Mentor Name: Grant Grothusen

Retinoblastoma is the most common childhood cancer of the eye, with more than 8,000 new cases yearly worldwide. While early detection and access to optimal clinical management portend a positive prognosis, potential acute and long-term risks of multimodal chemotherapy-related toxicities remain. Furthermore, retinoblastoma that has gone untreated or developed chemoresistance may necessitate eye removal (enucleation) in order to prevent lethal extraocular metastasis to the central nervous system (CNS). We have recently demonstrated that chimeric antigen receptor (CAR) T-cell immunotherapy directed against the highly expressed retinoblastoma cell surface molecule glypican-2 (GPC2) safely mediates strong anti-tumor effects against both intraocular and CNS metastatic preclinical retinoblastoma models. However, despite initial cancer control, some tumors relapsed after treatment, indicating a critical need to decipher retinoblastoma immune evasion mechanisms and develop next-generation cellular therapy strategies that can achieve durable remissions for this unrelenting pediatric cancer. Considering our preliminary data confirming that retinoblastomas substantially down-regulate cell surface GPC2 levels under GPC2 CAR T-cell pressure, but maintain levels of another retinoblastoma surface molecule, disialoganglioside GD2, here we propose to engineer dual CAR T-cells targeting both GPC2 and GD2 to overcome pediatric solid tumor antigen escape. This innovative approach will also be evaluated against neuroblastoma, another high-risk pediatric cancer that expresses high levels of GPC2 and GD2. Importantly, GPC2 CAR T-cells are currently under investigation in our ongoing first-in-human Phase I clinical trial in neuroblastoma (NCT05650749). Furthermore, GD2 CAR T-cells have shown clinical activity in neuroblastoma patients and have also been preclinically tested in retinoblastoma mouse models, suggesting feasibility of swiftly progressing our proposed dual-targeting approach to pediatric patients in dire need of additional therapeutic options. Towards our translational research goals, through this proposal we will establish genetically engineered cancer cellular models and apply them to robust in vitro investigations defining the efficacy of GPC2 and GD2 dual-targeting CAR T-cells against retinoblastoma and neuroblastoma. These studies will lay the critical foundation for further preclinical evaluations of efficacy and safety.