Cabaletta Bio, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31,2024

OR

Commission File Number 001-39103

(Exact name of Registrant as specified in its Charter)

Registrant’s telephone number, including area code: (267)759-3100

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 Section 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 Act). Yes☐ No☒

As of June 30, 2024 (the last business day of the registrant's most recently completed second fiscal quarter), the aggregate market value of the registrant's common stock held by non-affiliates was approximately $350 million based on the last reported sale price of the registrant's common stock on the Nasdaq Global Select Market on June 30, 2024.

The number of shares of registrant’s Common Stock outstanding as of March 27, 2025 was 50,743,101.

Table of Contents

i

Summary of the Material and Other Risks Associated with Our Business

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We are a clinical-stage company with a limited operating history, have incurred significant losses since our inception, and anticipate that we will continue to incur significant losses for the foreseeable future.

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We are highly dependent on our relationships with University of Pennsylvania, or Penn, and/or WuXi Advanced Therapies, Inc., or WuXi, for our current manufacturing needs for our Phase 1/2 RESETTM, or Restoring Self-Tolerance, clinical trials for resecabtagene autoleucel (rese-cel, formerly referred to as CABA-201) and our Phase 1 clinical trial of MuSK-CAART, or the MusCAARTes TMtrial, and if Penn's or WuXi's manufacturing capacity is reduced or otherwise delayed or limited, including due to legislative action, or if we, Penn, WuXi or any third-party manufacturers encounter difficulties in manufacturing our product candidates, this could adversely impact the supply of product candidates for and enrollment in our trials.

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We are reliant on intellectual property licensed to us by Penn and Nanjing IASO Biotherapeutics Co., Ltd., or IASO, and termination of one of these license agreements would result in the loss of significant rights, which would have a material adverse effect on our business.

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If we are unable to obtain and maintain sufficient intellectual property protection for our current product candidates and technologies or any future product candidates, we may not be able to compete effectively in our markets.

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We will need to raise substantial additional funding before we can expect to complete development of any of our product candidates or generate any revenues from product sales.

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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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If we are unable to successfully develop our current programs into a portfolio of product candidates, or experience significant delays in doing so, we may not realize the full commercial potential of our current and future product candidates.

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If we encounter difficulties enrolling patients in our RESETTM clinical trials for rese-cel or future clinical trials, these clinical development activities could be delayed or otherwise adversely affected.

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If we are unable to advance our product candidates through clinical development, obtain regulatory approval and ultimately commercialize our product candidates, or experience significant delays in doing so, our business will be materially harmed.

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Results of earlier studies may not be predictive of future study or trial results, and we may fail to establish an adequate safety and efficacy profile to conduct clinical trials or obtain regulatory approval for our product candidates.

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If serious adverse events, undesirable side effects or unexpected characteristics are identified during the development of any of our product candidates, we may need to delay, abandon or limit our further clinical development of those product candidates.

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Manufacturing and administering our product candidates is complex and we may encounter difficulties in technology transfer to a contract manufacturing organization.

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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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We may establish our own manufacturing facility and infrastructure in addition to or in lieu of relying on third parties for the manufacture of our product candidates, which will be costly and time-consuming, and which may not be successful.

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Our future success depends in part upon our ability to retain our key employees, consultants and advisors and to attract, retain and motivate other qualified personnel.

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We have identified conditions that raise substantial doubt about our ability to continue as a going concern. If we are unable to secure additional funding beyond our current cash position that enables our operations into the first half of 2026, we may be forced to delay, reduce or discontinue our product development programs efforts or other operations.

