable \| SOFR
Lessee, Lease, Description [Line Items]
Basis interest	5.25%
Tarzana Land and Building Acquired
Lessee, Lease, Description [Line Items]
Contractual commitment			$ 200,000	$ 4,000,000
Minimum
Lessee, Lease, Description [Line Items]
Original lease terms			2 years
Maximum
Lessee, Lease, Description [Line Items]
Original lease terms			5 years
Maximum \| Secured Mortgage Loan \| Loans Payable
Lessee, Lease, Description [Line Items]
Additional future principal (upto)	$ 32,900,000

Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands		12 Months Ended
	Dec. 07, 2023	Dec. 31, 2023 USD ($) institution segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Subsidiary, Sale of Stock [Line Items]
Stock split	0.05
Number of segments \| segment		1
Impairment recognized		$ 60,088	$ 1,741
Impairment of long lived asset held for use		68,200	1,900
Impairment of goodwill and intangible assets		15,800
Grant proceeds		100	1,600
Reimbursable research and development tax and expenditure credits		3,100	$ 3,100
Accounting standards update, extensible enumeration			Accounting Standards Update 2016-02 [Member]
Operating lease right-of-use assets		2,387	$ 12,457
Operating lease, liability		$ (4,627)
UNITED STATES \| Geographic Concentration Risk \| Cash and Cash Equivalents
Subsidiary, Sale of Stock [Line Items]
Number of financial institution \| institution		2
UNITED KINGDOM \| Geographic Concentration Risk \| Cash and Cash Equivalents
Subsidiary, Sale of Stock [Line Items]
Number of financial institution \| institution		1
Level 2 \| Buildings and Construction in Progress
Subsidiary, Sale of Stock [Line Items]
Impairment recognized		$ (41,500)
Assets Held for Sale
Subsidiary, Sale of Stock [Line Items]
Impairment of long lived asset held for use		16,300
Sold remaining assets held for sale		$ 1,600
Cumulative Effect, Period of Adoption, Adjustment
Subsidiary, Sale of Stock [Line Items]
Operating lease right-of-use assets				$ 12,500
Operating lease, liability				$ (7,600)

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Geographical Breakdown of Loss before Provision for Income Taxes

The geographical breakdown of loss before provision for income taxes is as follows (in thousands):


	Year Ended December 31,
	2023		2022
Domestic	$	(144,570)	$	(183,994)
Foreign	(11,517)		(41,256)
Loss before income taxes	$	(156,087)	$	(225,250)

Schedule of Components of the Provision for Income Taxes

The components of the provision for income taxes are as follows (in thousands):


	Year Ended December 31,
	2023		2022
Current provision for income taxes:
Domestic	$	—	$	13
Foreign	—		—
Total current	—		13
Deferred tax provision:
Domestic	—		—
Foreign	—		(2,086)
Total deferred	—		(2,086)
Total income tax expense (benefit)	$	—	$	(2,073)

Schedule of Effective Income Tax Rate Reconciliation

The following table presents a reconciliation of the Company’s statutory federal income tax rate and effective tax rate:


	Year Ended December 31,
	2023		2022
U.S. federal taxes at statutory rate	21.0	%	21.0	%
Stock-based compensation	(1.8)	%	(2.0)	%
Permanent differences and other	0.8	%	0.2	%
Statutory tax rate differences	3.4	%	1.1	%
Change in valuation allowance	(23.4)	%	(19.4)	%
Total	—	%	0.9	%

Schedule of Deferred Tax Assets and Liabilities

The components of deferred tax liabilities consist of the following (in thousands):


	Year Ended December 31,
	2023		2022
Deferred tax assets:
Net operating loss carryforwards	$	88,408	$	58,259
Research and development credits	4,915		4,915
Accrued compensation and benefits	107		352
Stock-based compensation	3,570		2,781
Capitalized research and development	19,432		20,966
Other temporary differences	8,279		517
Intangible assets	97		—
Fixed assets	1,496		—
Other	335		—
Total gross deferred tax assets	126,639		87,790
Less: valuation allowance	(126,639)		(86,285)
Total deferred tax assets, net	—		1,505
Deferred tax liabilities:
Intangible assets	—		—
Fixed assets	—		(420)
Other	—		(1,085)
Total gross deferred tax liabilities	—		(1,505)
Net deferred tax liabilities	$	—	$	—

Schedule of Unrecognized Tax Benefits Roll Forward

The components of unrecognized tax benefits consist of the following (in thousands):


Balance at December 31, 2022:	$	2,339
Additions in 2023	—
Balance at December 31, 2023:	$	2,339

Organization and Description of Business	12 Months Ended
Organization and Description of Business	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business Instil Bio, Inc. (the “Company”) is headquartered in Dallas, Texas and was incorporated in the state of Delaware in August 2018. The Company is a clinical-stage biopharmaceutical company focused on developing a pipeline of novel therapies. The Company seeks to in-license/acquire and develop novel therapeutic candidates in diseases with significant unmet medical need. The Company's first program is a tumor infiltrating lymphocyte (TIL) cell therapy for the treatment of cancer, which it acquired in 2020. In December 2022, the Company’s Board of Directors approved a strategic reprioritization of our preclinical and clinical development programs (referred to as the "2022 Plan"). This decision involved reallocating resources to focus on advancing ITIL-306, our CoStAR platform, and other next-generation TIL technologies. In January 2023, the Company approved an additional restructuring plan (referred to as the "2023 Plan") and announced the consolidation of the ITIL-306 Phase 1 clinical trial and related manufacturing of CoStAR-TIL to the Company’s active operations in Manchester, UK and stopped recruiting for the ITIL-306-201 clinical trial. The 2022 Plan and 2023 Plan are collectively referred to as (the “Plan”). On December 13, 2023, the Company entered into an agreement with a third-party to develop an autologous FRα CoStAR TIL, or the Collaboration Product, for potential open-label investigator-initiated trials, or IITs, in non-small cell lung cancer (NSCLC) in China. Initial feasibility studies for the Collaboration Product have been completed and, assuming continued collaboration progress, the next steps would be for the collaborator to lead opening IITs to enroll patients. The Collaboration Product will be manufactured by the collaborator utilizing the Company's proprietary FRα CoStAR construct in the collaborator’s manufacturing process. The collaborator has an option to exclusively license the Collaboration Product in China and Taiwan. In January 2024, concurrent with announcing the collaboration, the Company’s Board of Directors approved an additional restructuring plan (the “2024 Plan”), involving the closure of the Company’s UK manufacturing and clinical operations and cessation of the Company’s ITIL-306 clinical trial. The UK workforce reduction and related restructuring activities are expected to be substantially completed by the first half of 2024. We plan to retain certain key process development, research, and related personnel to advance early-stage pipeline development of CoStAR and other novel TIL technologies, and to support the Company’s collaboration.

