Inducible Myd88/Cd40 (Imc) Costimulation Provides Ligand-Dependent Tumor Eradication By Cd123-Specific Chimeric Antigen Receptor T Cells

Introduction: Promising clinical results with CD19-specific chimeric antigen receptor (CAR)-directed T cells for the treatment of B cell leukemia and lymphoma suggest that CARs may be effective in other hematological malignancies, such as acute myeloid leukemia (AML). CD123/IL-3Rα is an attractive CAR-T cell target due to its high expression on both AML blasts and leukemic stem cells (AML-LSCs). However, the antigen is also expressed at lower levels on normal stem cell progenitors presenting a major toxicity concern should CD123-specific CAR-T cells show long-term persistence. Here, we describe a CAR platform, "GoCAR-T", which uses a proliferation-deficient, first generation, CD123-specific CAR together with a ligand (rimiducid (Rim))-dependent costimulatory switch (inducible MyD88/CD40 (iMC)) to provide physician-controlled eradication of CD123+ tumor cells and regulate long-term CAR-T cell engraftment.