0001619856-24-000038 | 10-Q | XBRL Viewer

Leases (Tables)

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

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


	Three Months Ended March 31,
	2024		2023
Operating lease cost(1)	$	1,953	$	1,884
Short-term lease cost	63		63
Total lease cost	$	2,016	$	1,947

(1)Included $0.7 million and $0.6 million of variable lease cost related to operating expenses and taxes for the three months ended March 31, 2024, and 2023, respectively.

Schedule Of Supplemental Information Related To Leases

Supplemental information related to our leases was as follows (in thousands):


	Three Months Ended March 31,
	2024		2023
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	711	$	1,093

The following table summarizes the weighted-average remaining lease term and weighted-average discount rate for our corporate laboratory and office leases:


	March 31, 2024		December 31, 2023
Weighted-average remaining lease term (years)	7.1		7.4
Weighted-average discount rate	11.3	%	11.3	%

Summary of Future Minimum Lease Payment Under Leases

The following table summarizes a maturity analysis of our operating lease liabilities showing the aggregate lease payments as of March 31, 2024 (in thousands):


Remainder of 2024(1)	$	2,774
2025	4,475
2026	5,720
2027	5,922
2028	6,122
Thereafter	15,993
Total future undiscounted lease payments	41,006
Less imputed interest	(13,847)
Total discounted lease payments	27,159
Less current portion of lease liability	(1,264)
Noncurrent portion of lease liability	$	25,895

(1)Reflects an offset of $0.6 million related to incentives expected to be received in 2024.

Related Party Transactions	3 Months Ended
Related Party Transactions	Mar. 31, 2024
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Since December 31, 2023, there have been no new related party transactions, except as set forth below. For further information regarding our related parties, see Note 7 to the consolidated financial statements included in our Form 10-K. Pfizer Investment During the three months ended March 31, 2024, we recognized $0.6 million of revenue from our Information Rights Agreement with Pfizer, dated June 29, 2023, pursuant to which we had originally allocated $7.5 million as a contract with a customer under ASC Topic 606. We did not recognize any revenue from Pfizer during the three months ended March 31, 2023. As of March 31, 2024, there was approximately $5.6 million of related party deferred revenue ($2.5 million included in current liabilities and $3.1 million included in long-term liabilities) related to our performance obligation to Pfizer. As of December 31, 2023, there was approximately $6.2 million of related party deferred revenue ($2.5 million included in current liabilities and $3.7 million included in long-term liabilities) related to our performance obligation to Pfizer.

- 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

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+ Details

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Financial Instruments Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Assets:
Cash and cash equivalents	$ 49,400	$ 51,162	$ 52,744
U.S. Treasury bills
Assets:
Cash and cash equivalents	13,904	23,527
Commercial paper
Assets:
Cash and cash equivalents	23,858	9,759
Fair Value, Recurring
Assets:
Assets fair value	345,926	372,404
Liabilities:
Liabilities fair value	2,636	2,939
Fair Value, Recurring \| U.S. Treasury bills
Assets:
Assets fair value	239,369	262,439
Fair Value, Recurring \| Commercial paper
Assets:
Assets fair value	51,462	40,373
Fair Value, Recurring \| U.S. government agency bonds
Assets:
Assets fair value	33,073	40,185
Fair Value, Recurring \| Money market funds
Assets:
Assets fair value	11,638	17,876
Fair Value, Recurring \| Corporate debt securities
Assets:
Assets fair value	10,384	11,531
Fair Value, Recurring \| MSKCC success payments liability
Liabilities:
Liabilities fair value	2,636	2,939
Fair Value, Recurring \| Level 1
Assets:
Assets fair value	251,007	280,315
Liabilities:
Liabilities fair value	0	0
Fair Value, Recurring \| Level 1 \| U.S. Treasury bills
Assets:
Assets fair value	239,369	262,439
Fair Value, Recurring \| Level 1 \| Commercial paper
Assets:
Assets fair value	0	0
Fair Value, Recurring \| Level 1 \| U.S. government agency bonds
Assets:
Assets fair value	0	0
Fair Value, Recurring \| Level 1 \| Money market funds
Assets:
Assets fair value	11,638	17,876
Fair Value, Recurring \| Level 1 \| Corporate debt securities
Assets:
Assets fair value	0	0
Fair Value, Recurring \| Level 1 \| MSKCC success payments liability
Liabilities:
Liabilities fair value	0	0
Fair Value, Recurring \| Level 2
Assets:
Assets fair value	94,919	92,089
Liabilities:
Liabilities fair value	0	0
Fair Value, Recurring \| Level 2 \| U.S. Treasury bills
Assets:
Assets fair value	0	0
Fair Value, Recurring \| Level 2 \| Commercial paper
Assets:
Assets fair value	51,462	40,373
Fair Value, Recurring \| Level 2 \| U.S. government agency bonds
Assets:
Assets fair value	33,073	40,185
Fair Value, Recurring \| Level 2 \| Money market funds
Assets:
Assets fair value	0	0
Fair Value, Recurring \| Level 2 \| Corporate debt securities
Assets:
Assets fair value	10,384	11,531
Fair Value, Recurring \| Level 2 \| MSKCC success payments liability
Liabilities:
Liabilities fair value	0	0
Fair Value, Recurring \| Level 3
Assets:
Assets fair value	0	0
Liabilities:
Liabilities fair value	2,636	2,939
Fair Value, Recurring \| Level 3 \| U.S. Treasury bills
Assets:
Assets fair value	0	0
Fair Value, Recurring \| Level 3 \| Commercial paper
Assets:
Assets fair value	0	0
Fair Value, Recurring \| Level 3 \| U.S. government agency bonds
Assets:
Assets fair value	0	0
Fair Value, Recurring \| Level 3 \| Money market funds
Assets:
Assets fair value	0	0
Fair Value, Recurring \| Level 3 \| Corporate debt securities
Assets:
Assets fair value	0	0
Fair Value, Recurring \| Level 3 \| MSKCC success payments liability
Liabilities:
Liabilities fair value	$ 2,636	$ 2,939

Subsequent Events - Additional Information (Details) $ in Millions	Apr. 22, 2024 USD ($)
Subsequent Event
Subsequent Event [Line Items]
Litigation settlement, expense	$ 3.9

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes No income tax expense was recorded during each of the three-month periods ended March 31, 2024, and 2023 due to our operating losses.

- Definition

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

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-Topic 946
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+ Details

Balance Sheet Items (Tables)

3 Months Ended

Mar. 31, 2024

Balance Sheet Related Disclosures [Abstract]

Schedule of Other Receivables

Other receivables consisted of the following (in thousands):


	March 31, 2024		December 31, 2023
Patent cost reimbursements	$	1,067	$	1,403
Accrued interest on marketable securities	658		702
Other	—		181
Total	$	1,725	$	2,286

Schedule of Prepaid Expenses and Other Current Assets

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


	March 31, 2024		December 31, 2023
Prepaid contract manufacturing and clinical costs	$	4,486	$	3,942
Prepaid insurance	581		993
Other	1,846		1,220
Total	$	6,913	$	6,155

Schedule of Property and Equipment

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


	March 31, 2024		December 31, 2023
Lab equipment	$	17,164	$	15,581
Leasehold improvements	2,261		2,235
Computer equipment	906		895
Furniture and equipment	322		499
Construction in progress	8,368		8,204
Total property and equipment, gross	29,021		27,414
Less: accumulated depreciation and amortization	(9,854)		(9,144)
Property and equipment, net	$	19,167	$	18,270

Summary of Accrued Expenses and Other Current Liabilities

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


	March 31, 2024		December 31, 2023
Accrued employee compensation and related expenses	$	4,454	$	9,517
Accrued research and development expenses	7,594		8,720
Accrued litigation settlement	3,900		—
Accrued patent expenses	500		613
Accrued expenses related to sublicensing revenues	816		802
Credit card liability	426		377
Other	1,300		1,106
Total	$	18,990	$	21,135

Fair Value Measurements and Fair Value of Financial Instruments - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
MSKCC success payments liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Change in fair value	$ 0.3	$ 0.3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Deferred revenue, current	$ 2,827	$ 2,847
Deferred revenue, noncurrent	$ 5,428	$ 6,102
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares outstanding (in shares)	90,314,501	88,448,948
Common stock, shares issued (in shares)	90,314,501	88,448,948
Related Party
Deferred revenue, current	$ 2,487	$ 2,487
Deferred revenue, noncurrent	$ 3,108	$ 3,730

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Basis of Presentation and Principles of Consolidation

Our unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) and include our accounts and the accounts of our wholly owned subsidiaries. All intercompany accounts and transactions are eliminated in consolidation.

Use Of Estimates

Use of Estimates

The preparation of unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires our management to make estimates and assumptions that affect the reported amounts of assets and liabilities; the disclosure of contingent assets and liabilities at the date of our unaudited condensed consolidated financial statements; and the reported amounts of revenue, income, and expenses during the applicable reporting period. On an ongoing basis, we evaluate our estimates and assumptions, including those related to revenue recognition, stock-based compensation expense, accrued expenses related to research and development activities, valuation of the Memorial Sloan Kettering Cancer Center (“MSKCC”) success payments liability, operating lease right-of-use assets and liabilities, and income taxes. Our management bases its estimates on historical experience and various other assumptions that they believe to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates.

Segments

We operate and manage our business as one reportable operating segment, which is the business of developing a pipeline of allogeneic CAR-T and CAR-NK cell therapies. Our president and chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for allocating resources and evaluating financial performance. All long-lived assets are maintained in the United States.

Concentration of Credit Risk and Other Uncertainties

Concentrations of Credit Risk and Other Uncertainties

Financial instruments that potentially subject us to concentration of credit risk consist of cash and cash equivalents, accounts receivable, contract assets, other receivables, and investments in marketable securities and equity securities. Substantially all of our cash and cash equivalents are deposited in accounts at four financial institutions, and our account balances exceed federally insured limits. We mitigate the risks by investing in high-grade instruments, limiting our exposure to one issuer, and we monitor the ongoing creditworthiness of the financial institutions and issuers.

