The results of a new phase II trial, presented by Amanda Piquet at the 2026 American Academy of Neurology Annual Meeting (18–22 April 2026, Chicago, Illinois, USA), indicate that a chimeric antigen receptor (CAR) T cell therapy is beneficial in individuals with stiff person syndrome (SPS). SPS is an autoimmune disease that causes muscle stiffness and painful spasms, and no therapies are currently approved for this condition.

Mivocabtagene autoleucel (miv-cel) is an autologous CD19-targeting CAR T cell therapy with CD28 co-stimulation that is designed to deplete B cells and ‘reset’ the immune system. In the KYSA-8 trial, 26 adults with SPS, all of whom had previously shown an inadequate response to immunomodulatory therapies, underwent lymphodepletion followed by a single infusion of miv-cel. After a median follow-up period of 6.5 months, the participants showed a median improvement of 4.8 s in the timed 25-foot walk test. The improvement was sustained at 24 weeks in 16 of the participants.