Kyverna Therapeutics (NASDAQ:KYTX) shares climbed 14% on Monday after the company reported encouraging topline outcomes from its registrational Phase 2 KYSA-8 study evaluating mivocabtagene autoleucel (miv-cel) in patients with stiff person syndrome (SPS).
The clinical-stage biotech said the CAR T-cell therapy delivered statistically significant benefits across all primary and secondary endpoints. Patients treated with miv-cel recorded a median 46% improvement from baseline in the timed 25-foot walk test, with 81% exceeding the threshold considered clinically meaningful, defined as at least a 20% improvement.
In addition, two-thirds of patients who previously relied on walking aids no longer required assistance following treatment. All participants remained free from ongoing immunotherapy after receiving a single dose of the CD19-targeting CAR T-cell therapy.
“We are very pleased to share transformative topline data in stiff person syndrome, which could pave the way for miv-cel to become the first and only approved therapy in SPS and CAR T-cell therapy for autoimmune disease,” said Warner Biddle, Chief Executive Officer of Kyverna Therapeutics.
Miv-cel was generally well tolerated in the trial. No cases of high-grade cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome were reported. Some patients experienced Grade 3 or 4 neutropenia, a known and manageable side effect associated with CAR T therapies.
Stiff person syndrome is a rare and progressive autoimmune disorder that affects an estimated 6,000 patients in the United States and currently has no FDA-approved treatment options.
Based on the trial results, Kyverna plans to submit a Biologics License Application to the U.S. Food and Drug Administration for SPS in the first half of 2026. The therapy has already been granted both Regenerative Medicine Advanced Therapy and Orphan Drug designations for this indication.