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K, including the sections entitled “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” contains express or implied forward-looking statements that are based on our management’s belief and assumptions and on information currently available to our management. Although we believe that the expectations reflected in these forward-looking statements are reasonable, these statements relate to future events or our future operational or 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. Forward-looking statements in this Annual Report on Form 10-K include, but are not limited to, statements about:

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the success, cost and timing and conduct of our clinical trial program, including our Phase 1/2 RESETTM clinical trials for rese-cel, our MusCAARTes TMtrial, and any other product candidates, including statements regarding the timing of initiation, enrollment and completion of the clinical trials and the period during which the results of the clinical trials will become available;

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the expected timing and significance around the announcement of safety, biologic activity and/or any additional clinical data from our RESETTM clinical trials for rese-cel or MusCAARTes TMtrial;

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the timing of and our ability to obtain and maintain regulatory approval of our product candidates, including rese-cel, MuSK-CAART, and our other product candidates, in any of the indications for which we plan to develop them, and any related restrictions, limitations, and/or warnings in the label of an approved product candidate;

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our expectations for the tolerability and clinical activity of rese-cel and ability to advance this product candidate through our license agreement with IASO;

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the potential benefits of our Orphan Drug, Rare Pediatric Disease and Fast Track designations;

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our expected use of proceeds from sales of our common stock in “at-the-market” offerings and other offerings, and the period over which such proceeds, together with existing cash, will be sufficient to extend our current cash runway beyond our current expectations into the first half of 2026 and meet our operating needs, including our ability to continue as a going concern;

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our plans to pursue research and development of other product candidates;

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the potential advantages of our proprietary Cabaletta Approach for B cell Ablation platform, called our CABA® platform, and our product candidates;

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the extent to which our scientific approach and CABA® platform may potentially address a broad range of diseases;

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the potential benefits and success of our arrangements with Penn, the Children’s Hospital of Philadelphia, or CHOP, and WuXi;

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our ability to successfully leverage our research and translational insights;

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our expectations regarding the results observed with the similarly-designed construct employed in recent academic publications, including the dosing regimen, and the implications on rese-cel;

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our ability to successfully commercialize our product candidates, including rese-cel, MuSK-CAART and any other product candidates;

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the potential receipt of revenue from future sales of rese-cel, MuSK-CAART and any other product candidates, if approved;

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the rate and degree of market acceptance and clinical utility of rese-cel, MuSK-CAART and any other product candidates;

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our estimates regarding the potential market opportunity for rese-cel, MuSK-CAART and any other product candidates, and our ability to serve those markets;

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our sales, marketing and distribution capabilities and strategy, whether alone or with potential future collaborators;

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our ability to establish and maintain arrangements or a facility for manufacture of rese-cel, MuSK-CAART and any other product candidates;

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our ability to obtain funding for our operations, including funding necessary to initiate and complete our RESETTM clinical trials of rese-cel, our MusCAARTes TM trial and any ongoing preclinical studies of other product candidates;

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our expectations for the efficiency of the trial design for our RESETTM clinical trials for rese-cel and the potential success and therapeutic benefits of rese-cel, including our belief that rese-cel may enable an “immune system reset” and provide deep and durable responses in patients across an increasing number of autoimmune diseases;

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the potential achievement of milestones and receipt of payments under our collaborations;

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our ability to enter into additional collaborations with existing collaborators or other third parties;

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our expectations regarding our ability to obtain and maintain intellectual property protection for our product candidates and our ability to operate our business without infringing on the intellectual property rights of others;

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our expectations regarding international expansion and results of our efforts to do so;

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the success of competing therapies that are or become available, and our competitive position;

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the accuracy of our estimates regarding expenses, future revenues, capital requirements and needs for additional financing;

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the impact of government laws and regulations in the United States and foreign countries; and

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our ability to attract and retain key scientific or management personnel.

These factors should not be construed as exhaustive and should be read in conjunction with the other cautionary statements that are included in this Annual Report on Form 10-K. The forward-looking statements contained in this Annual Report on Form 10-K are made as of the date of this Annual Report on Form 10-K, and we undertake no obligations to publicly update or review any forward-looking statement, whether as a result of new information, future developments or otherwise. Therefore, you should not rely on these forward-looking statements as representing our views as of any date subsequent to the date of this Annual Report on Form 10-K.