In vivo CAR-T cell engineering: concept, research progress, potential challenges and enhancement strategies.

After decades of development and accumulation, chimeric antigen receptor (CAR)-T therapy has become a revolutionary immunotherapy method, which has triggered changes in treatment methods and concepts in the fields of cancer, autoimmune disorders, infection, fibrosis and other diseases. With the continuous expansion of indications and potential application fields, adoptive CAR-T therapy products are difficult to meet the expanding market demand and provide equal access to treatment due to their technical complexity and substantial production costs. These factors drive the development and practice of novel technologies, in this context, in vivo CAR-T therapy has been proposed: the in vivo or in situ programming of CAR-T cells to eliminate pathological cells through the delivery of CAR genes in vivo by viruses or engineered nanoparticles. This new technology pathway simplifies the manufacturing and therapeutic procedures, reduces treatment costs, and improves patient accessibility, which has excellent potential for clinical application. This article reviews recent advances in in vivo CAR-T therapy, compares the advantages and characteristics of this approach with traditional adoptive therapy, discusses the therapeutic risks and related challenges of in vivo CAR-T therapy, and emphasizes the guiding significance of adoptive therapy-based enhancement strategies for the development of in vivo CAR-T therapy.