Study of Gene Modified Donor T-cells Following TCR Alpha Beta Positive Depleted Stem Cell Transplant

This is a Phase 1/2 study evaluating the safety and feasibility of BPX-501 T cells infused after partially mismatched, related, TCR alpha beta T cell depleted hematopoietic stem cell transplant (HSCT) in pediatric patients. The purpose of this clinical trial is to determine whether BPX-501 infusion can enhance immune reconstitution in those patients with hematologic disorders, with the potential for reducing the severity and duration severe acute graft versus host disease (GvHD). The trial will also evaluate the treatment of GvHD by the infusion of dimerizer drug (AP1903/rimiducid) in those subjects who present with GVHD that does not adequately respond to standard of care therapy.