Publication Full Title: In vivo generation of anti-BCMA CAR-T cells in relapsed or refractory multiple myeloma: a phase 1 study.
Journal: Nature Medicine
Published: 25 March 2026
Publication Link: https://www.nature.com/articles/s41591-026-04244-6
Comment by: Pedro Asensi Cantó and Jaime Sanz, Haematologists, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
Summary
Autologous CAR-T cell therapy has transformed the management of relapsed or refractory multiple myeloma but remains limited by individualized manufacturing, treatment delays, lymphodepleting chemotherapy and high costs. In this first-in-human phase I study from Nature Medicine, Ning An and colleagues evaluated ESO-T01, an immune-shielded lentiviral vector designed to generate anti-BCMA CAR-T cells directly in vivo after a single intravenous infusion, thereby eliminating leukapheresis, ex vivo manufacturing and lymphodepletion.
Five heavily pretreated patients with relapsed/refractory multiple myeloma received a single dose of ESO-T01. CAR-T cells became detectable within days, expanded in vivo, and persisted over time without prior conditioning. Four of five patients achieved an objective response, including three stringent complete responses, while all evaluable responders became MRD-negative by day 60.
Treatment was associated with frequent but predictable immune-mediated toxicities. Cytokine release syndrome occurred in four patients, including three grade 3 events, one patient developed grade 1 immune effector cell-associated neurotoxicity syndrome. Importantly, no dose-limiting toxicities were observed. The investigators identified a distinctive biphasic inflammatory profile consisting of an early innate immune activation immediately after vector infusion followed several days later by adaptive CAR-T cell expansion. A fatal case related to extramedullary disease underscored the importance of careful patient selection and risk stratification.
Although based on only five patients, this study provides the first clinical evidence that in vivo CAR-T generation is feasible and capable of inducing clinically meaningful antitumor activity.
Comment
This study represents one of the most exciting technological advances in cellular therapy in recent years. The importance of the work lies less in the response rates, which are encouraging but derived from only five patients, and more in demonstrating that functional CAR-T cells can be generated directly within the patient without the conventional manufacturing process.
If confirmed in larger studies, this strategy could fundamentally change the accessibility of CAR-T therapy. Eliminating leukapheresis, centralized manufacturing, bridging therapy and lymphodepleting chemotherapy has the potential to shorten the interval from treatment decision to infusion from weeks to hours. Such simplification could substantially expand global access, particularly in healthcare systems where manufacturing capacity remains a major limitation.
Equally important, the study demonstrates that in vivo CAR-T therapy is not simply a more convenient version of conventional CAR-T therapy but appears to constitute a biologically distinct platform. The biphasic inflammatory response, driven initially by vector-mediated innate immune activation and subsequently by CAR-T expansion, suggests that toxicity monitoring and management may require new clinical paradigms rather than direct extrapolation from current CAR-T experience. This observation may have implications beyond multiple myeloma as in vivo engineering platforms are developed for additional hematologic malignancies and potentially autoimmune diseases.
Nevertheless, several limitations deserve emphasis. The study includes only five patients, has short follow-up, lacks a comparator arm, and cannot address long-term persistence, durability of response or insertional safety associated with lentiviral gene transfer. Moreover, the fatal neurological complication in a patient with bulky extramedullary disease reminds us that enthusiasm for disruptive technologies must remain balanced by careful clinical evaluation.
Overall, this paper should be viewed primarily as a proof-of-concept study. While it is far too early to conclude that in vivo CAR-T therapy will replace conventional manufactured products, it convincingly opens a new chapter in the evolution of cellular immunotherapy and will likely stimulate intensive clinical development over the coming years.