0000950170-24-023148 | 10-K | XBRL Viewer | Sensei Biotherapeutics INC

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Stock-Based Compensation - Summary of Stock Option Award Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Number of Stock Options, Outstanding balance	3,333,434
Number of Stock Options, Granted	783,371
Number of Stock Options, Forfeited	(401,919)
Number of Stock Options, Expired	(295,580)
Number of Stock Options, Outstanding balance	3,419,306	3,333,434
Number of Stock Options, Options expected to vest	1,235,761
Number of Stock Options, Exercisable	2,183,545
Weighted-Average Exercise Price, Outstanding balance	$ 8.8
Weighted-Average Exercise Price, Granted	1.27
Weighted-Average Exercise Price, Forfeited	5.77
Weighted-Average Exercise Price, Expired	12.39
Weighted-Average Exercise Price, Outstanding balance	7.12	$ 8.8
Weighted-Average Exercise Price, Options expected to vest	2.61
Weighted-Average Exercise Price, Exercisable	$ 9.68
Weighted-Average Remaining Contractual Term, Outstanding balance	7 years 3 months 14 days	8 years 1 month 2 days
Weighted-Average Remaining Contractual Term, Options expected to vest	8 years 6 months 21 days
Weighted-Average Remaining Contractual Term, Exercisable	6 years 6 months 25 days
Aggregate Intrinsic Value, Outstanding		$ 1

Marketable Securities

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

MARKETABLE SECURITIES

3. MARKETABLE SECURITIES

Marketable securities consist of the following as of December 31, 2023 and 2022 (in thousands):


	As of December 31, 2023
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Commercial paper	$	9,892	$	6	$	(2	)	$	9,896
Corporate bonds		37,063		—		(40	)		37,023
U.S. Government agencies		6,000		—		(173	)		5,827
Total	$	52,955		6	$	(215	)	$	52,746


	As of December 31, 2022
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Commercial paper	$	30,475	$	1	$	(33	)	$	30,443
Corporate bonds		52,848		—		(571	)		52,277
U.S. Government agencies		7,000		—		(399	)		6,601
Total	$	90,323		1	$	(1,003	)	$	89,321

As of December 31, 2023, all marketable securities held by the Company had remaining contractual maturities of one year or less.

As of December 31, 2023, $0.2 million of unrealized losses were associated with marketable securities with contractual maturities of one year or less.

There were no impairments of the Company’s assets measured and carried at fair value during the year ended December 31, 2023 and 2022.

Commitments and Contingencies - Summary of Maturity of Operating and Finance Lease Liabilities (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Operating
2024	$ 1,853
2025	1,734
2026	1,413
2027	59
Total future minimum lease payments	5,059
Less amount representing interest	491
Total lease liabilities	4,568
Financing
2024	900
2025	757
2026	107
Total future minimum lease payments	1,764
Less amount representing interest	124
Total lease liabilities	$ 1,640

Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended
	Aug. 15, 2023	Jul. 31, 2023	Jun. 01, 2023	May 23, 2023	Dec. 31, 2023	Jan. 01, 2023
Class Of Stock [Line Items]
Excise tax on repurchases						1.00%
Purchase transaction cost					$ 10,384
Cambrian Purchase Agreement [Member]
Class Of Stock [Line Items]
Shares repurchased and retired	1,587,302
Purchase price per share		$ 1.26
Share repurchase, agreed to purchase, shares		1,587,302
Aggregate purchase price		$ 2,000
Purchase Agreement [Member] \| Apeiron Parties
Class Of Stock [Line Items]
Purchase price per share				$ 1.58
Share repurchase, agreed to purchase, shares				4,454,248
Purchase transaction cost			$ 7,800
Negotiation of purchase agreement cost			$ 750

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Summary of Estimated Useful Lives of Property and Equipment

Depreciation is computed using the straight-line method over the following estimated useful lives:


Office equipment and furniture	3—7 years
Research equipment	1—7 years

Income Taxes - Reconciliation of Federal Statutory Income Tax Rate to Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	21.00%
State income taxes, net of federal benefit	12.10%	(4.70%)
Non-deductible transactions costs	(1.40%)
Other	(1.20%)	(0.20%)
Equity-based compensation	(1.50%)	0.50%
Change in valuation allowance	(29.00%)	(16.60%)

Stock-Based Compensation - Summary of Common Stock Warrant Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Number of Common Stock Warrants Outstanding, Beginning Balance	57,004
Number of Common Stock Warrants, Expired	(312)
Number of Common Stock Warrants Outstanding and Exercisable, Ending Balance	56,692
Weighted-Average Exercise Price Outstanding, Beginning Balance	$ 6.94
Weighted Average Exercise Price, Expired	144
Weighted-Average Exercise Price Outstanding and Exercisable, Ending Balance	$ 6.19
Weighted-Average Remaining Contractual Term Outstanding	1 year 1 month 28 days
Weighted-Average Remaining Contractual Term Outstanding and Exercisable		1 year 10 months 28 days

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 13,011	$ 17,795
Marketable securities	52,746	89,321
Prepaid expenses	1,168	1,129
Other current assets	325	344
Total current assets	67,250	108,589
Right of use assets - operating leases, net	4,330	5,355
Right of use assets - financing leases, net	1,543	2,319
Property and equipment, net	1,165	2,049
Other non-current assets	86	63
Total assets	74,374	118,375
Current liabilities:
Accounts payable and accrued liabilities	1,694	4,473
Compensation and employee benefits liabilities	1,510	2,462
Operating lease liabilities, current	1,567	1,251
Financing lease liabilities, current	872	880
Total current liabilities	5,643	9,066
Operating lease liabilities, non-current	3,001	4,323
Financing lease liabilities, non-current	768	1,579
Other non-current liabilities	67
Total liabilities	9,479	14,968
Commitments and contingencies (Note 6)
Stockholders' equity:
Preferred stock, $0.0001 par value and 10,000,000 shares authorized as of December 31, 2023 and December 31, 2022; zero shares issued and outstanding at December 31, 2023 and December 31, 2022, respectively
Common stock, $0.0001 par value and 250,000,000 shares authorized as of December 31, 2023 and December 31, 2022; 25,030,188 and 30,764,160 shares issued and outstanding at December 31, 2023 and December 31, 2022, respectively	3	3
Additional paid-in capital	296,996	302,202
Accumulated deficit	(231,895)	(197,794)
Accumulated other comprehensive loss	(209)	(1,004)
Total stockholders' equity	64,895	103,407
Total liabilities and stockholders' equity	$ 74,374	$ 118,375

Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 33,322	$ 27,151
Equity-based compensation	3,340	2,735
Research and development tax credit carryforwards	1,364	1,364
Capitalized R&D expenditures	12,235	9,026
Lease liabilities	1,344	1,433
Other accruals	1,071	1,027
Total deferred tax assets	52,676	42,736
Valuation allowance	(51,050)	(41,360)
Net deferred tax assets	1,626	1,376
Deferred tax liabilities:
'Right-of-use assets	(1,626)	(1,376)
'Total deferred tax liabilities	$ (1,626)	$ (1,376)

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Jan. 01, 2022
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 571	$ 614
Right of use assets - financing leases, net	$ 1,543	$ 2,319
Research Equipment
Property, Plant and Equipment [Line Items]
Right of use assets - financing leases, net			$ 2,200
Office Equipment and Furniture
Property, Plant and Equipment [Line Items]
Right of use assets - financing leases, net			$ 70

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,454	$ 5,812
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,022	1,987
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 3,432	$ 3,825

Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of Property and Equipment (Details)	Dec. 31, 2023
Minimum \| Office Equipment and Furniture
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Estimated useful life (in years)	3 years
Minimum \| Research Equipment
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Estimated useful life (in years)	1 year
Maximum \| Office Equipment and Furniture
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Estimated useful life (in years)	7 years
Maximum \| Research Equipment
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Estimated useful life (in years)	7 years

- Definition

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

+ References

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Equity - Summary of Common Stock Warrant activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Class Of Stock [Line Items]
Number of Common Stock Warrants Outstanding, Beginning Balance	57,004
Number of Common Stock Warrants, Expired	(312)
Number of Common Stock Warrants Outstanding, Ending Balance		57,004
Weighted-Average Exercise Price Outstanding, Beginning Balance	$ 6.94
Weighted Average Exercise Price, Expired	$ 144
Weighted-Average Exercise Price Outstanding, Ending Balance		$ 6.94
Weighted-Average Remaining Contractual Term, Outstanding	1 year 1 month 28 days
Warrant \| Equity and Debt Fundraising Events
Class Of Stock [Line Items]
Number of Common Stock Warrants Outstanding, Beginning Balance	412,262
Number of Common Stock Warrants Outstanding, Ending Balance	412,262	412,262
Weighted-Average Exercise Price Outstanding, Beginning Balance	$ 9.81
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- Definition

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

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Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Pay vs Performance Disclosure
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+ Details

Commitments and Contingencies - Summary of Lease Costs Recognized under ASC 842 Pertaining to Finance and Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Lease Cost:
Amortization of finance right-of-use assets	$ 780	$ 733
Interest on finance lease liabilities	143
Operating lease cost	1,796
Variable lease cost	671
Total lease costs	3,390
Operating Sublease income	(331)
Total lease costs, net	$ 3,059

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Summary of Property and Equipment, Net

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


	December 31, 2023			December 31, 2022
Research equipment	$	2,107		$	2,707
Office equipment and furniture		532			532
Leasehold improvement		253			253
Total property and equipment		2,892			3,492
Less accumulated depreciation and amortization		(1,727	)		(1,443	)
Property and equipment, net	$	1,165		$	2,049

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Rule 10B5-1 Arrangement Modified	false
Non-Rule 10B5-1 Arrangement Modified	false

