D3-GPC2–Directed CAR T Cells Are Safe and Efficacious in Preclinical Models of Neuroblastoma and Small Cell Lung Cancer

Abstract Purpose: We previously identified glypican 2 (GPC2) as a cell-surface MYCN-regulated neuroblastoma oncoprotein and developed a D3-GPC2 antibody that specifically binds a conformational, tumor-specific epitope conserved between mouse and human. Experimental Design: In this study, we sought to further validate GPC2 as an immunotherapeutic target and develop Investigational New Drug application–enabling data to support the clinical translation of D3-GPC2 chimeric antigen receptor (CAR) T cells. Results: Immunohistochemistry validated that GPC2 is widely expressed on human neuroblastomas, and flow cytometry showed high levels of cell-surface GPC2 on neuroblastoma cellular models. Second-generation D3-GPC2 CAR T cells with either a 4-1BB or CD28 co-stimulatory domain were selectively activated and induced potent neuroblastoma cell cytotoxicity in several complementary in vitro co-incubation assays. Conversely, no measurable cytotoxicity or D3-GPC2 CAR T-cell activation was observed in co-incubation studies with nine primary human normal tissue cell lines. Moreover, GPC2 CAR T cells induced significant regression of GPC2-expressing neuroblastoma xenografts. No GPC2 CAR-related toxicities were noted, including in comprehensive mouse necropsies performed after GPC2 CAR T-cell administration. Finally, to explore the potential broader clinical impact of GPC2 CAR T cells, we showed that they are also potently cytotoxic to preclinical models of GPC2-expressing small cell lung cancers. Conclusions: These data validate GPC2 as a bona fide CAR T-cell target in neuroblastoma and other cancers. The safety and preliminary efficacy of GPC2 CAR T cells are being tested in a first-in-human phase I clinical trial for children with relapsed/refractory neuroblastoma (NCT05650749).