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 cell surface oncoprotein glypican 2 (GPC2) is highly expressed on multiple lethal pediatric brain tumors, including medulloblastomas, embryonal tumors with multi-layered rosettes, other CNS embryonal tumors, as well as definable subsets of highly malignant gliomas. To target GPC2 on these pediatric brain tumors with adoptive cellular therapies and mitigate potential inflammatory neurotoxicity, we developed four mRNA chimeric antigen receptor (CAR) T cell constructs using the highly GPC2-specific fully human D3 single chain variable fragment. First, we validated and prioritized these 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 prioritized from these studies to GPC2-expressing medulloblastoma and high-grade glioma cell lines, showing significant GPC2-specific cell death in multiple models. Finally, locoregional delivery bi-weekly of two to four million 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.
One Sentence Summary Glypican 2 is expressed on the surface of multiple pediatric brain tumors and can be successfully targeted with mRNA chimeric antigen receptor T cells.
Competing Interest Statement
T.S. is currently employed by Spark Therapeutics. K.K. is currently employed by BioNTech and is an inventor on a patent related to use of nucleoside-modified mRNA. D.M.B. is currently employed by Tmunity Therapeutics. J.B.F., D.M.B, J.M.M., and K.R.B. hold patents for the discovery and development of immunotherapies for cancer, including patents related to GPC2-directed immunotherapies. K.R.B. and J.M.M. receive research funding from Tmunity for research on GPC2-directed immunotherapies and J.B.F., D.M.B, J.M.M., and K.R.B. receive royalties from Tmunity for licensing of GPC2-related intellectual property. J.M.M. is a founder of both Tantigen Bio and Hula Therapeutics, focused on cellular therapies for childhood cancers, but neither are working on GPC2-directed therapeutics. All other authors have nothing to disclose.