Naji Gehchan, MD, MBA, Chief Medical and Development Officer at Kyverna Therapeutics, discusses one-year data showing sustained benefits of KYV-101 (mivocabtagene autoleucel ; Miv-cel) in stiff person syndrome (SPS), along with longer-term follow-up data in generalized myasthenia gravis (gMG).
Understanding Stiff Person Syndrome and Generalized Myasthenia Gravis
SPS and gMG are rare neurological and neuromuscular disorders:
SPS: SPS is a rare, progressive neurological autoimmune disease that causes muscle stiffness and painful spasms that can affect walking and mobility. Up to 80% of patients lose their mobility over time, and there are currently no FDA-approved treatments.
gMG: gMG is a rare autoimmune neuromuscular disease characterized by muscle weakness and fatigue. As the disease progresses, it can interfere with daily activities, such as speaking, chewing, swallowing, and breathing.
One-Year Results Show Sustained Benefits of Miv-Cel in SPS
Positive one-year topline data from the KYSA-8 clinical trial (NCT06588491) were announced on September 24, 2026. KYSA-8 was a registrational, phase two, open-label, single-arm, multicenter study of miv-cel.
Miv-cel is a fully human, autologous, CD19-targeting CAR T-cell therapy with CD28 co-stimulation. It’s designed to achieve deep B-cell depletion, reset the immune system, and deliver durable drug-free, disease-free remission in autoimmune diseases with a single dose.
A total of 26 adult patients who had an inadequate response to at least one immunotherapy treatment participated in the study. Each participant received a single dose of miv-cel. Among patients who achieved a clinically meaningful improvement in the timed 25-foot walk at primary analysis, 95% maintained that benefit at 12 months. Of the 12 patients who needed a walking aid before treatment, 67% still did not require assistance at the 12-month follow-up. Furthermore, 92% of patients remained off chronic immunotherapies for SPS.
Phase 2 Findings Show Sustained Improvements of Miv-Cel in gMG
Also announced were longer-term follow-up data for its KYSA-6 trial (NCT06193889). KYSA-6 is a phase 2/3 trial evaluating miv-cel, administered as a single dose, in patients with gMG.
A total of seven adult patients participated in the study. Follow-up now extends to one year and beyond (up to 1.5 years) in five patients, with one patient at 9 months and another at 6 months. All seven participants achieved clinically meaningful improvements in both the Myasthenia Gravis Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores at 24 weeks, while all five participants with at least one year of follow-up maintained clinically meaningful improvements. Additionally, six of the seven patients remained off immunosuppressant therapies at their latest follow-up.
Safety Findings
Miv-cel continued to be well-tolerated in both studies. In the KYSA-8 trial, no high-grade cases of cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS) and no cases of immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS) were reported through the 12-month follow-up.
In the KYSA-6 trial, no high-grade CRS, no ICANS, and no cases of IEC-HS were reported during the available follow-up.
For more information, visit: https://ir.kyvernatx.com/news-releases/news-release-details/kyverna-therapeutics-reports-positive-one-year-data
To learn more about stiff person syndrome, myasthenia gravis, and other rare neurological and neuromuscular disorders, visit: https://checkrare.com/diseases/neurology-nervous-system-diseases/