Corporate Restructuring - Restructuring Liability (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring liability ending December 31, 2022	$ 5,434
Restructuring liability balance as of December 31, 2023	3,136
2023 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring liability ending December 31, 2022	5,434
Payments	(5,436)
Additions, net	3,138
Restructuring liability balance as of December 31, 2023	3,136
2023 Plan \| Employee Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring liability ending December 31, 2022	2,995
Payments	(4,543)
Additions, net	1,548
Restructuring liability balance as of December 31, 2023	0
2023 Plan \| Contract terminations
Restructuring Cost and Reserve [Line Items]
Restructuring liability ending December 31, 2022	2,439
Payments	(893)
Additions, net	1,590
Restructuring liability balance as of December 31, 2023	$ 3,136

- 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

Corporate Restructuring (Tables)

12 Months Ended

Dec. 31, 2023

Restructuring and Related Activities [Abstract]

Schedule of Total Amount Expected to be Incurred and Liability

The following table summarizes the restructuring and impairment charges by category (in thousands):


	Year Ended December 31,
	2023		2022
Asset impairment for goodwill and intangible assets	$	—	$	15,826
Asset impairment for leasehold improvements	2,644		1,202
Asset impairment for other fixed assets	—		705
One-time employee termination benefits	1,844		2,995
Building and construction work in progress impairment	41,542		—
Contract terminations expense	1,987		2,439
Right-of-use asset impairment	7,724		—
Impairment of long-lived assets held for sale	16,271		—
Total restructuring and impairment charges	$	72,012	$	23,167

Schedule of Realignment Non-cash Charges

The following table shows the liability related to the Plan (in thousands):


	Employee Benefits		Contract terminations		Total
Restructuring liability ending December 31, 2022	$	2,995	$	2,439	$	5,434
Payments	(4,543)		(893)		(5,436)
Additions, net	1,548		1,590		3,138
Restructuring liability balance as of December 31, 2023	$	—	$	3,136	$	3,136

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Schedule of Cash, Cash Equivalents and Restricted Cash


	December 31,
	2023		2022
Cash and cash equivalents	$	9,195	$	43,716
Restricted cash	1,501		—
Cash, cash equivalents and restricted cash	$	10,696	$	43,716

Schedule of Cash, Cash Equivalents and Restricted Cash


	December 31,
	2023		2022
Cash and cash equivalents	$	9,195	$	43,716
Restricted cash	1,501		—
Cash, cash equivalents and restricted cash	$	10,696	$	43,716

Schedule of Useful Lives

The estimated useful lives of the Company’s property, plant and equipment are as follows:


Laboratory equipment			5 years
Manufacturing equipment			5 years
Office and computer equipment			3 years
Building			35 years
Leasehold improvements			Shorter of remaining lease term or estimated useful life

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


	December 31,
	2023		2022
Land	$	31,243	$	31,243
Laboratory equipment	8,291		19,050
Buildings	102,433		32,778
Office and computer equipment	831		4,969
Leasehold improvements	1,424		4,340
Manufacturing equipment	2,017		8,803
Vehicles	—		64
Construction work-in-progress	—		104,117
Total property, plant and equipment, gross	146,239		205,364
Less: accumulated depreciation	(7,555)		(8,484)
Total property, plant and equipment, net	$	138,684	$	196,880

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Concentration of Credit Risk

Risks and Uncertainties

Segments

Cash, Cash Equivalents, Restricted Cash, Marketable Securities and Long-Term Investments

Marketable Securities

and comprehensive loss. For the year ended December 31, 2023 and 2022, there were no impairment losses for the investments.

Fair Value Measurement

Level 1 —Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

Property, Plant and Equipment, Net


Laboratory equipment			5 years
Manufacturing equipment			5 years
Office and computer equipment			3 years
Building			35 years
Leasehold improvements			Shorter of remaining lease term or estimated useful life

Impairment of Long-Lived Assets

Business Combinations

Goodwill and other Indefinite Lived Intangible Assets

Indefinite-lived intangible assets consist of goodwill and IPR&D acquired in a business combination.

Grant Proceeds

Research and Development Expenses

Stock-Based Compensation

See Note 7, Commitments and Contingencies, regarding the Company’s leases, below.