Licensees that represent 10% or more of our revenue and accounts receivable and contract assets were as follows:


	Revenue				Accounts Receivable and Contract Assets
	Three Months Ended				As of March 31, 2024		As of December 31, 2023
	March 31, 2024		March 31, 2023
Licensee A	25.3	%	17.6	%	29.5	%	*
Licensee B	23.1	%	22.0	%	36.6	%	47.5	%
Licensee C	—	%	45.9	%	—	%	*
Licensee D	25.6	%	—	%	—	%	*
Total	74.0	%	85.5	%	66.1	%	47.5	%

*Less than 10%

We monitor economic conditions to identify facts or circumstances that may indicate if any of our accounts receivable are not collectible or if contract assets should be impaired.

Recent Accounting Pronouncements Not Yet Adopted

In October 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2023-06, Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative. This ASU aligns the requirements in the Accounting Standards Codification (“ASC”) to the removal of certain disclosure requirements set out in Regulation S-X and Regulation S-K, announced by the U.S. Securities and Exchange Commission (“SEC”). The effective date for each amended topic in the ASC is either the date on which the SEC’s removal of the related disclosure requirement from Regulation S-X or Regulation S-K becomes effective or June 30, 2027, if the SEC has not removed the requirements by that date. Early adoption is prohibited. We are currently evaluating the impact of the new guidance and do not expect that the adoption of ASU 2023-06 will have a material impact on our consolidated financial statements.

In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. This ASU requires public entities to disclose information about their reportable segments’ significant expenses and other segment items on an interim and annual basis. Public entities with a single reportable segment are required to apply the disclosure requirements in ASU 2023-07, as well as all existing segment disclosures and reconciliation requirements in ASC 280 on an interim and annual basis. ASU 2023-07 is effective for fiscal years beginning after December 15, 2023, and for interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. We are currently evaluating the impact of the adoption of ASU 2023-07.

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. This ASU requires public entities, on an annual basis, to provide disclosure of specific categories in the rate reconciliation, as well as disclosure of income taxes paid disaggregated by jurisdiction. ASU 2023-09 is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. We are currently evaluating the impact of the adoption of ASU 2023-09.

In March 2024, the FASB issued ASU No. 2024-01, Compensation - Stock Compensation (Topic 718): Scope Application of Profits Interest and Similar Awards. The amendments in ASU 2024-01 improve consistent application of and simplify U.S. GAAP of Topic 718 by clarifying and amending existing guidance. ASU 2024-01 is effective for fiscal years beginning after December 15, 2024, and for interim periods within those annual periods, with early adoption permitted. We are currently evaluating the impact of the adoption of ASU 2024-01.

In March 2024, the FASB issued ASU No. 2024-02, Codification Improvements - Amendments to Remove References to the Concepts Statements. The amendments in ASU 2024-02 clarify and simplify references to certain concept statements within U.S. GAAP. ASU 2024-02 is effective for fiscal years beginning after December 15, 2024, with early application permitted. We are currently evaluating the impact of the adoption of ASU 2024-02.

- Definition

Disclosure of accounting policy for segment reporting.

+ References + Details

Revenue

3 Months Ended

Mar. 31, 2024

Revenue from Contract with Customer [Abstract]

Revenue

Disaggregation of Revenue

We disaggregate revenue by geographical market based on the location of research and development activities of our licensees and collaborators. The following table is a summary of revenue by geographic location for the three months ended March 31, 2024, and 2023 (in thousands):


	Three Months Ended March 31,
	2024		2023
United States	$	2,269	$	3,385
Rest of world	160		117
Total	$	2,429	$	3,502

During the three months ended March 31, 2024, we recognized $1.8 million of revenue related to performance obligations satisfied at a point in time, and we recognized $0.6 million of revenue related to performance obligations satisfied over time.

During the three months ended March 31, 2023, we recognized $1.9 million of revenue related to performance obligations satisfied at a point in time, and we recognized $1.6 million of revenue related to performance obligations satisfied over time.

Contract Balances

Accounts receivable relate to our right to consideration for performance obligations completed (or partially completed) for which we have an unconditional right to consideration. Our accounts receivable balances represent amounts that we billed to our licensees with invoices outstanding as of the end of a reporting period.

Contract assets are rights to consideration in exchange for a license that we have granted to a licensee when the right is conditional on something other than the passage of time. Our contract asset balances represent royalties and milestone payments from our other license agreements that are unbilled as of the end of a reporting period.

Contract liabilities consist of deferred revenue and relate to amounts invoiced to, or advance consideration received from, licensees that precede our satisfaction of the associated performance obligations. As of March 31, 2024, and December 31, 2023, our deferred revenue balance primarily resulted from the upfront payment received relating to our performance obligation to Pfizer Inc. (“Pfizer”). The remaining deferred revenue relates to upfront payments received under license agreements that also include nonrefundable annual license fees, which are accounted for as material rights for license renewals and are recognized at the point in time when annual license fees are paid by the licensees and the renewal periods begin.

The following table presents changes in our contract assets and liabilities during the three months ended March 31, 2024 (in thousands):


	Balance as of December 31, 2023		Additions		Deductions		Balance as of March 31, 2024
Accounts receivable	$	148	$	2,193	$	(1,424)	$	917

Contract assets:
Unbilled accounts receivable	$	1,425	$	971	$	(1,425)	$	971

Contract liabilities:
Deferred revenue, current and long-term	$	8,949	$	675	$	(1,369)	$	8,255

Unbilled accounts receivable decreased $0.5 million during the three months ended March 31, 2024, primarily due to the decrease in minimum annual royalties under our license agreements.

Deferred revenue decreased during the three months ended March 31, 2024, primarily due to the recognition of deferred revenue related to the satisfaction of our performance obligation to Pfizer. See Note 7 to our unaudited condensed consolidated financial statements included elsewhere in this Form 10-Q for additional information.

During the three months ended March 31, 2024, and 2023, we recognized $0.7 million and $1.1 million of revenue, respectively, which was included in the opening contract liabilities balances at the beginning of the respective periods.

Transaction Prices Allocated to Remaining Performance Obligations

Remaining performance obligations represent in aggregate the amount of a transaction price that has been allocated to performance obligations not delivered as of the end of a reporting period. The value of transaction prices allocated to remaining unsatisfied performance obligations as of March 31, 2024, was approximately $8.3 million. We expect to recognize approximately $2.8 million of remaining performance obligations as revenue in the next 12 months and to recognize the remainder thereafter.

Capitalized Contract Acquisition Costs and Fulfillment Costs

We did not incur any expenses to obtain our existing contracts, and costs to fulfill those contracts do not generate or enhance our resources. As such, no costs to obtain or fulfill a contract have been capitalized in any period.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
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-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-15

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
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-Section 50
-Paragraph 12
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-13

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org//606/tableOfContent

+ Details

Stock Based Compensation - Schedule of Stock Option Expenses Related to Employee and Non-Employee Stock Options Granted (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	$ 3,988	$ 3,131
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	1,617	1,310
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	$ 2,371	$ 1,821

Subsequent Events	3 Months Ended
Subsequent Events	Mar. 31, 2024
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On April 22, 2024, an agreement in principle was reached with the plaintiffs in the Bergman v. Caribou Biosciences, Inc., et al., Case Number 4:23-cv-01742-YGR (“Bergman Case”) to settle the Bergman Case for $3.9 million. The parties are negotiating a settlement agreement, which the court must approve before settlement is final. See Note 9 to our unaudited condensed consolidated financial statements included elsewhere in this Form 10-Q for additional information.

Common Stock (Tables)

3 Months Ended

Mar. 31, 2024

Equity [Abstract]

Schedule of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consisted of the following:


	As of March 31, 2024	As of December 31, 2023
Stock options, issued and outstanding	12,094,332	9,410,404
Stock options, authorized for future issuance	6,565,993	5,952,012
Stock available under our employee stock purchase plan	2,278,809	1,516,355
Unvested restricted stock units and performance-based restricted stock units	1,180,548	205,357
	22,119,682	17,084,128

Leases - Schedule Of Supplemental Information Related To Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Operating cash flows from operating leases	$ 711	$ 1,093
Operating lease, weighted average remaining lease term	7 years 1 month 6 days		7 years 4 months 24 days
Weighted-average discount rate	11.30%		11.30%

Fair Value Measurements and Fair Value of Financial Instruments

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements and Fair Value of Financial Instruments

The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows:

Level 1—Quoted prices in active markets for identical assets or liabilities.

Level 2—Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

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

Assets and liabilities measured at fair value are classified in their entireties based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires our management to make judgments and consider factors specific to the asset or liability.

Our financial instruments consist of Level 1, Level 2, and Level 3 financial instruments. We generally classify our marketable securities as Level 1 or Level 2. Instruments are classified as Level 2 when observable market prices for identical securities that are traded in less active markets are used. When observable market prices for identical securities are not available, such instruments are priced using benchmark curves, benchmarking of like securities, sector groupings, matrix pricing, and valuation models. These valuation models are proprietary to the pricing providers or brokers and incorporate a number of inputs including, in approximate order of priority: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including market research publications. For certain security types, additional inputs may be used, or some of the standard inputs may not be applicable. Evaluators may prioritize inputs differently on any given day for any security based on market conditions, and not all inputs listed are available for use in the evaluation process for each security valuation on any given day. Changes in the ability to observe valuation inputs may result in a reclassification of levels of certain securities within the fair value hierarchy. We recognize transfers into and out of levels within the fair value hierarchy in the period in which the actual event or change in circumstances that caused the transfer occurs. No such transfers occurred during the three months ended March 31, 2024, and 2023. Level 1 financial instruments are comprised of money market fund investments and U.S. Treasury bills. Level 2 financial instruments are comprised of commercial paper, corporate debt securities, and U.S. government agency bonds. Financial assets and liabilities are considered Level 3 when their fair values are determined using pricing models, discounted cash flow methodologies, or similar techniques, and at least one significant model assumption or input is unobservable. Level 3 financial instruments consist of the MSKCC success payments liability.