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating expenses:
Research and development	$ 18,299	$ 30,383
General and administrative	18,765	19,805
Total operating expenses	37,064	50,188
Loss from operations	(37,064)	(50,188)
Other income (expense):
Interest income	3,624	1,783
Interest expense	(144)	(219)
Loss on asset disposal	(302)
Other (expense) income, net	(215)	36
Net loss	$ (34,101)	$ (48,588)
Net loss per common share, basic	$ (1.22)	$ (1.58)
Net loss per common share, diluted	$ (1.22)	$ (1.58)
Weighted-average number of shares used in computing net loss per common share, basic	27,952,857	30,703,295
Weighted-average number of shares used in computing net loss per common share, diluted	27,952,857	30,703,295
Comprehensive loss:
Net loss	$ (34,101)	$ (48,588)
Other comprehensive items:
Unrealized gain (loss) on marketable securities	795	(671)
Total other comprehensive income (loss)	795	(671)
Total comprehensive loss	$ (33,306)	$ (49,259)

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Summary of Lease Costs Recognized under ASC 842 Pertaining to Finance and Operating Leases

The following table contains a summary of the lease costs recognized under ASC 842 pertaining to the Company’s finance and operating leases for the year ended December 31, 2023 (in thousands):


	Year Ended December 31,
	2023
Lease Cost:
Amortization of finance right-of-use assets	$	780
Interest on finance lease liabilities		143
Operating lease cost		1,796
Variable lease cost		671
Total lease costs		3,390
Operating Sublease income		(331	)
Total lease costs, net	$	3,059

Summary of Other Information Pertaining to Finance and Operating Leases

The following table contains a summary of other information pertaining to the Company’s finance and operating leases for the year ended December 31, 2023 (in thousands, except lease term and discount rate):


	Year Ended December 31,
	2023
Other Operating Lease Information:
Operating cash flows for operating leases	$	1,777
Operating cash flows for operating subleases	$	(316	)
Operating cash flows for finance leases	$	143
Financing cash flows from finance leases	$	761

Weighted average remaining lease term
Operating leases	2.8 years
Financing leases	2.1 years

Weighted average discount rate
Operating leases	7.7%
Financing leases	8.3%

Summary of Maturity of Operating and Finance Lease Liabilities

The following table presents the maturity of the Company’s operating and finance lease liabilities as of December 31, 2023 (in thousands):


	Operating		Financing
2024	$	1,853	$	900
2025		1,734		757
2026		1,413		107
2027		59		—
Total future minimum lease payments	$	5,059	$	1,764
Less amount representing interest		491		124
Total lease liabilities	$	4,568	$	1,640

Organization and Operations

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

ORGANIZATION AND OPERATIONS

1. ORGANIZATION AND OPERATIONS

Business

Sensei Biotherapeutics, Inc. (the “Company” or “Sensei”) is an immuno-oncology company that was incorporated in 1999 as a Maryland corporation until incorporated in Delaware on December 1, 2017. The Company is focused in the discovery and development of next-generation therapeutics for cancer patients.

Liquidity and capital resources

Since its inception, the Company has devoted substantially all of its resources to advancing development of its portfolio of programs, establishing and protecting its intellectual property, conducting research and development activities, organizing and staffing the Company, business planning, raising capital and providing general and administrative support for these operations. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry including, but not limited to, technical risks associated with the successful research, development and manufacturing of product candidates, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Current and future programs will require significant research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

Since its inception, the Company has incurred substantial losses and had a net loss of $34.1 million for the year ended December 31, 2023. As of December 31, 2023, the Company had an accumulated deficit of $231.9 million. The Company expects to generate operating losses and negative operating cash flows for the foreseeable future.

The Company expects that its cash, cash equivalents and marketable securities, as of December 31, 2023 of $65.8 million will be sufficient to fund its operations for at least the next twelve months from the date of issuance of these financial statements. The Company will need additional financing to support its continuing operations and pursue its growth strategy. Until such time as the Company can generate significant revenue from product sales, if ever, it expects to finance its operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and licensing arrangements. The Company may be unable to raise additional funds or enter into such other agreements when needed on favorable terms or at all. The inability to raise capital as and when needed would have a negative impact on the Company’s financial condition and its ability to pursue its business strategy. The Company will need to generate significant revenue to achieve profitability, and it may never do so.

Net Loss Per Share - Schedule of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Earnings Per Share [Abstract]
Net loss	$ (34,101)	$ (48,588)
Net loss per share-basic	$ (1.22)	$ (1.58)
Net loss per share-diluted	$ (1.22)	$ (1.58)
Weighted-average number of shares used in computing net loss per common share, basic	27,952,857	30,703,295
Weighted-average number of shares used in computing net loss per common share, diluted	27,952,857	30,703,295

- Definition

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

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- Definition

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

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+ Details

- Definition

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

+ References

+ Details

Equity

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

EQUITY

7. Equity

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are not entitled to receive dividends, unless declared by the board of directors.

Common Stock Warrants

The following is a summary of the common stock warrant activity related to common stock warrants issued in conjunction with equity and debt fundraising events for the years ended December 31, 2023 and 2022:


	Number of Common Stock Warrants		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2022		412,262	$	9.81		4.71	$	—
Granted		—		—		—		—
Exercised		—		—		—		—
Expired		—		—		—		—
Outstanding at December 31, 2023		412,262	$	9.81		3.71	$	—

Share Purchase Agreements

On May 23, 2023, the Company entered into a stock purchase agreement with Apeiron Investment Group Ltd., Presight Sensei Co-Invest Fund, L.P., Presight Sensei Co-Invest Management, L.L.C., Christian Angermayer, Apeiron SICAV Ltd. - Presight Capital Fund ONE, and Altarius Asset Management Ltd. (collectively, the “Apeiron Parties”). Pursuant to the Apeiron Purchase Agreement, the Company acquired 4,454,248 shares of its common stock (“Shares”) from the Apeiron Parties at a purchase price of $1.58 per share. The closing of the acquisition (the “Closing”) occurred on June 1, 2023, pursuant to which the Company paid approximately $7.8 million in the aggregate to the Aperion Parties, including $0.75 million for costs related to the negotiation and execution of the Apeiron Purchase Agreement. The acquired Shares were subsequently retired and canceled.

On July 31, 2023, the Company entered into a stock purchase agreement with Cambrian BioPharma, Inc. and its associates and controlled affiliates (“Cambrian”), pursuant to which the Company agreed to repurchase 1,587,302 shares of its common stock from

Cambrian at a price of $1.26 per share and for an aggregate purchase price of approximately $2.0 million. The transaction closed on August 15, 2023 and the 1,587,302 repurchased shares have been retired and cancelled.

On August 16, 2022, the Inflation Reduction Act of 2022 (“IRA”) was signed into law, which contains certain revisions to the Internal Revenue Code, including a 1% excise tax on the value of net corporate stock repurchases that is effective beginning on January 1, 2023. The excise tax is recorded as an incremental cost in equity on the Company's condensed consolidated balance sheets and was not significant as of December 31, 2023.

- Definition

The entire disclosure for equity.

+ References

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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

+ Details

Equity (Tables)

12 Months Ended

Dec. 31, 2023

Summary of Common Stock Warrant Activity

The following is a summary of the common stock warrant activity during the years ended December 31, 2023 and 2022:


	Number of Common Stock Warrants			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding and exercisable at December 31, 2022		57,004		$	6.94		1.91	$	—
Expired		(312	)		144		—		—
Outstanding and exercisable at December 31, 2023		56,692		$	6.19		1.16	$	—

Warrant | Equity and Debt Fundraising Events

Summary of Common Stock Warrant Activity


	Number of Common Stock Warrants		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2022		412,262	$	9.81		4.71	$	—
Granted		—		—		—		—
Exercised		—		—		—		—
Expired		—		—		—		—
Outstanding at December 31, 2023		412,262	$	9.81		3.71	$	—

Summary of Significant Accounting Policies - Additional Information (Details)			12 Months Ended
	Jul. 31, 2023 USD ($) $ / shares shares	May 23, 2023 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) Segment	Dec. 31, 2022 USD ($)
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Number of operating segment \| Segment			1
Impairment charges			$ 0	$ 0
Apeiron Parties
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Share repurchase liability, net of issuance cost, recorded at contractual value		$ 7,700,000
Purchase Agreement \| Apeiron Parties
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Share repurchase, agreed to purchase, shares \| shares		4,454,248
Purchase price per share \| $ / shares		$ 1.58
Cambrian Purchase Agreement
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Share repurchase, agreed to purchase, shares \| shares	1,587,302
Purchase price per share \| $ / shares	$ 1.26
Share repurchase liability, net of issuance cost, recorded at contractual value	$ 2,300,000
ASU 2016-02
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in accounting principle, accounting standards update, adopted			true
Change in accounting principle, accounting standards update, adoption date			Jan. 01, 2022
ASU 2016-13
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in accounting principle, accounting standards update, adopted			true
Change in accounting principle, accounting standards update, adoption date			Jan. 01, 2023
Change in accounting principle, accounting standards update, immaterial effect			true

Related-Party Transactions

12 Months Ended

Dec. 31, 2023

RELATED-PARTY TRANSACTIONS

10. RELATED-PARTY TRANSACTIONS

Service Agreement - Hope Farms

During 2020, the Company entered into a service agreement with Hope Farms at Disco Bay LLC (“Hope Farms”) to provide animal vaccination testing and provide samples to the Company (the “Hope Farms Service Agreement”). The Company’s Chief Research and Development Officer is a co-founder and partial owner of Hope Farms. Further, the CEO of Hope Farms is the spouse of the Company’s Chief Research and Development Officer. In October 2022, the Company and Hope Farms agreed to terminate the Hope Farms Services Agreement, effective as of September 30, 2022.

The Company recognized no expense and $103 thousand for the years ended December 31, 2023 and 2022, respectively, relating to the Hope Farms Service Agreement.

Service Agreement - Binney Street Partners

During 2022, the Company entered into a service agreement with Binney Street Partners LLC (“Binney Street Partners”) to provide business development services (the “BSP Service Agreement”). The Company subsequently hired a managing partner of Binney Street Partners to serve as the Company's Chief Business Officer, effective June 1, 2022. In September 2022, the Company and Binney Street Partners agreed to terminate the BSP Service Agreement, effective as of August 11, 2022.

