Reprogramming CD22 CAR-T cells in vivo using CD8-targeted mRNA-LNPs to treat hematological malignancies.

Ex vivo chimeric antigen receptor (CAR) T cell therapy has proven successful in patients with B cell hematologic malignancies. However, current approaches are limited by the requirement for personal manufacturing processes and by barriers such as limited efficacy against solid tumors, treatment-associated toxicities, insufficient CAR-T cell trafficking to the tumor microenvironment, on-target off-tumor effects, and tumor antigen escape. Here, we describe a novel delivery platform that overcomes many of these barriers by employing targeted lipid nanoparticles (LNPs) to reprogram circulating human T cells in vivo. Using a NANOBODYVHH (variable heavy domain of heavy chain)-based targeting moiety, we deliver mRNA encoding a novel CD22 CAR specifically to CD8+ cells, enabling transient functional CAR expression in vitro and in vivo. Our targeted LNP formulation allows for repeated dosing and minimizes mRNA expression in off-target cells. Furthermore, in a humanized Nalm6 tumor mouse model, non-stimulated T cells reprogrammed in vivo inhibit tumor cell growth. Our platform is a flexible and broadly applicable CAR-T treatment for hematologic malignancies, which promises to be adaptable to other diseases.