Cullinan Therapeutics, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31,2025

OR

Commission File Number:001-39856

(Exact name of registrant as specified in its charter)

(617)410-4650

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☐No ☒

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. Yes ☐No ☒

Indicate by check mark whether the Registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒No ☐

Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit such files). Yes ☒No ☐

Indicate by check mark whether the Registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the Registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the Registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report.☐

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the Registrant included in the filing reflect the correction of an error to previously issued financial statements.☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the Registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b). ☐

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐No ☒

The aggregate market value of the voting and non-voting common stock held by non-affiliates of the Registrant as of June 30, 2025 was $442.2 million based on the closing price of the Registrant's shares of common stock on the Nasdaq Global Select Market on such date.

The number of shares of the Registrant’s common stock outstanding as of February 23, 2026 was 60,526,128.

DOCUMENTS INCORPORATED BY REFERENCE

The Registrant intends to file a definitive proxy statement pursuant to Regulation 14A in connection with its 2026 Annual Meeting of Stockholders within 120 days of the end of the Registrant’s fiscal year ended December 31, 2025. Portions of such proxy statement are incorporated by reference into Part II, Item 5 and Part III of this Annual Report on Form 10-K.

Table of Contents

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K contains forward-looking statements which are made pursuant to the safe harbor provisions of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, that involve risks, uncertainties, and other factors that may cause actual results, levels of activity, performance, or achievements to be materially different from the information expressed or implied by these forward-looking statements. All statements, other than statements of historical facts, contained in this Annual Report on Form 10-K, including statements regarding our strategy, future operations, future financial position, future revenue, projected costs, prospects, plans and objectives of management, and expected market growth are forward-looking statements. The words “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “should,” “target,” “would”, and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.

Any forward-looking statements in this Annual Report on Form 10-K reflect our current views with respect to future events or to our future financial performance and involve known and unknown risks, uncertainties, and other factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. Factors that may cause actual results to differ materially from current expectations include, among other things, those listed in this Annual Report on Form 10-K and other filings with the Securities and Exchange Commission (the “SEC”), including the following:

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the commercial success, cost of development, and timing of the approval of our clinical-stage product candidates;

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the initiation, timing, progress, results, and cost of our research and development programs, and our current and future preclinical studies and clinical trials, including statements regarding the timing of initiation and completion of studies or clinical trials and related preparatory work, and the period during which the results of the trials will become available;

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our ability to submit, and obtain clearance of, any global regulatory filings, including new drug applications or investigational new drug applications, on our expected timelines, or at all;

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our ability to initiate, recruit, and enroll patients in and conduct our clinical trials at the pace that we project;

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our ability to obtain and maintain regulatory approval of our product candidates, and any related restrictions, limitations, or warnings in the label of any of our product candidates, if approved;

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the impacts of governmental legislation and regulations, including adverse effects from any potential future United States government shutdown;

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the effect of changes in global economic conditions, including uncertainties related to international trade policies, tariffs and supply chain dynamics, on our business and operations, including our expenses, supply chain, manufacturing processes, preclinical studies, and clinical trials;

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our ability to compete with companies currently marketing therapies or developing product candidates with targets or indications similar to our product candidates’ targets or indications;

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our reliance on third parties to conduct our clinical trials and to manufacture drug substance and drug product for use in our clinical trials;

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the size and growth potential of the markets for any of our current and future product candidates, and our ability to serve those markets;

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our ability to identify and advance through clinical development any additional product candidates;

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the commercialization of our current and future product candidates, if approved, including our ability to successfully build a specialty sales force and commercial infrastructure to market our current and future product candidates;

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our ability to identify research priorities and apply a risk-mitigated strategy to efficiently discover and develop current and future product candidates;

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our ability to retain and recruit key personnel;

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our ability to obtain and maintain adequate intellectual property rights;

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our expectations regarding government and third-party payor coverage, pricing, and reimbursement;

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our estimates of our expenses, ongoing losses, capital requirements, the sufficiency of our current resources, and our needs for or ability to obtain additional financing;

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the milestone payments that we may receive from Taiho Pharmaceutical Co., Ltd.;

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potential investments in our pipeline and the potential for such product candidates;

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the potential benefits of strategic collaboration agreements, our ability to enter into additional strategic collaborations or arrangements, and our ability to attract collaborators with development, regulatory, and commercialization expertise; and

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developments and projections relating to our competitors or our industry.

We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and investors should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions, and expectations disclosed in the forward-looking statements we make. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures, or investments we may make or collaborations or strategic partnerships we may enter into.

