Kyverna Therapeutics said its registrational Kysa-8 trial of miv-cel in stiff person syndrome met its primary endpoint, with 26 treated patients showing a median 46% improvement in timed 25-foot walk at 16 weeks, while 81% achieved at least a 20% reduction from baseline.
The company said 12 patients needed a walking aid at baseline, and 67% of them no longer required one by week 16. All 26 patients were off chronic immunotherapies at week 16 and remained so through last follow-up.
The study also hit all secondary endpoints. Kyverna reported mean improvements of 0.8 points on the modified Rankin scale, 1.6 points on the Hauser Ambulation Index, 1.5 points on the Distribution-of-Stiffness Index, and 3.2 points on the Heightened Sensitivity Scale, each with p-values below 0.0001.
On other measures, the company said patients showed more than a fourfold improvement over the minimal clinically important change in the 6-minute walk test, along with gains in physical and mental functioning on the SF-36. Kyverna also said gad65 autoantibody titers fell significantly.
Safety findings included no high-grade cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome. Grade 3/4 neutropenia occurred in four patients, and three patients had serious treatment-related adverse events, all of which resolved fully.
The trial’s data cut-off was Nov. 26, 2025, with median follow-up of 6.5 months, ranging from 4.4 to 12.2 months. A separate natural history study of 153 patients with stiff person syndrome found most had little or no improvement in timed 25-foot walk and increasingly relied on walking aids over time. Today the company's shares have moved 2.03% to a price of $8.03. For more information, read the company's full 8-K submission here.
