0001193125-26-210304 | 10-Q | XBRL Viewer | Cullinan Therapeutics INC

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Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Nature Of Business And Basis Of Presentation [Line Items]
Cash, cash equivalents, and short-term investments	$ 351,900
Long-term investments and interest receivable	41,400
Short-term investments	$ 276,804	$ 289,564

Net Loss per Share - Summary of Outstanding Equity Instruments Excluded from Computation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Equity instruments excluded from computation of diluted net loss per share (in shares)	21,334	19,547
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Equity instruments excluded from computation of diluted net loss per share (in shares)	14,804	12,076
Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Equity instruments excluded from computation of diluted net loss per share (in shares)	5,551	6,475
Restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Equity instruments excluded from computation of diluted net loss per share (in shares)	915	986
Employee stock purchase plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Equity instruments excluded from computation of diluted net loss per share (in shares)	64	10

Leases (Tables)

3 Months Ended

Mar. 31, 2026

Leases [Abstract]

Supplemental Cash Flow Information Relating to Leases

The following table summarizes supplemental cash flow information for the three months ended March 31, 2026 and 2025 (in thousands):


	Three Months Ended March 31,
	2026		2025
Cash paid for amounts included in measurement of lease liabilities:
Operating cash flows from operating leases	$	372	$	363

Summarizes of Future Minimum Lease Payments

The following table summarizes the Company’s future minimum lease payments as of March 31, 2026 (in thousands):


	March 31, 2026
Remainder of 2026	$	657
2027		1,190
2028		906
Total future minimum lease payments		2,753
Less: imputed interest		(370	)
Total lease liabilities at present value	$	2,383

Summarizes Lease Term and Discount Rate

The following table summarizes the weighted-average remaining lease term and discount rate as of March 31, 2026 and December 31, 2025:


	March 31, 2026			December 31, 2025
Weighted-average remaining lease term (in years)		2.5			2.8
Weighted-average discount rate		11.8	%		11.8	%

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2026	Apr. 30, 2026
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2026
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q1
Entity Registrant Name	CULLINAN THERAPEUTICS, INC.
Current Fiscal Year End Date	--12-31
Document Quarterly Report	true
Document Transition Report	false
Entity Central Index Key	0001789972
Securities Act File Number	001-39856
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-3879991
Entity Address, Address Line One	One Main Street
Entity Address, Address Line Two	Suite 1350
Entity Address, City or Town	Cambridge
Entity Address, Country	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	410-4650
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	CGEM
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	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		61,458,046

Accrued Expenses and Other Current Liabilities

3 Months Ended

Mar. 31, 2026

Accrued Expenses And Other Current Liabilities [Abstract]

Accrued Expenses and Other Current Liabilities

(4)

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following as of March 31, 2026 and December 31, 2025 (in thousands):


	March 31, 2026		December 31, 2025
Contracted research and development expenses	$	21,944	$	16,388
Employee compensation		2,991		9,952
Due to Taiho under collaboration agreement, net		5,633		8,784
Other current liabilities		1,352		996
Total accrued expenses and other current liabilities	$	31,920	$	36,120

Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Mar. 31, 2026
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	(2) Summary of Significant Accounting Policies Cullinan’s significant accounting policies have not changed materially from those disclosed in its annual audited consolidated financial statements and accompanying notes in the 2025 10-K. Recently Issued Accounting Pronouncements In November 2024, the FASB issued an accounting standards update to improve disclosures regarding the types of expenses included in commonly presented expense captions, including disaggregating the amounts of employee compensation, depreciation and amortization included within each income statement expense caption. This standard will be effective for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. Cullinan will adopt this standard on January 1, 2027 for 2027 annual reporting and interim periods beginning in 2028 and is evaluating the impact of adopting this standard on its consolidated financial statements and disclosures.

License and Collaboration Agreements

3 Months Ended

Mar. 31, 2026

License And Collaboration Agreements [Abstract]

License and Collaboration Agreements

(5)

License and Collaboration Agreements

Genrix License Agreement

In June 2025, the Company and Chongqing Genrix Biopharmaceutical Co., Ltd. (“Genrix”) entered into a license agreement (the “Genrix License Agreement”), pursuant to which Genrix granted Cullinan a global (excluding mainland China, Hong Kong, Macau and Taiwan), exclusive license to develop and commercialize velinotamig, a BCMAxCD3 T cell engager, in all fields of use.

Under the terms of the Genrix License Agreement, Cullinan paid Genrix an upfront license fee of $20.0 million. Genrix will be eligible to receive up to $292.0 million in milestone payments based on the achievement of development and regulatory milestones. Genrix is also eligible to receive up to an additional $400.0 million in net sales-based milestones as well as tiered royalties ranging from mid-single digit to mid-teens, as a percentage of net sales of licensed products.

Unless earlier terminated, the Genrix License Agreement will continue in effect on a country-by-country basis until the expiration of Cullinan’s royalty obligations in such country. The Genrix License Agreement may be terminated by either party for a material breach by the other party, subject to notice and cure provisions, or in the event of the other party’s insolvency. Additionally, subject to a notice period, Cullinan may terminate the Genrix License Agreement for convenience. In the Genrix License Agreement, each party made customary representations and warranties and agreed to customary covenants, including, without limitation, with respect to indemnification, for transactions of this type.

Cullinan evaluated the Genrix License Agreement and determined that the exclusive license to develop and commercialize velinotamig represented an asset acquisition of in-process research and development. The Company also determined that the asset had no alternative future use at the time of acquisition, and therefore, the upfront license fee of $20.0 million was recorded within research and development expenses in June 2025. As of March 31, 2026, no milestones have been achieved under the Genrix License Agreement.