The Company recognized no expense and $223 thousand for the years ended December 31, 2023 and 2022, respectively, relating to the BSP Service Agreement.

Purchase Agreement - Apeiron Investment Group

On May 23, 2023, the Company entered into a purchase agreement (the “Apeiron Purchase Agreement”) with Apeiron Investment Group Ltd., Presight Sensei Co-Invest Fund, L.P., Presight Sensei Co-Invest Management, L.L.C., Christian Angermayer, Apeiron SICAV Ltd. - Presight Capital Fund ONE, and Altarius Asset Management Ltd. (collectively, the “Apeiron Parties”), pursuant to which the Company agreed to purchase 4,454,248 shares of the Company’s common stock from certain of the Apeiron Parties for a purchase price of $1.58 per share. The closing of the purchase transaction was completed on June 1, 2023, pursuant to which the Company paid approximately $7.8 million in the aggregate to the Aperion Parties, including $0.75 million for costs related to the negotiation and execution of the Purchase Agreement. Prior to the closing, certain of the Apeiron Parties beneficially owned more than 5% of the Company's outstanding shares of common stock. Following the closing, the Apeiron Parties owned no outstanding shares of the Company’s common stock. The price per share and the transaction were unanimously approved by the independent directors of our board of directors.

Under the terms of the Apeiron Purchase Agreement, the Apeiron Parties agreed to withdraw their notice of intent to nominate director candidates for election to our board of directors at the 2023 annual meeting of stockholders. The Apeiron Parties additionally agreed to customary standstill restrictions, including an agreement to not acquire any additional shares of the Company’s voting securities or any of the Company’s indebtedness until the date that is the earlier of (i) four years from the date of the Apeiron Purchase Agreement and (ii) 30 days prior to the nomination deadline for the nomination of director candidates for election to our board of directors at the Company’s 2027 annual meeting of stockholders.

Purchase Agreement - Cambrian BioPharma, Inc.

On July 31, 2023, the Company entered into the Cambrian Purchase Agreement, pursuant to which the Company agreed to repurchase 1,587,302 shares of its common stock from Cambrian, a beneficial owner of more than 5% of the Company’s outstanding shares of common stock, at a purchase price of $1.26 per share and for an aggregate purchase price of approximately $2 million. The transaction closed on August 15, 2023 and the 1,587,302 repurchased shares were retired and cancelled on or about the date of the closing. James Peyer, a director of the Company, is the CEO of Cambrian. The price per share and the transaction were unanimously approved by the independent directors of our board of directors.

Under the terms of the Cambrian Purchase Agreement, Cambrian agreed to vote, until thirty days prior to the deadline for delivery of notice for the nomination of director candidates for election to our board of directors at the Company’s 2025 annual meeting of stockholders (the “Effective Period”), all of Cambrian’s shares of the Company’s common stock at all meetings of stockholders, as well as in any consent solicitations of the Company’s stockholders, in accordance with the board’s recommendations. In the event that Institutional Shareholder Services, Inc. and Glass Lewis & Co., LLC recommend otherwise with respect to any Company proposals (other than the election or removal of directors), Cambrian will be permitted to vote in accordance with such recommendations. Under the terms of the Cambrian Purchase Agreement, Cambrian has also agreed to certain standstill restrictions during the Effective Period including, among other things, with respect to nominating persons for election to the board of directors,

submitting any stockholder proposal for consideration at any stockholder meeting, soliciting any proxies, and conducting any “withhold” or similar campaign.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
-Section 50
-Paragraph 6
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-URI https://asc.fasb.org//1943274/2147480990/946-20-50-6

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 235
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-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
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-Publisher FASB
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//850/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Section 50
-Paragraph 1
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

+ Details

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy used to determine such fair values (in thousands):


	Fair value measurements at December 31, 2023
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Money market funds	$	12,233	$	—	$	—	$	12,233
Investments:
Commercial paper		—		9,896		—		9,896
Corporate bonds		—		37,023		—		37,023
U.S. Government agencies		—		5,827		—		5,827
Total	$	12,233	$	52,746	$	—	$	64,979


	Fair value measurements at December 31, 2022
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Commercial Paper	$	-	$	6,973	$	-	$	6,973
Money market funds		5,420		-		-		5,420
Investments:
Commercial paper		-		30,443		-		30,443
Corporate bonds		-		52,277		-		52,277
U.S. Government agencies		-		6,601		-		6,601
Total	$	5,420	$	96,294	$	-	$	101,714

Restructuring and Related charges - Schedule of Accrued Liabilities Activity Related to Restructuring Activities (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs, net	$ (8)	$ 204	$ 1,068
Cash payments	(36)	(1,125)	(103)
Ending balance		44	965
Personnel
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs, net	12	202	973
Cash payments	(30)	(1,054)	(103)
Ending balance		18	870
Other
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs, net	(20)	2	95
Cash payments	$ (6)	(71)
Ending balance		$ 26	$ 95

- 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

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation and Principles of Consolidation

The Company has prepared the accompanying consolidated financial statements in conformity with generally accepted accounting principles in the United States (“US GAAP”). The consolidated financial statements include those accounts of the Company and its subsidiaries after elimination of all intercompany accounts and transactions.

Use of Estimates

The preparation of consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of expenses during the reporting periods presented. Estimates are used for, but are not limited to, depreciation of equipment, fair value of financial instruments, the Company’s ability to continue as a going concern and contingencies. Actual results may differ from those estimates.

Cash and Cash Equivalents

Cash equivalents are highly liquid investments with an original maturity of 90 days or less at the date of purchase and consist of time deposits and investments in money market funds with commercial banks and financial institutions. As of December 31, 2023,

cash and cash equivalents included cash on deposit at commercial banks, commercial paper and a money market fund that invests in U.S. Government securities.

Marketable Securities

Investments consist of marketable securities with original maturities greater than 90 days. The Company has classified its investments with maturities beyond one year as short-term, based on their highly liquid nature and because such marketable securities represent the investment of cash that is available for current operations. The Company considers its investment portfolio of marketable securities to be available-for-sale. Accordingly, these investments are recorded at fair value (Level 2). Unrealized gains and losses are reported as the accumulated other comprehensive items in stockholders’ equity. Amortization and accretion of premiums and discounts are recorded in other income (expense). Realized gains or losses on debt securities are included in interest income or interest expense, respectively. If any adjustment to fair value reflects a decline in value of the investment, the Company considers all available evidence to evaluate the extent to which the decline is other than temporary and, if so, marks the investment to market on the Company’s statement of operations and comprehensive loss.

Leases

Effective January 1, 2022, the Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Update No. 2016-02, Leases (Topic 842) (“ASC 842”) using the modified retrospective method. At lease inception, the Company determines if an arrangement is or contains a lease, and if so, assesses the lease for classification as either an operating or finance lease. A lease is classified as a finance lease if any one of the following criteria are met: (i) the lease transfers ownership of the asset by the end of the lease term, (ii) the lease contains an option to purchase the asset that is reasonably certain to be exercised, (iii) the lease term is for a major part of the remaining useful life of the asset, (iv) the present value of the lease payments equals or exceeds substantially all of the fair value of the asset, or (v) the leased asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease. A lease is classified as an operating lease if it does not meet any of these criteria.

Leases with a term greater than one year are recognized on the balance sheet as right-of-use assets and current and non-current lease liabilities, as applicable. Leases with a term of one year or less are expensed as rent in the period incurred. The Company elected not to separate lease and non-lease components for all underlying assets. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. The incremental borrowing rate is determined by using the rate of interest that the Company would pay to borrow on a collateralized basis an amount equal to the lease payments for a similar term and in a similar economic environment. Lease terms include options to extend or terminate the lease when it is reasonably certain that the Company will exercise the options. For leases that existed prior to the adoption of ASC 842, the Company used the remaining lease term to determine the appropriate incremental borrowing rate.

Balance Sheet Risk

The Company maintains its cash in bank deposit and checking accounts that at times exceed insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to any significant credit risk.

Property and Equipment

Property and equipment are recorded at cost and depreciated or amortized over the estimated useful lives of the assets. Repairs or maintenance costs are expensed as incurred. Depreciation is computed using the straight-line method over the following estimated useful lives:


Office equipment and furniture	3—7 years
Research equipment	1—7 years

Impairment of Long-Lived Assets

Long-lived assets, such as property and equipment and right of use assets, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted cash flows expected to be generated by the asset. Impairment losses are then measured by comparing the fair value of assets to their carrying amounts. There were no impairments recorded for the years ended December 31, 2023 and 2022.

Fair Value of Financial Instruments

US GAAP requires disclosure of fair value information about financial instruments, whether or not recognized in the balance sheet, for which it is practicable to estimate that value. The framework provides a fair value hierarchy that prioritizes the inputs for the valuation techniques. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements) and minimizes the use of unobservable inputs. The most observable inputs are used, when available. The three levels of the fair value hierarchy are described as follows:

Level 1—Inputs to the valuation methodology are unadjusted quoted prices for identical assets or liabilities in active markets that the Company has the ability to access.

Level 2—Inputs to the valuation methodology include quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; inputs other than quoted prices that are observable for the asset or liability; and inputs that are derived from, or corroborated by, observable market data by correlation or other means.

Level 3—Inputs to the valuation methodology are unobservable and significant to the fair value measurement.

Research and Development

Research and development costs are expensed in the period incurred. Research and development costs include payroll and personnel expense; consulting costs; external contract research and development costs; raw materials and allocated overhead such as depreciation and amortization, rent and utilities. Advance payments for goods and services to be used in future research and development activities are recorded as prepaid expenses and are expensed over the service period as the services are provided or when the goods are consumed.