Recent Accounting Pronouncements Adopted

Recent Accounting Pronouncements Not Yet Adopted

Long-lived Assets and Disposal Groups Held for Sale Policy

Assets Held for Sale

Cover - USD ($) $ in Millions	12 Months Ended
Cover - USD ($) $ in Millions	Dec. 31, 2023	Mar. 19, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-40215
Entity Registrant Name	Instil Bio, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-2072195
Entity Address, Address Line One	3963 Maple Avenue, Suite 350
Entity Address, City or Town	Dallas
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75219
City Area Code	972
Local Phone Number	499-3350
Title of 12(b) Security	Common Stock, $0.000001 par value per share
Trading Symbol	TIL
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction	false
Entity Shell Company	false
Entity Public Float			$ 34.4
Entity Common Stock, Shares Outstanding		6,503,913
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s definitive proxy statement to be filed with the Securities and Exchange Commission (SEC) subsequent to the date hereof pursuant to Regulation 14A in connection with the registrant's 2024 Annual Meeting of Stockholders, are incorporated by reference into Part III of this Annual Report on Form 10-K. Such proxy statement will be filed with the SEC not later than 120 days after the conclusion of the registrant's fiscal year ended December 31, 2023.
Amendment Flag	false
Entity Central Index Key	0001789769
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2023

Fair Value Measurement - Level 3 Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	$ 8,242	$ 12,321
Change in fair value	(3,384)	(2,879)
Development milestone achieved	0	1,200
Fair value, ending balance	$ 4,858	$ 8,242

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 9,195	$ 43,716
Restricted cash	1,501	0
Marketable securities	141,161	217,204
Prepaid expenses and other current assets	8,902	8,458
Total current assets	160,759	269,378
Property, plant and equipment, net	138,684	196,880
Operating lease right-of-use assets	2,387	12,457
Long-term investments	23,161	0
Other long-term assets	639	3,413
Total assets	325,630	482,128
Current liabilities:
Accounts payable	1,212	2,359
Accrued expenses and other current liabilities	9,347	30,069
Contingent consideration, current portion	0	360
Total current liabilities	10,559	32,788
Contingent consideration, net of current portion	4,858	7,882
Operating lease liabilities, non-current	2,877	5,171
Loan payable	81,427	72,350
Other long-term liabilities	80	332
Total liabilities	99,801	118,523
Commitments and contingencies (Note 7)
Stockholders’ equity:
Preferred stock, par value $0.000001 per share; 10,000,000 shares authorized; zero shares issued and outstanding as of December 31, 2023, and 2022	0	0
Common stock, par value $0.000001 per share; 300,000,000 shares authorized; 6,503,913 shares issued and outstanding as of December 31, 2023, and 2022	0	0
Additional paid-in capital	807,158	788,992
Accumulated other comprehensive loss	(348)	(493)
Accumulated deficit	(580,981)	(424,894)
Total stockholders’ equity	225,829	363,605
Total liabilities and stockholders’ equity	$ 325,630	$ 482,128

Commitments and Contingencies - Future Minimum Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2024	$ 1,997
2025	1,820
2026	1,219
Total future lease payments	5,036
Less: imputed interest	(409)
Total lease liability balance	4,627
Less: current portion of operating lease liabilities	(1,750)	$ (2,381)
Total operating lease liabilities, non-current	$ 2,877	$ 5,171

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.000001	$ 0.000001
Preferred stock authorized (in shares)	10,000,000	10,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.000001	$ 0.000001
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	6,503,913	6,503,913
Common stock, shares outstanding (in shares)	6,503,913	6,503,913

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 18,166	$ 30,441
Research and development expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	1,549	11,882
General and administrative expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 16,617	$ 18,559

Fair Value Measurement

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurement

The fair value of cash and cash equivalents approximates carrying value since cash and cash equivalents consist of short-term highly liquid investments with maturities of less than three months at the time of purchase. Cash and cash equivalents are quoted market prices in active markets for identical assets and are therefore classified as Level 1 assets. Money market funds are open-end mutual funds that invest in cash, government securities, and/or repurchase agreements that are collateralized fully. To the extent that these funds are valued based upon the reported net asset value, they are categorized in Level 1 of the fair value hierarchy.

Short-term and long-term marketable securities comprised U.S. Treasury bills that are classified within Level 2 of the fair value hierarchy are valued based on other observable inputs, including broker or dealer quotations, alternative pricing sources or U.S. Government Treasury yield of appropriate term.

The following tables provide information by level for assets and liabilities that are measured at fair value on a recurring and nonrecurring basis:


	As of December 31, 2023
	Level 1		Level 2		Level 3		Total
	(In thousands)
Financial Assets
Money market funds	$	5,684	$	—	$	—	$	5,684
U.S. Treasury bills	—		164,322		—		164,322
Derivative financial instrument	—		1,055		—		1,055
Total	$	5,684	$	165,377	$	—	$	171,061
Financial Liabilities
Contingent consideration	$	—	$	—	$	4,858	$	4,858

	As of December 31, 2022
	Level 1		Level 2		Level 3		Total
	(In thousands)
Financial Assets
Money market funds	$	22,830	$	—	$	—	$	22,830
U.S. Treasury bills	—		217,204		—		217,204
Derivative financial instrument	—		2,202		—		2,202
Total	$	22,830	$	219,406	$	—	$	242,236
Financial Liabilities
Contingent consideration	$	—	$	—	$	8,242	$	8,242

There were no transfers in or out of Level 1, 2 and 3 measurements for the years ended December 31, 2023 and 2022. As of December 31, 2023 and 2022, there were no securities within Level 3 of the fair value hierarchy. The derivative financial instrument above relates to the interest rate swap discussed in Note 7, and is included in prepaid expenses and other current assets in the consolidated balance sheets.

As of December 31, 2023 and 2022, the fair value of the Company’s Loan (as defined in Note 7) was $72.3 million and $69.0 million, respectively. The fair value was determined on the basis of its net present value and is considered Level 2 in the fair value hierarchy (see Note 2).

The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands):


	Year Ended December 31, 2023
Fair value, beginning balance	$	8,242
Change in fair value	(3,384)
Development milestone achieved	—
Fair value, ending balance	$	4,858


	Year Ended December 31, 2022
Fair value, beginning balance	$	12,321
Change in fair value	(2,879)
Development milestone achieved	(1,200)
Fair value, ending balance	$	8,242

The Company’s acquisition of Immetacyte involved the potential for the payment of future contingent consideration upon the achievement of (i) certain product development milestones including, approval of studies and commencement and completion of certain product trials, or (ii) various other performance conditions including, receipt of final approval for the first marketing authorization and first commercial sale in certain geographical markets. Contingent consideration is recorded at the estimated fair value of the contingent payments on the acquisition date. The fair value of the contingent consideration is remeasured at the estimated fair value at each reporting period with the change in fair value recognized as income or expense within research and development expense in the consolidated statements of operations and comprehensive loss.