Taiho Agreements

Cullinan has a co-development agreement with an affiliate of Taiho Pharmaceutical Co., Ltd ("Taiho"), pursuant to which the Company is collaborating to develop zipalertinib for the treatment of a genetically defined subset of patients with non-small cell lung cancer (“NSCLC”), and Taiho will commercialize zipalertinib. For the agreed-upon indication, Taiho and Cullinan share development costs equally, and each party will receive 50% of any future pre-tax profits from potential U.S. sales of zipalertinib, subject to certain adjustments. For any additional indications that Taiho chooses to develop independently, Taiho will bear all development costs until it has sufficient data from such indication to support a commercial purpose or submission of zipalertinib for such indication. At such time, 50% of Taiho’s independent development costs, subject to certain adjustments, will be deducted from future pre-tax profits for potential U.S. sales of zipalertinib. In November 2025, Taiho independently initiated an ongoing global Phase 3 clinical trial evaluating zipalertinib in an additional indication.

The Company concluded that the co-development agreement with Taiho is a collaborative arrangement because Cullinan is an active participant in both the development of zipalertinib and the oversight of commercialization for zipalertinib. Amounts due to or from Taiho for zipalertinib development activities after the execution of the co-development agreement are recorded within research and development expenses or general and administrative expenses based on the nature of the activity. The following table summarizes each party’s respective share of costs incurred and paid by the other party for zipalertinib development activities for the three months ended March 31, 2026 and 2025 (in thousands):


	Three Months Ended March 31,
	2026		2025
Cullinan's share of zipalertinib research and development costs incurred by Taiho	$	5,811	$	5,617
Cullinan’s share of general and administrative costs incurred by Taiho	$	652	$	472
Taiho’s share of research and development costs incurred by Cullinan	$	830	$	1,374

Under a separate agreement, Cullinan is also eligible to receive up to $130.0 million from Taiho tied to epidermal growth factor receptor exon 20 non-small-cell lung cancer U.S. regulatory milestones. As of March 31, 2026, no milestone payments have been received under this agreement.

Other License and Collaboration Agreements

The Company has certain payment obligations that are contingent upon future events under various other license and collaboration agreements. Under these agreements, Cullinan will be required to make milestone payments upon successful completion and achievement of certain intellectual property, clinical, regulatory, and sales milestones and will be required to make royalty payments in connection with the sale of products developed under these agreements. During each of the three months ended March 31, 2026 and 2025, no milestone obligations were incurred under the Company’s other license and collaboration agreements.

Stockholders' Equity - Additional Information (Details)	3 Months Ended
Stockholders' Equity - Additional Information (Details)	Mar. 31, 2026 USD ($)
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Dividends declared	$ 0
Common stock, voting rights	Each share of common stock entitles the holder to one vote and to receive dividends when and if declared by the board of directors of the Company.
Number of shares of common stock, percentage	9.99%
Increase in number of shares of preferred stock, percentage	19.99%

Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2026

Financial Instruments Pledged as Collateral [Abstract]

Schedule of Short-term and Long-term Investment Marketable Securities by Security Type

Cullinan recognized its investments by security type at March 31, 2026 as follows (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Short-term investments
U.S. government notes	$	149,865	$	352	$	—		$	150,217
Corporate notes		116,860		23		(126	)		116,757
Asset-backed securities		9,801		29		—			9,830
Total short-term investments		276,526		404		(126	)		276,804
Long-term investments
Corporate notes		38,652		4		(155	)		38,501
Asset-backed securities		—		—		—			—
Total long-term investments		38,652		4		(155	)		38,501
Total investments	$	315,178	$	408	$	(281	)	$	315,305

Cullinan recognized its investments by security type at December 31, 2025 as follows (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Short-term investments
U.S. government notes	$	159,632	$	683	$	—		$	160,315
Corporate notes		119,368		119		(7	)		119,480
Asset-backed securities		9,717		52		—			9,769
Total short-term investments		288,717		854		(7	)		289,564
Long-term investments
Corporate notes		48,134		90		(2	)	$	48,222
U.S. government notes		9,963		85		—		$	10,048
Total long-term investments		58,097		175		(2	)		58,270
Total investments	$	346,814	$	1,029	$	(9	)	$	347,834

All of the Company's long-term investments as of March 31, 2026 and December 31, 2025 had maturities between one and two years from the respective balance sheet date. The Company did not recognize any credit loss relating to its investments during the three months ended March 31, 2026 and 2025.

Summary of Fair Value of Financial Assets Measured on Recurring Basis

The following table sets forth the fair value of Cullinan’s financial assets that were measured at fair value on a recurring basis as of March 31, 2026 (in thousands):


	Level 1		Level 2		Level 3		Total
Short-term investments
U.S. government notes	$	—	$	150,217	$	—	$	150,217
Corporate notes		—		116,757		—		116,757
Asset-backed securities		—		9,830		—		9,830
Total short-term investments		—		276,804		—		276,804
Long-term investments
Corporate notes		—		38,501		—		38,501
Total long-term investments		—		38,501		—		38,501
Total investments	$	—	$	315,305	$	—	$	315,305

The following table sets forth the fair value of the Company’s financial assets that were measured at fair value on a recurring basis as of December 31, 2025 (in thousands):


	Level 1		Level 2		Level 3		Total
Short-term investments
U.S. government notes	$	—	$	160,315	$	—	$	160,315
Corporate notes		—		119,480		—		119,480
Asset-backed securities		—		9,769		—		9,769
Total short-term investments		—		289,564		—		289,564
Long-term investments
Corporate notes		—		48,222		—		48,222
U.S. government notes		—		10,048		—		10,048
Total long-term investments		—		58,270		—		58,270
Total investments	$	—	$	347,834	$	—	$	347,834

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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

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

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

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

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

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

+ Details

License and Collaboration Agreements - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Jun. 30, 2025	Mar. 31, 2026	Mar. 31, 2025
License And Collaboration Agreements [Line Items]
Research and development costs		$ 42,123	$ 41,459
General and administrative Cost		$ 11,574	13,537
Genrix License Agreement \| Research and Development
License And Collaboration Agreements [Line Items]
Upfront license fee	$ 20,000
Pearl - Taiho
License And Collaboration Agreements [Line Items]
Percentage of profits from potential sales		50.00%
Percentage of Independent Development Costs		50.00%
RecievablesFromRelatedParty		$ 130,000
Pearl - Taiho \| Collaboration Agreements
License And Collaboration Agreements [Line Items]
Research and development costs		830	1,374
Genrix Biopharmaceutical Co, Ltd \| Genrix License Agreement
License And Collaboration Agreements [Line Items]
Upfront license fee		20,000
Genrix Biopharmaceutical Co, Ltd \| Maximum \| Genrix License Agreement
License And Collaboration Agreements [Line Items]
Milestone payments		292,000
Genrix Biopharmaceutical Co, Ltd \| Maximum \| Genrix License Agreement \| Sales Based [Member]
License And Collaboration Agreements [Line Items]
Milestone payments		400,000
Cullinan [Member] \| Collaboration Agreements
License And Collaboration Agreements [Line Items]
Research and development costs		5,811	5,617
General and administrative Cost		$ 652	$ 472

CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Operating activities:
Net loss	$ (49,661)	$ (48,501)
Adjustments to reconcile net loss to net cash used in operating activities:
Equity-based compensation expense	7,616	9,374
Accretion on marketable securities	(777)	(2,311)
Depreciation and amortization	79	76
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(662)	1,742
Accounts payable	1,667	1,720
Accrued expenses and other liabilities	(4,307)	(5,255)
Net cash used in operating activities	(46,045)	(43,155)
Investing activities:
Maturities of marketable securities	52,549	162,645
Purchase of marketable securities	(20,135)	(125,840)
Net cash provided by (used in) investing activities	32,414	36,805
Financing activities:
Issuance of common stock under equity-based compensation plans	380	0
Net cash provided by financing activities	380	0
Net increase in cash and cash equivalents	(13,251)	(6,350)
Cash and cash equivalents at beginning of period	88,332	83,005
Cash and cash equivalents at end of period	$ 75,081	$ 76,655

Equity-Based Compensation - Schedule of Equity-based Compensation Expense Categories In Consolidated Statements of Operations and Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total equity-based compensation	$ 7,616	$ 9,374
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total equity-based compensation	3,657	5,445
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total equity-based compensation	$ 3,959	$ 3,929

Segment Reporting - Summary of Financial Information of Reportable Segment (Details) - USD ($)
$ in Thousands

3 Months Ended

Mar. 31, 2026

Mar. 31, 2025

Segment Reporting Information [Line Items]

Total R&D program expense

$ 42,123

$ 41,459

Equity-based compensation

7,616

9,374

Loss from operations

(53,697)

(54,996)

Interest income

4,098

6,580

Other income (expense), net

(62)

(85)

Net loss

(49,661)

(48,501)

Operating Segments [Member]

Segment Reporting Information [Line Items]

Total R&D program expense

28,325

27,661

Equity-based compensation

7,616

9,374

R&D personnel and operations

9,839

9,831

General and administrative personnel

3,795

3,489

License agreement obligations

Other segment expenses

^[1]

4,122

4,603

Loss from operations

(53,697)

(54,996)

Interest income

4,098

6,580

Other income (expense), net

(62)

(85)

Net loss

(49,661)

(48,501)

Operating Segments [Member] | CLN-049 [Member]

Segment Reporting Information [Line Items]

Total R&D program expense

5,059

3,895

Operating Segments [Member] | CLN-617 [Member]

Segment Reporting Information [Line Items]

Total R&D program expense

685

1,793

Operating Segments [Member] | CLN-619 [Member]

Segment Reporting Information [Line Items]

Total R&D program expense

2,471

6,118

Operating Segments [Member] | CLN-978 [Member]

Segment Reporting Information [Line Items]

Total R&D program expense

9,665

4,673

Operating Segments [Member] | Early-stage programs [Member

Segment Reporting Information [Line Items]

Total R&D program expense

709

1,022

Operating Segments [Member] | Velinotamig [Member]

Segment Reporting Information [Line Items]

Total R&D program expense

2,803

Operating Segments [Member] | Zipalertinib [Member]

Segment Reporting Information [Line Items]

Total R&D program expense

$ 6,933

$ 10,160

[1]

Other segment expenses for the three months ended March 31, 2026 and 2025 include legal fees relating to patent and corporate matters; professional fees for accounting, auditing, tax, and administrative consulting services; insurance costs; marketing expenses; depreciation; and other operating costs.

Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2026 Segment
Accounting Policies [Abstract]
Number of operating segments	1

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Accounts Payable and Accrued Liabilities, Current [Abstract]
Contracted research and development expenses	$ 21,944	$ 16,388
Employee compensation	2,991	9,952
Due to Taiho under collaboration agreement, net	5,633	8,784
Other current liabilities	1,352	996
Total accrued expenses and other current liabilities	$ 31,920	$ 36,120

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Mar. 31, 2026
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Rule 10b5-1 Arrangement Modified	false
Non Rule 10b5-1 Arrangement Modified	false

Financial Instruments - Summary of Fair Value of Financial Assets Measured on Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	$ 276,804	$ 289,564
Total long-term investments	38,501	58,270
Assets Fair Value Disclosure, Total	315,305	347,834
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	0	0
Total long-term investments	0	0
Assets Fair Value Disclosure, Total	0	0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	276,804	289,564
Total long-term investments	38,501	58,270
Assets Fair Value Disclosure, Total	315,305	347,834
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	0	0
Total long-term investments	0	0
Assets Fair Value Disclosure, Total	0	0
U.S. Government Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	150,217	160,315
Total long-term investments		10,048
U.S. Government Notes \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	0	0
Total long-term investments		0
U.S. Government Notes \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	150,217	160,315
Total long-term investments		10,048
U.S. Government Notes \| Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	0	0
Total long-term investments		0
Asset-backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	9,830	9,769
Asset-backed Securities \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	0	0
Asset-backed Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	9,830	9,769
Asset-backed Securities \| Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	0	0
Corporate Note Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	116,757	119,480
Total long-term investments	38,501	48,222
Corporate Note Securities \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	0	0
Total long-term investments	0	0
Corporate Note Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	116,757	119,480
Total long-term investments	38,501	48,222
Corporate Note Securities \| Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	0	0
Total long-term investments	$ 0	$ 0

CONSOLIDATED BALANCE SHEETS (Parenthetical) (unaudited) - $ / shares	Mar. 31, 2026	Dec. 31, 2025
Statement of Financial Position [Abstract]
Preferred Stock par value	$ 0.0001	$ 0.0001
Preferred Stock, shares authorized	10,000,000	10,000,000
Preferred Stock, Share issued	481,989	555,935
Preferred stock, Share Outstanding	481,989	555,935
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	150,000,000
Common Stock, Shares Issued	61,451,380	60,244,136
Common stock, shares outstanding	61,451,380	60,244,136

Subsequent Event	3 Months Ended
Subsequent Event	Mar. 31, 2026
Subsequent Events [Abstract]
Subsequent Event	(12) Subsequent Event In April 2026, the Company entered into a sales agreement with TD Securities (USA) LLC ("TD Cowen") to establish an at-the-market equity offering program, pursuant to which Cullinan can offer and sell up to $200.0 million of the Company’s common stock through TD Cowen at prevailing market prices from time to time.

