To reduce the risk of graft rejection after allogeneic hematopoietic cell transplantation (alloHCT) for patients with acquired severe aplastic anemia (SAA), we introduced an intensified preparative regimen consisting of treosulfan 10g/m2/d on days -7, -6, cyclophosphamide 40 mg/kg/d on days -5, -4, -3, -2 and anti-thymocyte globulin 2 mg/kg/d on days -3, -2, -1. Six patients with the history of multiple transfusions were treated with alloHCT from either HLA-identical sibling (n=3) or an unrelated volunteer (n=3). Each, bone marrow and peripheral blood was used as a source of stem cells in three cases. All patients engrafted and achieved complete donor chimerism. None of the patients experienced severe organ toxicity. No severe acute graftversus- host-disease (GVHD) was observed; two patients experienced extensive chronic GVHD. At the median follow-up of 14.5 (13-27) months all patients remained alive and disease-free. Our observation indicates that treosulfan + cyclophosphamide + antithymocyte globulin conditioning is well-tolerated and allows stable engraftment in acquired SAA.

Keywords: Treosulfan, allogeneic hematopoietic cell transplantation, severe aplastic anemia