Clinical trial costs are a component of research and development expenses. The Company estimates expenses incurred for clinical trials that are in process based on services performed under contractual agreements with clinical research organizations and actual clinical investigators. Included in the estimates are (1) the fee per patient enrolled as specified in the clinical trial contract with each institution participating in the clinical trial and (2) progressive data on patient enrollments obtained from participating clinical trial sites and the actual services performed. Changes in clinical trial assumptions, such as the length of time estimated to enroll all patients, rate of screening failures, patient drop-out rates, number and nature of adverse event reports, and the total number of patients enrolled can impact the average and expected cost per patient and the overall cost of the clinical trial. The Company monitors the progress of the trials and their related activities and adjusts, when applicable, the accruals accordingly. Adjustments to accruals are charged to expense in the period in which the facts that give rise to the adjustment become known. In the event of early termination of a clinical trial or site, the Company would accrue an amount based on estimates of the remaining noncancellable obligations associated with winding down the clinical trial or cancelation of a participating site.

Stock-Based Compensation

The Company accounts for all stock-based compensation, including stock options and warrants, at fair value and recognizes stock-based compensation expense for those equity awards, net of actual forfeitures, over the requisite service period, which is generally the vesting period of the respective award.

Prior to February 3, 2021 the fair value of the Company’s stock options and warrants on the date of grant was determined by the Company with the assistance of a third-party valuation specialist in accordance with the guidance in the American Institute of Certified Public Accountants Valuation Guide, Valuation of Privately-Held-Company Equity Securities Issued as Compensation, as the Company’s common stock was not actively traded.

Income Taxes

Income taxes are accounted for using the asset and liability method of accounting for taxes. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the consolidated financial statement carrying amounts of existing assets and liabilities and their respective tax bases, including operating loss carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the year 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 that includes the enactment date.

A valuation allowance is established when necessary to reduce net deferred tax assets to the amount expected to be realized through future operations. Income tax expense consists of taxes payable for the current period and the net change during the period in deferred tax assets and liabilities.

The Company evaluates its uncertain tax positions based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is more likely than not to be realized. Potential interest and penalties associated with any uncertain tax positions are recorded as a component of income tax expense. Management has evaluated the Company’s tax position and concluded that the Company has taken no uncertain tax positions that would require adjustment or disclosure in the consolidated financial statements.

Net Loss Per Share

The Company follows the two-class method when computing net loss per share as the Company has issued shares that meet the definition of participating securities. The two-class method determines net loss per share for each class of common and participating securities according to dividends declared or accumulated, and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed.

Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net loss attributable to common stockholders is computed by adjusting net loss attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted loss per share attributable to common stockholders is computed by dividing the diluted net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period, including potential dilutive common stock. For purpose of this calculation, outstanding stock options, stock warrants and convertible preferred stock are considered potential dilutive common stock and are excluded from the computation of net loss per share as their effect is anti-dilutive.

The Company’s convertible preferred stock contractually entitles the holders of such shares to participate in dividends but does not contractually require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reports a net loss, such losses are not allocated to such participating securities. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive shares of common stock are not assumed to be outstanding if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the years ended December 31, 2023 and 2022.

Segments

Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the chief operating decision maker (“CODM”), in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s CODM is its chief executive officer. The Company has determined it operates in one segment.

Emerging Growth Company Status

The Company is an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act of 2012 ("the JOBS Act"), and may take advantage of reduced reporting requirements that are otherwise applicable to public companies. Section 107 of the JOBS Act exempts emerging growth companies from being required to comply with new or revised financial accounting standards until private companies are required to comply with those standards. The Company has elected to use the extended transition period for complying with new or revised accounting standards unless otherwise state.

The Company will remain an “emerging growth company” until the earliest of (i) December 31, 2026, (ii) the last day of the fiscal year in which it has total annual gross revenues of $1.235 billion or more, (iii) the date on which it has issued more than $1.0 billion in nonconvertible debt during the previous three years or (iv) the date on which it is deemed to be a large accelerated filer under the rules of the Securities and Exchange Commission (“SEC”), which generally is when it has more than $700 million in market value of its stock held by non-affiliates.

Share Purchase Agreements

In 2023, the Company executed two share repurchase agreements: the Apeiron Purchase Agreement (“Apeiron Purchase Agreement”) on May 23, 2023 for 4,454,248 shares at $1.58 each and the Cambrian Purchase Agreement (the “Cambrian Purchase Agreement”) on July 31, 2023 for 1,587,302 shares at $1.26 each. Both agreements involved repurchasing shares and subsequently retiring them, more fully explained in note 7.

The Apeiron Purchase Agreement and the Cambrian Purchase Agreement were liabilities in accordance with ASC 480, Distinguishing Liabilities from Equity, resulting in unconditional forward purchase contracts that required physical settlement by

repurchase of a fixed number of the Company's shares for cash and recorded as treasury stock transactions. At inception, the liability of $7.7 million for the Apeiron Purchase Agreement and $2.3 million for the Cambrian Purchase Agreement, net of issuance costs, were recorded at the contractual value because the fair value exceeded the contractual value of the shares on May 23, 2023 and July 31, 2023, respectively.

Recently Issued Accounting Standards

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. ASU 2016-13 provides guidance for estimating credit losses on certain types of financial instruments, including trade receivables, by introducing an approach based on expected losses. ASU 2016-13 also amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. The guidance requires a modified retrospective transition method and early adoption is permitted. In November 2019, FASB issued ASU No. 2019-10, Financial Instruments – Credit Losses, Derivatives and Hedging, and Leases (“ASU 2019-10”), which defers the adoption of ASU 2016-13 for smaller reporting companies until periods beginning after December 15, 2022. The Company has adopted the new guidance as of January 1, 2023, and it did not have a material impact on its financial statements and related disclosures.

In December 2023, the FASB issued ASU 2023-09, "Income Taxes (Topic 740): Improvements to Income Tax Disclosures". ASU 2023-09 is intended to enhance the transparency and decision usefulness of income tax disclosures. The amendments in ASU 2023-09 address investor requests for enhanced income tax information primarily through changes to the rate reconciliation and income taxes paid information. Early adoption is permitted. A public entity should apply the amendments in ASU 2023-09 prospectively to all annual periods beginning after December 15, 2024. The Company is currently evaluating the impact of this standard on our consolidated financial statements and related disclosures.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

STOCK-BASED COMPENSATION

8. STOCK-BASED COMPENSATION

2018 Equity Incentive Plan

The Company’s 2018 Stock Incentive Plan (the “2018 Plan”), provided for the Company to grant qualified incentive options, nonqualified options, stock grants and other stock-based awards to employees and non-employees to purchase the Company’s common stock. Upon the effectiveness of the 2021 Plan (as defined below), the Company ceased issuing new awards under the 2018 Plan.

2021 Equity Incentive Plan

The Company’s 2021 Equity Incentive Plan (the “2021 Plan”) was approved by the board of directors on January 27, 2021 and the Company’s stockholders on January 28, 2021, and became effective on the execution of the underwriting agreement related to the Company's initial public offering. The 2021 Plan provides for the grant of incentive stock options to employees, including employees of any parent or subsidiary corporations, and for the grant of nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance awards and other forms of stock awards to employees, directors, and consultants, including employees and consultants of the Company’s affiliates. The number of shares initially reserved for issuance under the 2021 Plan was 5,000,000, which began automatically increasing on January 1 of each calendar year, starting on January 1, 2022 through January 1, 2031, in an amount equal to 4.0% of the total number of shares of the Company’s capital stock outstanding on the last day of the calendar month before the date of each automatic increase, or a lesser number of shares determined by the board of directors. As of December 31, 2023, 2,498,584 shares remained available for issuance pursuant to the 2021 Plan.

In December 2023, the Company's compensation committee determined that the automatic increase of available shares for calendar year 2024 would be reduced from 4.0% to 2.0% of the Company's capital stock. This follows last year's decision to decrease the annual increase from 4% to 1%. As a result, on January 1, 2024 the number of shares available for issuance pursuant to the 2021 Plan increased to 2,999,187 shares.

2021 Employee Stock Purchase Plan

The 2021 Employee Stock Purchase Plan (the “2021 ESPP”) was approved by the Company’s board of directors on January 27, 2021 and became effective on the execution of the underwriting agreement related to the initial public offering. A total of 333,333 shares of common stock were initially reserved for issuance under the 2021 ESPP, which will automatically increase on January 1 of each calendar year, beginning on January 1, 2022 through January 1, 2031, by an amount equal to 1.0% of the total shares of common stock outstanding on December 31st of the preceding calendar year. The purchase price of the shares under the 2021 ESPP are at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the purchase date. As of December 31, 2023, the Company had issued 152,432 shares under the 2021 ESPP. As of December 31, 2023, 794,632 shares were available to be issued under the 2021 ESPP, which increased to 1,044,933 shares as of January 1, 2024.

Stock Options

The Company has granted options to purchase shares of common stock to employees and nonexecutive directors pursuant to the 2021 Plan at a weighted average fair value of $0.99 per share and $2.47 per share during the years ended December 31, 2023 and 2022, respectively. The Company uses the Black-Scholes option-pricing model to estimate the fair value of the stock options on the applicable grant dates.

The following is a summary of the stock option award activity during the years ended December 31, 2023 and 2022:


	Number of Stock Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2022		3,333,434		$	8.80		8.09	$	1
Granted		783,371		$	1.27
Forfeited		(401,919	)	$	5.77
Expired		(295,580	)	$	12.39
Outstanding at December 31, 2023		3,419,306		$	7.12		7.29		—
Options expected to vest as of December 31, 2023		1,235,761		$	2.61		8.56		—
Exercisable at December 31, 2023		2,183,545		$	9.68		6.57		—

No stock options were exercised in the year ended December 31, 2023. The aggregate intrinsic value of stock options exercised in the year ended December 31, 2022 was $0.1 million.

The total fair value of options vested during the years ended December 31, 2023 and 2022 was $4.4 million and $8.2 million, respectively.

At December 31, 2023, there was approximately $4.1 million of unrecognized stock-based compensation expense associated with the stock options, which is expected to be recognized over a weighted-average period of 1.52 years.

At December 31, 2022, there was approximately $8.8 million of unrecognized stock-based compensation expense associated with the stock options, which is expected to be recognized over a weighted-average period of 2.16 years.

