Exhibit 99.1

Cabaletta Bio Reports Fourth Quarter and Full Year 2025 Financial Results and Provides Business Update

Rese-cel myositis BLA submission on track for 2027 based on a 17-patient, single arm registrational cohort design, including an outpatient dosing option

No-preconditioning program enrolling in lupus and PV; anticipating initial RESET-SLE™ data in 1H26 and durability data from the RESET-SLE and RESET-PV® trials throughout 2026

Automated manufacturing of rese-cel with Cellares’ Cell Shuttle™ underway in the RESET™ clinical program, offering the potential to produce rese-cel for thousands of patients per year with minimal capital investment

Pivotal trial designs announced for SLE and LN single arm cohorts, each with ~25 patients; on track to announce SSc design in 1H26; FDA registrational design discussions and no preconditioning data will inform pivotal plans across the rese-cel program

Complete Phase 1/2 data to be presented in 1H26 from the RESET-SSc™, RESET-SLE and RESET-MG™ trials evaluating rese-cel with preconditioning

PHILADELPHIA, March 23, 2026 -- Cabaletta Bio, Inc. (Nasdaq: CABA), a late-stage clinical biotechnology company focused on developing and launching the first curative targeted cell therapies designed specifically for patients with autoimmune diseases, today reported financial results for the fourth quarter and full year ended December 31, 2025, and provided a business update.

“As we advance our core clinical programs for rese-cel with preconditioning and standard manufacturing, we have meaningfully advanced two potentially transformative innovations: rese-cel with no preconditioning and automated manufacturing using the Cellares Cell Shuttle. Clinical data on both innovations are on track to be shared in the first half of this year with durability data to follow later this year. Clinical data currently suggest that rese-cel offers a competitive profile that may reliably deliver an immune reset following a single, weight-based infusion with a safety profile that facilitates outpatient delivery with – or potentially without – preconditioning,” said Steven Nichtberger, M.D., Chief Executive Officer of Cabaletta.

Recent Operational Highlights and Upcoming Anticipated Milestones

Rese-cel: Rese-cel (resecabtagene autoleucel) is an investigational, autologous CAR T cell therapy engineered with a fully human CD19 binder and a 4-1BB co-stimulatory domain, designed specifically for the treatment of autoimmune diseases. Administered as a single, weight-based infusion, rese-cel has demonstrated the ability to transiently, reliably and deeply deplete CD19-positive cells, with the goal of resetting the immune system and achieving durable clinical responses without the need for chronic therapy. Cabaletta is evaluating rese-cel in the RESET™ (REstoring SElf-Tolerance) clinical development program, which includes multiple

ongoing company-sponsored trials across a broad range of autoimmune diseases in rheumatology, neurology and dermatology.

Fourth Quarter and Full Year 2025 Financial Results

About Cabaletta Bio

Cabaletta Bio (Nasdaq: CABA) is a late-stage clinical biotechnology company focused on developing and launching the first curative targeted cell therapies designed specifically for patients with autoimmune diseases. The CABA™ platform encompasses two complementary strategies which aim to advance the discovery and development of engineered T cell therapies with the potential to become deep and durable, perhaps curative, treatments for a broad range of autoimmune diseases. The lead CARTA (Chimeric Antigen Receptor T cells for Autoimmunity) strategy is prioritizing the development of rese-cel, a 4-1BB-containing fully human CD19-CAR T cell investigational therapy. Rese-cel is currently being evaluated in the RESET™ (REstoring SElf-Tolerance) clinical development program spanning multiple therapeutic areas, including rheumatology, neurology and dermatology. Cabaletta Bio’s headquarters and labs are located in Philadelphia, PA. For more information, please visit www.cabalettabio.com and connect with us on LinkedIn.

