Adapter-mediated redirection of anti-lymphoma CAR T cells for flexible multi-antigen targeting

CD19-directed chimeric antigen receptor (CAR) T cell therapy is a novel therapy approach that is effective in many patients suffering from B cell malignancies resulting in unprecedented response rates and long-term survival. Still, loss of the targeted antigen from the tumor cell surface is a major resistance mechanism leading to antigen-negative relapse in a substantial fraction of patients. In this study, we enhance conventional CAR T cell therapy by introducing the ability for adapter-mediated redirection of CAR T cells towards alternative tumor targets in the event of antigen loss. To this end, we produce conventional and adapter dual (ConvAD) CAR T cells that co-express a lymphoma-specific conventional CAR and a P329G adapter CAR. The P329G CAR binds the P329G amino acid substitution in specifically Fc-mutated human antibodies, which in turn are antigen-specific and thereby redirect the adapter CAR to the targeted antigen in a modular fashion. The ConvAD CAR platform combines the strong, clinically proven anti-tumor efficacy of a conventional CAR with the modular and externally steerable redirection capabilities of an adapter CAR. In B cell non-Hodgkin lymphoma (B-NHL), we demonstrate, that ConvAD CAR T cells maintain robust functionality against the primary antigen of the conventional CAR while enabling modular redirection to additional targets through antigen-specific adapter antibodies. We show that ConvAD CAR T cells have unique bimodal functionality acting through engagement of both, the conventional CAR and the P329G CAR. This dual reactivity allows ConvAD CAR T cells to prevent antigen-negative tumor relapse through flexible targeting of additional antigens. In B-NHL models of antigen loss, multi-antigen targeting ConvAD CAR T cells outperform conventional CAR T cells, P329G CAR T cells and even bispecific CAR T cells in vitro an in vivo. Thus, the ConvAD CAR platform meets a critical medical need by enabling effective multi antigen targeting to overcome antigen escape in lymphoma.