Kyverna Therapeutics posted the full KYSA-8 dataset for miv-cel in stiff person syndrome at the American Academy of Neurology annual meeting, showing a 46% improvement over baseline on the timed 25-foot walk primary endpoint at week 16 across all 26 patients. Every primary, secondary and exploratory endpoint was positive. If FDA clears it, miv-cel would be the first CAR-T therapy ever cleared for an autoimmune disease.
The numbers don’t leave room for doubt. Eighty-one percent of patients hit clinically meaningful improvement, defined as at least a 20% reduction from baseline. Eight of 12 patients who needed walking aids at baseline no longer required them at week 16. All 26 patients discontinued every immunomodulatory and immunosuppressant therapy.
SPS has no FDA-approved treatments and affects roughly 1 to 2 people per million. Natural history data from the University of Colorado and Johns Hopkins showed that 70% of SPS patients saw T25FW improvements of less than 20% over a 10-year period on off-label options, and walking aid use climbed 73% by the end of that analysis. Miv-cel’s mechanism, CD19 B-cell depletion to drive an immune reset, also reduced GAD65 autoantibody levels consistent with its design.
The FDA hasn’t asked Kyverna for a randomized trial. CEO Warner Biddle confirmed that to Fierce Biotech, noting the agency is “very well aware” of the unmet need and the data’s strength. FDA’s rejection of uniQure’s external control cohort plan is a live reminder that the agency can move the goalposts.
Kyverna reported a 100% response rate in seven generalized myasthenia gravis patients at 24 weeks. The phase 3 registrational portion of KYSA-6 is now enrolling.
Biddle said Kyverna anticipates filing for full approval.
— Sarah Chen