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Highlights
- Miv-cel met the primary and all secondary efficacy endpoints at Week 16 with statistically significant improvements in mobility and disease-related measures.
- Eighty-one percent of patients achieved more than a 20% improvement in the timed 25-foot walk following a single infusion.
- No high-grade cytokine release syndrome or neurotoxicity events were reported in the trial.
Kyverna Therapeutics, Inc. (Nasdaq:KYTX), a clinical-stage biopharmaceutical company focused on developing cell therapies for autoimmune diseases, has announced positive topline results from KYSA-8, its registrational Phase 2 clinical trial evaluating mivocabtagene autoleucel (miv-cel) in patients with stiff person syndrome (SPS). The trial assessed the safety and efficacy of a single dose of the CD19-targeting CAR T-cell therapy in patients with inadequate responses to existing treatment options.
KYSA-8 Trial Overview
KYSA-8 is a single-arm, open-label, multicenter registrational Phase 2 trial designed to evaluate miv-cel in patients diagnosed with stiff person syndrome. A total of 26 adult patients with SPS who had shown inadequate response to non-approved treatment options were enrolled, dosed, and followed through the primary analysis time point at Week 16, with continued follow-up ongoing.
Participants received lymphodepletion using cyclophosphamide and fludarabine prior to a single infusion of miv-cel at a target dose of 1×10⁸ CAR T cells. The primary endpoint was the change from baseline in the timed 25-foot walk, while secondary endpoints assessed multiple measures of functional mobility and disease severity.
Primary Endpoint Results
At Week 16, miv-cel demonstrated a statistically significant improvement in the primary endpoint of mobility as measured by the timed 25-foot walk. The median improvement from baseline was 46%, with a p-value of 0.0002, meeting the trial’s primary endpoint. A total of 81% of treated patients exceeded a 20% improvement threshold, which is considered clinically meaningful in SPS.
Secondary Endpoint Outcomes
The trial also met all secondary efficacy endpoints with high statistical significance, with all reported p-values below 0.0001. Improvements were observed across the Modified Rankin Scale, Distribution-of-stiffness Index, Hauser Ambulation Index, and Heightened Sensitivity Scale.
Among the 12 patients who required walking aids prior to treatment, 67% no longer needed assistance to walk by Week 16. In addition, all patients remained free from immunotherapies, and no patients required rescue therapy as of the last follow-up.
Safety and Tolerability Profile
Miv-cel was reported to be well tolerated in the KYSA-8 trial. No high-grade cases of cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome were observed. Grade 3 or 4 neutropenia, a known adverse event associated with CAR T-cell therapies, occurred in some patients and was managed during the study.
Regulatory Pathway and Next Steps
Based on the topline data, Kyverna plans to submit a Biologics License Application to the U.S. Food and Drug Administration for miv-cel in SPS in the first half of 2026. The therapy has received both Regenerative Medicine Advanced Therapy and Orphan Drug designations for this indication. Kyverna also plans to present the full SPS dataset at a medical conference in 2026.
About Kyverna Therapeutics
Kyverna Therapeutics is a clinical-stage biopharmaceutical company focused on the development of cell therapies for patients with autoimmune diseases, with miv-cel as its lead CAR T-cell therapy program.