Restricted Stock Units

The Company has granted restricted stock units with service-based vesting conditions.

The following is a summary of the restricted stock unit activity during the year ended December 31, 2023:


	Restricted Stock Units			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2022		215,854		$	3.69
Granted		361,597		$	1.45
Vested		(298,536	)	$	2.00
Forfeited		(45,957	)	$	2.92
Unvested at December 31, 2023		232,958		$	2.53

Pursuant to the 2021 Plan, the Company granted restricted stock units which vest annually over a period of one, two, three or four years.

At December 31, 2023, there was approximately $0.4 million of unrecognized stock-based compensation expense associated with the restricted stock units which is expected to be recognized over a weighted-average period of 2.26 years.

At December 31, 2022, there was approximately $0.5 million of unrecognized stock-based compensation expense associated with the restricted stock units which is expected to be recognized over a weighted-average period of 2.8 years.

Common Stock Warrants

The following is a summary of the common stock warrant activity during the years ended December 31, 2023 and 2022:


	Number of Common Stock Warrants			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding and exercisable at December 31, 2022		57,004		$	6.94		1.91	$	—
Expired		(312	)		144		—		—
Outstanding and exercisable at December 31, 2023		56,692		$	6.19		1.16	$	—

As of December 31, 2023, there was no unrecognized stock-based compensation expense associated with the common stock warrants.

During 2023 and 2022, the Company utilized the Black-Scholes option-pricing model for estimating the fair value of the stock options and common stock warrants granted. The following table presents the assumptions and the Company’s methodology for developing each of the assumptions used:


	Year Ended December 31,
	2023	2022
Volatility	93%-97%	94%-97%
Expected term (years)	5.5-7.0	5.5-7.0
Risk-free interest rate	3.6%–4.7%	1.7%-4.2%
Dividend rate	—%	—%

•

Volatility—The Company estimates the expected volatility of its common stock at the date of grant based on the historical volatility of comparable public companies over the expected term.

•

Expected life—The expected life is estimated as the contractual term.

•

Risk-free interest rate—The risk-free rate for periods within the estimated life of the stock award is based on the U.S. Treasury yield curve in effect at the time of grant.

•

Dividend rate—The assumed dividend yield is based upon the Company’s expectation of not paying dividends in the foreseeable future.

Stock-based compensation expense was recorded in the following line items in the consolidated statements of operations for the years ended December 31, 2023 and 2022 (in thousands):


	Year Ended December 31,
	2023		2022
Research and development	$	1,022	$	1,987
General and administrative		3,432		3,825
Total stock-based compensation expense	$	4,454	$	5,812

Other Current Liabilities - Summary of Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Other Liabilities Disclosure [Abstract]
Compensation and employee benefits liabilities	$ 1,510	$ 2,462

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating activities
Net loss	$ (34,101)	$ (48,588)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	4,454	5,812
Depreciation and amortization	571	614
(Accretion) amortization on marketable securities	(1,056)	231
Non-cash lease expense	1,357	1,194
Amortization of financing lease right-of-use assets	780	733
Realized gain on marketable securities		(15)
Loss (gain) on fixed asset disposition	302	(15)
Changes in operating assets and liabilities:
Prepaid expenses	(99)	(582)
Other assets	22	5
Accounts payable and accrued liabilities	(2,331)	2,017
Compensation and employee benefits	(650)	709
Operating lease liabilities	(1,337)	(1,125)
Other liabilities	65	(16)
Net cash used in operating activities	(32,023)	(39,026)
Investing activities
Purchases of property and equipment	(180)	(321)
Purchases of short-term investments	(21,149)	(46,869)
Sales of short-term investments		7,864
Maturities of short-term investments	59,575	89,260
Proceeds from sale of property and equipment	166	15
Net cash provided by investing activities	38,412	49,949
Financing activities
Principal payments for financing leases	(761)	(629)
Proceeds from the exercise of common stock options		238
Payment of employee restricted stock tax withholdings	(76)
Employee stock purchase plan proceeds	48	104
Payments for repurchase of common stock	(10,384)
Net cash used in financing activities	(11,173)	(287)
Net (decrease) increase in cash and cash equivalents	(4,784)	10,636
Cash and cash equivalents at beginning of period	17,795	7,159
Cash and cash equivalents at end of period	13,011	17,795
Supplemental disclosure of noncash financing information:
Share repurchase issuance costs	(86)
Issuance of equity in exchange for compensation included in compensation and employee benefits	302
Property and equipment disposals included in other assets	25
Initial measurement of operating lease right-of-use assets	331	6,549
Initial measurement of operating lease liabilities	$ 331	6,699
Initial measurement of finance lease right-of-use assets		$ 704

CONSOLIDATED STATEMENTS OF COMMON STOCK AND STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2021	$ 146,513	$ 3	$ 296,049	$ (149,206)	$ (333)
Beginning balance, shares at Dec. 31, 2021		30,609,029
Stock-based compensation expense	5,779		5,779
Exercise of options into common stock	238		238
Exercise of options into common stock, Shares		73,784
Employee stock purchase plan expense	136		136
Employee stock purchase plan expense, Shares		81,347
Unrealized gain (loss) on marketable securities	(671)				(671)
Net loss	(48,588)			(48,588)
Ending balance at Dec. 31, 2022	103,407	$ 3	302,202	(197,794)	(1,004)
Ending balance, shares at Dec. 31, 2022		30,764,160
Stock-based compensation expense	4,454		4,454
Issuance of equity in exchange for compensation	302		302
Issuance of equity in exchange for compensation, Shares		208,510
Surrender of shares for tax withholding	(76)		(76)
Surrender of shares for tax withholding, Shares		(50,343)
Purchase agreement, net of issuance costs and excise tax	(9,934)		(9,934)
Purchase agreement, net of issuance costs and excise tax, Shares		(6,041,550)
Vesting of restricted stock shares, shares		90,026
Employee stock purchase plan expense	48		48
Employee stock purchase plan expense, Shares		59,385
Unrealized gain (loss) on marketable securities	795				795
Net loss	(34,101)			(34,101)
Ending balance at Dec. 31, 2023	$ 64,895	$ 3	$ 296,996	$ (231,895)	$ (209)
Ending balance, shares at Dec. 31, 2023		25,030,188

Stock-Based Compensation - Summary of Restricted Stock Unit Activity (Details) - Restricted Stock Units	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Restricted Stock Units, Unvested balance \| shares	215,854
Restricted Stock Units, Granted \| shares	361,597
Restricted Stock Units, Vested \| shares	(298,536)
Restricted Stock Units, Forfeited \| shares	(45,957)
Restricted Stock Units, Unvested balance \| shares	232,958
Weighted-Average Grant Date Fair Value, Unvested balance \| $ / shares	$ 3.69
Weighted-Average Grant Date Fair Value, Granted \| $ / shares	1.45
Weighted-Average Grant Date Fair Value, Vested \| $ / shares	2
Weighted-Average Grant Date Fair Value, Forfeited \| $ / shares	2.92
Weighted-Average Grant Date Fair Value, Unvested balance \| $ / shares	$ 2.53

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	25,030,188	30,764,160
Common stock, shares outstanding	25,030,188	30,764,160

Fair Value Measurements

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

. FAIR VALUE MEASUREMENTS


	Fair value measurements at December 31, 2023
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Money market funds	$	12,233	$	—	$	—	$	12,233
Investments:
Commercial paper		—		9,896		—		9,896
Corporate bonds		—		37,023		—		37,023
U.S. Government agencies		—		5,827		—		5,827
Total	$	12,233	$	52,746	$	—	$	64,979


	Fair value measurements at December 31, 2022
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Commercial Paper	$	-	$	6,973	$	-	$	6,973
Money market funds		5,420		-		-		5,420
Investments:
Commercial paper		-		30,443		-		30,443
Corporate bonds		-		52,277		-		52,277
U.S. Government agencies		-		6,601		-		6,601
Total	$	5,420	$	96,294	$	-	$	101,714

When developing fair value estimates, the Company maximizes the use of observable inputs and minimizes the use of unobservable inputs. When available, the Company uses quoted market prices to measure fair value. The valuation technique used to measure fair value for the Company's Level 1 and Level 2 assets is a market approach, using prices and other relevant information generated by market transactions involving identical or comparable assets. If market prices are not available, the fair value measurement is based on models that use primarily market-based parameters including yield curves, volatilities, credit ratings and currency rates. In certain cases where market rate assumptions are not available, the Company is required to make judgments about assumptions market participants would use to estimate the fair value of a financial instrument.

There were no transfers among Level 1, Level 2 or Level 3 categories in the years ended December 31, 2023 and 2022.

- 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

Restructuring and Related Charges

12 Months Ended

Dec. 31, 2023

Restructuring and Related Activities [Abstract]

RESTRUCTURING AND RELATED CHARGES

13. RESTRUCTURING AND RELATED CHARGES

In December 2022, the Company began implementing a restructuring plan to reduce operating costs primarily associated with a reduction in the Company's workforce (the “Restructuring”).

In connection with the Restructuring, the Company incurred expenses within research and development and general and administrative expenses of $0.2 million during the year ended December 31, 2023. These costs primarily related to one-time termination benefits and ongoing benefit arrangements, both of which included severance payments and extended benefits coverage support and were contingent upon the impacted employees’ execution and non-revocation of separation agreements. Aggregate costs in connection with the Restructuring also included certain contract termination costs.

