Preclinical optimization of a GPC2-targeting CAR T cell therapy for neuroblastoma

Background: Although most patients with newly diagnosed high-risk neuroblastoma (NB) achieve remission after initial therapy, more than 50% experience late relapses caused by minimal residual disease (MRD) and succumb to their cancer. Therapy strategies to target MRD may benefit these children. We developed a new chimeric antigen receptor (CAR) targeting glypican (GPC)2 and conducted iterative preclinical engineering of the CAR structure to maximize its anti-tumor efficacy before clinical translation. Methods: We evaluated different GPC2-CAR constructs by measuring the CAR activity against several NB cell lines in vitro. NOD-SCID mice engrafted with human NB cell lines or orthotopic patient-derived xenograft (PDX) and treated with human CAR T cells served as in vivo models. Mechanistic studies were performed using single-cell RNA-sequencing. Results: Applying stringent in vitro assays and orthotopic in vivo NB models, we demonstrated that our single-chain variable fragment, CT3, integrated into a CAR backbone with a CD28 hinge, CD28 transmembrane, and 4-1BB co-stimulatory domain elicits the best preclinical anti-NB activity compared to other tested CAR constructs. This enhanced activity was associated with an enrichment of CD8+ effector T cells in the tumor-microenvironment and upregulation of several effector molecules such as GNLY, GZMB, ZNF683, and HMGN2. Finally, we also showed that the CT3.28H.BB? CAR was more potent than a recently clinically tested GD2-targeted CAR to control NB in vivo. Conclusion: Given the robust preclinical activity of CT3.28H.BB?, these promising results warrant further clinical testing in children with NB. Overall design: 2 donors, 3 GPC2-CAR constructs and one untransduced control. We manufactured the cells and performed single-cell RNA-seq after cell manufacturing. We then injected the cells into tumor-bearing mice and harvested tumors to perform the same analysis on cells from the TME.