8-K: Cabaletta Bio Reports Strong Clinical Data for Rese-cel in Autoimmune Diseases and Outlines Accelerated Regulatory Path

Cabaletta Bio announced compelling new clinical and translational data for its lead investigational therapy, rese-cel, across multiple autoimmune disease trials, alongside the termination of its At-The-Market (ATM) equity program.

Summary

• Cabaletta Bio, Inc. (CABA) mutually agreed with TD Securities (USA) LLC to immediately terminate their Sales Agreement (ATM Program) as of June 11, 2025, with no termination penalties.
• Prior to termination, 2,609,865 ATM Shares were sold for gross proceeds of $7,881,380, leaving $192,118,620 of ATM Shares available for sale under the program.
• The company presented new clinical and translational data from 18 evaluable patients treated with rese-cel (resecabtagene autoleucel, formerly CABA-201) across the RESET-Myositis, RESET-SLE, and RESET-SSc trials at the EULAR 2025 Congress.
• In the RESET-Myositis trial, 7 out of 8 patients achieved a clinical response off all immunomodulators, with responses sustained; 4 ASyS and DM patients achieved clinically meaningful TIS responses (3 major TIS).
• In the RESET-SLE trial, 7 out of 7 patients achieved a clinical response off all immunomodulators and glucocorticoids, with all non-renal SLE patients achieving DORIS and the first lupus nephritis patient achieving DORIS and a complete renal response.
• In the RESET-SSc trial, both patients in the severe skin cohort showed meaningful modified Rodnan Skin Score (mRSS) improvements after discontinuing immunomodulatory drugs and steroids, sustained out to 6 months in the first patient.
• Overall safety data from 18 patients with 4+ weeks follow-up showed 94% had no or Grade 1 Cytokine Release Syndrome (CRS) and 89% had no Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS), with two previously reported ICANS events.
• Rese-cel demonstrated rapid and transient B cell reduction in peripheral blood within the first month, with repopulation observed around two months, generally expressing a transitional, naive phenotype; tissue-resident B cell depletion was confirmed via lymph node biopsy.
• The RESET clinical trial program enrollment is accelerating, with 51 patients actively enrolled and 24 patients dosed across 67 US clinical sites as of May 30, 2025.
• Cabaletta plans to initiate enrollment in two registrational myositis cohorts (~15 patients each) in 2H25, with a Biologics License Application (BLA) submission planned for 2027.
• Registrational discussions with the FDA for SLE/LN are scheduled for 3Q25, and anticipated for scleroderma in 4Q25 and myasthenia gravis in 1H26.

Sentiment

Score: 9

Explanation: The sentiment is highly positive due to overwhelmingly strong clinical efficacy and safety data for rese-cel across multiple severe autoimmune diseases, coupled with clear and accelerated regulatory pathways. The termination of the ATM program is a minor financial note with no penalties, overshadowed by the significant clinical progress and strategic clarity.

Positives

• Rese-cel demonstrated compelling clinical efficacy across multiple autoimmune diseases, with high rates of clinical response and patients discontinuing immunomodulators and steroids.
• In RESET-Myositis, 7 of 8 patients achieved clinical response off immunomodulators, with sustained responses and major TIS responses in ASyS and DM patients.
• In RESET-SLE, all 7 patients achieved clinical response off immunomodulators and glucocorticoids, with non-renal SLE patients achieving DORIS and the first LN patient achieving complete renal response.
• In RESET-SSc, both patients showed meaningful mRSS improvements and the first patient met CRISS criteria, indicating potential for drug-free clinical response.
• The safety profile of rese-cel appears favorable, with 94% of patients experiencing no or Grade 1 CRS and 89% having no ICANS, which is considerably lower than observed in cancer CAR T patients.
• Translational data confirmed deep and transient B cell depletion in both peripheral blood and tissues, supporting the mechanism of action.
• Cabaletta has achieved FDA alignment on a registrational pathway for myositis, with registrational cohorts on track to initiate enrollment in 2H25 and a BLA submission planned for 2027.
• The company is pursuing accelerated regulatory discussions for SLE/LN, SSc, and myasthenia gravis, indicating a clear and rapid path to potential market entry for multiple indications.
• The clinical trial program is accelerating enrollment, with 51 patients actively enrolled and 24 dosed across an expanding network of 67 clinical sites.
• The termination of the ATM program incurred no penalties, indicating a clean exit from that financing mechanism.

Negatives

• The ATM program was terminated after only $7,881,380 of the potential $200,000,000 was raised, indicating limited utilization of this capital-raising facility.
• One Grade 4 ICANS event was observed in the RESET-SLE trial and one Grade 3 ICANS event in the RESET-SSc trial, both previously reported.
• One patient in the RESET-SSc trial experienced a related serious adverse event (SAE) of neutropenic fever.
• While responses were observed in IMNM patients, the TIS responses were more modest compared to other myositis subtypes, consistent with published data.

Risks

• Risks related to regulatory filings and potential clearance of rese-cel.
• The risk that signs of biologic activity or persistence observed in interim data 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 results observed with similarly-designed constructs employed in academic publications may not be indicative of the results achieved with rese-cel.
• 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 the 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 Regenerative Medicine Advanced Therapy, Orphan Drug Designation, and Fast Track Designation.
• Risks related to Cabaletta's ability to protect and maintain its intellectual property position.
• Risks related to fostering and maintaining successful relationships with 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.
• 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.
• The Company's ability to fund its operations and continue as a going concern.