The following table summarizes the accrued liabilities activity recorded in connection with the Restructuring, including the reduction in workforce in December 2022 and related activities as of December 31, 2023 (in thousands):


	Personnel			Other			Total
Balance at January 1, 2022	$	—		$	—		$	—
Restructuring and other costs, net		973			95			1,068
Cash payments		(103	)		—			(103	)
Balance at December 31, 2022		870			95			965
Restructuring and other costs, net		202			2			204
Cash payments		(1,054	)		(71	)		(1,125	)
Balance at March 31, 2023		18			26			44
Restructuring and other costs, net		12			(20	)		(8	)
Cash payments		(30	)		(6	)		(36	)
Balance at June 30, 2023		—			—			—
Balance at September 30, 2023		—			—			—
Balance at December 31, 2023	$	—		$	—		$	—

Restructuring and Related Charges - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and related charges, Description	In December 2022, the Company began implementing a restructuring plan to reduce operating costs primarily associated with a reduction in the Company's workforce (the “Restructuring”).
Implementing restructuring plan	Dec. 30, 2022
Research and Development and General and Administrative Expenses
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 0.2

- 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

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2023	Feb. 23, 2024	Jun. 30, 2023
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Registrant Name	Sensei Biotherapeutics, Inc.
Entity Central Index Key	0001829802
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		25,070,980
Entity Public Float			$ 18.7
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Document Financial Statement Error Correction	false
ICFR Auditor Attestation Flag	false
Entity File Number	001-39980
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-1863385
Entity Address, Address Line One	1405 Research Blvd
Entity Address, Address Line Two	Suite 125
Entity Address, City or Town	Rockville
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	20850
City Area Code	240
Local Phone Number	243-8000
Document Annual Report	true
Document Transition Report	false
Auditor Firm ID	34
Auditor Name	Deloitte & Touche LLP
Auditor Location	Baltimore, Maryland
Documents Incorporated by Reference	Certain information required in Part III of this Annual Report on Form 10-K will be included in an amendment to this Annual Report on Form 10-K, filed with the Commission within 120 days after December 31, 2023, and is incorporated by reference herein.
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	SNSE
Security Exchange Name	NASDAQ
Series A Preferred Stock Purchase Rights
Document Information [Line Items]
Title of 12(b) Security	Series A Preferred Stock Purchase Rights
No Trading Symbol Flag	true
Security Exchange Name	NASDAQ

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2017
Income Tax Disclosure [Line Items]
Uncertain or unrecognized tax position	$ 0
Percentage of ownership or cumulative change	50.00%
Ownership positions of stockholders rolling period	3 years
Increase in valuation allowance	$ 9,690,000
Change recorded to equity	$ 200,000
Portion of net operating loss carryforwards expiration beginning year	2023
Research and Development
Income Tax Disclosure [Line Items]
Tax credit carryforwards	$ 1,364,000
Tax credit carryforwards expiration beginning year	2034
Federal
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 134,624,000	$ 96,573,000
Remaining net operating losses carryforward period	20 years
State
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 78,765,000

Subsequent Events - Additional Information (Details) - 2021 Equity Incentive Plan - Options - Subsequent Event $ in Millions	Feb. 15, 2024 USD ($) shares
Subsequent Event [Line Items]
Fair value of debt \| $	$ 0.3
Conversion of preferred stock to common stock upon closing of the initial public offering, shares \| shares	515,586

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value of Recurring - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Assets:
Total	$ 64,979	$ 101,714
Level 1
Assets:
Total	12,233	5,420
Level 2
Assets:
Total	52,746	96,294
Money Market Funds
Assets:
Cash equivalents fair value disclosure	12,233	5,420
Money Market Funds \| Level 1
Assets:
Cash equivalents fair value disclosure	12,233	5,420
Commercial Paper
Assets:
Cash equivalents fair value disclosure		6,973
Investments fair value disclosure	9,896	30,443
Commercial Paper \| Level 2
Assets:
Cash equivalents fair value disclosure		6,973
Investments fair value disclosure	9,896	30,443
Corporate Bonds
Assets:
Investments fair value disclosure	37,023	52,277
Corporate Bonds \| Level 2
Assets:
Investments fair value disclosure	37,023	52,277
U.S. Government Agencies
Assets:
Investments fair value disclosure	5,827	6,601
U.S. Government Agencies \| Level 2
Assets:
Investments fair value disclosure	$ 5,827	$ 6,601

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of Stock Option Award Activity

The following is a summary of the stock option award activity during the years ended December 31, 2023 and 2022:


	Number of Stock Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2022		3,333,434		$	8.80		8.09	$	1
Granted		783,371		$	1.27
Forfeited		(401,919	)	$	5.77
Expired		(295,580	)	$	12.39
Outstanding at December 31, 2023		3,419,306		$	7.12		7.29		—
Options expected to vest as of December 31, 2023		1,235,761		$	2.61		8.56		—
Exercisable at December 31, 2023		2,183,545		$	9.68		6.57		—

Summary of Restricted Stock Unit Activity

The following is a summary of the restricted stock unit activity during the year ended December 31, 2023:


	Restricted Stock Units			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2022		215,854		$	3.69
Granted		361,597		$	1.45
Vested		(298,536	)	$	2.00
Forfeited		(45,957	)	$	2.92
Unvested at December 31, 2023		232,958		$	2.53

Summary of Common Stock Warrant Activity

The following is a summary of the common stock warrant activity during the years ended December 31, 2023 and 2022:


	Number of Common Stock Warrants			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding and exercisable at December 31, 2022		57,004		$	6.94		1.91	$	—
Expired		(312	)		144		—		—
Outstanding and exercisable at December 31, 2023		56,692		$	6.19		1.16	$	—

Summary of Fair Value Assumptions and Methodology

The following table presents the assumptions and the Company’s methodology for developing each of the assumptions used:


	Year Ended December 31,
	2023	2022
Volatility	93%-97%	94%-97%
Expected term (years)	5.5-7.0	5.5-7.0
Risk-free interest rate	3.6%–4.7%	1.7%-4.2%
Dividend rate	—%	—%

Summary of Stock-Based Compensation Expense

Stock-based compensation expense was recorded in the following line items in the consolidated statements of operations for the years ended December 31, 2023 and 2022 (in thousands):


	Year Ended December 31,
	2023		2022
Research and development	$	1,022	$	1,987
General and administrative		3,432		3,825
Total stock-based compensation expense	$	4,454	$	5,812

Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Total property and equipment	$ 2,892	$ 3,492
Less accumulated depreciation and amortization	(1,727)	(1,443)
Property and equipment, net	1,165	2,049
Research Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	2,107	2,707
Office Equipment and Furniture
Property Plant And Equipment [Line Items]
Total property and equipment	532	532
Leasehold Improvement
Property Plant And Equipment [Line Items]
Total property and equipment	$ 253	$ 253

Commitments and Contingencies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Sale Leaseback Transaction [Line Items]
Lease expiration year	2027
Letters of credit outstanding amount	$ 678
Sublease income	331
Office Space
Sale Leaseback Transaction [Line Items]
Sublease income	$ 331

Organization and Operations - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss	$ (34,101)	$ (48,588)
Accumulated deficit	(231,895)	$ (197,794)
Cash, cash equivalents and marketable securities	$ 65,800

- Definition

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

+ References

+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Commitments and Contingencies - Summary of Other Information Pertaining to Finance and Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Other Operating Lease Information:
Operating cash flows for operating leases	$ 1,777
Operating cash flows for operating subleases	(316)
Operating cash flows for finance leases	143
Financing cash flows from finance leases	$ 761	$ 629
Weighted average remaining lease term
Operating leases	2 years 9 months 18 days
Financing leases	2 years 1 month 6 days
Weighted average discount rate
Operating leases	7.70%
Financing leases	8.30%

Related-Party Transactions - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended
	Aug. 15, 2023	Jul. 31, 2023	Jun. 01, 2023	May 23, 2023	Dec. 31, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Purchase transaction cost					$ 10,384
Service Agreement \| Hope Farms
Related Party Transaction [Line Items]
Expenses recognized with related party transactions					0	$ 103
Service Agreement \| Binney Street Partners LLC
Related Party Transaction [Line Items]
Expenses recognized with related party transactions					$ 0	$ 223
Purchase Agreement \| Apeiron Parties
Related Party Transaction [Line Items]
Share repurchase, agreed to purchase, shares				4,454,248
Purchase price per share				$ 1.58
Purchase transaction cost			$ 7,800
Negotiation of purchase agreement cost			$ 750
Company 's outstanding shares of common stock				5.00%
Cambrian Purchase Agreement
Related Party Transaction [Line Items]
Share repurchase, agreed to purchase, shares		1,587,302
Purchase price per share		$ 1.26
Aggregate purchase price		$ 2,000
Shares repurchased and retired	1,587,302
Cambrian Purchase Agreement \| Cambrian BioPharma, Inc.
Related Party Transaction [Line Items]
Company 's outstanding shares of common stock		5.00%

Employee Retirement Plan	12 Months Ended
Employee Retirement Plan	Dec. 31, 2023
Retirement Benefits [Abstract]
EMPLOYEE RETIREMENT PLAN	9. EMPLOYEE RETIREMENT PLAN The Company maintains a defined contribution 401(k) profit-sharing plan (the “Plan”) for all employees. Under the Plan, participants may make voluntary contributions up to the maximum amount allowable by law. The Plan is based on employees’ salary deferral, and the Company matches employees’ contributions up to 4% of the employees’ base salary. Employees are 100% vested in the Company’s match contributions. During the years ended December 31, 2023 and 2022, the Company’s matching contributions were $240 thousand and $326 thousand, respectively.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
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+ Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Income Tax Expense

Income tax expense consists of the following (in thousands):


	Year Ended December 31,
	2023			2022
Current:
Federal	$	—		$	—
State		—			—
Current tax provision		—			—
Deferred:
Federal		(5,749	)		(10,351	)
State		(4,141	)		2,307
Deferred tax benefit		(9,890	)		(8,044	)
Less change in valuation allowance		9,890			8,044
Total income tax provision	$	—		$	—

Reconciliation of Federal Statutory Income Tax Rate to Effective Income Tax Rate

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


	Year Ended December 31,
	2023			2022
Federal statutory income tax rate		21.0	%		21.0	%
State income taxes, net of federal benefit		12.1			(4.7	)
Non-deductible transactions costs		(1.4	)		—
Other		(1.2	)		(0.2	)
Equity-based compensation		(1.5	)		0.5
Change in valuation allowance		(29.0	)		(16.6	)
Effective income tax rate	— %			— %

