EsoBiotec provided extended follow-up data for ESO-T01, an in vivo BCMA CAR-T approach in four relapsed or refractory multiple myeloma patients. In the update, dual-phase cytokine release syndrome (grades 1–3) and grade ≥3 hematotoxicities remained central safety signals; one patient developed grade 1 ICANS. Efficacy showed high initial responses, with an objective response rate of 100% (two stringent complete responses and two partial responses). However, durability was limited: one patient maintained a stringent complete response for 15 months, and the median progression-free survival was 4.0 months (range 3.0–15.0). The company attributed the persistence profile to the need for further optimization of the in vivo CAR-T platform, with extramedullary involvement noted in relapses and diverse salvage therapies after progression.