Net Loss per Share (Tables)

3 Months Ended

Mar. 31, 2026

Earnings Per Share [Abstract]

Summary of Calculation of Basic and Diluted Net Loss Per Share

The following tables set forth the calculation of basic and diluted net loss per share for the three months ended March 31, 2026 and 2025 (in thousands, except per share data):


	Three Months Ended March 31,
	2026						2025
	Common Stock			Preferred Stock			Common Stock			Preferred Stock
Numerator:
Net loss - basic and diluted	$	(45,485	)	$	(4,176	)	$	(43,698	)	$	(4,803	)
Denominator:
Weighted-average shares outstanding — basic and diluted		60,462			555			58,905			648
Net loss per share:
Basic and diluted	$	(0.75	)	$	(7.52	)	$	(0.74	)	$	(7.42	)

Summary of Outstanding Equity Instruments Excluded from Computation of Diluted Net Income (Loss) Per Share

The following table sets forth potential common shares that were excluded from the computation of diluted net loss per share attributable to common stockholders of Cullinan for the three months ended March 31, 2026 and 2025 because their effect would have been anti-dilutive (in thousands):


	Three Months Ended March 31,
	2026		2025
Stock options		14,804		12,076
Preferred stock		5,551		6,475
Restricted stock units		915		986
Employee stock purchase plan		64		10
Total		21,334		19,547

Segment Reporting (Tables)

3 Months Ended

Mar. 31, 2026

Segment Reporting [Abstract]

Financial Information of Reportable Segment

Financial information of the Company’s reportable segment for the three months ended March 31, 2026 and 2025 are as follows (in thousands):


	Three Months Ended March 31,
	2026			2025
Research and development ("R&D") programs:
CLN-049	$	5,059		$	3,895
CLN-617		685			1,793
CLN-619		2,471			6,118
CLN-978		9,665			4,673
Early-stage programs		709			1,022
Velinotamig		2,803			—
Zipalertinib		6,933			10,160
Total R&D program expense		28,325			27,661
Equity-based compensation		7,616			9,374
R&D personnel and operations		9,839			9,831
General and administrative personnel		3,795			3,489
License agreement obligations		—			38
Other segment expenses(1)		4,122			4,603
Loss from operations		(53,697	)		(54,996	)
Other income (expense):
Interest income		4,098			6,580
Other income (expense), net		(62	)		(85	)
Net loss	$	(49,661	)	$	(48,501	)

(1)

Leases - Summary of Future Minimum Payments Due Under Operating Lease (Details) $ in Thousands	Mar. 31, 2026 USD ($)
Lessee, Operating Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract]
Remainder of 2026	$ 657
2027	1,190
2028	906
Total future minimum lease payments	2,753
Less: imputed interest	(370)
Total lease liabilities at present value	$ 2,383

Subsequent Event (Additional Information) (Details) $ in Millions	1 Months Ended
	Apr. 30, 2026 USD ($)
Subsequent Event [Member] \| Sales Agreement [Member] \| Cullinan [Member]
Subsequent Event [Line Items]
Proceeds from sale of equity	$ 200.0

Segment Reporting (Additional Information) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2026 USD ($) Segment	Mar. 31, 2025 USD ($)
Segment Reporting [Abstract]
Number of operating segments	1
Number of reportable segments	1
Expenditures for Long-Lived Assets \| $	$ 0	$ 0

CONSOLIDATED BALANCE SHEETS (unaudited) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Current assets:
Cash and cash equivalents	$ 75,081	$ 88,332
Short-term investments	276,804	289,564
Prepaid expenses and other current assets	9,522	8,860
Total current assets	361,407	386,756
Property and equipment, net	342	421
Operating lease right-of-use assets	2,437	2,630
Other assets	297	297
Long-term investments	38,501	58,270
Total assets	402,984	448,374
Current liabilities:
Accounts payable	2,509	841
Accrued expenses and other current liabilities	31,920	36,120
Operating lease liabilities, current	725	780
Total current liabilities	35,154	37,741
Long-term liabilities:
Operating lease liabilities, net of current portion	1,658	1,903
Total liabilities	36,812	39,644
Commitments and contingencies (Note 8)
Stockholders' equity:
Preferred stock, $0.0001 par value, 10,000,000 shares authorized as of March 31, 2026 and December 31, 2025; 481,989 and 555,935 shares issued and outstanding as of March 31, 2026 and December 31, 2025, respectively.	0	0
Common stock, $0.0001 par value, 150,000,000 shares authorized as of March 31, 2026 and December 31, 2025; 61,451,380 and 60,244,136 shares issued and outstanding as of March 31, 2026 and December 31, 2025, respectively	6	6
Additional paid-in capital	1,003,819	995,823
Accumulated other comprehensive income (loss)	127	1,020
Accumulated deficit	(637,780)	(588,119)
Total stockholders' equity	366,172	408,730
Total liabilities and stockholders' equity	$ 402,984	$ 448,374

Equity-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2026

Share-Based Payment Arrangement [Abstract]

Schedule of Equity-based Compensation Expense Categories In Consolidated Statements of Operations and Comprehensive Income (Loss)

Cullinan recorded equity-based compensation in the following expense categories in the consolidated statements of operations and comprehensive income (loss) for the three months ended March 31, 2026 and 2025 (in thousands):


	Three Months Ended March 31,
	2026		2025
General and administrative	$	3,657	$	5,445
Research and development		3,959		3,929
Total equity-based compensation	$	7,616	$	9,374

Segment Reporting

3 Months Ended

Mar. 31, 2026

Segment Reporting [Abstract]

Segment Reporting

(11)

Segment Reporting

The Company operates and manages the business as one reporting and one operating segment, which is the business of developing immunology and oncology therapies. Cullinan has determined that its Chief Executive Officer is the chief operating decision maker ("CODM"). Cullinan’s CODM reviews financial information on an aggregate basis and uses net loss as presented in the consolidated statement of operations and comprehensive income (loss) for purposes of allocating resources and evaluating financial performance.

