Kyverna reports one-year KYSA-8 results for miv-cel in stiff person syndrome, showing 49% walking improvement and 77% clinically meaningful response.
Written By: Aasritha Thippavajjala, PharmD
Reviewed by: Pharmacally Editorial Team
Kyverna Therapeutics reported one-year results from KYSA-8, its registrational Phase 2 trial of mivocabtagene autoleucel (miv-cel; KYV-101), an investigational CD19-directed chimeric antigen receptor (CAR T)-cell therapy for stiff person syndrome (SPS). Announced on October 21, 2026, the findings showed sustained improvements in walking performance, disability and stiffness following a single administration. Lead investigator Amanda Piquet, M.D., presented the data as poster P0364 at MS Toronto 2026, the joint ACTRIMS-ECTRIMS meeting.
KYSA-8 Trial Design and Patient Population
KYSA-8 (NCT06588491) is a multicenter, single-arm Phase 2 study evaluating miv-cel in adults with SPS who had an inadequate response to at least one previous immunotherapy. Kyverna reported one-year efficacy and safety findings for 26 patients, while the ClinicalTrials.gov record lists an enrollment of 27 participants. The available sources do not explain this difference.
The primary efficacy endpoint was change from baseline in the timed 25-foot walk (T25FW) at week 16, alongside safety assessments. Secondary endpoints evaluated disability, mobility, stiffness and hypersensitivity using the Modified Rankin Scale (mRS), Hauser Ambulation Index (HAI), Distribution-of-Stiffness Index (DSI) and Heightened Sensitivity Scale (HSS).
Walking Improvement Sustained Through One Year
Median T25FW performance improved by 49% from baseline at one year, compared with 46% at week 16. A clinically meaningful improvement, defined as at least a 20% reduction in walking completion time, was achieved by 20 of 26 patients (77%) at one year, versus 21 of 26 (81%) at week 16. The one-year result was statistically significant (p<0.0001).
Among 12 patients who required walking aids before treatment, eight (67%) no longer required assistance at one year. More than one-third of patients also completed the T25FW in under five seconds, although the company did not specify the exact number or assessment timepoint.
At one year, mean scores improved from baseline across all four secondary measures: mRS by −1.0 (p=0.0003), HAI by −1.7 (p<0.0001), DSI by −1.6 (p<0.0001) and HSS by −2.8 (p<0.0001). Lower scores indicate better outcomes on these measures. Additionally, 24 of 26 patients (92%) remained free of chronic immunotherapy for SPS.
Safety and Exploratory Findings
Kyverna reported no high-grade cytokine release syndrome (CRS), no high-grade immune effector cell-associated neurotoxicity syndrome (ICANS), and no cases of immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS) during one-year follow-up.
Grade 3 or 4 neutropenia occurred in five patients and was described as manageable. Serious treatment-related adverse events occurred in three patients, all of which had resolved. The announcement did not provide detailed descriptions of these events or a complete breakdown of lower-grade adverse events.
Exploratory results showed that median improvement in six-minute walk distance increased from 89 metres at week 16 to 119 metres at one year. Kyverna also reported sustained improvements in physical functioning and mental health on the 36-item Short Form Health Survey (SF-36), describing the results as comparable to those of healthy adults without providing underlying scores. B-cell reconstitution was observed alongside sustained clinical benefit and antibody reduction, although quantitative data were not disclosed.
Clinical Interpretation
The findings suggest that miv-cel may provide sustained functional improvement after a single administration in adults with treatment-refractory SPS. The persistence of walking improvements, alongside the proportion of patients remaining free of chronic immunotherapy, provides a clinically relevant signal in a population with limited treatment options.
However, KYSA-8 was a single-arm study without a concurrent control group, and the one-year analysis included 26 patients. The results therefore do not establish superiority over existing treatments or demonstrate sustained remission in every patient. The small population and limited detailed safety reporting also restrict assessment of uncommon or delayed adverse events. Longer follow-up and additional evidence will be needed to establish durability and the overall benefit-risk profile.
Regulatory Outlook
Kyverna said the one-year dataset further strengthens its biologics license application (BLA) package for miv-cel in SPS. In September 2026, the company stated that it expected to complete its rolling BLA submission in the fourth quarter of 2026. The October announcement did not confirm completion of the submission or provide an FDA decision timeline. Miv-cel remains investigational, and its safety and efficacy have not been established by the US Food and Drug Administration.
References
Kyverna Therapeutics. Kyverna Therapeutics Presents Full One-Year Registrational Data Set Demonstrating Sustained Clinical Benefit of Miv-cel in Stiff Person Syndrome at MS Toronto. October 21, 2026.
ClinicalTrials.gov. KYSA-8: A Study of Anti-CD19 Chimeric Antigen Receptor T-Cell Therapy in Subjects with Treatment-Refractory Stiff Person Syndrome. ClinicalTrials.gov ID NCT06588491.
About the Writer
Aasritha Thippavajjala (Linkedin) is a pharm D student and aspiring medical writer with medical writing, clinical training experience and a strong interest in clinical research and patient safety She has hands-on exposure to clinical pharmacy activities including medication profile assessment, clinical case review, identification of potential drug-related problems, ADR awareness, patient counselling, and clinical documentation. She has also gained experience in medical literature review, evidence synthesis, and scientific communication through her published review article on digital twin-based patient simulation and her poster presentation at the 74th Indian Pharmaceutical Congress. Certified in ICH Good Clinical Practice (E6(R3)) and Scientific Writing in Health Research, she is passionate about applying her clinical knowledge and research skills to medical writing ,clinical research and contributing to accurate, evidence-based healthcare.