SYST-12 D2C7 CAR: A NOVEL CAR T CELL THAT SIMULTANEOUSLY TARGETS WILDTYPE EGFR AND ITS MUTANT ISOFORM EGFRVIII FOR TREATMENT OF GLIOMA AND BRAIN METASTASES

INTRODUCTION: Chimeric antigen receptor (CAR) T-cells represent a revolutionary class of immunotherapy, achieving considerable success in hematological cancers but generally failing to control solid tumors, including gliomas, partly due to the lack of a ubiquitously-expressed target antigen. In this study, we engineered a novel CAR T-cell consisting of the D2C7scfv targeting moiety that binds a shared epitope between EGFR and EGFRvIII. EGFR is the most homogeneous antigen on glial brain tumors, and the mutant EGFR variant, EGFRvIII, is present on a considerable subset of high grade gliomas. CAR T-cells targeting EGFRvIII alone fail to treat tumors possessing as few as 5-10% EGFRvIII-negative cell. Thus, D2C7 CAR is expected to be superior to the EGFRvIII CAR. METHODS: We retrovirally transduced T-cells with a vector encoding the D2C7scFv in tandem with intracellular signaling domains of CD28, 4-1BB, and CD3ζ to generate D2C7 CAR. We co-cultured D2C7 CAR or control CAR with fluorescently-tagged tumor cells expressing either EGFRwt or EGFRvIII to validate efficacy and specificity by flow cytometry. To determine in vivo efficacy, EGFRwt or EGFRvIII-expressing tumors were implanted intracranially in immunodeficient NSG mice. 48 hours later, D2C7 CAR, VIII CAR, or Mock CAR were administered intracranially and mice were monitored for survival. RESULTS: D2C7 CAR specifically killed tumor cells that expressed either EGFRwt or EGFRvIII, but not cells that lacked EGFR. Intracranial D2C7 CAR administration resulted in significantly prolonged survival of mice bearing EGFRwt or EGFRvIII tumors compared to Mock CAR controls. Importantly, D2C7 CAR significantly benefitted mice bearing a heterogeneous mix of EGFRwt and EGFRvIII tumor cells, a model of tumor heterogeneity. CONCLUSIONS: D2C7 CAR is efficacious against EGFRwt/EGFRvIII heterogeneous tumors. Intracranial administration of D2C7 CAR is predicted to safely and effectively treat a large cohort of patients due to the relatively high prevalence of EGFR and/or EGFRvIII-expressing brain tumors.