Naji Gehchan, MD, MBA, Chief Medical and Development Officer at Kyverna Therapeutics, discusses primary analysis of KYV-101 for the treatment of stiff person syndrome (SPS).
SPS is a progressive neuromuscular condition caused by increased muscle activity due to decreased inhibition of the central nervous system. Symptoms may include extreme muscle stiffness, rigidity and painful spasms in the trunk and limbs. People with SPS often have heightened sensitivity to noise, sudden movements, and emotional distress, which can set off muscle spasms. The syndrome affects twice as many women as men. It is thought to have an autoimmune component and is often associated with diabetes, as well as other autoimmune diseases.
Miv-cel (mivocabtagene autoleucel, KYV-101) is a fully human, autologous CD19 CAR T-cell therapy designed to target anti-CD19, a protein involved in various types of autoimmune diseases. Positive primary analysis results from its registrational trial, KYSA-8 clinical trial of miv-cel (mivocabtagene autoleucel, KYV-101) in SPS was presented at the 2026 American Academy of Neurology Annual Meeting (AAN 2026).
KYSA-8 is a single-arm registrational phase 2 study evaluating KYV-101 in patients with SPS. The primary endpoints are the change from baseline in the Timed 25-Foot Walk (T25FW) at 16 weeks and the incidence and severity of adverse events. Secondary endpoints measuring disability, stiffness, hypersensitivity, and mobility include the Modified Rankin Scale (mRS), Distribution-of-stiffness Index (DSI), Heightened Sensitivity Scale (HSS), and Hauser Ambulation Index (HAI), respectively. A total of 26 patients who had an inadequate response to off-label immunomodulatory treatment options received a single dose of 1×108 KYV-101 CAR T cells. The median follow-up was 6.5 months after infusion.
The trial met its primary endpoint, demonstrating a statistically significant improvement in the T25FW at week 16, with a median improvement of 46% from baseline, regardless of baseline patient- and disease-related characteristics. 81% of patients achieved clinically meaningful improvement, with nearly 1/3 of all patients walking at the speed of healthy adults by week 16. Of the 12 patients requiring a walking aid at baseline, 67% no longer needed walking assistance at week 16. Additionally, all patients remained free of chronic immunotherapies at week 16 and through last follow-up.
The trial also met all secondary endpoints with significant mean improvements in mRS, HAI, DSI, and HSS of -0.8, -1.6, -1.5, and -3.2 points, respectively.
In exploratory endpoints, sustained clinical benefit associated with deep, transient B-cell depletion and broad immune reset, significant reductions in GAD65-autoantibody titers associated with SPS, and improvements in physical and mental functioning, including a more than 4-fold improvement over the minimal clinically important change in the 6-Minute Walk Test (6-MWT), and normalization toward healthy population benchmarks across the 36-Item Short Form Health Survey (SF-36) domains, were observed.
KYV-101 was well tolerated with no high-grade cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS) observed. Grade 3/4 neutropenia, a known adverse event associated with lymphodepletion and CAR T-cell therapy, was observed in four patients and was manageable. Serious treatment-related adverse events occurred in three patients, all of which resolved fully without sequelae.
CHAPTERS
Introduction 00:00
Stiff Person Syndrome Overview 00:34
KYSA-8 Clinical Trial 1:59
Measuring Disability 3:45
Rise in Disease Awareness 4:50
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Primary Analysis of KYV-101 for the Treatment of Stiff Person Syndrome
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