Financial information of the Company’s reportable segment for the three months ended March 31, 2026 and 2025 are as follows (in thousands):


	Three Months Ended March 31,
	2026			2025
Research and development ("R&D") programs:
CLN-049	$	5,059		$	3,895
CLN-617		685			1,793
CLN-619		2,471			6,118
CLN-978		9,665			4,673
Early-stage programs		709			1,022
Velinotamig		2,803			—
Zipalertinib		6,933			10,160
Total R&D program expense		28,325			27,661
Equity-based compensation		7,616			9,374
R&D personnel and operations		9,839			9,831
General and administrative personnel		3,795			3,489
License agreement obligations		—			38
Other segment expenses(1)		4,122			4,603
Loss from operations		(53,697	)		(54,996	)
Other income (expense):
Interest income		4,098			6,580
Other income (expense), net		(62	)		(85	)
Net loss	$	(49,661	)	$	(48,501	)

(1)

All of the Company’s long-lived assets were located in the U.S. as of each of March 31, 2026 and 2025. There were no expenditures for long-lived assets in the three months ended March 31, 2026 or the three months ended March 31, 2025.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/exampleRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/exampleRef
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Reference 13: http://www.xbrl.org/2003/role/exampleRef
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Reference 14: http://www.xbrl.org/2003/role/exampleRef
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Reference 15: http://www.xbrl.org/2003/role/exampleRef
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Reference 16: http://www.xbrl.org/2003/role/exampleRef
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+ Details

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Operating expenses:
Research and development	$ 42,123	$ 41,459
General and administrative expense	11,574	13,537
Total operating expenses	53,697	54,996
Loss from operations	(53,697)	(54,996)
Other income (expense):
Interest income	4,098	6,580
Other expense, net	(62)	(85)
Net loss	(49,661)	(48,501)
Comprehensive income (loss):
Net loss	(49,661)	(48,501)
Unrealized gain (loss) on investments	(893)	638
Comprehensive loss	(50,554)	(47,863)
Common Stock
Other income (expense):
Net loss	$ (45,485)	$ (43,698)
Basic and diluted net loss per share attributable to Cullinan:
Net loss per share, basic	$ (0.75)	$ (0.74)
Net loss per share, diluted	$ (0.75)	$ (0.74)
Weighted-average shares used in computing basic and diluted net loss per share attributable to Cullinan:
Weighted-average shares outstanding - basic	60,462	58,905
Weighted-average shares outstanding - diluted	60,462	58,905
Preferred Stock
Other income (expense):
Net loss	$ (4,176)	$ (4,803)
Basic and diluted net loss per share attributable to Cullinan:
Net loss per share, basic	$ (7.52)	$ (7.42)
Net loss per share, diluted	$ (7.52)	$ (7.42)
Weighted-average shares used in computing basic and diluted net loss per share attributable to Cullinan:
Weighted-average shares outstanding - basic	555	648
Weighted-average shares outstanding - diluted	555	648

Financial Instruments - Schedule of Short-term and Long-term Investment Marketable Securities by Security Type (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Available For Sale Securities Fair Value To Amortized Cost Basis [Line Items]
Amortized Cost	$ 315,178	$ 346,814
Gross Unrealized Gains	408	1,029
Gross Unrealized Losses	(281)	(9)
Estimated Fair Value	315,305	347,834
Long Term Investment
Available For Sale Securities Fair Value To Amortized Cost Basis [Line Items]
Amortized Cost	38,652	58,097
Gross Unrealized Gains	4	175
Gross Unrealized Losses	(155)	(2)
Estimated Fair Value	38,501	58,270
Long Term Investment \| U.S. Government Notes
Available For Sale Securities Fair Value To Amortized Cost Basis [Line Items]
Amortized Cost		9,963
Gross Unrealized Gains		85
Gross Unrealized Losses		0
Estimated Fair Value		10,048
Long Term Investment \| Asset-backed Securities
Available For Sale Securities Fair Value To Amortized Cost Basis [Line Items]
Amortized Cost	0
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Estimated Fair Value	0
Long Term Investment \| Corporate Note Securities
Available For Sale Securities Fair Value To Amortized Cost Basis [Line Items]
Amortized Cost	38,652	48,134
Gross Unrealized Gains	4	90
Gross Unrealized Losses	(155)	(2)
Estimated Fair Value	38,501	48,222
Short Term Investments
Available For Sale Securities Fair Value To Amortized Cost Basis [Line Items]
Amortized Cost	276,526	288,717
Gross Unrealized Gains	404	854
Gross Unrealized Losses	(126)	(7)
Estimated Fair Value	276,804	289,564
Short Term Investments \| U.S. Government Notes
Available For Sale Securities Fair Value To Amortized Cost Basis [Line Items]
Amortized Cost	149,865	159,632
Gross Unrealized Gains	352	683
Gross Unrealized Losses	0	0
Estimated Fair Value	150,217	160,315
Short Term Investments \| Asset-backed Securities
Available For Sale Securities Fair Value To Amortized Cost Basis [Line Items]
Amortized Cost	9,801	9,717
Gross Unrealized Gains	29	52
Gross Unrealized Losses	0	0
Estimated Fair Value	9,830	9,769
Short Term Investments \| Corporate Note Securities
Available For Sale Securities Fair Value To Amortized Cost Basis [Line Items]
Amortized Cost	116,860	119,368
Gross Unrealized Gains	23	119
Gross Unrealized Losses	(126)	(7)
Estimated Fair Value	$ 116,757	$ 119,480