During the year of acquisition, the Company determined the fair value of the contingent consideration by probability weighting scenarios of milestone achievements to determine the expected future contingent consideration payment, discounted to present value using an 8% discount rate based on the Company’s pre-tax cost of debt on the acquisition date. The probability of payments ranged from 20% to 100% and the timing of future payments ranged from 2026 to 2028. Determinations of the likelihood of milestone achievements, which trigger payouts related to the contingent consideration, as well as the probabilities for various scenarios used in the Company’s calculations, were based on internal unobservable projections.

During the year ended December 31, 2023, the change of fair value related to the contingent consideration was due to the discontinuation of the ITIL-306-202 development program, the change in present value for the passage of time, as well as expected dates and probabilities of milestone achievement revisions.

During the year ended December 31, 2022, the change of fair value related to the contingent consideration was due to the Company recognizing development milestones of $1.2 million, the discontinuation of the ITIL-168 development program, the change in present value for the passage of time, as well as expected dates and probabilities of milestone achievement revisions.

- 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

Net Loss Per Share (Details)		12 Months Ended
Net Loss Per Share (Details)	Mar. 23, 2021	Dec. 31, 2023 shares	Dec. 31, 2022 shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares (in shares)		799,622	1,053,997
Conversion ratio	1.2
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares (in shares)		799,622	1,053,997

Stock-Based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

2021 Equity Incentive Plan

In March 2021, the Company adopted the 2021 Equity Incentive Plan (the “2021 Plan”), which became effective in connection with the Company’s initial public offering (“IPO”). The 2021 Plan was approved by the Company’s Board of Directors and stockholders in March 2021. The 2021 Plan is an equity incentive plan pursuant to which the Company may grant the following awards: (i) incentive stock options; (ii) nonstatutory stock options; (iii) stock appreciation rights; (iv) restricted stock awards; (v) restricted stock unit awards; (vi) performance awards; and (vii) other forms of stock awards to employees, directors, and consultants, including employees and consultants of the Company’s affiliates. The 2021 Plan is a successor to the Company’s 2018 Stock Incentive Plan (the “2018 Plan”). Following the effectiveness of the 2021 Plan, no further grants may be made under the 2018 Plan; however, any outstanding equity awards granted under the 2018 Plan will continue to be governed by the terms of the 2018 Plan.

The number of shares available for future issuance under the 2021 Plan is the sum of (1) 433,000 new shares of common stock, (2) 209,722 remaining shares of common stock reserved under the 2018 Plan that became available for issuance upon the effectiveness of the 2021 Plan and (3) the number of shares of common stock subject to outstanding awards under the 2018 Plan when the 2021 Plan became effective that thereafter expire or are forfeited, canceled, withheld to satisfy tax withholding or to purchase or exercise an award, repurchased by the Company or are otherwise terminated. The number of shares of common stock reserved for issuance under the 2021 Plan will automatically increase on January 1 of each year, for a period of ten years, from January 1, 2022 continuing through January 1, 2031, by 5% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Company’s Board of Directors. Stock options granted by the Company to employees generally vest over four years with a one-year cliff.

As of December 31, 2023, 659,608 shares of common stock remained available for issuance under the 2021 Plan. As of December 31, 2023, the total number of shares authorized for issuance under the 2021 Plan was 642,722 shares.

The following summarizes option activity under the 2021 Plan as of December 31, 2023:


	Shares Available for Grant	Shares Issuable Under Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contract Term (in years)	Aggregate Intrinsic Value (in thousands)
Balance, December 31, 2021	492,819	1,018,861	$	103.31	8.75	$	247,880
Additional Shares Authorized	—
Options granted(1)	(300,707)	300,707	$	157.48
Options forfeited	213,121	(213,121)	$	153.73
Options exercised	—	(52,450)	$	29.44
Balance, December 31, 2022	405,233	1,053,997	$	112.25	7.22	$	711
Additional Shares Authorized	—
Options granted(1)	(271,921)	271,921	$	12.68
Options forfeited	526,296	(526,296)	$	97.80
Options exercised	—	—	$	—
Balance, December 31, 2023	659,608	799,622	$	87.90	7.18	$	101
Exercisable, December 31, 2023		511,932	$	89.22	6.62	$	101
Vested and expected to vest, December 31, 2023		511,932	$	89.22	6.62	$	101

______________________________________________________________

(1) Includes 4,796 and 14,762 stock options during the years ended December 31, 2023 and 2022, respectively, subject to only performance conditions.

The aggregate intrinsic value disclosed in the above table is based on the difference between the exercise price of the stock option and the estimated fair value of the Company’s common stock as of the respective period-end dates. There were zero and 52,450 stock options exercised during the years ended December 31, 2023 and 2022, respectively. The aggregate intrinsic value of stock options exercised during the years ended December 31, 2023 and 2022, was nil, respectively. The weighted-average grant date fair value of stock options granted during the years ended December 31, 2023 and 2022, was $8.74 and $103.83 per share, respectively.

The following table sets forth stock-based compensation included in the Company’s statement of operations and comprehensive loss (in thousands):


	Year Ended December 31,
	2023		2022
Research and development expense	$	1,549	$	11,882
General and administrative expense	16,617		18,559
Total stock-based compensation expense	$	18,166	$	30,441

As of December 31, 2023 and 2022, there was $22.4 million and $55.0 million of total unrecognized compensation cost related to unvested stock options granted under the 2021 Plan (excluding performance awards), which is expected to be recognized over a weighted average period of 1.39 years and 1.98 years, respectively.

