In the phase II portion of the KYSA-6 trial, seven patients with generalized myasthenia gravis received a single infusion of the CD19-targeting CAR-T cell therapy miv-cel after lymphodepletion. At 24 weeks, all participants maintained clinically meaningful improvements on both the MG-ADL and QMG scales, with mean reductions of 8.3 and 11.7 points from baseline, respectively. They also remained free of immunotherapies, including high-dose steroids, nonsteroidal immunosuppressive agents, and FcRn or complement inhibitors.
Safety findings were notable for the absence of severe cytokine release syndrome, ICANS, or IEC-HS; CRS was low-grade and manageable. Two patients experienced grade 4 neutropenia, one resolving within 10 days and another managed with G-CSF and resolving within two months. With a median follow-up of 13.9 months, five patients maintained improvements through one year or longer, and six remained off immunosuppressants at last follow-up. At that point, 57% of participants had minimal symptom expression, defined as an MG-ADL score of 0 or 1.
The investigators noted evidence of immune reset and preserved humoral immunity in three patients with antibody levels assessed before the study. Miv-cel has been used in more than 100 patients across multiple indications, and the authors cited prior durable benefit in three German patients lasting over 24 months. The randomized phase III portion of KYSA-6, comparing miv-cel with standard care, is ongoing.