Components of Deferred Tax Assets and Liabilities

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


	December 31,
	2023			2022
Net operating loss carryforwards	$	33,322		$	27,151
Equity-based compensation		3,340			2,735
Research and development tax credit carryforwards		1,364			1,364
Capitalized R&D expenditures		12,235			9,026
Lease liabilities		1,344			1,433
Other accruals		1,071			1,027
Total deferred tax assets	$	52,676		$	42,736
Valuation allowance		(51,050	)		(41,360	)
Net deferred tax assets	$	1,626		$	1,376

Deferred tax liabilities:
'Right-of-use assets	$	(1,626	)	$	(1,376	)
'Total deferred tax liabilities	$	(1,626	)	$	(1,376	)
'Net deferred tax assets (liability)	$	—		$	—

Stock-Based Compensation - Summary of Fair Value Assumptions and Methodology (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Volatility, Minimum	93.00%	94.00%
Volatility, Maximum	97.00%	97.00%
Risk-free interest rate, Minimum	3.60%	1.70%
Risk-free interest rate, Maximum	4.70%	4.20%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	5 years 6 months	5 years 6 months
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	7 years	7 years

- Definition

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

+ References

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+ Details

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

6. COMMITMENTS AND CONTINGENCIES

Operating Lease

As of December 31, 2023, the Company leased office and laboratory facilities under operating leases, which expire at various dates through 2027. The Company had $678 thousand in letters of credit outstanding as security on certain of these leases. As part of its adoption of ASC 842, the Company recorded operating right-of-use assets and operating lease liabilities for these leases as of January 1, 2022.

The Company entered into an operating sublease agreement on January 18, 2023 (the "Sublease") with respect to part of its existing Boston office and laboratory facilities (the "Head Lease"). The Company accounted for the Head Lease and the Sublease as separate contracts and there was no effect on the right-of-use asset or lease liability associated with the Head Lease. The Sublease has an effective end date of June 30, 2024. The Head Lease rent expense is presented separately from income related to the Sublease and both are reported as components of operating expenses on the condensed consolidated statements of operations and comprehensive loss. The Company recorded $331 thousand of income related to the Sublease for the year ended December 31, 2023.

Finance Leases

The Company leases research equipment and furniture under finance leases.

The following table contains a summary of the lease costs recognized under ASC 842 pertaining to the Company’s finance and operating leases for the year ended December 31, 2023 (in thousands):


	Year Ended December 31,
	2023
Lease Cost:
Amortization of finance right-of-use assets	$	780
Interest on finance lease liabilities		143
Operating lease cost		1,796
Variable lease cost		671
Total lease costs		3,390
Operating Sublease income		(331	)
Total lease costs, net	$	3,059


	Year Ended December 31,
	2023
Other Operating Lease Information:
Operating cash flows for operating leases	$	1,777
Operating cash flows for operating subleases	$	(316	)
Operating cash flows for finance leases	$	143
Financing cash flows from finance leases	$	761

Weighted average remaining lease term
Operating leases	2.8 years
Financing leases	2.1 years

Weighted average discount rate
Operating leases	7.7%
Financing leases	8.3%

The following table presents the maturity of the Company’s operating and finance lease liabilities as of December 31, 2023 (in thousands):


	Operating		Financing
2024	$	1,853	$	900
2025		1,734		757
2026		1,413		107
2027		59		—
Total future minimum lease payments	$	5,059	$	1,764
Less amount representing interest		491		124
Total lease liabilities	$	4,568	$	1,640

License Agreements

In the normal course of business, the Company enters into licensing agreements with various parties to obtain the right to make, use, and sell licensed products currently in development.

Litigation

The Company records estimated losses from loss contingencies, such as a loss arising from a litigation, when it determines that it is probable a liability has been incurred and the amount of loss can be reasonably estimated. Litigation is subject to many factors that are difficult to predict so that there can be no assurance, in the event of a material unfavorable result in one or more claims, the Company will not incur material costs.

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Summary of Marketable Securities

Marketable securities consist of the following as of December 31, 2023 and 2022 (in thousands):


	As of December 31, 2023
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Commercial paper	$	9,892	$	6	$	(2	)	$	9,896
Corporate bonds		37,063		—		(40	)		37,023
U.S. Government agencies		6,000		—		(173	)		5,827
Total	$	52,955		6	$	(215	)	$	52,746


	As of December 31, 2022
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Commercial paper	$	30,475	$	1	$	(33	)	$	30,443
Corporate bonds		52,848		—		(571	)		52,277
U.S. Government agencies		7,000		—		(399	)		6,601
Total	$	90,323		1	$	(1,003	)	$	89,321

Employee Retirement Plan - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Company's matching contributions vesting percentage	100.00%
Accrued expense	$ 240	$ 326
Maximum
Defined Benefit Plan Disclosure [Line Items]
Percentage of company matching contributions of employee's base salary	4.00%

Marketable Securities - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Marketable Securities [Line Items]
Fair Value	$ 52,746	$ 89,321
Marketable Securities
Marketable Securities [Line Items]
Amortized Cost	52,955	90,323
Unrealized Gains	6	1
Unrealized Losses	(215)	(1,003)
Fair Value	52,746	89,321
Marketable Securities \| Commercial Paper
Marketable Securities [Line Items]
Amortized Cost	9,892	30,475
Unrealized Gains	6	1
Unrealized Losses	(2)	(33)
Fair Value	9,896	30,443
Marketable Securities \| Corporate Bonds
Marketable Securities [Line Items]
Amortized Cost	37,063	52,848
Unrealized Losses	(40)	(571)
Fair Value	37,023	52,277
Marketable Securities \| U.S. Government Agencies
Marketable Securities [Line Items]
Amortized Cost	6,000	7,000
Unrealized Losses	(173)	(399)
Fair Value	$ 5,827	$ 6,601

Fair Value Measurements - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value, transfer of liabilities, from level 1 to level 2	$ 0	$ 0
Fair value, transfer of liabilities from level 2 to level 1	0	0
Fair value, transfer of assets into level 3	0	0
Fair value, transfer of assets out of level 3	0	0
Fair value, transfer of liabilities into level 3	0	0
Fair value, transfer of liabilities out of level 3	$ 0	$ 0

Marketable Securities - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Marketable Securities [Line Items]
Marketable securities, unrealized loss position, fair value	$ 200,000
Impairment of investments	$ 0	$ 0
Maximum
Marketable Securities [Line Items]
Marketable securities remaining maturity term	1 year
Marketable securities unrealized loss position, maturity term	1 year

Net Loss Per Share - Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Stock Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from calculation of diluted net loss per share	3,419,306	3,333,434
Unvested Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from calculation of diluted net loss per share	232,958	215,854
Warrants Issued to Employees and Contractor to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from calculation of diluted net loss per share	56,692	57,004
Warrants Issued Related to Convertible Notes and Other Equity Agreements
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from calculation of diluted net loss per share	412,262	412,262

Property and Equipment, Net

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT, NET

4. PROPERTY AND EQUIPMENT, NET

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


	December 31, 2023			December 31, 2022
Research equipment	$	2,107		$	2,707
Office equipment and furniture		532			532
Leasehold improvement		253			253
Total property and equipment		2,892			3,492
Less accumulated depreciation and amortization		(1,727	)		(1,443	)
Property and equipment, net	$	1,165		$	2,049

Depreciation and amortization expense for the years ended December 31, 2023 and 2022 was $0.6 million and $0.6 million, respectively.

Effective January 1, 2022, the Company adopted ASC 842 and reclassed capital leases that were previously classified as property and equipment, net were presented as right of use assets - financing leases, net on the Company's consolidated balance sheet. $2.2 million relates to items previously classified under research equipment and $70 thousand relates to items previously classified under office equipment and furniture on the table above. These leases are further described in Note 6.

Net Loss Per Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

NET LOSS PER SHARE

12. NET LOSS PER SHARE

Basic and diluted net loss per share attributable to common stockholders is calculated as follows (in thousands except share and per share amounts):


	Year Ended December 31,
	2023			2022
Net loss	$	(34,101	)	$	(48,588	)
Net loss per share—basic and diluted	$	(1.22	)	$	(1.58	)
Weighted-average number of shares used in computing net loss per share—basic and diluted		27,952,857			30,703,295

The following outstanding potentially dilutive securities have been excluded from the calculation of diluted net loss per share, as their effect is anti-dilutive:


	For the Year Ended December 31,
	2023		2022
Stock options to purchase common stock		3,419,306		3,333,434
Unvested restricted stock units		232,958		215,854
Warrants issued to employees and contractor to purchase common stock		56,692		57,004
Warrants issued related to convertible notes and other equity agreements		412,262		412,262

Subsequent Events

12 Months Ended

Dec. 31, 2023

Subsequent Events [Abstract]

SUBSEQUENT EVENTS

14. SUBSEQUENT EVENTS

Bonus Conversion to Equity

In January 2024, the compensation committee of the board of directors approved a deviation from the usual method of payment of annual bonuses for the Company's executives and other senior management. Approximately one-third of their annual bonuses were paid out in the form of stock options in lieu of cash. As a result, on February 15, 2024, the Company granted options exercisable for 515,586 shares of common stock under the 2021 Plan with a grant date fair value of $0.3 million.

Debt - Additional Information (Details)	Dec. 31, 2022 $ / shares
Debt Instrument [Line Items]
Exercise price per share	$ 6.94

- 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
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(a))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-3

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

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481568/470-20-55-69B

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69C
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481568/470-20-55-69C

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
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-URI https://asc.fasb.org//1943274/2147481568/470-20-55-69E

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69F
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481568/470-20-55-69F

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

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

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

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

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

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1D
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1D

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1D

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Paragraph 1D
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1D

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Name Accounting Standards Codification
-Section 50
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Reference 21: http://www.xbrl.org/2003/role/disclosureRef
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Reference 22: http://www.xbrl.org/2003/role/disclosureRef
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Reference 23: http://www.xbrl.org/2003/role/disclosureRef
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Reference 24: http://www.xbrl.org/2003/role/disclosureRef
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Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation and Principles of Consolidation

Use of Estimates

Cash and Cash Equivalents

cash and cash equivalents included cash on deposit at commercial banks, commercial paper and a money market fund that invests in U.S. Government securities.

