ENGINEERING T CELLS TARGETING GPC2 FOR TREATING NEUROBLASTOMA

BACKGROUND AND SIGNIFICANCE: Neuroblastoma is a rare pediatric cancer that forms in immature nerve tissue of infants and accounts for 10 to 15 percent of cancer-related deaths in children. The five-year survival for high-risk neuroblastoma is 50% with current treatment practices being a combination of surgery, chemotherapy, and radiation. A more effective therapy is therefore needed to improve overall patient outcomes. METHODS: The CT3 mouse antibody that targets GPC2 was previously identified in the lab and has shown activity in the chimeric antigen receptor (CAR) T cell format against neuroblastoma. Humanization of the CT3 antibody was also done through CDR grafting in human germline sequences to prevent potential adverse immunogenic effects when treating patients. In the present study, the CT3 antibody and humanized CT3 (hCT3) antibody were engineered into T cells based on the engineered gamma/delta TCR scaffold (called AbTCR). The activities of the CT3 and hCT3 AbTCRs were tested in luciferase-based cell killing assays and xenograft mouse models. RESULTS: Humanized CT3 retains a comparable binding affinity for GPC2. The hCT3 CAR T cell showed its ability to regress tumor expression in mice. Furthermore, the mice treated with the CT3 AbTCR showed tumor regression while the mice treated with the hCT3 AbTCR became tumor free three weeks after treatment. CONCLUSIONS: Overall, the hCT3 AbTCR T cells are very active when combating neuroblastoma tumors in mice. The efficacy at a low treatment dosage indicates that the GPC2 targeted hCT3 AbTCRs are a promising therapeutic for the treatment of neuroblastoma and other GPC2 positive cancers in patients.