393. Engineering Armored T Cell Receptor-Mimic (TCRm) Chimeric Antigen Receptor (CAR) T Cells Specific for the Intracellular Protein Wilms Tumor 1 (WT1) for Treatment of Hematologic and Solid Malignancies

Abstract

Adoptive therapy with chimeric antigen receptor (CAR) T cells specific for CD19 is clinically successful in a limited set of leukemias and most CARs studied are targeted against external antigens. Wilms Tumor Antigen 1 (WT1) protein (WT1) is an intracellular antigen overexpressed in many cancers, including leukemias and solid malignancies and is thus an appealing, broadly applicable target. We have engineered the first armored T cell receptor-mimic (TCRm) CAR against WT1. Derived from the ESK1 antibody, the second generation CAR, WT1-28z, is reactive with the RMFPNAPYL peptide of WT1 that is processed and presented on the surface of cells in the context of HLA-A*02:01. WT1-28z was further modified to secrete human IL-12 cytokine, thus creating the armored CAR WT1-28z/IL-12. T cells expressing WT1-28z or WT1-28z/IL-12 are cytotoxic against a range of both hematological and solid tumors. Importantly, both WT1-directed T cells are specific for the WT1-HLA-A*02:01 complex and are not reactive against cells that do not express both HLA-A*02:01 and WT1. In established SCID/Beige mouse models of either acute leukemia or ovarian cancer, one dose of WT1-28z T cells prolongs survival of mice over untreated or irrelevant antigen-specific CAR T cell treated mice. Furthermore, one dose of the armored WT1-28z/IL12 CAR T cells further significantly prolongs survival of mice in both models over WT1-28z CAR T cell treated mice, with a subset of mice whose disease was eradicated. The armored TCRm CAR T cells against WT1 are effective in eradicating disease in both hematologic and solid tumors and may hold great clinical potential to expand on the success of CAR T cell therapy.