Development of chimeric antigen receptor T cells targeting cell surface U5 snRNP for the treatment of acute myeloid leukemia

Sloan-Kettering Inst Can Research, New York NY

Investigators

Abstract

Despite recent U.S. FDA approval of therapies for patients with acute myeloid leukemia (AML), clinical outcomes for AML patients continue to remain poor. Other than allogeneic stem cell transplant, there are no effective immunotherapies for AML, and this is, in part, due to a lack of known antigens which are unique to AML and not present on vital normal hematopoietic precursors. Hence, there is an urgent and critical need for novel therapies to improve outcomes in AML. To this end, we recently identified unique expression of the RNA helicase U5 snRNP200, on the surface of AML cells but not normal hematopoietic precursors. Anti-U5 snRNP200 therapeutic antibodies, originally isolated from AML patient in long term remission following allogeneic transplant, were efficacious across immunocompetent AML models. Genome-wide screens to identify regulators of AML cell surface U5 snRNP200 expression revealed that cell membrane localization of U5 snRNP200 required surface expression of the Fcγ receptor CD32A. Exhaustive evaluation of cell surface U5 snRNP200 expression on normal hematopoietic cells and non-hematopoietic tissues revealed that U5 snRNP200 expression was absent from the surface from normal cells except for robust expression on B-cells. The primary goals of this proposal are to develop novel cellular immunotherapies targeting U5 snRNP complex members and probe the mechanistic basis for their cell membrane localization in AML. Our preliminary data identify that the therapeutic anti-U5 snRNP200 antibodies which are most efficacious require engagement of activating Fcγ receptors and immune effector cells, factors often impaired in AML patients. We therefore have now developed novel chimeric antigen receptor (CAR) T cells targeting U5 snRNP200 and observed early evidence of their efficacy in preclinical models of AML. Importantly, CAR T cells which simultaneously target U5 snRNP200 and secrete IL-18, a cytokine known to upregulate CD32A (and consequently also cell surface U5 snRNP200) have augmented anti-tumor efficacy. We therefore hypothesize that IL-18 secreting CAR T cells targeting U5 snRNP200 will be a novel effective and safe cell therapy for AML. We further hypothesize that cell surface U5 snRNP200 expression may modulate CD32 signaling in a manner that provides mitogenic benefit to leukemia cells. Finally, we have found that additional U5 snRNP complex member EFTUD2, which physically interacts with U5 snRNP200 in the nucleus, is also translocated to the AML cell surface. This proposal will (1) test the efficacy and safety of CAR T cells directed against U5 snRNP200 in human and syngeneic mouse models of AML, (2) identify the mechanistic basis for cell surface U5 snRNP200 localization and potential requirement of this cell surface protein in AML, and (3) evaluate the cell surface distribution of additional U5 snRNP components and therapeutic potential of anti-EFTUD2 CAR T cells (either alone or in combination with anti-U5 snRNP200 CAR T cells).