The role of plerixafor in conditioning regimens before unmanipulated bone marrow transplantation in patients with Wiscott–Aldrich syndrome

   Our previous experience of using plerixafor and granulocyte colony stimulating factor (G-CSF) in addition to treosulfan-based conditioning in patients with Wiscott–Aldrich syndrome (WAS) demonstrated efficacy and a decreased risk of severe graft failure after hematopoietic stem cell transplantation (HSCT) with TCRab + /CD19 + graft depletion. Because of the remaining risk of graft failure in WAS patients following HSCT with unmanipulated grafts reported in a number of large-scale retrospective studies, we used plerixafor and G-CSF in conditioning regimens in 6 WAS patients who received native bone marrow as a graft source. None of the patients developed severe organ toxicity in the early post-transplantation period. All of them had long-term full donor chimerism in whole blood and the CD3 + line and a good graft function. At the last follow-up, 5 patients are alive at 3.7 to 74.7 months after HSCT (median follow-up time: 24.0 months). One patient died of chronic lung graft-versus-host-disease at 18 months after the transplantation. Despite limited experience, we believe that additional hematopoietic stem cell mobilization with plerixafor and G-CSF in treosulfan-based conditioning regimens may be effective in WAS patients undergoing HSCT with an unmanipulated graft. The study was approved by the Independent Ethics Committee and the Scientific Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. Key words: plerixafor, conditioning regimen, hematopoietic stem cell transplantation, Wiscott–Aldrich syndrome, unmanipulated graft