Enhancing the effectiveness of y8 T cells by mRNA transfection of chimeric antigen receptors or bispecific T cell engagers

Adoptive cell therapy (ACT) utilizing yb T cells is becoming a promising option for the treatment of cancer, because it offers an off-the-shelf allogeneic product that is safe, potent, and clinically effective. Approaches to engineer or enhance immunecompetent cells for ACT, like expression of chimeric antigen receptors (CARs) or combination treatments with bispecific T cell engagers, have improved the specificity and cytotoxic potential of ACTs and have shown great promise in preclinical and clinical settings. Here, we test whether electroporation of yb T cells with CAR or secreted bispecific T cell engager (sBite) mRNA is an effective approach to improve the cytotoxicity of yb T cells. Using a CD19-specific CAR, approximately 60% of yb T cells are modified after mRNA electroporation and these cells show potent anticancer activity in vitro and in vivo against two CD19-positive cancer cell lines. In addition, expression and secretion of a CD19 sBite enhances yb T cell cytotoxicity, both in vitro and in vivo, and promotes killing of target cells by modified and unmodified yb T cells. Taken together, we show that transient transfection of yb T cells with CAR or sBite mRNA by electroporation can be an effective treatment platform as a cancer therapeutic.