The following table sets forth our financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):


	Fair Value Measurements as of March 31, 2024
	Total		Level 1		Level 2		Level 3
Assets:
U.S. Treasury bills ($13,904 included in cash and cash equivalents)	$	239,369	$	239,369	$	—	$	—
Commercial paper ($23,858 included in cash and cash equivalents)	51,462		—		51,462		—
U.S. government agency bonds	33,073		—		33,073		—
Money market fund investments (included in cash and cash equivalents)	11,638		11,638		—		—
Corporate debt securities	10,384		—		10,384		—
Total fair value of assets	$	345,926	$	251,007	$	94,919	$	—
Liabilities:
MSKCC success payments liability	$	2,636	$	—	$	—	$	2,636
Total fair value of liabilities	$	2,636	$	—	$	—	$	2,636


	Fair Value Measurements as of December 31, 2023
	Total		Level 1		Level 2		Level 3
Assets:
U.S. Treasury bills ($23,527 included in cash and cash equivalents)	$	262,439	$	262,439	$	—	$	—
Commercial paper ($9,759 included in cash and cash equivalents)	40,373		—		40,373		—
U.S. government agency bonds	40,185		—		40,185		—
Money market fund investments (included in cash and cash equivalents)	17,876		17,876		—		—
Corporate debt securities	11,531		—		11,531		—
Total fair value of assets	$	372,404	$	280,315	$	92,089	$	—
Liabilities:
MSKCC success payments liability	$	2,939	$	—	$	—	$	2,939
Total fair value of liabilities	$	2,939	$	—	$	—	$	2,939

The fair value and amortized cost of cash equivalents and available-for-sale marketable securities by major security type as of March 31, 2024, and December 31, 2023 are presented in the following tables (in thousands):


	As of March 31, 2024
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses		Estimated Fair Value
U.S. Treasury bills ($13,904 included in cash and cash equivalents)	$	239,568	$	12	$	(211)	$	239,369
Commercial paper ($23,858 included in cash and cash equivalents)	51,491		—		(29)		51,462
U.S. government agency bonds	33,159		—		(86)		33,073
Money market fund investments (included in cash equivalents)	11,638		—		—		11,638
Corporate debt securities	10,393		7		(16)		10,384
Total cash equivalents and marketable securities	$	346,249	$	19	$	(342)	$	345,926

Classified as:
Cash and cash equivalents							$	49,400
Marketable securities, short-term							244,588
Marketable securities, long-term							51,938
Total cash equivalents and marketable securities							$	345,926


	As of December 31, 2023
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses		Estimated Fair Value
U.S. Treasury bills ($23,527 included in cash and cash equivalents)	$	262,328	$	331	$	(220)	$	262,439
Commercial paper ($9,759 included in cash and cash equivalents)	40,386		—		(13)		40,373
U.S. government agency bonds	40,295		1		(111)		40,185
Money market fund investments (included in cash equivalents)	17,876		—		—		17,876
Corporate debt securities	11,489		50		(8)		11,531
Total cash equivalents and marketable securities	$	372,374	$	382	$	(352)	$	372,404

Classified as:
Cash and cash equivalents							$	51,162
Marketable securities, short-term							277,665
Marketable securities, long-term							43,577
Total cash equivalents and marketable securities							$	372,404

The following table presents the fair value of available-for-sale marketable securities by contractual maturities (in thousands):


	March 31, 2024
Due in less than one year	$	244,588
Due in one to five years	51,938
Total	$	296,526

The following table sets forth a summary of the changes in the fair value of our Level 3 financial liability (in thousands):


	MSKCC Success Payments Liability
Balance at December 31, 2023	$	2,939
Change in fair value	(303)
Balance at March 31, 2024	$	2,636

Our liability for the MSKCC success payments is carried at fair value and changes are recognized as expense or income as part of other income (expense) until the success payments liability is paid or expires. We recorded a $0.3 million and $0.3 million change in the fair value of the MSKCC success payments liability as a gain in other income (expense) in our unaudited condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2024, and 2023, respectively.

The table below summarizes key assumptions used in the valuation of the MSKCC success payments liability:


	As of December 31, 2023
Fair value of common stock	$	5.73
Risk-free interest rate	3.88%
Expected volatility	79%
Probability of achieving multiple of Initial Share Price(1)	5.2% to 18.1%
Expected term (years)	3.7 to 5.2

(1)MSKCC is entitled to certain success payments if our common stock fair value increases, during a specified time period, by certain multiples of value based on a comparison of the fair market value of our common stock to $5.1914 per share, adjusted for any future stock splits (“Initial Share Price”). For further information regarding our agreement with MSKCC, see Note 4 to the consolidated financial statements included in our Form 10-K.

The computation of expected volatility was estimated using a combination of available information about the historical volatility of stocks of similar publicly traded companies for a period matching the expected term assumption and the historical and implied volatility of our stock. The risk-free interest rate, expected volatility, and expected term assumptions depend on the time period from the initiation of our AMpLify phase 1 clinical trial for our CB-012 product candidate utilizing the know-how, biological materials, and intellectual property licensed under the Exclusive License Agreement, dated November 13, 2020, with MSKCC (“MSKCC Agreement”) until the estimated timing of marketing approval for this product candidate from the U.S. Food and Drug Administration (“FDA”). In addition, we incorporated the estimated number and timing of valuation measurement dates in the calculation of the MSKCC success payments liability.

As of March 31, 2024, we did not note any significant changes to the inputs used in the MSKCC success payments liability fair value calculation, other than a change in the fair value of our common stock to $5.14 per share.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (41,234)	$ (28,044)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	710	589
Gain on disposal of fixed assets	0	(34)
Change in fair value of equity securities	0	15
Stock-based compensation expense	3,988	3,131
Change in fair value of MSKCC success payments liability	(303)	(255)
Acquired in-process research and development	1,500	0
Accretion of discounts on investments in marketable securities, net	(1,539)	(1,494)
Non-cash lease expense	524	515
Changes in operating assets and liabilities:
Accounts receivable	(770)	(1,331)
Contract assets	454	607
Other receivables	561	545
Prepaid expenses and other current assets	(758)	1,811
Other assets	(209)	62
Accounts payable	2,720	1,502
Accrued expenses and other current liabilities	(2,204)	(4,138)
Deferred revenue, current and long-term	(694)	(1,097)
Operating lease liabilities	51	(323)
Net cash used in operating activities	(37,203)	(27,939)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities of marketable securities	97,088	98,665
Purchases of marketable securities	(71,184)	(75,931)
Purchases of property and equipment	(1,448)	(2,031)
Payments to acquire in-process research and development	(1,500)	0
Net cash provided by investing activities	22,956	20,703
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	489	519
Proceeds from purchases of common stock under employee stock purchase plan	667	0
Proceeds from issuance of common stock related to our at-the-market equity offering program, net of offering expenses	11,329	1,123
Net cash provided by financing activities	12,485	1,642
NET DECREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	(1,762)	(5,594)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH — BEGINNING OF PERIOD	51,208	58,384
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH — END OF PERIOD	49,446	52,790
RECONCILIATION OF CASH, CASH EQUIVALENTS, AND RESTRICTED CASH
Cash and cash equivalents	49,400	52,744
Restricted cash	46	46
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH ON THE BALANCE SHEET	49,446	52,790
SUPPLEMENTAL SCHEDULE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Purchases of property and equipment included in accounts payable and accrued expenses	851	1,714
Offering costs included in accrued expenses	$ 0	$ 116

Net Loss Per Share (Tables)

3 Months Ended

Mar. 31, 2024

Earnings Per Share [Abstract]

Basic and Diluted Net Income Per Share

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


	Three Months Ended March 31,
	2024		2023
Numerator:
Net loss	$	(41,234)	$	(28,044)
Denominator:
Weighted-average common shares outstanding used to compute net loss per share, basic and diluted	89,302,937		61,186,514
Net loss per share, basic and diluted	$	(0.46)	$	(0.46)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

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


	As of March 31, 2024	As of March 31, 2023
Stock options outstanding	12,094,332	9,102,960
RSUs issued and outstanding	1,128,191	236,169
Shares committed under ESPP	108,788	149,350
	13,331,311	9,488,479

Stock Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		32 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Dec. 31, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)	22,119,682		22,119,682	17,084,128
Stock options granted during period (in shares)	2,913,727
Unrecognized stock based-compensation expenses	$ 35,000		$ 35,000
Weighted-average period (in years)	2 years 9 months 18 days
Stock-based compensation expense	$ 3,988	$ 3,131
RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period (in years)	3 years 4 months 24 days
Unrecognized stock-based compensation expense, excluding options	$ 7,100		7,100
Stock-based compensation expense	427	$ 191
Performance Restricted Stock Units (PRSU)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense, excluding options	$ 600		$ 600
Shares committed under ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)	2,278,809		2,278,809	1,516,355
Accrued liabilities	$ 200		$ 200
Employee
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted during period (in shares)	2,913,727	2,536,340
Weighted average grant date fair value (in dollars per share)	$ 4.59	$ 4.13
2021 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)	6,565,993		6,565,993
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock in connection with at-the-market offering, net of offering expenses (in shares)			329,602

