Abstract Pediatric brain tumors are the leading cause of cancer death in children and new targeted therapies are urgently needed. Glypican 2 (GPC2) is highly expressed on multiple pediatric central nervous system (CNS) tumors, including embryonal tumors and high-grade gliomas. Following initial proof-of-concept using mRNA-based CAR T cells, we optimized a lentiviral-based GPC2 CAR using a D3 GPC2 antibody with CD28 transmembrane and 4-1BB/CD3zeta co-stimulatory domains (D3-GPC2-BBz CAR) which is being tested in neuroblastoma (NCT05650749). Here we tested D3-GPC2-BBz CARs in GPC2-expressing pediatric CNS tumors. D3-GPC2-BBz CAR T cells were selectively cytotoxic to group 3 medulloblastoma cell lines in vitro: 7316-4509 showed 75% reduction in cell viability at 1:5 E:T ratio, p0.01, and 7316-10374 showed 75% reduction in cell viability at 1:1 E:T ratio, p0.05. Similarly, GPC2 CAR T cells showed robust antitumor activity against a H3G34 high-grade glioma cell line KNS42: 69% reduction in cell viability at 5:1 E:T ratio, p0.001. In a 7316-4509 group 3 orthotopic xenograft, lateral ventricle delivery of a single 1e6 dose of D3-GPC2-BBz CAR T cells resulted in durable tumor regression (mean radiance at 95 days 1.40e6 vs. 1.09e9 for control CD19 CARs, p0.0001) with substantially prolonged overall survival (OS; median survival 200 days vs. 147 days for CD19 CARs, p0.0001). In a thalamic H3K27M DMG orthotopic xenograft model (7316-3058), lateral ventricle delivery of a single 1e6 dose of GPC2 CAR T cells also significantly extended OS (87 vs. 69 days for CD19 CARs, p0.0001). No toxicity was observed in GPC2 CAR-treated animals, including no evidence of tumor inflammation-associated neurotoxicity. Overall, ventricular delivery of D3-GPC2-BBz CAR T cells showed potent antitumor efficacy in preclinical models of pediatric CNS tumors without toxicity, supporting the clinical testing of GPC2 CAR T cells in children with GPC2-expressing CNS tumors.
Pan et al. (Fri,) studied this question.