IL-7/IL-15/IL-21 cytokine-fusion scaffold generates highly functional CAR T cells enriched in long-lived T memory stem cells

Functional persistence of chimeric antigen receptor T cells (CAR T cells) is limited by conventional CAR T cell manufacturing using anti-CD3/CD28 (αCD3/28) stimulation, which generates terminally differentiated and shorter-lived CAR T cells. We demonstrated that HCW9206, a unique protein scaffold linking interleukin-7 (IL-7), an IL-15/IL-15 receptor α (IL-15Rα) complex, and IL-21, generates CAR T cells without requiring αCD3/28 activation, which are highly enriched in long-lived T memory stem cells (T_SCM cells) (>50%) and display potent activity across distinct disease models, HIV-1 or B cell leukemia. In a humanized mouse HIV infection model, HCW9206-generated anti-HIV duoCAR T cells suppressed viremia more effectively than αCD3/28-generated anti-HIV duoCAR T cells. In a xenograft leukemia mouse model, a recall proliferative response and complete clearance of leukemia rechallenge were displayed by HCW9206-generated but not by αCD3/28-generated anti-CD19 CAR T cells. HCW9206, a first-in-class cytokine scaffold-based platform, enables production of more potent CAR T cell-based immunotherapies by generating a CAR T cell population, which is highly functional and also markedly enriched for long-lived T_SCM cells. This strategy is broadly applicable to increase persistence and functionality of CAR T cells, enhancing their efficacy for treating infectious disease and cancer.