Myeloid-Derived Suppressor Cells and Checkpoint Immune Regulators' Expression in Allogeneic SCT Using FluBuATG

This study is examining a chemotherapy regimen and immune suppressive medications in the setting of an allogeneic stem cell transplant. A pilot clinical trial to characterize the incidence, prevalence and function of myeloid-derived suppressor cells (MDSCs) and immune checkpoint regulators (V-domain Ig Suppressor of T-cell Activation \[VISTA\], cytotoxic T-lymphocyte- associated protein 4 \[CTLA-4\], programmed death-ligand 1 \[PD-L1\]) during early immune recovery following an allogeneic stem cell transplant. The site will use a myeloablative regimen of fludarabine with busulfan, adopted from CALGB 100801, to define clinical endpoints, including engraftment, 100 day survival and one year survival (Objective #1). The site will characterize the incidence, prevalence and function of MDSCs and immune checkpoint regulators in patients' blood and bone marrow following transplantation (Objective #2). The site will correlate these laboratory results with clinical outcomes and the incidence of graft-versus-host disease (GVHD). As an exploratory aim, in those patients experiencing GVHD and requiring treatment, the site will define the MDSCs frequency and checkpoint regulator expression and correlate these results with the patient's response to GVHD therapy.