The fair value of the Company’s stock option awards was estimated at the date of grant using a Black-Scholes option pricing model with the following assumptions:


	Year Ended December 31,
	2023				2022
Expected term (in years)	5.28		—	6.08	6.10		—	6.26
Expected volatility	76.19	%	—	77.56%	72.08	%	—	74.30%
Risk-free interest rate	3.54	%	—	4.01%	1.61	%	—	4.21%
Fair value of common stock	$11.18		—	$15.20	$26.60		—	$268.20
Expected dividend yield	—%				—%

The Black-Scholes option pricing model requires the use of highly subjective assumptions which determine the fair value of stock-based awards. These assumptions include:

Expected term—The expected term represents the period that stock-based awards are expected to be outstanding and is determined as the average of the time-to-vesting and the contractual life of the awards.

Expected volatility—Since the Company is privately held and does not have any trading history for its common stock, the expected volatility was 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.

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 awards.

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

Performance Awards

During the years ended December 31, 2023 and 2022, 4,796 and 14,762 stock options were granted to both employees and non-employees based upon performance conditions and strategic transactions. 2023 performance grants are expected to be recognized over a weighted average period of 0.37 years, and the 2022 performance grants are expected to be recognized over a weighted average period of 3.17 years. A strategic transaction has been defined as (a) a change in control, or (b) certain corporate and business goals specific to the employee's performance or employment agreement. Included in stock-based compensation expense for the year ended December 31, 2023 is $4.2 million related to awards where performance conditions were achieved. As of December 31, 2023 and 2022, the Company had $5.1 million and $10.6 million of unrecognized compensation cost relating to these performance awards, calculated using the accelerated attribution method and the grant date fair value of the awards, respectively.

Employee Stock Purchase Plan

In March 2021, the Company adopted the Employee Stock Purchase Plan (the “ESPP”), which became effective in connection with the IPO. The ESPP was adopted by the Company’s Board of Directors and stockholders in March 2021, but the Company has not yet commenced offerings to employees under the ESPP. The ESPP initially provides participating employees with the opportunity to purchase up to an aggregate of 61,850 shares of common stock. The number of shares reserved under the ESPP automatically increases on January 1 of each year through and until January 1, 2031, in an amount equal to the lesser of (i) 1% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, and (ii) 123,700 shares; provided, however, that before the date of any such increase, the Board of Directors may determine that such increase will be less than the amount set forth in clauses (i) and (ii).

Income Taxes - Unrecognized Tax Benefits (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at December 31, 2022:	$ 2,339
Additions in 2023	0
Balance at December 31, 2023:	$ 2,339

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Option Activity

The following summarizes option activity under the 2021 Plan as of December 31, 2023:


	Shares Available for Grant	Shares Issuable Under Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contract Term (in years)	Aggregate Intrinsic Value (in thousands)
Balance, December 31, 2021	492,819	1,018,861	$	103.31	8.75	$	247,880
Additional Shares Authorized	—
Options granted(1)	(300,707)	300,707	$	157.48
Options forfeited	213,121	(213,121)	$	153.73
Options exercised	—	(52,450)	$	29.44
Balance, December 31, 2022	405,233	1,053,997	$	112.25	7.22	$	711
Additional Shares Authorized	—
Options granted(1)	(271,921)	271,921	$	12.68
Options forfeited	526,296	(526,296)	$	97.80
Options exercised	—	—	$	—
Balance, December 31, 2023	659,608	799,622	$	87.90	7.18	$	101
Exercisable, December 31, 2023		511,932	$	89.22	6.62	$	101
Vested and expected to vest, December 31, 2023		511,932	$	89.22	6.62	$	101

______________________________________________________________

(1) Includes 4,796 and 14,762 stock options during the years ended December 31, 2023 and 2022, respectively, subject to only performance conditions.

Schedule of Stock-Based Compensation Expense

The following table sets forth stock-based compensation included in the Company’s statement of operations and comprehensive loss (in thousands):


	Year Ended December 31,
	2023		2022
Research and development expense	$	1,549	$	11,882
General and administrative expense	16,617		18,559
Total stock-based compensation expense	$	18,166	$	30,441

Schedule of Valuation Assumptions

The fair value of the Company’s stock option awards was estimated at the date of grant using a Black-Scholes option pricing model with the following assumptions:


	Year Ended December 31,
	2023				2022
Expected term (in years)	5.28		—	6.08	6.10		—	6.26
Expected volatility	76.19	%	—	77.56%	72.08	%	—	74.30%
Risk-free interest rate	3.54	%	—	4.01%	1.61	%	—	4.21%
Fair value of common stock	$11.18		—	$15.20	$26.60		—	$268.20
Expected dividend yield	—%				—%

Fair Value Measurement - Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financial Assets
U.S. Treasury bills	$ 141,200	$ 217,200
Fair Value, Recurring
Financial Assets
Derivative financial instrument	1,055	2,202
Total	171,061	242,236
Financial Liabilities
Contingent consideration	4,858	8,242
Fair Value, Recurring \| U.S. Treasury bills
Financial Assets
U.S. Treasury bills	164,322	217,204
Fair Value, Recurring \| Money market funds
Financial Assets
Money market funds	5,684	22,830
Fair Value, Recurring \| Level 1
Financial Assets
Derivative financial instrument	0	0
Total	5,684	22,830
Financial Liabilities
Contingent consideration	0	0
Fair Value, Recurring \| Level 1 \| U.S. Treasury bills
Financial Assets
U.S. Treasury bills	0	0
Fair Value, Recurring \| Level 1 \| Money market funds
Financial Assets
Money market funds	5,684	22,830
Fair Value, Recurring \| Level 2
Financial Assets
Derivative financial instrument	1,055	2,202
Total	165,377	219,406
Financial Liabilities
Contingent consideration	0	0
Fair Value, Recurring \| Level 2 \| U.S. Treasury bills
Financial Assets
U.S. Treasury bills	164,322	217,204
Fair Value, Recurring \| Level 2 \| Money market funds
Financial Assets
Money market funds	0	0
Fair Value, Recurring \| Level 3
Financial Assets
Derivative financial instrument	0	0
Total	0	0
Financial Liabilities
Contingent consideration	4,858	8,242
Fair Value, Recurring \| Level 3 \| U.S. Treasury bills
Financial Assets
U.S. Treasury bills	0	0
Fair Value, Recurring \| Level 3 \| Money market funds
Financial Assets
Money market funds	$ 0	$ 0

