A pivotal Phase II study, KYSA-8, presented at AAN 2026, revealed significant clinical improvements for adults battling Stiff Person Syndrome (SPS) with CAR-T therapy. The single infusion of miv-cel led to rapid gains in walking speed and reduced stiffness.
SPS, a progressive autoimmune neurologic disorder, causes severe muscle stiffness and spasms that significantly impair mobility. This study evaluated miv-cel, an autologous CD19 CAR-T-cell therapy, in patients inadequately treated by prior therapies.
The primary endpoint, a change in timed 25-foot walk, was met, showing a 45.6% median improvement at Week 16, sustained at 44.4% by Week 24. Secondary outcomes, including mobility and stiffness measures, also demonstrated significant improvements.
The safety profile showed common adverse events like neutropenia and cytokine release syndrome, all manageable and resolved without lasting effects. Notably, all patients remained free of other immunomodulatory therapies for SPS post-treatment.
These findings position miv-cel as a promising advance for a rare disease with a major unmet medical need.