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
CURRENT ASSETS
Cash and cash equivalents	$ 49,400	$ 51,162
Marketable securities, short-term	244,588	277,665
Accounts receivable	917	148
Contract assets	971	1,425
Other receivables	1,725	2,286
Prepaid expenses and other current assets	6,913	6,155
Total current assets	304,514	338,841
NON-CURRENT ASSETS
Investments in equity securities	7,753	7,753
Marketable securities, long-term	51,938	43,577
Property and equipment, net	19,167	18,270
Operating lease, right of use assets	21,659	22,182
Other assets	1,794	1,586
TOTAL ASSETS	406,825	432,209
CURRENT LIABILITIES
Accounts payable	5,940	3,120
Accrued expenses and other current liabilities	18,990	21,135
Operating lease liabilities, current	1,264	1,200
Deferred revenue ($2,487 and $2,487 from related party, respectively)	2,827	2,847
Total current liabilities	29,021	28,302
LONG-TERM LIABILITIES
Deferred revenue, net of current portion ($3,108 and $3,730 from related party, respectively)	5,428	6,102
MSKCC success payments liability	2,636	2,939
Operating lease liabilities, non-current	25,895	25,908
Deferred tax liabilities	556	557
Total liabilities	63,536	63,808
COMMITMENTS AND CONTINGENCIES (Note 9)
STOCKHOLDERS’ EQUITY
Common stock, par value $0.0001 per share, 300,000,000 shares authorized at March 31, 2024, and December 31, 2023, respectively; 90,314,501 and $88,448,948 shares issued and outstanding as of March 31, 2024, and December 31, 2023, respectively	9	8
Additional paid-in-capital	684,121	667,648
Accumulated other comprehensive (loss) income	(322)	30
Accumulated deficit	(340,519)	(299,285)
Total stockholders’ equity	343,289	368,401
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 406,825	$ 432,209

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Tax Disclosure [Abstract]
Income tax expense	$ 0	$ 0

- Definition

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

+ References + Details

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Revenue	$ 2,429	$ 3,502
Operating expenses:
Research and development	33,788	25,709
General and administrative	14,643	8,909
Total operating expenses	48,431	34,618
Loss from operations	(46,002)	(31,116)
Other income (expense):
Change in fair value of equity securities	0	(15)
Change in fair value of MSKCC success payments liability	303	255
Other income, net	4,465	2,832
Total other income	4,768	3,072
Net loss	(41,234)	(28,044)
Other comprehensive income (loss):
Net unrealized (loss) gain on available-for-sale marketable securities, net of tax	(352)	788
Net comprehensive loss	$ (41,586)	$ (27,256)
Net loss per share, basic (in dollars per share)	$ (0.46)	$ (0.46)
Net loss per share, diluted (in dollars per share)	$ (0.46)	$ (0.46)
Weighted-average common shares outstanding, basic (in shares)	89,302,937	61,186,514
Weighted-average common shares outstanding, diluted (in shares)	89,302,937	61,186,514

Balance Sheet Items - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Accrued employee compensation and related expenses	$ 4,454	$ 9,517
Accrued research and development expenses	7,594	8,720
Accrued litigation settlement	3,900	0
Accrued patent expenses	500	613
Accrued expenses related to sublicensing revenues	816	802
Credit card liability	426	377
Other	1,300	1,106
Total	$ 18,990	$ 21,135

401(k) Savings Plan	3 Months Ended
401(k) Savings Plan	Mar. 31, 2024
Retirement Benefits [Abstract]
401(K) Savings Plan	401(k) Savings Plan In 2017, we established a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code of 1986, as amended (“Tax Code”). Our 401(k) plan is available to all employees and allows participants to defer a portion of their annual compensation on a pretax basis subject to applicable laws. We also provide a 4% match for employee contributions up to a certain limit. During the three months ended March 31, 2024, and 2023, we contributed $0.4 million and $0.3 million, respectively, to our 401(k) plan.

Related Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Jun. 29, 2023
Related Party Transaction [Line Items]
Revenue	$ 2,429,000	$ 3,502,000
Deferred revenue	8,255,000		$ 8,949,000
Deferred revenue ($2,487 and $2,487 from related party, respectively)	2,827,000		2,847,000
Deferred revenue, net of current portion ($3,108 and $3,730 from related party, respectively)	5,428,000		6,102,000
Pfizer \| Related Party
Related Party Transaction [Line Items]
Revenue	600,000	$ 0
Deferred revenue	5,600,000		6,200,000	$ 7,500,000
Deferred revenue ($2,487 and $2,487 from related party, respectively)	2,500,000		2,500,000
Deferred revenue, net of current portion ($3,108 and $3,730 from related party, respectively)	$ 3,100,000		$ 3,700,000

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479941/924-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-5

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

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147482810/280-10-50-40

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-41

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-4

+ Details

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

There have been no changes to the significant accounting policies disclosed in Note 2 to the annual consolidated financial statements for the year ended December 31, 2023, included in our Annual Report on Form 10-K (“Form 10-K”).

Basis of Presentation and Principles of Consolidation

Use of Estimates

Segments

Concentrations of Credit Risk and Other Uncertainties

Licensees that represent 10% or more of our revenue and accounts receivable and contract assets were as follows:


	Revenue				Accounts Receivable and Contract Assets
	Three Months Ended				As of March 31, 2024		As of December 31, 2023
	March 31, 2024		March 31, 2023
Licensee A	25.3	%	17.6	%	29.5	%	*
Licensee B	23.1	%	22.0	%	36.6	%	47.5	%
Licensee C	—	%	45.9	%	—	%	*
Licensee D	25.6	%	—	%	—	%	*
Total	74.0	%	85.5	%	66.1	%	47.5	%

*Less than 10%

We monitor economic conditions to identify facts or circumstances that may indicate if any of our accounts receivable are not collectible or if contract assets should be impaired. No allowance for credit losses or contract asset impairment was recorded as of March 31, 2024, or December 31, 2023.

Recent Accounting Pronouncements Not Yet Adopted

Revenue (Tables)

3 Months Ended

Mar. 31, 2024

Revenue from Contract with Customer [Abstract]

Schedule of Disaggregation of Revenue

The following table is a summary of revenue by geographic location for the three months ended March 31, 2024, and 2023 (in thousands):


	Three Months Ended March 31,
	2024		2023
United States	$	2,269	$	3,385
Rest of world	160		117
Total	$	2,429	$	3,502

Schedule of Changes in Company's Contract Assets and Liabilities

The following table presents changes in our contract assets and liabilities during the three months ended March 31, 2024 (in thousands):


	Balance as of December 31, 2023		Additions		Deductions		Balance as of March 31, 2024
Accounts receivable	$	148	$	2,193	$	(1,424)	$	917

Contract assets:
Unbilled accounts receivable	$	1,425	$	971	$	(1,425)	$	971

Contract liabilities:
Deferred revenue, current and long-term	$	8,949	$	675	$	(1,369)	$	8,255

Stock Based Compensation

3 Months Ended

Mar. 31, 2024

Share-Based Payment Arrangement [Abstract]

Stock Based Compensation

Stock-Based Compensation

Equity Incentive Plans

In July 2021, our board of directors adopted and our stockholders approved the 2021 Equity Incentive Plan (“2021 Plan”) that became effective on July 22, 2021. As of March 31, 2024, we had 6,565,993 shares available for issuance under the 2021 Plan.

The following table summarizes stock option activity under our equity incentive plans during the three months ended March 31, 2024:


	Stock Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)(1)

Outstanding at December 31, 2023	9,410,404	$	8.03	8.0	$	6,432
Options granted	2,913,727	6.70
Options exercised	(134,347)	3.64
Options cancelled or forfeited	(95,452)	11.73
Outstanding at March 31, 2024	12,094,332	$	7.73	8.2	$	4,031
Exercisable at March 31, 2024	4,824,205	$	8.18	7.0	$	3,161
Vested and expected to vest at March 31, 2024	12,094,332	$	7.73	8.2	$	4,031

(1)The aggregate intrinsic value is calculated as the difference between the stock option exercise price and the estimated fair value of the underlying common stock at the end of each reporting period referenced above.

Grant Date Fair Value

During the three months ended March 31, 2024, and 2023, we granted 2,913,727 and 2,536,340 stock options to employees with a weighted average grant date fair value of $4.59 and $4.13, respectively.

We estimated the fair value of each employee stock option award on the grant date using the Black-Scholes option-pricing model based on the following assumptions:

Three Months Ended March 31,

2024

2023

Volatility

75.7% to 75.9%

74.9% to 75.0%

Expected term (in years)

5.0 to 6.0

Risk-free interest rate

4.0% to 4.3%

3.5% to 4.1%

Expected dividend yield

0.0%

As of March 31, 2024, there was $35.0 million of unrecognized stock-based compensation expense related to employee stock options that is expected to be recognized over a weighted-average period of 2.8 years.

Restricted Stock Units

During the three months ended March 31, 2024, we granted 995,767 restricted stock units (“RSUs”) and did not grant any performance-based RSUs (“PSUs”) under the 2021 Plan. A summary of the status of and change in unvested RSUs and PSUs as of March 31, 2024 was as follows:


	Number of Shares Underlying Outstanding RSUs and PSUs	Weighted-Average Grant Date Fair Value per RSU and PSU
Unvested, January 1, 2024	205,357	$	8.49
Granted	995,767	6.81
Vested	(15,000)	10.64
Forfeited	(5,576)	8.65
Unvested, March 31, 2024	1,180,548	$	7.04

The PSUs were granted to our executive officers and will vest contingent upon the achievement of a clinical milestone for CB-010 during a performance period ending December 31, 2024, and an executive officer’s continued

employment during the performance period. As of March 31, 2024, the achievement of this milestone was not considered probable and, therefore, no stock-based compensation was recorded.

As of March 31, 2024, the total unrecognized stock-based compensation expense related to unvested RSUs was $7.1 million, which is expected to be recognized over the remaining weighted-average vesting period of 3.4 years. As of March 31, 2024, there was approximately $0.6 million of unrecognized stock-based compensation expense related to unvested PSUs.

Employee Stock Purchase Plan (“ESPP”)

In July 2021, our board of directors adopted and our stockholders approved the ESPP, which became effective on July 22, 2021. We have issued 329,602 shares of common stock under the ESPP as of March 31, 2024. We recorded $0.2 million in accrued liabilities related to contributions withheld as of March 31, 2024.

