Phase separation of chimeric antigen receptor promotes immunological synapse maturation and persistent cytotoxicity

Major challenges of CAR-T cell therapy include poor antigen sensitivity and cell persistence. Here we report a solution to these issues by exploiting CAR phase separation. We found that incorporation of an engineered CD3e motif, EB6I, to the conventional 28Z or BBZ CAR induced self-phase separation through cation-π interactions. EB6I CAR can form a mature immunological synapse with CD2 corolla to transduce efficient antigen and costimulatory signaling, while its tonic signaling remains at low levels. Functionally, EB6I CAR-T cells exhibited improved signaling and cytoxicity against low-antigen tumor and persistent tumor killing function. In multiple primary and relapsed murine tumor models, EB6I CAR-T cells exerted better antitumor functions than conventional CAR-T cells against blood and solid cancers. This study thus unveils a new CAR engineering strategy to improve CAR-T cell immunity by leveraging molecular condensation and signaling integration. To assess the long-term antritumor functions of the CD19.28Z/E28Z/EB6I28Z CAR-T cells, we continuously challenged CAR-T cells with multiple rounds of tumor cells. CAR-T cells with/without tumor cell challenge were sorted for RNA-seq.