CD40L-HVEM dual costimulatory receptor-T cells promote endogenous macrophage reprogramming and increased therapeutic efficacy against AML 4502

Abstract Description Acute myeloid leukemia (AML) is the most common leukemia among adults (80%) and has a low 5-year survival rate (32%). AML cells create an immunosuppressive tumor microenvironment (TME) within the bone marrow that induces pro-tumor programming of immune cells, including CD206+ macrophages that are significantly associated with worse outcomes for AML patients (**P<0.01). Pro-tumor macrophages can be re-polarized to antitumor programming with CD40 stimulation and we hypothesized that adoptive cell therapy (ACT) T cells could be engineered to deliver CD40 signals to macrophages in the TME. We developed a new class of membrane-bound fusion proteins, Dual Costimulatory Receptors (DCR), that combine the CD40 ligand (CD40L) ectodomain (to induce macrophage reprogramming) with a costimulatory TNFR-family endodomain (to enhance T cell persistence and function). CD40L-HVEM DCR-T cell therapy induced macrophage antitumor programming and significantly enhanced survival (***P<0.001) in a murine AML model, outperforming native CD40L overexpression and other CD40L DCRs. In triple culture live-cell imaging studies with T cells, macrophages, and AML cells, CD40L-HVEM DCR-T cells induced synergistic eradication of tumor, with macrophages showing increased phagocytosis of tumor cells, demonstrating restored antitumor functionality. Here, we provide evidence that strategies that employ both innate and adaptive immunity provide safe and effective therapeutic efficacy against AML. Funding Sources Stand up to Cancer Fred Hutch/University of Washington Cancer Consortium Washington Research Foundation Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)