SYST-14 D2C7 CAR EFFECTIVELY AND SAFELY TREATS EGFRWT AND EGFRVIII-EXPRESSING TUMORS FOLLOWING INTRACRANIAL ADMINISTRATION

Abstract

Abstract Glioblastoma (GBM) is the most aggressive primary brain cancer with a median survival of less than 16 months. Therefore, significant treatment advances are of critical need. Immunotherapies, such as chimeric antigen receptor (CAR) T cells, have achieved remarkable success in eliminating hematological cancers. Unfortunately, CARs have overall failed to control solid tumors. One major reason for this failure is tumor heterogeneity, a characteristic especially true of GBM. In GBM, EGFRvIII is a commonly targeted tumor antigen; however, only a subset of tumor cells will express EGFRvIII. Thus, EGFRvIII-negative cells easily escape EGFRvIII-targeting CAR therapies. A better approach would be to target multiple antigens or an antigen that is more homogeneously expressed throughout the tumor. More commonly than EGFRvIII expression, glioma cells overexpress the wildtype isoform of EGFR (EGFRwt). Simultaneously targeting EGFRvIII and EGFRwt, instead of targeting each independently, with a CAR will theoretically expand the amount of tumor that will be eliminated by the CAR. Here, we adapted the D2C7scFv that binds both EGFRwt and EGFRvIII into a third generation CAR. D2C7 CAR potently and specifically killed EGFRwt and EGFRvIII-expressing U87 glioma, but not U87 with EGFR knocked out. In xenograft models, intracranially administered D2C7 CAR significantly prolonged survival of mice bearing orthotopic U87vIII, U87 (EGFRwt), and heterogeneous U87/U87vIII tumors compared tocontrols. Additionally, D2C7 CAR was an effective treatment in an orthotopic EGFR-expressing medulloblastoma model. Furthermore, D2C7 CAR treatment led to a significant survival benefit in mice bearing intrancranial A431, an aggressive, EGFR-expressing carcinoma line, a model of metastasis to the brain. Importantly, D2C7 CAR did not show reactivity towards normal tissue with EGFR expression, suggesting a tumor-specific epitope of EGFR is being targeted. Together, these data provide evidence that D2C7 CAR can treat EGFR/EGFRvIII heterogeneous or homogeneous primary or metastatic brain tumors with potentially little-to-no off-tumor toxicity.