Financial Instruments

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Financial Instruments

Marketable securities classified as available-for-sale at December 31, 2023 and 2022 consisted of the following (in thousands):


	December 31, 2023
	Maturity	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. Treasury bills	Less than one year	$	141,075	$	86	$	—	$	141,161
U.S. Treasury bills	Between one and two years	23,134		27		—		23,161
		$	164,209	$	113	$	—	$	164,322


	December 31, 2022
	Maturity	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. Treasury bills	Less than one year	$	217,669	$	—	$	(465)	$	217,204

As of December 31, 2023 and 2022, marketable securities that had contractual maturities less than one year are classified as current because management considers these marketable securities to be available for current operations. As of December 31, 2023 and 2022, marketable securities that had contractual maturities between one and two years are classified as long-term because management considers these marketable securities to be available for operations beyond one year. The Company does not intend to sell its marketable securities and it is not likely that the Company will be required to sell these securities before recovery of their amortized cost bases. There were $141.2 million marketable securities and $23.2 million long-term investments maturing in less than two years

classified as available-for-sale at December 31, 2023. There were $217.2 million marketable securities classified as available-for-sale at December 31, 2022.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Operating Lease Obligations

The Company currently leases office spaces and laboratory spaces located in Greater Los Angeles, California, Dallas, Texas, and the United Kingdom. The Company’s leased facilities have original lease terms ranging from 2 to 5 years that predominately require the Company to provide a security deposit, while certain leases provide the right for the Company to renew the lease upon the expiration of the initial lease term, and various leases have scheduled rent increases on an annual basis. The exercise of lease renewal options for the Company’s existing leases is at the Company’s sole discretion, and not included in the measurement of right-of-use asset or lease liability as they are not reasonably certain to be exercised. Certain leases have leasehold improvements and are being amortized over the shorter of the estimated useful life of the improvements or the remaining life of the lease, such improvements incurred by the Company will revert to the landlord at the expiration of the lease and will be removed from Company’s consolidated balance sheets.

The Company’s lease costs consist of the following (in thousands):


	Year Ended December 31,
	2023		2022
Short-term lease cost	$	375	$	1,155
Operating lease cost	2,185		4,852
Variable lease cost	1,170		1,096
Total lease cost	$	3,730	$	7,103

The following table summarizes cash flow information related to the Company’s lease obligations (in thousands):


	Year Ended December 31,
	2023		2022
Cash paid for operating lease liabilities	$	2,308	$	3,258

The following table summarizes the Company’s lease assets and liabilities (in thousands):


	As of December 31,
	2023		2022
Operating lease right-of-use assets	$	2,387	$	12,457
Current operating lease liabilities	$	1,750	$	2,381
Non-current operating lease liabilities	$	2,877	$	5,171

The following table summarizes other supplemental information related to the Company’s lease obligations:


	As of December 31,
	2023		2022
Weighted-average remaining lease term (in years)	2.60		3.29
Weighted-average discount rate	6.75	%	6.75	%

Future minimum lease payments under operating lease liabilities were (in thousands):


	As of December 31, 2023
2024	$	1,997
2025	1,820
2026	1,219
Total future lease payments	5,036
Less: imputed interest	409
Total lease liability balance	4,627
Less: current portion of operating lease liabilities	1,750
Total operating lease liabilities, non-current	$	2,877

During the year ended December 31, 2023, the Company evaluated its remaining right-of-use assets for impairment, as the Plan has resulted in a cessation of use for several locations. The Company determined these assets were impaired, and recognized an impairment loss of $7.2 million for the year ended December 31, 2023 and nil for the year ended December 31, 2022, in addition to a loss on termination of $0.5 million for the year ended December 31, 2023 and nil for the year ended December 31, 2022, which were recorded in the consolidated statements of operations and comprehensive loss in the line item “restructuring and impairment charges” (see Note 12).

Construction Commitments

The Company’s contractual commitments for the development of the Tarzana project are limited to unreimbursed spend by the general contractor and as such, as of December 31, 2023, was $0.2 million, which is contractually committed to the development of this project.

During the year ended December 31, 2023, the Company entered into lease termination agreements for several office and laboratory spaces located in the United States as a part of the Plan. As consideration for the terminations, the Company agreed to pay certain landlord’s termination fees of approximately $0.4 million, which are recorded in the consolidated statements of operations and comprehensive loss in the line item “restructuring and impairment charges” (see Note 12).

Legal Proceedings

From time to time, the Company may have certain contingent liabilities that arise in the ordinary course of its business activities. The Company accrues a liability for such matters when it is probable that future expenditures will be made and that such expenditures can be reasonably estimated. Significant judgment is required to determine both probability and the estimated amount. The Company does not expect that the resolution of these matters will have a material adverse effect on its financial position, results of operations or cash flows.

