EsoBiotec provided extended follow-up for in vivo BCMA CAR-T therapy ESO-T01 in relapsed or refractory multiple myeloma. Updated data through a maximum 15-month follow-up showed an objective response rate of 100% in the four-patient cohort, with durable response in one patient for the full period; however, the update also highlighted limited persistence after progression in the remaining patients. The company reiterated safety observations, reporting no immunogenicity- or integration-related toxicities beyond earlier signals. Median progression-free survival was reported as 4.0 months, while median overall survival was extended by diverse salvage therapies after progression. For the field, the update is notable because in vivo CAR-T aims to reduce manufacturing and logistics constraints compared with ex vivo products. Yet the durability constraints documented here highlight the central engineering challenge: achieving sustained in vivo activity without inducing unacceptable toxicity.