You should read this Annual Report on Form 10-K and the documents that we reference herein and have filed or incorporated by reference as exhibits hereto completely and with the understanding that our actual future results may be materially different from what we expect. We do not assume any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

This Annual Report on Form 10-K also contains estimates, projections, and other information concerning our industry, our business, and the markets for our product candidates. Information that is based on estimates, forecasts, projections, market research, or similar methodologies is inherently subject to uncertainties, and actual events or circumstances may differ materially from events and circumstances that are assumed in this information. Unless otherwise expressly stated, we obtained this industry, business, market, and other data from our own internal estimates and research as well as from reports, research surveys, studies, and similar data prepared by market research firms and other third parties, industry, medical and general publications, government data, and similar sources. While we are not aware of any misstatements regarding any third-party information presented in this Annual Report on Form 10-K, their estimates, in particular, as they relate to projections, involve numerous assumptions, are subject to risks and uncertainties and are subject to change based on various factors, including those discussed under the section titled “Risk Factors” and elsewhere in this Annual Report on Form 10-K.

References to Cullinan in this Annual Report on Form 10-K

Unless otherwise stated or the context indicates otherwise, all references herein to “Cullinan,” “Cullinan Therapeutics, Inc.,” “we,” “us,” “our,” “our company,” “the Company,” and similar references refer to Cullinan Therapeutics, Inc. and its consolidated subsidiaries, and “our board of directors” and “the Board” refer to the board of directors of Cullinan Therapeutics, Inc.

Summary of the Material and Other Risks Associated with Our Business

Below is a summary of the principal factors that make an investment in our common stock speculative or risky. This summary does not address all of the risks that we face. Additional discussion of the risks summarized in this risk factor summary, and other risks that we face, are summarized in “Risk Factors” and should be carefully considered, together with other information in this Annual Report on Form 10-K and our other filings with the Securities and Exchange Commission, before making an investment decision regarding our common stock.

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We are early in our development efforts and are substantially dependent on our lead product candidates. If we are unable to advance these or any of our other current and future product candidates through clinical development, or to obtain regulatory approval and ultimately commercialize any such product candidates, either by ourselves or with or by third parties or if we experience significant delays in doing so, our business may be materially harmed.

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Difficulty in enrolling patients has delayed, and in the future could delay or prevent clinical trials of our product candidates and ultimately delay or prevent regulatory approval.

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Interim, “topline”, and preliminary data from our clinical trials that we announce or publish may change as more patient data become available and are subject to confirmation, audit, and verification procedures that could result in material changes in the final data.

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Our product candidates may cause undesirable side effects or have other properties that delay or prevent their regulatory approval, limit their commercial potential, or result in significant negative consequences following any potential marketing approval.

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Our limited operating history may make it difficult for you to evaluate the success of our business to date and to assess our future viability.

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We have incurred significant losses since inception, and we expect to incur losses over the next several years and may not be able to achieve or sustain revenues or profitability in the future.

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We will require substantial additional funding to develop and commercialize our current and future product candidates. If we are unable to raise capital when needed, we would be compelled to delay, reduce, or eliminate our product development programs or other operations.

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We may not be successful in our efforts to build a pipeline of product candidates with commercial value.

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Certain agreements provide our licensors, collaborators, or other shareholders in our development subsidiaries with rights that could delay or impact the potential sale of our development subsidiaries or could impact our ability to sell assets, or enter into strategic alliances, collaborations, or licensing arrangements with other third parties.

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Our reliance on a limited number of employees presents operational challenges that may adversely affect our business.

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We face substantial competition, which may result in others discovering, developing, or commercializing products before or more successfully than we do.

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If we are unable to obtain and maintain patent and other intellectual property protection for our current and future product candidates and technology, or if the scope of intellectual property protection obtained is not sufficiently broad, our competitors could develop and commercialize products and technology similar or identical to ours, and our ability to commercialize any of our current or future product candidates or technology may be adversely affected.

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We currently rely and expect to continue to rely on the outsourcing of the majority of our development functions to third parties to conduct our preclinical studies and clinical trials. If these third parties do not properly and successfully carry out their contractual duties or meet expected deadlines, we may not be able to obtain regulatory approval of or commercialize our product candidates.

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We currently rely and expect to rely in the future on third parties to manufacture our product candidates. Our business could be harmed if the third-party manufacturers fail to provide us with sufficient quantities of our product candidates or fail to do so on acceptable timelines or at acceptable quality levels or prices.

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We are highly dependent on our key personnel. If we are not successful in retaining highly qualified personnel, we may not be able to successfully implement our business strategy.