Stock-Based Compensation Expense

We recorded stock-based compensation expense related to employee equity-based awards grants in our unaudited condensed consolidated statements of operations and comprehensive loss as follows (in thousands):


	Three Months Ended March 31,
	2024		2023
Research and development	$	1,617	$	1,310
General and administrative	2,371		1,821
Total	$	3,988	$	3,131

The above stock-based compensation expense related to the following equity-based awards (in thousands):


	Three Months Ended March 31,
	2024		2023
Stock options	$	3,489	$	2,798
ESPP	72		142
RSUs	427		191
Total	$	3,988	$	3,131

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Fair Value and Amortized Cost of Cash Equivalents and Available-for-Sale Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Cash, cash equivalents, and available-for-sale, amortized cost	$ 346,249	$ 372,374
Cash and cash equivalents, Amortized Cost Basis	49,400	51,162	$ 52,744
Unrealized Gains	19	382
Unrealized Losses	(342)	(352)
Available-for-sale marketable securities and cash and cash equivalents, Estimated Fair Value	345,926	372,404
Marketable securities, short-term	244,588	277,665
Marketable securities, long-term	51,938	43,577
U.S. Treasury bills
Debt Securities, Available-for-Sale [Line Items]
Cash and cash equivalents, Amortized Cost Basis	13,904	23,527
Commercial paper
Debt Securities, Available-for-Sale [Line Items]
Cash and cash equivalents, Amortized Cost Basis	23,858	9,759
Money market funds
Debt Securities, Available-for-Sale [Line Items]
Cash and cash equivalents, Amortized Cost Basis	11,638	17,876
Cash and cash equivalents, Estimated Fair Value	11,638	17,876
U.S. Treasury bills
Debt Securities, Available-for-Sale [Line Items]
Cash, cash equivalents, and available-for-sale, amortized cost	239,568	262,328
Unrealized Gains	12	331
Unrealized Losses	(211)	(220)
Available-for-sale marketable securities and cash and cash equivalents, Estimated Fair Value	239,369	262,439
U.S. government agency bonds
Debt Securities, Available-for-Sale [Line Items]
Available-for-sale marketable securities, Amortized Cost Basis	33,159	40,295
Unrealized Gains	0	1
Unrealized Losses	(86)	(111)
Available-for-sale marketable securities, Estimated Fair Value	33,073	40,185
Commercial paper
Debt Securities, Available-for-Sale [Line Items]
Cash, cash equivalents, and available-for-sale, amortized cost		40,386
Available-for-sale marketable securities, Amortized Cost Basis	51,491
Unrealized Gains	0	0
Unrealized Losses	(29)	(13)
Available-for-sale marketable securities and cash and cash equivalents, Estimated Fair Value		40,373
Available-for-sale marketable securities, Estimated Fair Value	51,462
Corporate debt securities
Debt Securities, Available-for-Sale [Line Items]
Available-for-sale marketable securities, Amortized Cost Basis	10,393	11,489
Unrealized Gains	7	50
Unrealized Losses	(16)	(8)
Available-for-sale marketable securities, Estimated Fair Value	$ 10,384	$ 11,531

Stock Based Compensation - Schedule of Estimated Fair Value of Stock Options on the Grant Date Using Black-Scholes Option-Pricing Model (Details)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Volatility	75.70%	74.90%
Expected term (in years)	5 years	5 years
Risk-free interest rate	4.00%	3.50%
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Volatility	75.90%	75.00%
Expected term (in years)	6 years	6 years
Risk-free interest rate	4.30%	4.10%

- Definition

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

+ References

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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480483/718-10-35-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-Section 50
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-Subparagraph (c)(1)(ii)
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-Section 50
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-Subparagraph (c)(1)(iii)
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-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
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-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(02)
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-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(03)
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-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(04)
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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-Subparagraph (c)(2)(i)
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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
-Topic 718
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-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
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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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Reference 20: http://www.xbrl.org/2003/role/disclosureRef
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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 24: http://www.xbrl.org/2003/role/disclosureRef
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Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
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Reference 26: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 2
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Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
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-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

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

+ Details

Balance Sheet Items - Schedule of Other Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Patent cost reimbursements	$ 1,067	$ 1,403
Accrued interest on marketable securities	658	702
Other	0	181
Total	$ 1,725	$ 2,286

Fair Value Measurements and Fair Value of Financial Instruments - Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Due in less than one year	$ 244,588	$ 277,665
Due in one to five years	51,938	$ 43,577
Total	$ 296,526

Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 2024

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

The following table summarizes stock option activity under our equity incentive plans during the three months ended March 31, 2024:


	Stock Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)(1)

Outstanding at December 31, 2023	9,410,404	$	8.03	8.0	$	6,432
Options granted	2,913,727	6.70
Options exercised	(134,347)	3.64
Options cancelled or forfeited	(95,452)	11.73
Outstanding at March 31, 2024	12,094,332	$	7.73	8.2	$	4,031
Exercisable at March 31, 2024	4,824,205	$	8.18	7.0	$	3,161
Vested and expected to vest at March 31, 2024	12,094,332	$	7.73	8.2	$	4,031

Schedule of Estimated Fair Value of Stock Options on the Grant Date Using Black-Scholes Option-Pricing Model

We estimated the fair value of each employee stock option award on the grant date using the Black-Scholes option-pricing model based on the following assumptions:

Three Months Ended March 31,

2024

2023

Volatility

75.7% to 75.9%

74.9% to 75.0%

Expected term (in years)

5.0 to 6.0

Risk-free interest rate

4.0% to 4.3%

3.5% to 4.1%

Expected dividend yield

0.0%

Schedule of Restricted Stock Units Activity (RSUs)

A summary of the status of and change in unvested RSUs and PSUs as of March 31, 2024 was as follows:


	Number of Shares Underlying Outstanding RSUs and PSUs	Weighted-Average Grant Date Fair Value per RSU and PSU
Unvested, January 1, 2024	205,357	$	8.49
Granted	995,767	6.81
Vested	(15,000)	10.64
Forfeited	(5,576)	8.65
Unvested, March 31, 2024	1,180,548	$	7.04

Schedule of Stock-Based Compensation Expenses Recorded in the Condensed Consolidated Statements of Operations and Comprehensive Loss


	Three Months Ended March 31,
	2024		2023
Research and development	$	1,617	$	1,310
General and administrative	2,371		1,821
Total	$	3,988	$	3,131

Schedule of Stock-Based Compensation Expense Related to Equity-Based Awards

The above stock-based compensation expense related to the following equity-based awards (in thousands):


	Three Months Ended March 31,
	2024		2023
Stock options	$	3,489	$	2,798
ESPP	72		142
RSUs	427		191
Total	$	3,988	$	3,131

Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Summary Of Provision For Credit Losses and other Uncertainties

Licensees that represent 10% or more of our revenue and accounts receivable and contract assets were as follows:


	Revenue				Accounts Receivable and Contract Assets
	Three Months Ended				As of March 31, 2024		As of December 31, 2023
	March 31, 2024		March 31, 2023
Licensee A	25.3	%	17.6	%	29.5	%	*
Licensee B	23.1	%	22.0	%	36.6	%	47.5	%
Licensee C	—	%	45.9	%	—	%	*
Licensee D	25.6	%	—	%	—	%	*
Total	74.0	%	85.5	%	66.1	%	47.5	%

*Less than 10%

401(k) Savings Plan - Additional Information (Details) - 2017 Plan - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, Employer matching contribution percent of match	4.00%
Employer contribution	$ 0.4	$ 0.3

Revenue - Additional Information (Details1) $ in Millions	Mar. 31, 2024 USD ($)
Disaggregation Of Revenue [Line Items]
Remaining performance obligations	$ 8.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-04-01
Disaggregation Of Revenue [Line Items]
Remaining performance obligations	$ 2.8
Remaining performance obligation, expected timing of satisfaction, period	12 months

- Definition

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

+ References + Details

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Change in Fair Value of Financial Liability (Details) - MSKCC success payments liability - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Change in fair value	$ (300)	$ (300)
Level 3
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at December 31, 2023	2,939
Change in fair value	(303)
Balance at March 31, 2024	$ 2,636

Leases

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

Leases

Operating Lease Obligations

As of March 31, 2024, we had operating leases for our laboratory and office space in Berkeley, California, consisting of approximately 75,000 square feet, with remaining lease terms up to 8.3 years. Certain of our laboratory and office space lease agreements include options to extend the terms for a period of five years and also contain provisions for future rent increases. In addition to base rent, we pay our share of operating expenses and taxes.

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


	Three Months Ended March 31,
	2024		2023
Operating lease cost(1)	$	1,953	$	1,884
Short-term lease cost	63		63
Total lease cost	$	2,016	$	1,947

(1)Included $0.7 million and $0.6 million of variable lease cost related to operating expenses and taxes for the three months ended March 31, 2024, and 2023, respectively.

Supplemental information related to our leases was as follows (in thousands):


	Three Months Ended March 31,
	2024		2023
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	711	$	1,093

The following table summarizes the weighted-average remaining lease term and weighted-average discount rate for our corporate laboratory and office leases:


	March 31, 2024		December 31, 2023
Weighted-average remaining lease term (years)	7.1		7.4
Weighted-average discount rate	11.3	%	11.3	%

The following table summarizes a maturity analysis of our operating lease liabilities showing the aggregate lease payments as of March 31, 2024 (in thousands):


Remainder of 2024(1)	$	2,774
2025	4,475
2026	5,720
2027	5,922
2028	6,122
Thereafter	15,993
Total future undiscounted lease payments	41,006
Less imputed interest	(13,847)
Total discounted lease payments	27,159
Less current portion of lease liability	(1,264)
Noncurrent portion of lease liability	$	25,895

(1)Reflects an offset of $0.6 million related to incentives expected to be received in 2024.

Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2024 USD ($) segment	Dec. 31, 2023 USD ($)
Accounting Policies [Abstract]
Number of operating segment	1
Number of reportable segment	1
Allowance for doubtful accounts \| $	$ 0	$ 0

Common Stock - Schedule of Common Stock Reserved for Future Issuance (Details) - USD ($) $ / shares in Units, $ in Millions		2 Months Ended	3 Months Ended
	Aug. 09, 2022	Aug. 31, 2023	Mar. 31, 2024	Dec. 31, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)			22,119,682	17,084,128
Authorized amount under shelf registration	$ 400.0
At The Market ATM Offering
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate offering price (up to)			$ 12.3
Common stock shares sold (in shares)			1,762,806
Public offering price (in dollars per share)			$ 7.32
Aggregate gross proceeds			$ 12.9
At The Market ATM Offering \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate offering price (up to)	$ 100.0
Public Stock Offering
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate offering price (up to)		$ 134.4
Common stock shares sold (in shares)		22,115,384
Public offering price (in dollars per share)		$ 6.50
Aggregate gross proceeds		$ 143.7
Over-Allotment Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares sold (in shares)		2,884,615
Stock options, issued and outstanding
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)			12,094,332	9,410,404
Stock options, authorized for future issuance
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)			6,565,993	5,952,012
Stock available under our employee stock purchase plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)			2,278,809	1,516,355
Unvested restricted stock units and performance-based restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)			1,180,548	205,357

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net loss	$ (41,234)	$ (28,044)

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Assumptions Used in Valuation of MSKCC Success Payments Liability (Details)	12 Months Ended
	Dec. 31, 2023 $ / shares	Mar. 31, 2024
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common stock value per share (in dollars per share)	$ 5.1914
Fair value of common stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, measurement input	5.73	5.14
Risk-free interest rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, measurement input	0.0388
Expected volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, measurement input	0.79
Probability of achieving multiple of Initial Share Price \| Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, measurement input	0.052
Probability of achieving multiple of Initial Share Price \| Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, measurement input	0.181
Expected term (years) \| Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability assumptions term	3 years 8 months 12 days
Expected term (years) \| Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability assumptions term	5 years 2 months 12 days

Net Loss Per Share - Computation of the Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	13,331,311	9,488,479
Stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	12,094,332	9,102,960
Restricted Stock Units RSU and Performance-Based RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	1,128,191	236,169
Shares committed under ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	108,788	149,350

Summary of Significant Accounting Policies - Schedule of Concentration of Credit Risk and other Uncertainties (Details) - Customer Concentration Risk	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Revenue \| Major Customers
Concentration Risk [Line Items]
Total	74.00%	85.50%
Revenue \| Licensee A
Concentration Risk [Line Items]
Total	25.30%	17.60%
Revenue \| Licensee B
Concentration Risk [Line Items]
Total	23.10%	22.00%
Revenue \| Licensee C
Concentration Risk [Line Items]
Total	0.00%	45.90%
Revenue \| Licensee D
Concentration Risk [Line Items]
Total	25.60%	0.00%
Accounts Receivable and Contract Assets \| Major Customers
Concentration Risk [Line Items]
Total	66.10%		47.50%
Accounts Receivable and Contract Assets \| Licensee A
Concentration Risk [Line Items]
Total	29.50%
Accounts Receivable and Contract Assets \| Licensee B
Concentration Risk [Line Items]
Total	36.60%		47.50%
Accounts Receivable and Contract Assets \| Licensee C
Concentration Risk [Line Items]
Total	0.00%
Accounts Receivable and Contract Assets \| Licensee D
Concentration Risk [Line Items]
Total	0.00%

Description of the Business, Organization, and Liquidity	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the Business, Organization, and Liquidity	Description of the Business, Organization, and Liquidity Business and Organization Caribou Biosciences, Inc. (“Company” or “we”) is a clinical-stage Clustered Regularly Interspaced Short Palindromic Repeats (“CRISPR”) genome-editing biopharmaceutical company dedicated to developing transformative therapies for patients with devastating diseases. Our genome-editing platform, including our novel chRDNA (CRISPR hybrid RNA-DNA, or “chRDNA,” pronounced “chardonnay”) technology, enables more precise genome editing to develop cell therapies that are armored to improve activity against diseases. We are advancing a pipeline of allogeneic, or off-the-shelf, cell therapies from our chimeric antigen receptor (“CAR”) T (“CAR-T”) cell and CAR-natural killer (“CAR-NK”) cell platforms as readily available therapeutic treatments for patients. We incorporated in October 2011 as a Delaware corporation and are headquartered in Berkeley, California. We have four wholly owned subsidiaries: Antler Holdco, LLC, incorporated in Delaware in April 2019; Microbe Holdco, LLC, incorporated in Delaware in June 2020; Arboreal Holdco, LLC, incorporated in Delaware in November 2020; and Biloba Holdco, LLC, incorporated in Delaware in April 2021. Our wholly owned subsidiaries hold interests in our equity investments and do not have operating activities. Liquidity We have incurred operating losses and negative cash flows from operations since our inception and we had an accumulated deficit of $340.5 million as of March 31, 2024. During the three months ended March 31, 2024, we incurred a net loss of $41.2 million and used $37.2 million of cash in operating activities. We expect to continue to incur substantial losses, and our ability to achieve and sustain profitability will depend on the successful development, regulatory approval, and commercialization of our product candidates and on our ability to generate sufficient revenue to support our cost structure. We may never achieve profitability and, unless and until we do, we will need to continue to raise additional capital. Our management expects that existing cash, cash equivalents, and marketable securities of $345.9 million as of March 31, 2024, will be sufficient to fund our current operating plan for at least the next 12 months from the date of issuance of our unaudited condensed consolidated financial statements.

Stock Based Compensation - Schedule of Restricted Stock Units Activity (RSUs) (Details)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Number of Shares Underlying Outstanding RSUs and PSUs
Granted (in shares) \| shares	995,767
Weighted-Average Grant Date Fair Value per RSU and PSU
Granted, Weighted-Average Grant Date Fair Value per RSU (in dollars per share) \| $ / shares	$ 6.81
Restricted Stock Units RSU and Performance-Based RSUs
Number of Shares Underlying Outstanding RSUs and PSUs
Unvested, beginning of period (in shares) \| shares	205,357
Vested (in shares) \| shares	(15,000)
Forfeited (in shares) \| shares	(5,576)
Unvested, end of period (in shares) \| shares	1,180,548
Weighted-Average Grant Date Fair Value per RSU and PSU
Unvested, Weighted-Average Grant Date Fair Value per RSU, Beginning Balance (in dollars per share) \| $ / shares	$ 8.49
Vested, Weighted-Average Grant Date Fair Value per RSU and PRSU (in dollars per share) \| $ / shares	10.64
Forfeited, Weighted-Average Grant Date Fair Value per RSU and PRSU (in dollars per share) \| $ / shares	8.65
Unvested, Weighted-Average Grant Date Fair Value per RSU, Ending Balance (in dollars per share) \| $ / shares	$ 7.04

Stock Based Compensation - Schedule of Stock-based Compensation Expense Related to Equity-Based Awards (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	$ 3,988	$ 3,131
Stock options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	3,489	2,798
ESPP
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	72	142
RSUs
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	$ 427	$ 191

Balance Sheet Items - Schedule of Property And Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 29,021	$ 27,414
Less: accumulated depreciation and amortization	(9,854)	(9,144)
Property and equipment, net	19,167	18,270
Lab equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	17,164	15,581
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	2,261	2,235
Computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	906	895
Furniture and equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	322	499
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 8,368	$ 8,204

Leases - Summary of Future Minimum Commitments Under Lease Contracts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Remainder of 2024	$ 2,774
2025	4,475
2026	5,720
2027	5,922
2028	6,122
Thereafter	15,993
Total future undiscounted lease payments	41,006
Less imputed interest	(13,847)
Total discounted lease payments	27,159
Less current portion of lease liability	(1,264)	$ (1,200)
Operating lease liabilities, non-current	25,895	$ 25,908
Expected incentive offset in first year	$ 600

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2022		61,029,184
Beginning balance at Dec. 31, 2022	$ 300,871	$ 6	$ 499,598	$ (1,518)	$ (197,215)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock plans (in shares)		70,271
Issuance of common stock upon employee stock plans	404		404
Issuance of common stock on exercise of options (in shares)		55,433
Issuance of common stock on exercise of options	115		115
Issuance of common stock in connection with at-the-market offering, net of offering expenses (in shares)		168,635
Issuance of common stock in connection with our at-the-market equity offering program, net of offering expenses	1,007		1,007
Stock-based compensation expense	3,131		3,131
Net loss	(28,044)				(28,044)
Other comprehensive income (loss)	788			788
Ending balance (in shares) at Mar. 31, 2023		61,323,523
Ending balance at Mar. 31, 2023	278,272	$ 6	504,255	(730)	(225,259)
Beginning balance (in shares) at Dec. 31, 2023		88,448,948
Beginning balance at Dec. 31, 2023	368,401	$ 8	667,648	30	(299,285)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock plans (in shares)		122,035
Issuance of common stock upon employee stock plans	$ 667		667
Issuance of common stock on exercise of options (in shares)	134,347	134,347
Issuance of common stock on exercise of options	$ 489		489
Issuance of common stock in connection with at-the-market offering, net of offering expenses (in shares)		1,594,171
Issuance of common stock in connection with our at-the-market equity offering program, net of offering expenses	$ 11,330	$ 1	11,329
Issuance of common stock on RSU release (in shares)	15,000
Stock-based compensation expense	$ 3,988		3,988
Net loss	(41,234)				(41,234)
Other comprehensive income (loss)	(352)			(352)
Ending balance (in shares) at Mar. 31, 2024		90,314,501
Ending balance at Mar. 31, 2024	$ 343,289	$ 9	$ 684,121	$ (322)	$ (340,519)

Balance Sheet Items - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Prepaid contract manufacturing and clinical costs	$ 4,486	$ 3,942
Prepaid insurance	581	993
Other	1,846	1,220
Total	$ 6,913	$ 6,155

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Mar. 31, 2024 shares
Trading Arrangements, by Individual
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Jason O’Byrne [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	On February 23, 2024, Jason O’Byrne, our chief financial officer, adopted a Rule 10b5-1 trading arrangement, providing for the sale from time to time of up to 44,336 shares of common stock in amounts and at prices determined in accordance with plan terms. The trading arrangement is intended to satisfy the affirmative defense in Rule 10b5-1(c) under the Exchange Act. The duration of the trading arrangement is until November 20, 2024, or earlier if all transactions under the trading arrangement are completed.
Name	Jason O’Byrne
Title	chief financial officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	February 23, 2024
Arrangement Duration	271 days
Aggregate Available	44,336

