Antigen Specificity and Cell Engineering Determine CAR T Cell Efficacy in Group 3 Medulloblastoma

Group 3 medulloblastoma (G3MB) is a devastating disease of the central nervous system (CNS) that primarily affects infants and children. Chimeric antigen receptor (CAR) T cell therapy holds the promise to improve outcomes for CNS malignancies, but few studies have focused specifically on G3MB. We used publicly available datasets to demonstrate EphA2 and B7-H3 expression in primary G3MB and validated expression in patient-derived cell lines. EphA2-CAR T cells had greater cytolytic activity, persistence, and TH1 cytokine production than B7-H3-CAR T cells in coculture assays with MYC-driven G3MB cell lines in vitro. In vivo, EphA2-CAR T cells demonstrated superior tumor control and improved survival compared to B7-H3-CAR T cells in 2 of 3 orthotopic G3MB models. B7-H3-CAR T cells outperformed EphA2-CAR T cells in one model in which the antigen density of EphA2 was 5-fold lower than for B7-H3. The limited antitumor activity of EphA2-CAR T cells could be overcome with second genetic modifications that increase T cell functionality including deletion of DNMT3A or the expression of a constitutively active IL-18 chimeric cytokine receptor. Thus, our study nominates EphA2-CAR T cells as a promising alternative to B7-H3-CAR T cells, which are actively being explored in clinical studies for medulloblastoma.