Equity-Based Compensation

3 Months Ended

Mar. 31, 2026

Share-Based Payment Arrangement [Abstract]

Equity-Based Compensation

(7)

Equity-Based Compensation


	Three Months Ended March 31,
	2026		2025
General and administrative	$	3,657	$	5,445
Research and development		3,959		3,929
Total equity-based compensation	$	7,616	$	9,374

License and Collaboration Agreements (Tables)

3 Months Ended

Mar. 31, 2026

License And Collaboration Agreements [Abstract]

Summary of Research and Development Costs Related to Collaboration and License Agreements

The following table summarizes each party’s respective share of costs incurred and paid by the other party for zipalertinib development activities for the three months ended March 31, 2026 and 2025 (in thousands):


	Three Months Ended March 31,
	2026		2025
Cullinan's share of zipalertinib research and development costs incurred by Taiho	$	5,811	$	5,617
Cullinan’s share of general and administrative costs incurred by Taiho	$	652	$	472
Taiho’s share of research and development costs incurred by Cullinan	$	830	$	1,374

Net Loss per Share - Summary of Calculation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Common Stock
Numerator:
Net loss - basic and diluted	$ (45,485)	$ (43,698)
Denominator
Weighted-average shares outstanding - basic	60,462	58,905
Weighted-average shares outstanding - diluted	60,462	58,905
Net loss per share:
Basic	$ (0.75)	$ (0.74)
Diluted	$ (0.75)	$ (0.74)
Preferred Stock
Numerator:
Net loss - basic and diluted	$ (4,176)	$ (4,803)
Denominator
Weighted-average shares outstanding - basic	555	648
Weighted-average shares outstanding - diluted	555	648
Net loss per share:
Basic	$ (7.52)	$ (7.42)
Diluted	$ (7.52)	$ (7.42)

Commitments and Contingencies

3 Months Ended

Mar. 31, 2026

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

(8)

Commitments and Contingencies

The Company enters into contracts in the normal course of business with contract research organizations, contract manufacturing organizations, and other third parties for preclinical research studies, clinical trials and testing and manufacturing services. These agreements generally include cancellation clauses.

Indemnification Agreements

In the ordinary course of business, Cullinan may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and executive officers that will require Cullinan, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in certain cases, unlimited. To date, Cullinan has not incurred any material costs as a result of such indemnifications. The Company is not aware of any indemnification arrangements that could have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its consolidated financial statements as of March 31, 2026 and December 31, 2025.

Legal Proceedings

Cullinan is not currently party to, or aware of, any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. Cullinan expenses as incurred the costs related to such legal proceedings.

Royalty Transfer Agreements

The Company's CLN-049 development subsidiary is party to royalty transfer agreements with two charitable foundations. Under these royalty transfer agreements, the charitable foundations are collectively entitled to receive a low single digit royalty percentage of all global net sales of any products developed by the development subsidiary, subject to limitations after patent expirations and on intellectual property developed after a change of control. Cullinan has deemed these royalty transfer agreements to be freestanding financial instruments that should be accounted for at fair value. The Company concluded that these instruments had no value at the inception of the agreements.

Cullinan has not had any applicable net sales from its products and as a result, has not paid or incurred any royalties under these agreements as of March 31, 2026. Given the early-stage nature of the underlying technologies and inherent risks associated with obtaining regulatory approval and achieving commercialization, the Company ascribed no value to the royalty transfer agreements as of March 31, 2026 and December 31, 2025.

Leases - Supplemental Cash Flow Information Relating to Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Leases [Abstract]
Operating cash flows from operating leases	$ 372	$ 363

Nature of Business and Basis of Presentation

3 Months Ended

Mar. 31, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of Business and Basis of Presentation

(1)

Nature of Business and Basis of Presentation

Organization

Cullinan Therapeutics, Inc., together with its consolidated subsidiaries ("Cullinan" or "the Company"), is a clinical-stage biopharmaceutical company developing therapies for autoimmune diseases and cancer that was incorporated in September 2016 and has a principal place of business in Cambridge, Massachusetts.

Liquidity

The Company has a history of significant operating losses and has had negative cash flows from operations since its inception and expects to continue to generate operating losses for the foreseeable future. Cullinan’s ultimate success depends on the outcome of its research and development activities as well as its ability to commercialize the Company’s product candidates. Cullinan is subject to a number of risks including, but not limited to, the need to obtain adequate additional funding for the ongoing and planned clinical development of its product candidates. Due to the numerous risks and uncertainties associated with pharmaceutical development, government regulation, potential commercialization, intellectual property, and our reliance on third parties, the Company is unable to accurately predict the timing or amount of funds required to complete development of its product candidates, and costs could exceed Cullinan’s expectations for a number of reasons, including reasons beyond the Company’s control.

Since inception, Cullinan has funded its operations primarily through the sale of equity securities and from licensing or selling the rights to its product candidates. The Company expects that its cash, cash equivalents, and short-term investments of $351.9 million, and long-term investments and interest receivable of $41.4 million as of March 31, 2026, will be sufficient to fund its operating expenses and capital expenditure requirements through the next twelve months from the date of issuance of these consolidated financial statements.

Basis of Presentation

The accompanying unaudited consolidated financial statements of the Company have been prepared in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial reporting and include the accounts of Cullinan and its consolidated subsidiaries. Intercompany balances and transactions have been eliminated in consolidation.

In the opinion of Cullinan’s management, the unaudited consolidated financial statements reflect all adjustments, which are normal and recurring in nature, and necessary for fair financial statement presentation. The preparation of these unaudited consolidated financial statements and accompanying notes in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported. Actual results could differ materially from those estimates. These unaudited consolidated financial statements and accompanying notes should be read in conjunction with the Company’s annual audited consolidated financial statements and accompanying notes included in its Annual Report on Form 10-K for the fiscal year ended December 31, 2025 (the "2025 10-K").