Commitments and Contingencies - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Litigation settlement, amount awarded to other party	$ 3.9

Condensed Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenue	$ 2,429	$ 3,502
Related Party
Revenue	$ 622	$ 0

- Definition

+ References

+ Details

Significant Agreements - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development	$ 33,788,000	$ 25,709,000
General and administrative	14,643,000	8,909,000
Future payments for milestones	160,200,000
Intellia Therapeutics, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development	1,300,000	400,000
General and administrative	200,000	800,000
Intellia Therapeutics, Inc. \| Patents
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reduction in general and administrative expenses	100,000	400,000
Collaboration and License Agreement with AbbVie
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues	$ 0	$ 1,600,000

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

+ Details

Significant Agreements	3 Months Ended
Significant Agreements	Mar. 31, 2024
Significant Agreements [Abstract]
Significant Agreements	Significant Agreements Since December 31, 2023, there have been no material changes to the key terms of our significant agreements. For further information regarding our significant agreements, see Note 4 to the consolidated financial statements included in our Form 10-K. During the three months ended March 31, 2023, we recognized $1.6 million in revenue associated with the now-terminated Collaboration and License Agreement, dated February 9, 2021 (as amended, “AbbVie Agreement”) with AbbVie Manufacturing Management Unlimited Company (“AbbVie”). No revenue was recognized under the AbbVie Agreement during the three months ended March 31, 2024, as the AbbVie Agreement was terminated effective October 25, 2023. As of March 31, 2024, and December 31, 2023, we had no amounts recorded in accounts receivable, contract assets, or deferred revenue in our consolidated balance sheets related to the AbbVie Agreement. Our significant agreements may include nonrefundable, upfront payments; annual license maintenance fees; sublicensing fees; obligations to reimburse for patent prosecution and maintenance fees; success payments; regulatory clinical and commercial milestones; and royalty payments. Our obligation to make such payments is contingent upon milestones being achieved, licensed products being commercialized, and the agreements remaining in effect. For the three months ended March 31, 2024, and 2023, we recorded $1.3 million and $0.4 million, respectively, as research and development expense in our unaudited condensed consolidated statements of operations and comprehensive loss related to our significant agreements. For the three months ended March 31, 2024, and 2023, we recorded $0.2 million and $0.8 million, respectively, as general and administrative expense for patent prosecution and maintenance costs in our unaudited condensed consolidated statements of operations and comprehensive loss, which includes reimbursements of patent prosecution and maintenance costs of $0.1 million and $0.4 million, respectively. As of March 31, 2024, certain license and assignment agreements included potential future payments from us for development, regulatory, and sales milestones totaling approximately $160.2 million.

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Research, Manufacturing, and License Agreements We enter into various agreements in the ordinary course of business, such as those with contract manufacturing organizations (“CMOs”), suppliers, clinical research organizations (“CROs”), clinical trial sites, licensors, assignors, and the like. These agreements provide for termination by either party in certain circumstances, generally with less than one-year notice and are, therefore, cancellable contracts and, if cancelled, are not anticipated to have a material effect on our unaudited condensed consolidated financial condition, results of operations, or cash flows. Some of these agreements also include contingent payments that will become payable if and when certain development, regulatory, clinical, and/or commercial milestones are achieved by us. As of March 31, 2024, the satisfaction and timing of such contingent payments is uncertain and cannot be reasonably estimated. Guarantees and Indemnifications In the ordinary course of business, we enter into agreements that contain a variety of representations and warranties and provide for certain indemnifications by us. Our exposure under these agreements is unknown because claims may be made against us in the future. To date, we have not paid any claims or been required to defend any action related to our indemnification obligations. As of March 31, 2024, and December 31, 2023, we did not have any material indemnification claims that were probable or reasonably possible, and consequently, we have not recorded related liabilities. Litigation From time to time, we may become involved in litigation arising in the ordinary course of business. We record a liability for such litigation when it is probable that future losses will be incurred and if such losses can be reasonably estimated. Significant judgment by us is required to determine both probability and the estimated amount. On April 11, 2023, a putative class action lawsuit was filed in the U.S. District Court for the Northern District of California against our company and certain of our officers and current and former members of our board of directors, Bergman v. Caribou Biosciences, Inc., et al., Case Number 4:23-cv-01742-YGR (“Bergman Case”). The Bergman complaint challenges disclosures regarding our company’s business, operations, and prospects, specifically with respect to the alleged durability of CB-010’s therapeutic effect and the product candidate’s clinical and commercial prospects, in alleged violation of Sections 11 and 15 of the Securities Act of 1933, as amended (“Securities Act”) and Sections 10(b) and 20(a) of the Exchange Act. On September 18, 2023, plaintiffs filed an amended complaint adding the IPO underwriters as defendants and making substantially the same allegations as the original complaint. On November 14, 2023, we filed a motion to dismiss the amended complaint for failure to state a claim. Motion to dismiss briefing was completed on February 21, 2024. On April 22, 2024, we reached an agreement in principle with plaintiffs to settle the Bergman Case for $3.9 million, which is included in general and administrative expense for the three months ended March 31, 2024, in exchange for a full release of the putative class’s claims against us and all of our current and former officers, current and former members of our board of directors, the IPO underwriters, and the other named defendant. The parties are negotiating a settlement agreement, which the court must approve before settlement is final. On March 22, 2023, a putative class action lawsuit was filed in Superior Court of the State of California for the County of Alameda against our company and certain of our officers and current and former members of our board of directors, Lowry v. Caribou Biosciences, Inc., et al., Case Number T23-1084 (“Lowry Case”). The Lowry Case challenges disclosures regarding our company’s business, operations, and prospects, specifically with respect to the alleged durability of CB-010’s therapeutic effect and the product candidate’s clinical and commercial prospects, in alleged violation of Sections 11 and 15 of the Securities Act. The allegations and claims in the Lowry Case are substantially similar to the Securities Act claims asserted in the Bergman Case. On April 26, 2023, we filed a motion to stay the Lowry Case during the pendency of the parallel federal court litigation in the Bergman Case, and, on July 11, 2023, our motion to stay was denied. On September 11, 2023, plaintiff filed an amended complaint making substantially the same allegations as the original complaint. On November 9, 2023, we filed a motion to dismiss the amended complaint on the grounds that our certification of incorporation mandates that Securities Act claims against us be brought in federal court. On February 28, 2024, the court granted our motion to dismiss and, on April 15, 2024, the court entered an order of dismissal.

Revenue - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation Of Revenue [Line Items]
Decrease in unbilled accounts receivable	$ (454)	$ (607)
Revenue recognized included in the opening contract liabilities balance	700	1,100
Transaction price allocated to the remaining performance obligations	8,300
Point in Time
Disaggregation Of Revenue [Line Items]
Revenue recognized, performance obligation, amount	1,800	1,900
Over Time
Disaggregation Of Revenue [Line Items]
Revenue recognized, performance obligation, amount	$ 600	$ 1,600

- 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

Revenue - Schedule of Changes in Company's Contract Assets and Liabilities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Accounts receivable
Accounts receivable, Beginning Balance	$ 148
Accounts receivable, Additions	2,193
Accounts receivable, Deductions	(1,424)
Accounts receivable, Ending Balance	917
Contract assets:
Unbilled accounts receivable, Beginning Balance	1,425
Unbilled accounts receivable, Additions	971
Unbilled accounts receivable, Deductions	(1,425)
Unbilled accounts receivable, Ending Balance	971
Contract liabilities:
Deferred revenue, current and long-term, Beginning Balance	8,949
Deferred revenue, current and long-term, Additions	675
Deferred revenue, current and long-term, Deductions	(1,369)
Deferred revenue, current and long-term, Ending Balance	$ 8,255

Leases - Schedule Of Components Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 1,953	$ 1,884
Short-term lease cost	63	63
Total lease cost	2,016	1,947
Variable lease cost	$ 700	$ 600

Fair Value Measurements and Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Schedule of Financial Instruments Measured on Recurring Basis

The following table sets forth our financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):


	Fair Value Measurements as of March 31, 2024
	Total		Level 1		Level 2		Level 3
Assets:
U.S. Treasury bills ($13,904 included in cash and cash equivalents)	$	239,369	$	239,369	$	—	$	—
Commercial paper ($23,858 included in cash and cash equivalents)	51,462		—		51,462		—
U.S. government agency bonds	33,073		—		33,073		—
Money market fund investments (included in cash and cash equivalents)	11,638		11,638		—		—
Corporate debt securities	10,384		—		10,384		—
Total fair value of assets	$	345,926	$	251,007	$	94,919	$	—
Liabilities:
MSKCC success payments liability	$	2,636	$	—	$	—	$	2,636
Total fair value of liabilities	$	2,636	$	—	$	—	$	2,636


	Fair Value Measurements as of December 31, 2023
	Total		Level 1		Level 2		Level 3
Assets:
U.S. Treasury bills ($23,527 included in cash and cash equivalents)	$	262,439	$	262,439	$	—	$	—
Commercial paper ($9,759 included in cash and cash equivalents)	40,373		—		40,373		—
U.S. government agency bonds	40,185		—		40,185		—
Money market fund investments (included in cash and cash equivalents)	17,876		17,876		—		—
Corporate debt securities	11,531		—		11,531		—
Total fair value of assets	$	372,404	$	280,315	$	92,089	$	—
Liabilities:
MSKCC success payments liability	$	2,939	$	—	$	—	$	2,939
Total fair value of liabilities	$	2,939	$	—	$	—	$	2,939

Schedule of Fair Value and Amortized Cost of Cash Equivalents and Available-for-Sale Marketable Securities


	As of March 31, 2024
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses		Estimated Fair Value
U.S. Treasury bills ($13,904 included in cash and cash equivalents)	$	239,568	$	12	$	(211)	$	239,369
Commercial paper ($23,858 included in cash and cash equivalents)	51,491		—		(29)		51,462
U.S. government agency bonds	33,159		—		(86)		33,073
Money market fund investments (included in cash equivalents)	11,638		—		—		11,638
Corporate debt securities	10,393		7		(16)		10,384
Total cash equivalents and marketable securities	$	346,249	$	19	$	(342)	$	345,926

