Comparing a Novel Anti-BCMA NanoCAR with a Conventional ScFv-Based CAR for the Treatment of Multiple Myeloma.

Multiple myeloma (MM) is an incurable hematologic malignancy arising from clonal plasma cells, with poor long-term outcomes due to inevitable relapse after conventional therapies. Chimeric antigen receptor (CAR) T-cell immunotherapy targeting B-cell maturation antigen (BCMA) has shown remarkable efficacy in relapsed patients. Conventional CARs employ single-chain variable fragments (scFvs), whereas single-domain antibodies (sdAb or VHHs) offer advantages such as small size, high stability, and potentially reduced immunogenicity. We designed and evaluated a novel anti-BCMA nanoCAR-T based on the VHH Nb17, compared with the conventional scFv-based CAR-T CT103a. Nb17 demonstrated strong BCMA binding and was incorporated into a CAR construct. Both nanoCAR-T and CT103a were generated via lentiviral transduction of primary T cells. Their cytotoxicity, cytokine secretion, degranulation, memory phenotype, and gene expression were assessed in vitro, along with antitumor activity in vivo. Nb17-nanoCAR-T demonstrated specific cytotoxicity, cytokine release (IL-2, TFNa, IFNg), and CD107a degranulation comparable to CT103a. Transcriptomic analysis revealed overlapping pathways between both CARs. Upon rechallenge, both CARs showed enhanced proliferation compared with untransduced T cells. In vivo, Nb17-nanoCAR-T and CT103a eradicated tumors in NSG mice. These findings demonstrate Nb17-nanoCAR-T exhibits potent anti-myeloma efficacy comparable to scFv-based CAR-T, supporting its potential as a promising therapeutic alternative.