Debt

In June 2022, the Company’s wholly owned subsidiary, Complex Therapeutics Mezzanine LLC, and the Company’s wholly owned indirect subsidiary, Complex Therapeutics LLC, entered into a mortgage construction loan and mezzanine construction loan (together, the “Loan”) secured by its Tarzana, California land and building (the “Property”) which is substantially complete and is waiting for final certificate of occupancy from the city of Los Angeles. The initial principal amount of the Loan was $52.1 million, with additional future principal of up to $32.9 million to fund ongoing Property construction costs. The Loan principal is payable in July 2025, with the option to extend until July 2027. As of December 31, 2023, the outstanding principal amount under the Loan was $82.8 million and unamortized debt issuance costs were $1.4 million. During the year ended December 31, 2023, $0.6 million in additional principal was paid in accordance with the lender agreement. The Loan is guaranteed by the Company and secured by the Property, and bears interest at one-month Secured Overnight Financing Rate, plus

5.25% per annum. The Company discontinued capitalizing interest on June 2023 as the building was substantially complete. The Loan contains customary negative and affirmative covenants that include limitations on the ability of the Company to enter into significant contracts and incur additional debt. The Company is also required to maintain consolidated net worth and liquid assets of at least $85.0 million as of December 31, 2023 and 2022 as defined in the loan agreement. As of December 31, 2023, the Company was in compliance with the covenants of the Loan. The Company is also required to maintain certain insurance coverage on the Property. In connection with the Loan, the Company entered into an interest rate swap to effectively limit its maximum interest rate, as discussed in Note 5.

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


	As of December 31,
	2023		2022
Principal amount	$	82,837	$	74,755
Unamortized debt issuance cost	(1,410)		(2,405)
Net carrying amount	$	81,427	$	72,350

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


	Year Ended December 31,
	2023		2022
Contractual interest expense	$	4,214	$	1,302
Amortization of debt issuance cost	995		581
Total interest expense related to the Loan	$	5,209	$	1,883

Indemnifications

The Company has entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. The Company currently has directors’ and officers’ insurance coverage that reduces its exposure and enables the Company to recover a portion of any future amounts paid. No liability associated with such indemnifications was recorded as of December 31, 2023 and 2022.

Other Commitments

In the normal course of business, the Company enters into contracts and various purchase agreements commitments with third-party vendors for clinical research services, products and other services from third parties for operating purposes. These agreements generally provide for termination or cancellation, other than for costs already incurred. As of December 31, 2023, the Company had $3.1 million in commitment for contract terminations as part of the Plan. As of December 31, 2022, the Company had $3.0 million in commitments related to one-time employee termination benefits and $2.4 million in commitments for contract terminations as part of the Plan (see Note 12).

The Company has entered into an agreement with a third-party to collaborate on the development of the Collaboration Product with the aim of enrolling patients in investigator-initiated (“IIT”) clinical trials in China. During the year ended December 31, 2023, the Company paid $0.3 million in milestone payments. Additional milestone payments of $2.6 million were made during the first quarter of 2024 and upon successful completion of future milestones the Company may be required to pay up to $3.4 million for clinical development and related activities.

Commitments and Contingencies

Operating Lease Obligations

The Company’s lease costs consist of the following (in thousands):


	Year Ended December 31,
	2023		2022
Short-term lease cost	$	375	$	1,155
Operating lease cost	2,185		4,852
Variable lease cost	1,170		1,096
Total lease cost	$	3,730	$	7,103

The following table summarizes cash flow information related to the Company’s lease obligations (in thousands):


	Year Ended December 31,
	2023		2022
Cash paid for operating lease liabilities	$	2,308	$	3,258

The following table summarizes the Company’s lease assets and liabilities (in thousands):


	As of December 31,
	2023		2022
Operating lease right-of-use assets	$	2,387	$	12,457
Current operating lease liabilities	$	1,750	$	2,381
Non-current operating lease liabilities	$	2,877	$	5,171

The following table summarizes other supplemental information related to the Company’s lease obligations:


	As of December 31,
	2023		2022
Weighted-average remaining lease term (in years)	2.60		3.29
Weighted-average discount rate	6.75	%	6.75	%

Future minimum lease payments under operating lease liabilities were (in thousands):


	As of December 31, 2023
2024	$	1,997
2025	1,820
2026	1,219
Total future lease payments	5,036
Less: imputed interest	409
Total lease liability balance	4,627
Less: current portion of operating lease liabilities	1,750
Total operating lease liabilities, non-current	$	2,877

Construction Commitments

Legal Proceedings

Debt

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


	As of December 31,
	2023		2022
Principal amount	$	82,837	$	74,755
Unamortized debt issuance cost	(1,410)		(2,405)
Net carrying amount	$	81,427	$	72,350

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


	Year Ended December 31,
	2023		2022
Contractual interest expense	$	4,214	$	1,302
Amortization of debt issuance cost	995		581
Total interest expense related to the Loan	$	5,209	$	1,883

Indemnifications

Other Commitments

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Property, Plant and Equipment, Net

The estimated useful lives of the Company’s property, plant and equipment are as follows:


Laboratory equipment			5 years
Manufacturing equipment			5 years
Office and computer equipment			3 years
Building			35 years
Leasehold improvements			Shorter of remaining lease term or estimated useful life

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


	December 31,
	2023		2022
Land	$	31,243	$	31,243
Laboratory equipment	8,291		19,050
Buildings	102,433		32,778
Office and computer equipment	831		4,969
Leasehold improvements	1,424		4,340
Manufacturing equipment	2,017		8,803
Vehicles	—		64
Construction work-in-progress	—		104,117
Total property, plant and equipment, gross	146,239		205,364
Less: accumulated depreciation	(7,555)		(8,484)
Total property, plant and equipment, net	$	138,684	$	196,880

Schedule of Accrued Expenses and Other Current Liabilities

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


	December 31,
	2023		2022
Accrued construction costs	$	—	$	12,359
Accrued compensation and benefits	1,026		3,273
Accrued operational expenses	1,412		2,203
Accrued restructuring costs	3,136		5,434
Accrued research, development and clinical trial expenses	1,833		3,827
Operating lease liabilities, current	1,750		2,381
Other current liabilities	190		592
Total accrued expenses and other current liabilities	$	9,347	$	30,069