Classified as:
Cash and cash equivalents							$	49,400
Marketable securities, short-term							244,588
Marketable securities, long-term							51,938
Total cash equivalents and marketable securities							$	345,926


	As of December 31, 2023
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses		Estimated Fair Value
U.S. Treasury bills ($23,527 included in cash and cash equivalents)	$	262,328	$	331	$	(220)	$	262,439
Commercial paper ($9,759 included in cash and cash equivalents)	40,386		—		(13)		40,373
U.S. government agency bonds	40,295		1		(111)		40,185
Money market fund investments (included in cash equivalents)	17,876		—		—		17,876
Corporate debt securities	11,489		50		(8)		11,531
Total cash equivalents and marketable securities	$	372,374	$	382	$	(352)	$	372,404

Classified as:
Cash and cash equivalents							$	51,162
Marketable securities, short-term							277,665
Marketable securities, long-term							43,577
Total cash equivalents and marketable securities							$	372,404

Investments Classified by Contractual Maturity Date

The following table presents the fair value of available-for-sale marketable securities by contractual maturities (in thousands):


	March 31, 2024
Due in less than one year	$	244,588
Due in one to five years	51,938
Total	$	296,526

Schedule of Change in Fair Value of Financial Liability

The following table sets forth a summary of the changes in the fair value of our Level 3 financial liability (in thousands):


	MSKCC Success Payments Liability
Balance at December 31, 2023	$	2,939
Change in fair value	(303)
Balance at March 31, 2024	$	2,636

Schedule of Assumptions Used in Valuation of MSKCC Success Payments Liability

The table below summarizes key assumptions used in the valuation of the MSKCC success payments liability:


	As of December 31, 2023
Fair value of common stock	$	5.73
Risk-free interest rate	3.88%
Expected volatility	79%
Probability of achieving multiple of Initial Share Price(1)	5.2% to 18.1%
Expected term (years)	3.7 to 5.2

Balance Sheet Items - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization expense related to property and equipment	$ 0.7	$ 0.6

Net Loss Per Share

3 Months Ended

Mar. 31, 2024

Earnings Per Share [Abstract]

Net Loss Per Share

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


	Three Months Ended March 31,
	2024		2023
Numerator:
Net loss	$	(41,234)	$	(28,044)
Denominator:
Weighted-average common shares outstanding used to compute net loss per share, basic and diluted	89,302,937		61,186,514
Net loss per share, basic and diluted	$	(0.46)	$	(0.46)

Because we were in a net loss position for all periods presented, basic net loss per share is the same as diluted net loss per share for all periods, as the inclusion of all common stock equivalents outstanding would have been anti-dilutive. Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:


	As of March 31, 2024	As of March 31, 2023
Stock options outstanding	12,094,332	9,102,960
RSUs issued and outstanding	1,128,191	236,169
Shares committed under ESPP	108,788	149,350
	13,331,311	9,488,479

Revenue - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation Of Revenue [Line Items]
Revenue	$ 2,429	$ 3,502
United States
Disaggregation Of Revenue [Line Items]
Revenue	2,269	3,385
Rest of world
Disaggregation Of Revenue [Line Items]
Revenue	$ 160	$ 117

- 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

- Definition

+ References

+ Details

Common Stock

3 Months Ended

Mar. 31, 2024

Equity [Abstract]

Common Stock

Common stock reserved for future issuance consisted of the following:


	As of March 31, 2024	As of December 31, 2023
Stock options, issued and outstanding	12,094,332	9,410,404
Stock options, authorized for future issuance	6,565,993	5,952,012
Stock available under our employee stock purchase plan	2,278,809	1,516,355
Unvested restricted stock units and performance-based restricted stock units	1,180,548	205,357
	22,119,682	17,084,128

Shelf Registration Statement

On August 9, 2022, we filed a shelf registration statement on Form S-3 (“Shelf Registration Statement”) with the SEC. The Shelf Registration Statement allows us to sell from time to time up to $400.0 million of common stock, preferred stock, debt securities, warrants, rights, or units comprised of any combination of these securities, for our own account in one or more offerings (including the $100.0 million of common stock reserved for our at-the-market equity offering program). The SEC declared the Shelf Registration Statement effective on August 16, 2022. The terms of any offering under the Shelf Registration Statement are established at the time of such offering, as described in a prospectus supplement to the Shelf Registration Statement filed with the SEC prior to the completion of any such offering.

In July and August 2023, we issued and sold a total of 22,115,384 shares of our common stock in an underwritten follow-on public offering at a price to the public of $6.50 per share, which included the full exercise of the underwriters’ right to purchase 2,884,615 additional shares of our common stock. The total gross proceeds from the offering were approximately $143.7 million ($134.4 million net of underwriting discounts and commissions and offering expenses). The shares were issued pursuant to the Shelf Registration Statement.

At-the-market Equity Offering Program

On August 9, 2022, we entered into an at-the-market Open Market Sale AgreementSM (“ATM Sales Agreement”) with Jefferies LLC (“Jefferies”), pursuant to which, through Jefferies as sales agent, we may from time to time, sell shares of our common stock having an aggregate offering price of up to $100.0 million in gross proceeds under the Shelf Registration Statement. As of March 31, 2024, we have sold 1,762,806 shares of our common stock under the ATM Sales Agreement, at an average price per share of $7.32 for aggregate gross proceeds of $12.9 million ($12.3 million net of offering expenses).

Description of the Business, Organization, and Liquidity - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) subsidiary	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of subsidiaries \| subsidiary	4
Accumulated deficit	$ 340,519		$ 299,285
Net loss	41,234	$ 28,044
Cash used in operating activities	37,203	$ 27,939
Cash, cash equivalents and short term marketable securities	$ 345,900

- 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

Balance Sheet Items

3 Months Ended

Mar. 31, 2024

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Items

Other receivables consisted of the following (in thousands):


	March 31, 2024		December 31, 2023
Patent cost reimbursements	$	1,067	$	1,403
Accrued interest on marketable securities	658		702
Other	—		181
Total	$	1,725	$	2,286

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


	March 31, 2024		December 31, 2023
Prepaid contract manufacturing and clinical costs	$	4,486	$	3,942
Prepaid insurance	581		993
Other	1,846		1,220
Total	$	6,913	$	6,155

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


	March 31, 2024		December 31, 2023
Lab equipment	$	17,164	$	15,581
Leasehold improvements	2,261		2,235
Computer equipment	906		895
Furniture and equipment	322		499
Construction in progress	8,368		8,204
Total property and equipment, gross	29,021		27,414
Less: accumulated depreciation and amortization	(9,854)		(9,144)
Property and equipment, net	$	19,167	$	18,270

Depreciation and amortization expenses related to property and equipment were $0.7 million and $0.6 million, for the three months ended March 31, 2024, and 2023, respectively.

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


	March 31, 2024		December 31, 2023
Accrued employee compensation and related expenses	$	4,454	$	9,517
Accrued research and development expenses	7,594		8,720
Accrued litigation settlement	3,900		—
Accrued patent expenses	500		613
Accrued expenses related to sublicensing revenues	816		802
Credit card liability	426		377
Other	1,300		1,106
Total	$	18,990	$	21,135

Cover - shares	3 Months Ended
Cover - shares	Mar. 31, 2024	May 02, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
Document Transition Report	false
Entity File Number	001-40631
Entity Registrant Name	Caribou Biosciences, Inc.
Entity Incorporation State Country Code	DE
Entity Tax Identification Number	45-3728228
Entity Address Address Line1	2929 7th Street
Entity Address, Address Line Two	Suite 105
Entity Address City Or Town	Berkeley
Entity Address, State and Province	CA
Entity Address Postal Zip Code	94710
City Area Code	510
Local Phone Number	982-6030
Security12b Title	Common Stock, par value $0.0001 per share
Trading Symbol	CRBU
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		90,317,771
Entity Central Index Key	0001619856
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q1
Amendment Flag	false
Document Fiscal Year Focus	2024

Leases - Additional Information (Details)	Mar. 31, 2024 ft²
Commitments and Contingencies Disclosure [Abstract]
Area of real estate property (in square feet)	75,000
Remaining lease term (in years)	8 years 3 months 18 days
Lease renewal term (in years)	5 years

Stock Based Compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Stock Options
Outstanding, Beginning Balance (in shares)	9,410,404
Granted (in shares)	2,913,727
Exercised (in shares)	(134,347)
Cancelled or forfeited (in shares)	(95,452)
Outstanding, Ending Balance (in shares)	12,094,332	9,410,404
Exercisable (in shares)	4,824,205
Vested and expected to vest (in shares)	12,094,332
Weighted- Average Exercise Price
Outstanding, Beginning Balance (in dollars per share)	$ 8.03
Granted (in dollars per share)	6.70
Exercised (in dollars per share)	3.64
Cancelled or forfeited (in dollars per share)	11.73
Outstanding, Ending Balance (in dollars per share)	7.73	$ 8.03
Exercisable (in dollars per share)	8.18
Vested and expected to vest (in dollars per share)	$ 7.73
Weighted- Average Remaining Contractual Term (years)
Outstanding (in years)	8 years 2 months 12 days	8 years
Exercisable (in years)	7 years
Vested and expected to vest (in years)	8 years 2 months 12 days
Aggregate Intrinsic Value (in thousands)(1)
Outstanding	$ 4,031	$ 6,432
Exercisable	3,161
Vested and expected to vest	$ 4,031

Net Loss Per Share - Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Numerator:
Net loss	$ (41,234)	$ (28,044)
Denominator:
Weighted-average common shares outstanding, basic (in shares)	89,302,937	61,186,514
Weighted-average common shares outstanding, diluted (in shares)	89,302,937	61,186,514
Net loss per share, basic (in dollars per share)	$ (0.46)	$ (0.46)
Net loss per share, diluted (in dollars per share)	$ (0.46)	$ (0.46)

- 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

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- Definition

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

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+ Details