Evaluating Efficacy of B7-H3-CAR T Cells Administered at the End of Upfront Map Chemotherapy in Patients With Newly Diagnosed High-Risk Osteosarcoma

The purpose of this study is to assess the safety, feasibility, and effectiveness of a consolidative B7-H3 CAR T cell therapy in patients with newly diagnosed high-risk osteosarcoma who have undergone upfront standard chemotherapy. Primary Objectives: \- To evaluate 1-year RFS from the time of SJCARB7H3\_41BBL infusion for patients with newly diagnosed metastatic osteosarcoma who received standard chemotherapy. Secondary Objectives: * To evaluate the OS from time of SJCARB7H3\_41BBL infusion for patients with newly diagnosed metastatic osteosarcoma who received standard chemotherapy. * To evaluate the feasibility of delivering SJCARB7H3\_41BBL at the end of standard therapy in patients with newly diagnosed metastatic osteosarcoma. * To describe the safety of autologous SJCARB7H3\_41BBL therapy when delivered at the end of standard therapy in patients with newly diagnosed metastatic osteosarcoma.