In Vivo CAR-T Engineering Could Slash Costs and Complexity of Cancer Immunotherapy

CAR-T cell therapy has transformed outcomes for patients with relapsed or refractory hematologic malignancies, with FDA-approved products targeting CD19 and BCMA demonstrating landmark responses. Yet widespread adoption remains constrained by a manufacturing process that can take weeks, cost hundreds of thousands of dollars per patient, and requires specialized infrastructure unavailable in many parts of the world.

In vivo CAR-T engineering sidesteps these barriers by delivering CAR-encoding genetic constructs directly into a patient's circulating T cells using viral or non-viral vectors—essentially converting the patient's body into an autologous bioreactor. This review from Gao et al. (Biomarker Research, 2026) comprehensively examines the two primary delivery modalities. Viral vectors—particularly lentiviral vectors (LVs)—offer stable genomic integration and durable CAR expression, with surface engineering strategies (anti-CD3, anti-CD7, anti-CD8 antibodies) enabling selective T cell targeting. Non-viral platforms, especially lipid nanoparticles (LNPs), provide modular, scalable manufacturing and can carry mRNA payloads for transient CAR expression, reducing genomic integration risk but requiring repeat dosing.

The commercial pipeline is rapidly expanding. At least ten products are in Phase I trials as of early 2026, spanning targets including CD19, BCMA, CD20, CD22, TROP2, and GPC3, and indications ranging from B-cell lymphoma and multiple myeloma to autoimmune disease and solid tumors. The first clinical proof-of-concept came from ESO-T01 (EsoBiotec), a T cell-targeted lentiviral vector carrying a BCMA CAR: all four patients treated at the lowest dose achieved objective responses, including two complete responses, in relapsed/refractory multiple myeloma. This established early feasibility and safety signals for the platform.

Despite this momentum, significant translational hurdles remain. Vector immunogenicity—both innate immune sensing of viral capsids and adaptive responses to delivery components—can limit efficacy and safety. Achieving precise cellular tropism to avoid off-target transduction of non-T cells (e.g., tumor cells expressing CD19 that could be inadvertently transduced by CD19 CAR vectors) is critical. Toxicities familiar from ex vivo CAR-T therapy, including cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS), remain relevant concerns. Regulatory frameworks for systemic in vivo genetic reprogramming are not yet well-defined, and harmonized guidelines are urgently needed.

Looking forward, innovations in vector tropism engineering, innate immune evasion, RNA-based programmable payloads, and scalable GMP-compatible manufacturing are converging to make in vivo CAR-T a viable next-generation platform—potentially extending beyond oncology into autoimmune diseases and other therapeutic areas.