D2C7 CAR: A novel CAR T cell that simultaneously targets wildtype EGFR and its mutant isoform EGFRvIII for treatment of glioma

Abstract

Brain tumors are the leading cause of cancer death in children and a significant cause of morbidity and mortality in adults. Conventional treatments are suboptimal, thus signifying the need for novel therapeutic strategies, such as immunotherapy. Chimeric antigen receptor (CAR) T cells represent a revolutionary class of immunotherapy, achieving considerable success in eliminating hematological cancers but generally failing to control solid tumors in part due to the lack of a suitably-expressed target antigen. Epidermal growth factor receptor (EGFR) is the most ubiquitous and homogeneous antigen on glial brain tumors, and EGFR-directed therapies have been hotly pursued. Moreover, the mutant EGFR variant, EGFRvIII, is present on a subset of pediatric and adult high grade gliomas, representing a targetable, tumor-specific antigen. Unfortunately, CAR T cells targeting EGFRvIII fail to treat tumors possessing as few as 5–10% EGFRvIII-negative cells due to antigen escape. Thus, a CAR T cell that can target both EGFR and EGFRvIII is expected to be superior to a CAR that targets EGFRvIII alone. In this study, we developed a novel third generation CAR T cell consisting of the D2C7scfv targeting moiety that binds a shared epitope between EGFR and EGFRvIII. This D2C7 CAR was able to specifically and potently kill tumor cells expressing wildtype EGFR or EGFRvIII. Importantly, D2C7 CAR significantly prolonged survival of mice bearing EGFR or EGFRvIII-expressing gliomas of both adult (U87) and pediatric (DAOY) origin. Toxicity experiments involving EGFR-expressing human skin grafts provided evidence that D2C7 CAR is safe and effective when administered intracranially to mice bearing intracranial tumors.