Evaluating CAR-T Miv-Cel in Stiff Person Syndrome: Amanda Piquet, MD, FAAN

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“Miv-cell demonstrated efficacy and safety in SPS… We showed videos… of patients using a walker at baseline, and essentially putting that walker aside and being able to walk quickly and normally down the hallway. It was just incredible to see that outcome, and we just don't see this in our current off-label use of therapies in this disease today.”

At the 2026 American Academy of Neurology (AAN) Annual Meeting, held April 18 to 22 in Chicago, Illinois, Amanda Piquet, MD, the director of the Autoimmune Neurology Program and Celine Dion Foundation Endowed Chair in Autoimmune Neurology at the University of Colorado, reported findings from a phase 2 single-arm registrational trial evaluating Kyverna Therapeutics’ mivocabtagene autoleucel (miv-cel, also known as KYV-101), an autologous antiCD19 chimeric antigen receptor T-cell (CAR-T) therapy, in patients with stiff person syndrome (SPS), a rare, progressive autoimmune neurological disorder characterized by fluctuating rigidity and episodic muscle spasms for which no FDA-approved therapies currently exist. NeurologyLive® sat down with Piquet on the conference floor to learn more about the results she presented.

Piquet explained that the trial enrolled 26 patients with SPS who were refractory to at least 1 prior immunotherapy. The primary end point was percent change from baseline in the timed 25-foot walk at 16 weeks. Investigators observed a median 46% improvement in that measure, a clinically meaningful change given that a 20% improvement is generally considered a clinically significant threshold in this context. At baseline, 12 patients required walking assistance to complete the 25-foot walk; at 16 weeks, 63% of those individuals no longer required assistance. Across the combined primary and secondary end points (which included the modified Rankin Scale, Hauser Ambulation Index, Stiffness Index, and a hypersensitivity scale) 96% of patients showed improvement in at least 1 measure.

Piquet noted that no high-grade cytokine release syndrome (CRS) or immune effector cell–associated neurotoxicity syndrome (ICANS) events were observed, characterizing the safety profile as consistent with expectations for this class of therapy. She described the functional changes observed during the trial, including patients who relied on walkers at baseline ambulating without assistance by week 16, as outcomes not previously achievable with available off-label treatment approaches such as intravenous immunoglobulin.

Piquet emphasized that the current data reflect the 16-week primary end point window, with follow-up extending to approximately 6.5 months at the time of data cutoff. The total trial duration is 12 months, and she identified long-term durability of response as a key unanswered question to be addressed as the dataset matures.