Forward-Looking Statements

This press release contains “forward-looking statements” of Cabaletta Bio within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including without limitation, express or implied statements regarding: Cabaletta’s business plans and objectives as a whole; Cabaletta’s ability to realize its vision of launching the first curative targeted cell therapy designed specifically for patients with autoimmune diseases; Cabaletta’s ability to successfully complete research and further development and commercialization of its drug candidates in current or future indications, including the timing and results of Cabaletta’s clinical trials and its ability to conduct and complete clinical trials; expectation that clinical results will support rese-cel’s safety and activity profile; statements regarding the timing of interactions with the FDA, including review of safety information from Cabaletta’s ongoing clinical trials and discussions with the FDA on potential registrational pathways for rese-cel, including the timing of

registrational designs related thereto; Cabaletta’s ability to leverage its emerging clinical data and its efficient development strategy; Cabaletta’s belief that it has meaningfully advanced two potentially transformative innovations; Cabaletta’s expectation around its clinical data that suggests that rese-cel can reliably deliver an immune reset following a single weight-based infusion with a safety profile that facilitates outpatient delivery with or potentially without preconditioning; Cabaletta’s ability to capitalize on and potential benefits resulting from its research and translational insights; the clinical significance of the clinical data read-out at upcoming scientific meetings and timing thereof; Cabaletta’s expectations around the potential success and therapeutic benefits of rese-cel; the Company’s advancement of separate Phase 1/2 clinical trials of rese-cel in patients with SLE, myositis, SSc, gMG and PV and advancement RESET-MS trial, including updates related to status, enrollment, safety data, efficiency of clinical trial design and timing of initial data and durability data read-outs or otherwise; Cabaletta’s plans of discussions with the FDA on registrational cohort designs and timing thereof; Cabaletta’s plans to announce additional clinical data from the RESET trials throughout 2026, including complete Phase 1/2 data to be presented in 1H26 from the RESET-SSc, RESET-SLE and RESET-MG trials evaluating rese-cel with preconditioning; Cabaletta’s expectations that the additional clinical data from the RESET trials will inform discussions with the FDA regarding registrational cohort designs for rese-cel in various indications; Cabaletta’s plans to submit a BLA for rese-cel in myositis in 2027 and obtain regulatory approval from the FDA and other regulatory authorities; Cabaletta’s plans to implement automated manufacturing of rese-cel with Cellares’ Cell Shuttle, including timing of initial clinical experience and durability data and its expectation that it can enable scalability to treat thousands of patients per year with minimal capital investment; and Cabaletta’s use of capital, expense and other financial results in the future and its ability to fund operations into the fourth quarter of 2026.

Any forward-looking statements in this press release are based on management’s current expectations and beliefs of future events and are subject to a number of risks and uncertainties that could cause actual results to differ materially and adversely from those set forth in or implied by such forward-looking statements. These risks and uncertainties include, but are not limited to: risks related to regulatory filings and potential clearance; the risk that signs of biologic activity or persistence may not inform long-term results; Cabaletta’s ability to demonstrate sufficient evidence of safety, efficacy and tolerability in its preclinical studies and clinical trials of rese-cel; the risk that the results observed with the similarly-designed construct employed in academic publications, including due to the dosing regimen, are not indicative of the results we seek to achieve with rese-cel; risks that results from one program may not translate to results for another program; risks that modifications to trial design or approach may not have the intended benefits and that the trial design may need to be further modified; risks related to clinical trial site activation, delays in enrollment generally or enrollment rates that are lower than expected; delays related to assessment of clinical trial results; risks related to unexpected safety or efficacy data observed during clinical studies; risks related to volatile market and economic conditions and public health crises; Cabaletta’s ability to retain and recognize the intended incentives conferred by Orphan Drug Designation and Fast Track Designation or other designations for its product candidates, as applicable; risks related to Cabaletta’s ability to protect and maintain its intellectual property position; risks related to fostering and maintaining successful relationships with Cabaletta’s collaboration and manufacturing partners; uncertainties related to the initiation and conduct of studies and other development requirements for its product candidates; the risk that any one or more of Cabaletta’s product candidates will not be successfully developed and/or commercialized; and the risk that the initial

or interim results of preclinical studies or clinical studies will not be predictive of future results in connection with future studies. For a discussion of these and other risks and uncertainties, and other important factors, any of which could cause Cabaletta’s actual results to differ from those contained in the forward-looking statements, see the section entitled “Risk Factors” in Cabaletta’s most recent annual report on Form 10-K as well as discussions of potential risks, uncertainties, and other important factors in Cabaletta’s other subsequent filings with the Securities and Exchange Commission. All information in this press release is as of the date of the release, and Cabaletta undertakes no duty to update this information unless required by law.

CABALETTA BIO, INC.

SELECTED FINANCIAL DATA

(unaudited; in thousands, except share and per share data)

Statements of Operations

Selected Balance Sheet Data

Contacts:

Anup Marda
Chief Financial Officer
investors@cabalettabio.com