Development of GPC2-directed chimeric antigen receptors using mRNA for pediatric brain tumors

Abstract

Pediatric brain tumors are the leading cause of cancer death in children with an urgent need for innovative therapies. Here we show that the neuroblastoma cell surface oncoprotein glypican 2 (GPC2) is also highly expressed on multiple lethal pediatric brain tumors, including medulloblastomas, embryonal tumors with multi-layered rosettes, other CNS embryonal tumors, as well as a subset of highly malignant gliomas including H3 G35 mutant gliomas and some H3 K28M diffuse midline gliomas. To target GPC2 on these pediatric brain tumors with adoptive cellular therapies and to mitigate potential inflammatory neurotoxicity, we developed four mRNA chimeric antigen receptor (CAR) T cell constructs using the highly GPC2-specific, fully human D3 scFv that targets a conformational epitope on human and murine GPC2. First, we validated and prioritized these GPC2-directed mRNA CARs using in vitro cytotoxicity and T cell degranulation assays with GPC2-expressing neuroblastoma cells. Next, we expanded the testing of the two most potent GPC2-directed CAR constructs (D3V3 and D3V4) prioritized from these studies to GPC2-expressing medulloblastoma and high-grade glioma models, showing significant GPC2-specific cell death in multiple medulloblastoma and HGG cellular models. Finally, locoregional delivery of both GPC2-directed mRNA CAR T cells induced significant and sustained tumor regression in two orthotopic medulloblastoma models, and significantly prolonged survival in an aggressive orthotopic thalamic diffuse midline glioma model. No GPC2-directed CAR T cell related neurologic or systemic toxicity was observed. Taken together, these data show that GPC2 is a highly differentially expressed cell surface protein on multiple malignant pediatric brain tumors that can be targeted safely with local delivery of mRNA CAR T cells.

OpenPBTA: An Open Pediatric Brain Tumor Atlas

“…Expression and copy number analyses were used to demonstrate that GPC2 is a highly expressed and copy number gained immunotherapeutic target in ETMRs, medulloblastomas, choroid plexus carcinomas, H3 wildtype high-grade gliomas, as well as DMGs. This led Foster and colleagues to subsequently develop a chimeric antigen receptor (CAR) directed against GPC2 , for which they show preclinical efficacy in mouse models 11 . Moreover, OpenPBTA has enabled a framework to support real-time integration of clinical trial subjects as each was enrolled on the PNOC008 high-grade glioma clinical trial 72 , allowing researchers and clinicians to link tumor biology to translational impact through clinical decision support during tumor board discussions.…”