Amanda Piquet, MD, FAAN, on Assessing Miv-Cel in Stiff Person Syndrome

This interview was originally published on our sister site, NeurologyLive®.

“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.”

Data from a phase 2 single-arm registrational trial evaluating Kyverna Therapeutics’ mivocabtagene autoleucel (miv-cel; also known as KYV-101), an autologous anti-CD19 chimeric antigen receptor T-cell (CAR-T) therapy for stiff person syndrome (SPS), were presented at the 2026 American Academy of Neurology (AAN) Annual Meeting, held April 18 to 22 in Chicago, Illinois. Amanda Piquet, MD, director of the Autoimmune Neurology Program and holder of the Celine Dion Foundation Endowed Chair in Autoimmune Neurology at the University of Colorado, reported the findings and subsequently spoke with CGTLive®’s sister site NeurologyLive® on the conference floor. SPS is a rare, progressive autoimmune neurological disorder defined by fluctuating muscle rigidity and episodic spasms, and currently lacks any FDA-approved treatment options.

The trial enrolled 26 patients with SPS who had received at least 1 prior unsuccessful immunotherapy. The primary end point was percent change from baseline to week 16 in the timed 25-foot walk. A median improvement of 46% was observed—a result that exceeds the 20% threshold generally regarded as clinically meaningful in this setting. Among the 12 patients who required walking assistance at baseline, 63% were able to complete the 25-foot walk without assistance by week 16. When evaluating both the primary and secondary end points together—encompassing the modified Rankin Scale, Hauser Ambulation Index, Stiffness Index, and a hypersensitivity scale—96% of participants demonstrated improvement on 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.