Haploidentical Allogeneic Transplant With Post-transplant Infusion of Regulatory T-cells

This is dose-escalation study intended to evaluate the use of classification determinant 15-positive (CD15+), CD4+, CD127dim, and FoxP3+ regulatory T-cells (T-reg cells) supplemented by conventional T-cells (T-con cells), to enhance the efficacy of allogeneic (CliniMACS CD34+ selected) hematopoietic stem cell transplantation (allo-HSCT), in the setting of leukemia, lymphoma, and myelodysplastic syndrome (MDS). This study investigates amelioration of the impaired immune recovery and address the significant relapse incidence in the haploidentical HSCT setting. Pre-transplant myeloablative conditioning will be melphalan; thiotepa; fludarabine and rabbit antithymocyte globulin (rATG). Stem cell rescue will be with CD34+ selected cells. The rescue infusion will be supplemented with infusions of regulatory T-cells (T-reg) and conventional T-cells (T-con) from the same donor collection, on Treatment Days 14 and 16 respectively. CD34+ cell infusion day is Treatment Day 0. T-reg cells are those cells enriched by immunomagnetic selection of CD25+ cells, and further purified by flow cytometric cell sorting for the CD15+, CD4+, CD127dim, FoxP3+ cell population. These cells are an enriched but naturally-occurring T-cell population. T-con cells are unseparated/unfractionated cells, ie, as collected by the peripheral blood stem cells apheresis procedure. Post-transplant follow-up is for 5 years.