Marketable Securities

Leases

Balance Sheet Risk

Property and Equipment


Office equipment and furniture	3—7 years
Research equipment	1—7 years

Impairment of Long-Lived Assets

Fair Value of Financial Instruments

Level 1—Inputs to the valuation methodology are unadjusted quoted prices for identical assets or liabilities in active markets that the Company has the ability to access.

Level 3—Inputs to the valuation methodology are unobservable and significant to the fair value measurement.

Research and Development

Stock-Based Compensation

Income Taxes

Net Loss Per Share

Segments

Emerging Growth Company Status

Share Purchase Agreements

Recently Issued Accounting Standards

Stock-Based Compensation - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Jan. 01, 2024	Jan. 01, 2022	Jan. 27, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average fair value per share of options granted	$ 0.99	$ 2.47
Aggregate intrinsic value of stock options exercised	$ 100,000
Grant date fair value of options vested	4,400,000	$ 8,200,000
Unrecognized stock-based compensation expense	$ 4,100,000	$ 8,800,000
Weighted-average period	1 year 6 months 7 days	2 years 1 month 28 days
Common Stock Warrants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense	$ 0
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period	2 years 3 months 3 days	2 years 9 months 18 days
Unrecognized stock-based compensation expense	$ 400,000	$ 500,000
2021 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance	2,498,584			5,000,000
Number of capital stock outstanding percentage	4.00%
2021 Equity Incentive Plan \| Restricted Stock Units \| Vesting Period One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	1 year
2021 Equity Incentive Plan \| Restricted Stock Units \| Vesting Period Two
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	2 years
2021 Equity Incentive Plan \| Restricted Stock Units \| Vesting Period Three
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
2021 Equity Incentive Plan \| Restricted Stock Units \| Vesting Period Four
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	4 years
2021 Equity Incentive Plan \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance			2,999,187
2021 Equity Incentive Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of increase of available shares	4.00%
Percentage of decrease in annual increase of available shares	4.00%
2021 Equity Incentive Plan \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of increase of available shares	2.00%
Percentage of decrease in annual increase of available shares	1.00%
2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance	794,632				333,333
Percentage of number of shares of capital stock outstanding on last day of preceding year	1.00%
Purchase price of fair value common stock, percent	85.00%
Shares issued under plan	152,432
2021 Employee Stock Purchase Plan \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance			1,044,933

Restructuring and Related Charges (Tables)

12 Months Ended

Dec. 31, 2023

Restructuring and Related Activities [Abstract]

Schedule of Accrued Liabilities Activity Related to Restructuring Activities

The following table summarizes the accrued liabilities activity recorded in connection with the Restructuring, including the reduction in workforce in December 2022 and related activities as of December 31, 2023 (in thousands):


	Personnel			Other			Total
Balance at January 1, 2022	$	—		$	—		$	—
Restructuring and other costs, net		973			95			1,068
Cash payments		(103	)		—			(103	)
Balance at December 31, 2022		870			95			965
Restructuring and other costs, net		202			2			204
Cash payments		(1,054	)		(71	)		(1,125	)
Balance at March 31, 2023		18			26			44
Restructuring and other costs, net		12			(20	)		(8	)
Cash payments		(30	)		(6	)		(36	)
Balance at June 30, 2023		—			—			—
Balance at September 30, 2023		—			—			—
Balance at December 31, 2023	$	—		$	—		$	—

Income Taxes - Schedule of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Deferred:
Federal	$ (5,749)	$ (10,351)
State	(4,141)	2,307
Deferred tax benefit	(9,890)	(8,044)
Less change in valuation allowance	$ 9,890	$ 8,044

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

INCOME TAXES

11. INCOME TAXES

Income tax expense consists of the following (in thousands):


	Year Ended December 31,
	2023			2022
Current:
Federal	$	—		$	—
State		—			—
Current tax provision		—			—
Deferred:
Federal		(5,749	)		(10,351	)
State		(4,141	)		2,307
Deferred tax benefit		(9,890	)		(8,044	)
Less change in valuation allowance		9,890			8,044
Total income tax provision	$	—		$	—

The components of the Company’s loss before income tax expense in comprised solely of domestic sources. The effective income tax rate for the years ended December 31, 2023 and 2022 was different from the federal statutory income tax rate primarily due to the change in valuation allowance against deferred tax assets and permanent differences primarily related to equity based compensation. The reconciliation of the federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2023			2022
Federal statutory income tax rate		21.0	%		21.0	%
State income taxes, net of federal benefit		12.1			(4.7	)
Non-deductible transactions costs		(1.4	)		—
Other		(1.2	)		(0.2	)
Equity-based compensation		(1.5	)		0.5
Change in valuation allowance		(29.0	)		(16.6	)
Effective income tax rate	— %			— %

The Company’s deferred tax assets consist primarily of its net operating loss, equity-based compensation, research and development tax credit carryforwards and capitalized research and development expenditures, along with other minor temporary differences. No amounts are being considered as an uncertain tax position or disclosed as an unrecognized tax benefit. The Company has provided a valuation allowance against its total net deferred tax assets because the Company’s ability to generate sufficient future taxable income is uncertain.

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


	December 31,
	2023			2022
Net operating loss carryforwards	$	33,322		$	27,151
Equity-based compensation		3,340			2,735
Research and development tax credit carryforwards		1,364			1,364
Capitalized R&D expenditures		12,235			9,026
Lease liabilities		1,344			1,433
Other accruals		1,071			1,027
Total deferred tax assets	$	52,676		$	42,736
Valuation allowance		(51,050	)		(41,360	)
Net deferred tax assets	$	1,626		$	1,376

Deferred tax liabilities:
'Right-of-use assets	$	(1,626	)	$	(1,376	)
'Total deferred tax liabilities	$	(1,626	)	$	(1,376	)
'Net deferred tax assets (liability)	$	—		$	—

The Company has incurred annual net operating losses in each year since inception. The Company believes it could be subject to certain limitations on the utilization of these net operating losses pursuant to Internal Revenue Code Section 382. Therefore, the Company has not reflected the benefit of any such net operating loss carryforwards in the financial statements. Due to the Company’s history of losses, and lack of other positive evidence, the Company has determined that it is more likely than not that its net deferred tax assets will not be realized, and therefore, the net deferred tax assets are fully offset by a valuation allowance at December 31, 2023 and 2022.

Future realization of the tax benefits of existing temporary differences and net operating loss carryforwards ultimately depends on the existence of sufficient taxable income within the carryforward period. As of December 31, 2023 and 2022, the Company performed an evaluation to determine whether a valuation allowance was needed. The Company considered all available evidence, both positive and negative, which included the results of operations for the current and preceding years. The Company determined that it was not possible to reasonably quantify future taxable income and determined that it is more likely than not that all of the deferred tax assets will not be realized. Accordingly, the Company maintained a full valuation allowance as of December 31, 2023 and 2022.

The utilization of NOLs and tax credit carryforwards to offset future taxable income may be subject to an annual limitation as a result of ownership changes that have occurred previously or may occur in the future. Under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, (“IRC”), a corporation that undergoes an ownership change may be subject to limitations on its ability to utilize its pre-change NOLs and other tax attributes otherwise available to offset future taxable income and/or tax liability. An ownership change is defined as a cumulative change of 50% or more in the ownership positions of certain stockholders during a rolling three-year period. The Company has not completed a formal study to determine if any ownership changes within the meaning of IRC Section 382 and 383 have occurred as of December 31, 2023. An ownership change would restrict its ability to use its NOLs or tax credit carryforwards and could require the Company to pay federal or state income taxes earlier than would be required if such limitations were not in effect.

The Company’s valuation allowance increased during the year by $9,690 thousand for the year ended December 31, 2023 due primarily to the generation of net operating losses and a $200 thousand change recorded to equity.

As of December 31, 2023, the Company has net operating loss carryforwards for federal and state tax reporting purposes of $134,624 thousand and $78,765 thousand, respectively, a portion of which expire beginning in 2023. Net operating loss carryforwards generated after December 31, 2017 for federal tax reporting purposes of $96,573 thousand have an indefinite life. The remaining federal net operating losses are subject to a 20-year carryforward period. As of December 31, 2023, the Company has research and development tax credit carryforwards of approximately $1,364 thousand, which expire beginning in 2034.

The Company evaluates its uncertain tax positions under ASC 740-10, which requires that realization of an uncertain income tax position be recognized in the financial statements. The benefit to be recorded in the financial statements is the amount most likely to be realized assuming a review by tax authorities having all relevant information and applying current conventions. The Company concluded that there are no uncertain tax positions in any of the periods presented.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. The earliest tax years that remain subject to examination by jurisdiction is 2020 for both federal and state. However, to the extent the Company utilizes net operating losses from years prior to 2020, the statute remains open to the extent of the net operating losses or other credits are utilized.

- Definition

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

+ References

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

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

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

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

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

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

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

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

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

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

+ Details

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Schedule of Basic and Diluted Net Loss Per Share

Basic and diluted net loss per share attributable to common stockholders is calculated as follows (in thousands except share and per share amounts):


	Year Ended December 31,
	2023			2022
Net loss	$	(34,101	)	$	(48,588	)
Net loss per share—basic and diluted	$	(1.22	)	$	(1.58	)
Weighted-average number of shares used in computing net loss per share—basic and diluted		27,952,857			30,703,295

Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share

The following outstanding potentially dilutive securities have been excluded from the calculation of diluted net loss per share, as their effect is anti-dilutive:


	For the Year Ended December 31,
	2023		2022
Stock options to purchase common stock		3,419,306		3,333,434
Unvested restricted stock units		232,958		215,854
Warrants issued to employees and contractor to purchase common stock		56,692		57,004
Warrants issued related to convertible notes and other equity agreements		412,262		412,262