Stock-Based Compensation - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Shares Available for Grant
Beginning balance (in shares)		405,233	492,819
Additional Shares Authorized (in shares)	433,000	0	0
Options granted (in shares)		(271,921)	(300,707)
Options forfeited (in shares)		526,296	213,121
Ending balance (in shares)		659,608	405,233	492,819
Shares Issuable Under Options
Beginning balance (in shares)		1,053,997	1,018,861
Options granted (in shares)		271,921	300,707
Options forfeited (in shares)		(526,296)	(213,121)
Options exercised (in shares)		0	(52,450)
Ending balance (in shares)		799,622	1,053,997	1,018,861
Exercisable (in shares)		511,932
Vested and expected to vest (in shares)		511,932
Weighted- Average Exercise Price
Beginning balance (in dollars per share)		$ 112.25	$ 103.31
Options granted (in dollars per share)		12.68	157.48
Options forfeited (in dollars per share)		97.80	153.73
Options exercised (in dollars per share)		0	29.44
Ending balance (in dollars per share)		87.90	$ 112.25	$ 103.31
Exercisable, weighted-average exercise price (in dollars per share)		89.22
Vested and expected to vest, weighted-average exercise price (in dollars per share)		$ 89.22
Balance, weighted-average remaining contract term		7 years 2 months 4 days	7 years 2 months 19 days	8 years 9 months
Exercisable, weighted-average remaining contract term		6 years 7 months 13 days
Vested and expected to vest, weighted-average remaining contract term		6 years 7 months 13 days
Balance, aggregate intrinsic value		$ 101	$ 711	$ 247,880
Exercisable, aggregate intrinsic value		101
Vested and expected to vest, aggregate intrinsic value		$ 101
Performance Shares
Shares Available for Grant
Options granted (in shares)		(4,796)	(14,762)
Shares Issuable Under Options
Options granted (in shares)		4,796	14,762

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Schedule of Lease Cost

The Company’s lease costs consist of the following (in thousands):


	Year Ended December 31,
	2023		2022
Short-term lease cost	$	375	$	1,155
Operating lease cost	2,185		4,852
Variable lease cost	1,170		1,096
Total lease cost	$	3,730	$	7,103

The following table summarizes cash flow information related to the Company’s lease obligations (in thousands):


	Year Ended December 31,
	2023		2022
Cash paid for operating lease liabilities	$	2,308	$	3,258

The following table summarizes the Company’s lease assets and liabilities (in thousands):


	As of December 31,
	2023		2022
Operating lease right-of-use assets	$	2,387	$	12,457
Current operating lease liabilities	$	1,750	$	2,381
Non-current operating lease liabilities	$	2,877	$	5,171

The following table summarizes other supplemental information related to the Company’s lease obligations:


	As of December 31,
	2023		2022
Weighted-average remaining lease term (in years)	2.60		3.29
Weighted-average discount rate	6.75	%	6.75	%

Schedule of Future Minimum Lease Payments

Future minimum lease payments under operating lease liabilities were (in thousands):


	As of December 31, 2023
2024	$	1,997
2025	1,820
2026	1,219
Total future lease payments	5,036
Less: imputed interest	409
Total lease liability balance	4,627
Less: current portion of operating lease liabilities	1,750
Total operating lease liabilities, non-current	$	2,877

Schedule of Net Carrying Amount of the Loan

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


	As of December 31,
	2023		2022
Principal amount	$	82,837	$	74,755
Unamortized debt issuance cost	(1,410)		(2,405)
Net carrying amount	$	81,427	$	72,350

Schedule of Interest Expense Related to the Loan

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


	Year Ended December 31,
	2023		2022
Contractual interest expense	$	4,214	$	1,302
Amortization of debt issuance cost	995		581
Total interest expense related to the Loan	$	5,209	$	1,883

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

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+ Details

Financial Instruments - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Available-for-sale	$ 141,200	$ 217,200
Long-term investments	$ 23,161	$ 0

Balance Sheet Components - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued construction costs	$ 0	$ 12,359
Accrued compensation and benefits	1,026	3,273
Accrued operational expenses	1,412	2,203
Accrued restructuring costs	3,136	5,434
Accrued research, development and clinical trial expenses	1,833	3,827
Operating lease liabilities, current	1,750	2,381
Other current liabilities	190	592
Total accrued expenses and other current liabilities	$ 9,347	$ 30,069
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Total accrued expenses and other current liabilities	Total accrued expenses and other current liabilities

Fair Value Measurement - Narrative (Details) $ in Millions	12 Months Ended
Fair Value Measurement - Narrative (Details) $ in Millions	Dec. 31, 2022 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Prepaid expenses and other current assets	Prepaid expenses and other current assets
Contingent consideration payments	$ 1.2
Measurement Input, Discount Rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Measurement input			0.08
Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Payment probability			20.00%
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Payment probability			100.00%
Secured Mortgage Loan \| Level 2 \| Loans Payable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of loan	$ 69.0	$ 72.3

Equity	12 Months Ended
Equity	Dec. 31, 2023
Equity [Abstract]
Equity	Equity Common Stock Each share of common stock has the right to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and if declared by the Board of Directors, subject to the prior rights of holders of all classes of stock outstanding having priority rights as to dividends. No cash dividends have been declared by the Board of Directors from inception. As of December 31, 2023, the Company had 6,503,913 shares of common stock outstanding. Preferred Stock Activity The Company’s current amended and restated certificate of incorporation authorizes the Company to issue up to 10,000,000 shares of preferred stock at $0.000001 par value per share. The Board of Directors is authorized to provide for the issuance of the preferred stock in one or more series, and to fix the number of shares and to determine or alter for each such series, such voting powers, full or limited, or no voting powers, and such designation, preferences, and relative, participating, optional, or other rights and such qualifications, limitations, or restrictions thereof, as shall be stated and expressed in subsequent resolution or resolutions adopted by the board providing for the issuance of such shares. As of December 31, 2023 and 2022 there were no shares of preferred stock issued or outstanding.

- Definition

The entire disclosure for equity.

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+ Details