Future Outlook

Cabaletta Bio plans to leverage its recent FDA alignment on a registrational pathway in myositis to engage in near-term interactions with the FDA for registrational program designs for SLE/LN (3Q25), scleroderma (4Q25), and myasthenia gravis (1H26). The company anticipates initiating enrollment in two registrational myositis cohorts in the second half of 2025, with an initial Biologics License Application (BLA) submission planned for myositis in 2027. They also aim to advance manufacturing processes, including evaluating a whole blood process to eliminate apheresis and completing commercial-ready drug product tech transfer by 2H25, to support future commercial supply.

Management Comments

• David J. Chang, M.D., Chief Medical Officer of Cabaletta, stated: "These new clinical and translational findings reinforce our belief that a single, weight-based dose of rese-cel leads to deep B cell depletion and compelling clinical data in patients with myositis, lupus and systemic sclerosis, with nearly all patients off immunomodulators and steroids."
• Dr. Chang also commented: "Patients are seeking a drug-free, symptom-free life, which is rarely, if ever, achieved with currently approved therapies. We believe the clinical data on rese-cel indicate its potential to achieve this aspiration and ultimately change treatment paradigms for autoimmune diseases."
• Dr. Chang further added: "As we continue to execute across the RESET clinical development program with accelerating enrollment across a broad portfolio of indications with over 50 patients actively enrolled at more than 65 active clinical sites, we plan to leverage our recent FDA alignment on a registrational pathway in myositis to engage in near-term interactions with the FDA on registrational program designs for SLE/LN, SSc and MG and move closer to our goal of launching rese-cel as the first targeted curative cell therapy for patients with autoimmune diseases."

Industry Context

Cabaletta Bio is positioned at the forefront of developing targeted cell therapies for autoimmune diseases, a rapidly evolving field. Their rese-cel program, a CD19-CAR T cell therapy, aims to provide a 'drug-free, symptom-free life' for patients, a significant unmet need in chronic autoimmune conditions where current treatments often require lifelong immunosuppression with considerable side effects. The company's strategy of pursuing multiple indications (myositis, lupus, scleroderma, myasthenia gravis) and seeking accelerated regulatory pathways positions it as a potential leader in transforming treatment paradigms for these conditions, moving beyond traditional immunomodulators and biologics.

Comparison to Industry Standards

• The frequency and severity of Cytokine Release Syndrome (CRS) and Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS) events observed with rese-cel (~94% no/Grade 1 CRS, ~89% no ICANS) are considerably lower than those typically observed in CAR T cell therapies used for cancer patients.
• The deep B cell depletion achieved by rese-cel is consistent with academic studies in autoimmune disease, which have shown CD19-CAR T cell therapy to achieve deeper depletion than monoclonal antibodies (mAbs).
• Rese-cel's product design, including its 4-1BB costimulatory domain and fully human binder, is noted to have similar in vitro and in vivo activity to constructs used in academic studies in autoimmunity, such as the FMC63 binder.
• The weight-based dosing strategy for rese-cel is consistent with approaches used in academic studies, suggesting a validated dosing paradigm for autoimmune CAR T therapies.
• The observed clinical recurrences in less than 5% of ~150 autoimmune patients dosed with cell therapy (across industry and academia) highlight the potential for durable responses, with one reported relapse in an IIM patient after ~9 months of drug-free remission, which was subsequently treated with BCMA-CAR T.
• The company's focus on achieving 'drug-free, symptom-free' life for patients sets a high bar compared to current standard-of-care therapies for autoimmune diseases, which often involve chronic medication and rarely achieve complete remission without ongoing treatment.

Stakeholder Impact

• **Shareholders**: The positive clinical data and clear regulatory pathway for rese-cel could significantly increase the company's valuation and share price, indicating strong potential for future revenue and market leadership. The termination of the ATM program, while not fully utilized, removes a potential source of dilution.
• **Patients**: Patients suffering from severe autoimmune diseases like myositis, lupus, and scleroderma could benefit immensely from rese-cel, which shows potential for drug-free, symptom-free remission, a significant improvement over current chronic therapies.
• **Employees**: Continued positive clinical development and a clear path to commercialization could lead to job security, growth opportunities, and potential expansion within the company.
• **Healthcare Providers**: The potential for a curative, single-infusion therapy could change treatment paradigms, offering a new, highly effective option for managing complex autoimmune conditions.
• **Regulatory Authorities**: The company's proactive engagement with the FDA and alignment on registrational pathways demonstrate a commitment to rigorous development and could facilitate faster approval processes for a much-needed therapy.

Next Steps

• Initiate enrollment in two registrational myositis cohorts (~15 patients each) in 2H25.
• Engage in registrational discussions with the FDA for SLE/LN in 3Q25.
• Engage in anticipated registrational discussions with the FDA for scleroderma in 4Q25.
• Engage in anticipated registrational discussions with the FDA for myasthenia gravis in 1H26.
• Complete commercial-ready drug product tech transfer process with Lonza in 2H25.
• Plan process qualification and validation activities for commercial supply (LVV process at Oxford, Drug product process at Lonza).
• Continue accelerating enrollment across the RESET clinical trial program.
• Present complete Phase 1/2 data for rese-cel.
• Evaluate whole blood process to eliminate apheresis for T cell collection.
• Plan for a Biologics License Application (BLA) submission in myositis in 2027.

Key Dates

Recommendation

Keywords

Cabaletta Bio, rese-cel, CABA-201, CAR T cell therapy, autoimmune diseases, myositis, lupus, systemic lupus erythematosus, lupus nephritis, scleroderma, systemic sclerosis, clinical trials, RESET program, FDA alignment, Biologics License Application, EULAR Congress, drug-free remission, B cell depletion, immunomodulators, glucocorticoids, cytokine release syndrome, ICANS, registrational cohorts, biotechnology, cell therapy