Kyverna Reports One-Year Data for Miv-cel in Stiff Person Syndrome and Generalized Myasthenia Gravis

Kyverna Therapeutics has reported one-year topline data from KYSA-8, its registrational Phase 2 trial evaluating miv-cel (mivocabtagene autoleucel; KYV-101) in stiff person syndrome (SPS), alongside longer-term Phase 2 follow-up from KYSA-6, its registrational Phase 2/3 trial in generalized myasthenia gravis (gMG). The company reported sustained clinical responses and a consistent safety profile following a single dose of the investigational therapy.

One-Year Data in Stiff Person Syndrome

The KYSA-8 (NCT06588491) data included 26 patients with SPS with 12-month follow-up, based on a July 2026 database lock. Kyverna had previously reported that the trial’s primary endpoint and all key secondary endpoints were achieved with statistical significance.

The median improvement from baseline in the Timed 25-Foot Walk (T25FW) was 49% at month 12, compared with 46% at week 16 (p<0.0001). Among patients who achieved a clinically meaningful improvement, defined as a greater than 20% reduction from baseline at the primary analysis, 95% sustained that benefit at one year.

More than one-third of patients completed the T25FW in less than five seconds. Of the 12 patients who required a walking aid before treatment, 67% continued without assistance at the latest follow-up. Improvements in secondary endpoints also remained consistent at 12 months, with reported p values ranging from less than 0.0001 to 0.0003.

Kyverna also reported that 92% of patients remained free of chronic immunotherapies for SPS. During the one-year follow-up, miv-cel was reported to be well tolerated, with no high-grade cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), or immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS).

Longer-Term Data in Generalized Myasthenia Gravis

The Phase 2 portion of KYSA-6 (NCT06193889) included seven patients with moderate to severe gMG who had previously failed immunosuppressant therapies, including FcRn and complement inhibitors. As of the June 2026 data cutoff, follow-up extended to one year or longer in five patients, with one patient at nine months and another at six months.

All seven patients achieved clinically meaningful improvement in Myasthenia Gravis Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores at 24 weeks. Mean reductions from baseline were 8.3 points for MG-ADL and 11.7 points for QMG.

Among the five patients who reached one year or longer of follow-up, clinically meaningful improvements in MG-ADL, QMG and Myasthenia Gravis Composite (MGC) scores were maintained. Minimal symptom expression, defined by an MG-ADL score of 0 or 1, was maintained in 57% of patients at the latest follow-up.

All seven patients remained free of immunotherapies for MG at 24 weeks, including nonsteroidal immunosuppressive therapies, high-dose steroids above 10 mg, and FcRn and complement inhibitors. At the latest follow-up, six of seven patients, or 86%, remained off immunosuppressants.

Safety findings in the Phase 2 gMG cohort were consistent with those reported in SPS. Kyverna reported no high-grade CRS, ICANS, or IEC-HS during follow-up.

Expert Perspective

Amanda Piquet, M.D., FAAN, Director of Autoimmune Neurology at the University of Colorado Anschutz School of Medicine and lead investigator of KYSA-8, said the sustained improvements observed after a single dose of miv-cel included mobility, stiffness and other disease-specific measures, alongside a well-tolerated safety profile.

Kyverna Chief Medical and Development Officer Naji Gehchan, M.D., said clinically meaningful responses in gMG were sustained to at least one year, with nearly all patients remaining off immunosuppressant therapies. He also highlighted miv-cel’s fully human CD19 CAR T-cell design with CD28 co-stimulation as a distinguishing feature of the investigational therapy.

Development and Regulatory Plans

Kyverna intends to include the one-year SPS data in its rolling Biologics License Application (BLA) submission, which the company said is on track for completion in the fourth quarter of 2026. The full KYSA-8 dataset is scheduled to be presented at MS Toronto, the joint ACTRIMS-ECTRIMS meeting, from October 21–23, 2026, in Toronto.

Additional longer-term Phase 2 data from KYSA-6 are scheduled for oral presentation at the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) Annual Meeting on September 29, 2026, in Orlando, Florida.

The Phase 3 portion of KYSA-6 remains ongoing, with enrollment expected to be completed in mid-2027. The global Phase 3 study is designed as an approximately 60-patient, randomized, open-label crossover trial evaluating miv-cel against standard of care.

Miv-cel is an investigational, fully human, autologous, CD19-targeting CAR T-cell therapy with CD28 co-stimulation. In KYSA-8, it is being evaluated in adults with SPS who had an inadequate response to at least one immunotherapy treatment. In the Phase 2 portion of KYSA-6, seven patients with moderate to severe gMG received a single dose after failing prior immunosuppressant therapies.

The findings provide longer-term follow-up from two registrational clinical programs evaluating miv-cel in neurologic autoimmune diseases. Continued follow-up from the ongoing studies will provide additional data on the durability, safety and clinical outcomes associated with the therapy.

Reference

Kyverna Therapeutics Reports Positive One-Year Data Demonstrating Durable Clinical Responses and Favorable Safety Profile for Miv-cel in Stiff Person Syndrome and Generalized Myasthenia Gravis, Kyverna Therapeutics, 24 September 2026

KYSA-8: A Study of Anti-CD19 Chimeric Antigen Receptor T-Cell (CD19 CAR T) Therapy, in Subjects With Treatment Refractory Stiff Person Syndrome, ClinicalTrials.gov ID NCT06588491

KYSA-6: A Study of Anti-CD19 Chimeric Antigen Receptor T-Cell Therapy, in Patients With Generalized Myasthenia Gravis, ClinicalTrials.gov ID NCT06193889