Cabaletta Initiates Myositis Registrational Cohort to Evaluate 17 Patients

Translate registrational pathways with rese-cel into a pipeline in a product across autoimmune diseases Initiation of myositis registrational cohort: Cabaletta initiated the U.S. Food and Drug Administration-aligned dermatomyositis and antisynthetase syndrome registrational cohort in December 2025. These subtypes affect approximately 70,000 patients in the U.S., with DM comprising approximately 60,000 patients. The registrational cohort is expected to evaluate 17 patients with a 16-week primary endpoint of moderate or major total improvement score response while off immunomodulators and on no or low-dose steroids. Data from the Phase 1/2 RESET-Myositis trial presented at ACR Convergence 2025 demonstrated that all DM patients with sufficient follow-up who would have met key inclusion criteria in the registrational cohort achieved the registrational primary endpoint with durability throughout the follow-up period as long as one year. Based on that data, Cabaletta elected to expand the registrational trial by 3 patients to permit enrollment of approximately 14 DM patients aligned with natural U.S. prevalence estimates. If successful, data from this cohort will support Cabaletta's first projected Biologics License Application submission for rese-cel in myositis next year. FDA alignment on new registrational cohort designs in SLE and LN: Cabaletta has aligned with the FDA on registrational cohort designs in RESET-SLE to evaluate the current rese-cel weight-based dose of 1 million cells/kg in a single infusion with preconditioning, including two independent, single-arm cohorts, one consisting of patients with non-renal systemic lupus erythematosus and one consisting of patients with lupus nephritis, each evaluating approximately 25 patients with unique endpoints in each cohort. Cabaletta will provide an update on next steps for these cohorts later this year subject to dose-ranging data evaluating rese-cel without preconditioning in lupus patients. Additional RMAT designation granted and registrational cohort alignments and initiations anticipated in 2026: The FDA has recently granted a Regenerative Medicine Advanced Therapy designation to rese-cel for the treatment of systemic sclerosis. Cabaletta is continuing to engage with the FDA to align on registrational cohort designs for RESET-SSc and anticipates providing an update regarding registrational alignment for RESET-SSc in 1H26 and RESET-MGin mid-2026. Advance fully automated, scalable manufacturing with Cellares to support the anticipated post-approval market expansion of rese-cel Automated manufacturing of rese-cel using the Cellares Cell Shuttle and Cellares Cell Q to initiate imminently: Investigational New Drug amendment clearance has been obtained to use the Cellares Cell Shuttle to manufacture rese-cel. This is a first for any autologous CAR T program. The IND submission included three engineering runs that demonstrated product consistency compared to existing rese-cel manufacturing runs at current contract development and manufacturing organizations and is the result of the collaboration between Cabaletta and Cellares since 2023. This follows the previously announced completion of the Technology Adoption Program which successfully demonstrated the ability of Cellares' Cell Shuttle to automate the rese-cel manufacturing process. Cabaletta anticipates clinical manufacturing data in the first half of 2026, which is intended to confirm overall supply chain GMP readiness, including supply chain logistics, for Cellares-produced rese-cel implementation across the rese-cel portfolio. The Company continues to work with its existing manufacturing partners to support the myositis registrational trial and launch-readiness efforts for rese-cel. The Cellares Integrated Development and Manufacturing Organization Smart Factory can enable unprecedented scale with minimal capital investment, rapid expansion to global capacity, lower manufacturing cost and improve scheduling flexibility for rese-cel after commercialization. Expand the clinical experience of rese-cel and in combination with process innovations to deliver an industry-leading therapy for patients and physicians No preconditioning dose-escalation ongoing in RESET-PV: Following the presentation of the first rese-cel data demonstrating biologic activity and early clinical responses without preconditioning at the 2025 European Society of Gene & Cell Therapy Annual Congress, Cabaletta is now evaluating rese-cel at a higher dose without preconditioning in patients with pemphigus vulgaris with additional patients currently enrolled. Additional durability data from patients dosed at the initial dose and initial clinical data from patients dosed at the higher dose are expected in 1H26. No preconditioning cohort added in RESET-SLE: Cabaletta has incorporated a dose-escalation cohort without preconditioning in RESET-SLE, which is the current focus for the trial. This decision was based on the safety and activity data at the initial dose evaluating rese-cel without preconditioning in the RESET-PV study and the clinical responses observed in lupus following complete B cell depletion after administration of rese-cel with preconditioning. Pending dose-ranging clinical data anticipated in 2026, Cabaletta will evaluate pursuing alignment with the FDA on a registrational pathway for the no preconditioning cohort. Complete Phase 1/2 data readouts across three RESETtrials expected in 1H26: Following the presentation of complete Phase 1/2 clinical data from RESET-Myositis cohorts in 2025, Cabaletta anticipates complete Phase 1/2 clinical data from cohorts in RESET-SLE, RESET-SSc and RESET-MG in 1H26.