Net Loss per Share

3 Months Ended

Mar. 31, 2026

Earnings Per Share [Abstract]

Net Loss per Share

(10)

Net Loss per Share

The Company computes net loss per share for its common stock and preferred stock using the two-class method required for multiple classes of common stock. The two-class method is an earnings (loss) allocation method under which earnings (loss) per share is calculated for each class of common stock.

The following tables set forth the calculation of basic and diluted net loss per share for the three months ended March 31, 2026 and 2025 (in thousands, except per share data):


	Three Months Ended March 31,
	2026						2025
	Common Stock			Preferred Stock			Common Stock			Preferred Stock
Numerator:
Net loss - basic and diluted	$	(45,485	)	$	(4,176	)	$	(43,698	)	$	(4,803	)
Denominator:
Weighted-average shares outstanding — basic and diluted		60,462			555			58,905			648
Net loss per share:
Basic and diluted	$	(0.75	)	$	(7.52	)	$	(0.74	)	$	(7.42	)

Cullinan used the treasury stock method for equity awards and the if converted method for preferred stock to determine the number of dilutive shares outstanding in each period. The following table sets forth potential common shares that were excluded from the computation of diluted net loss per share attributable to common stockholders of Cullinan for the three months ended March 31, 2026 and 2025 because their effect would have been anti-dilutive (in thousands):


	Three Months Ended March 31,
	2026		2025
Stock options		14,804		12,076
Preferred stock		5,551		6,475
Restricted stock units		915		986
Employee stock purchase plan		64		10
Total		21,334		19,547

Leases - Summary of Weighted Average Remaining Lease Terms and Discount Rates (Details)	Mar. 31, 2026	Dec. 31, 2025
Leases [Abstract]
Weighted-average remaining lease term (in years)	2 years 6 months	2 years 9 months 18 days
Weighted-average discount rate	11.80%	11.80%

Stockholders' Equity

3 Months Ended

Mar. 31, 2026

Stockholders' Equity Note [Abstract]

Stockholders' Equity

(6)

Stockholders' Equity

Common Stock

Each share of common stock entitles the holder to one vote and to receive dividends when and if declared by the board of directors of the Company. No dividends have been declared through March 31, 2026.

Preferred Stock

Each share of preferred stock is convertible into ten shares of common stock at the option of the holder at any time, subject to certain limitations, including that the holder is prohibited from converting preferred stock into common stock if, as a result of such conversion, the holder, together with its affiliates, would beneficially own a number of shares of common stock more than 9.99% of the total common stock then issued and outstanding immediately following the conversion of such shares of preferred stock. Holders of the preferred stock are permitted to increase this percentage to an amount not to exceed 19.99% upon 60 days' notice.

Shares of preferred stock generally have no voting rights, except as required by law and except that the consent of a majority of the holders of the outstanding preferred stock will be required to amend the terms of the preferred stock. In the event of the Company’s liquidation, dissolution or winding up, holders of preferred stock will participate pari passu with any distribution of proceeds to holders of common stock. Holders of preferred stock are entitled to receive when, as, and if dividends are declared and paid on the common stock, an equivalent dividend, calculated on an as-converted basis. Shares of preferred stock are otherwise not entitled to dividends.

The preferred stock ranks (i) senior to any class or series of capital stock of Cullinan created specifically ranking by its terms junior to the preferred stock; (ii) on parity with the common stock and any class or series of capital stock of the Company created specifically ranking by its terms on parity with the preferred stock; and (iii) junior to any class or series of capital stock of Cullinan created specifically ranking by its terms senior to any preferred stock, in each case, as to distributions of assets upon liquidation, dissolution or winding up of the Company, whether voluntarily or involuntarily.

The Company determined that the preferred stock should be classified as permanent equity.

- Definition

The entire disclosure for equity.

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+ Details

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2026

Accounting Policies [Abstract]

Recently Issued Accounting Pronouncements

In November 2024, the FASB issued an accounting standards update to improve disclosures regarding the types of expenses included in commonly presented expense captions, including disaggregating the amounts of employee compensation, depreciation and amortization included within each income statement expense caption. This standard will be effective for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. Cullinan will adopt this standard on January 1, 2027 for 2027 annual reporting and interim periods beginning in 2028 and is evaluating the impact of adopting this standard on its consolidated financial statements and disclosures.

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (unaudited) - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balances Begning at Dec. 31, 2024	$ 590,328		$ 6	$ 958,695	$ (133)	$ (368,240)
Balances, shares Begning at Dec. 31, 2024		647,500	58,510,610
Issuance of common stock under equity-based compensation plans, Shares			188,309
Equity-based compensation	9,374			9,374
Unrealized loss on investments	638				638
Net Loss	(48,501)					(48,501)
Balances Ending at Mar. 31, 2025	551,839		$ 6	968,069	505	(416,741)
Balances, shares Ending at Mar. 31, 2025		647,500	58,698,919
Balances Begning at Dec. 31, 2025	408,730		$ 6	995,823	1,020	(588,119)
Balances, shares Begning at Dec. 31, 2025		555,935	60,244,136
Issuance of common stock upon conversion of preferred stock, Shares		(73,946)	739,460
Issuance of common stock under equity-based compensation plans, Shares			467,784
Issuance of common stock under equity-based compensation plans	380			380
Equity-based compensation	7,616			7,616
Unrealized loss on investments	(893)				(893)
Net Loss	(49,661)					(49,661)
Balances Ending at Mar. 31, 2026	$ 366,172		$ 6	$ 1,003,819	$ 127	$ (637,780)
Balances, shares Ending at Mar. 31, 2026		481,989	61,451,380

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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

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

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+ Details

License and Collaboration Agreements - Summary of Research and Development Costs Related to Collaboration and License Agreements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
License And Collaboration Agreements [Line Items]
Research and development costs	$ 42,123	$ 41,459
General and administrative expense	11,574	13,537
Collaboration Agreements \| Cullinan [Member]
License And Collaboration Agreements [Line Items]
Research and development costs	5,811	5,617
General and administrative expense	652	472
Collaboration Agreements \| Pearl - Taiho
License And Collaboration Agreements [Line Items]
Research and development costs	$ 830	$ 1,374

Reorganization and Reverse Stock Split - Summary of LLC Units Previously Reported as Redeemable Preferred Units or Temporary Equity Converted Reclassified to Equity (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2025	Dec. 31, 2024
Stockholders' Equity (Members' Deficit)
Common Stock	$ 6	$ 6
Additional paid-in capital	1,003,819	995,823
Accumulated other comprehensive income (loss)	127	1,020
Accumulated deficit	(637,780)	(588,119)
Total Stockholders' Equity (Members' Deficit)	$ 366,172	$ 408,730	$ 551,839	$ 590,328

- Definition

Amount, after tax, of accumulated increase (decrease) in equity from transaction and other event and circumstance from nonowner source.

