CAR-T and nanoCAR-T for multiple myeloma: Does smaller mean smarter ?

Multiple myeloma (MM) is an incurable hematologic malignancy of plasma cells with a high rate of relapse. Chimeric antigen receptor T lymphocyte (CART) immunotherapy has shown remarkable results in relapse patients. Single-domain antibody (sdAb) offers an excellent alternative to scFv, due to its simple, small, and stable folding structure, therefore avoiding tonic signaling. Despite the development of numerous nanoCARTs, there is limited data demonstrating direct differences and their mechanisms. This project aims to characterize the activity of a nanoCART compared to a standard CART and elucidate mechanisms driving these differences. These findings may reveal new potential targets for novel CART designs. An anti-BCMA sdAb was generated and tested for BCMA binding on MM cell lines before incorporating it into a CAR sequence. A nanoCART and standard CART were generated by lentiviral transduction on primary T cells, and their killing capacity, cytokine production, exhaustion, and memory properties compared in coculture with MM cell lines. sdAb17 binds excellently to BCMA expressed on MM cells and was integrated in a NanoCART, that exhibits specific killing capacity, cytokine production (IL-2, TFNa, IFNg) and degranulation markers (like CD107a) in the same way than a clinical approved scFv-based CART called CT103a. Morevoer, nanoCART and this CART proliferate furthermore and exhausted less than untransduced T cells upon rechallenge with MM cells. Our nanoCART demonstrates excellent anticancer efficacy in vitro. Further investigation at transcriptomic level may reveal the mechanistic difference as well as in vivo experiments in a mice model.