+ References + Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

- Definition

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

+ References

+ Details

Commitment and Contingencies (Additional Information) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Indemnification Agreement [Member]
Loss Contingencies [Line Items]
Accrued liabilities	$ 0	$ 0
Royalty Transfer Agreements [Member]
Loss Contingencies [Line Items]
Royalties under obligation	$ 0

- Definition

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

+ References

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+ Details

Leases - Additional Information (Details) $ in Millions	3 Months Ended
Leases - Additional Information (Details) $ in Millions	Mar. 31, 2026 USD ($) ft²
Lessee Lease Description [Line Items]
Operating Lease expense \| $	$ 0.3
Massachusetts
Lessee Lease Description [Line Items]
Operating lease rentable area \| ft²	14,000

Financial Instruments

3 Months Ended

Mar. 31, 2026

Financial Instruments Pledged as Collateral [Abstract]

Financial Instruments

(3)

Financial Instruments

Investments

Cullinan recognized its investments by security type at March 31, 2026 as follows (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Short-term investments
U.S. government notes	$	149,865	$	352	$	—		$	150,217
Corporate notes		116,860		23		(126	)		116,757
Asset-backed securities		9,801		29		—			9,830
Total short-term investments		276,526		404		(126	)		276,804
Long-term investments
Corporate notes		38,652		4		(155	)		38,501
Asset-backed securities		—		—		—			—
Total long-term investments		38,652		4		(155	)		38,501
Total investments	$	315,178	$	408	$	(281	)	$	315,305

Cullinan recognized its investments by security type at December 31, 2025 as follows (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Short-term investments
U.S. government notes	$	159,632	$	683	$	—		$	160,315
Corporate notes		119,368		119		(7	)		119,480
Asset-backed securities		9,717		52		—			9,769
Total short-term investments		288,717		854		(7	)		289,564
Long-term investments
Corporate notes		48,134		90		(2	)	$	48,222
U.S. government notes		9,963		85		—		$	10,048
Total long-term investments		58,097		175		(2	)		58,270
Total investments	$	346,814	$	1,029	$	(9	)	$	347,834

Fair Value of Financial Instruments

The following table sets forth the fair value of Cullinan’s financial assets that were measured at fair value on a recurring basis as of March 31, 2026 (in thousands):


	Level 1		Level 2		Level 3		Total
Short-term investments
U.S. government notes	$	—	$	150,217	$	—	$	150,217
Corporate notes		—		116,757		—		116,757
Asset-backed securities		—		9,830		—		9,830
Total short-term investments		—		276,804		—		276,804
Long-term investments
Corporate notes		—		38,501		—		38,501
Total long-term investments		—		38,501		—		38,501
Total investments	$	—	$	315,305	$	—	$	315,305

The following table sets forth the fair value of the Company’s financial assets that were measured at fair value on a recurring basis as of December 31, 2025 (in thousands):


	Level 1		Level 2		Level 3		Total
Short-term investments
U.S. government notes	$	—	$	160,315	$	—	$	160,315
Corporate notes		—		119,480		—		119,480
Asset-backed securities		—		9,769		—		9,769
Total short-term investments		—		289,564		—		289,564
Long-term investments
Corporate notes		—		48,222		—		48,222
U.S. government notes		—		10,048		—		10,048
Total long-term investments		—		58,270		—		58,270
Total investments	$	—	$	347,834	$	—	$	347,834

As of March 31, 2026 and December 31, 2025, the fair values of Cullinan's cash and cash equivalents, prepaid expenses and other current assets, accounts payable, accrued expenses and other current liabilities approximated their carrying values due to the short-term nature of these instruments.

Accrued Expenses and Other Current Liabilities (Tables)

3 Months Ended

Mar. 31, 2026

Accrued Expenses And Other Current Liabilities [Abstract]

Summary of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following as of March 31, 2026 and December 31, 2025 (in thousands):


	March 31, 2026		December 31, 2025
Contracted research and development expenses	$	21,944	$	16,388
Employee compensation		2,991		9,952
Due to Taiho under collaboration agreement, net		5,633		8,784
Other current liabilities		1,352		996
Total accrued expenses and other current liabilities	$	31,920	$	36,120

Leases

3 Months Ended

Mar. 31, 2026

Leases [Abstract]

Leases

(9)

Leases

Cullinan has an operating lease for approximately 14,000 square feet of office space in a multi-tenant building in Cambridge, Massachusetts, which commenced in August 2022 and expires in September 2028. Lease expense consisted of operating lease costs of $0.3 million in each of the three months ended March 31, 2026 and 2025.

The following table summarizes supplemental cash flow information for the three months ended March 31, 2026 and 2025 (in thousands):


	Three Months Ended March 31,
	2026		2025
Cash paid for amounts included in measurement of lease liabilities:
Operating cash flows from operating leases	$	372	$	363

The following table summarizes the Company’s future minimum lease payments as of March 31, 2026 (in thousands):


	March 31, 2026
Remainder of 2026	$	657
2027		1,190
2028		906
Total future minimum lease payments		2,753
Less: imputed interest		(370	)
Total lease liabilities at present value	$	2,383

The following table summarizes the weighted-average remaining lease term and discount rate as of March 31, 2026 and December 31, 2025:


	March 31, 2026			December 31, 2025
Weighted-average remaining lease term (in years)		2.5			2.8
Weighted-average discount rate		11.8	%		11.8	%