Posttransplant cyclophosphamide for haploidentical stem cell transplantation in children with Wiskott-Aldrich syndrome

BACKGROUND: Hematopoietic stem cell transplantation (HSCT) is the curative treatment for Wiskott-Aldrich syndrome (WAS). However, it is difficult to find a matched donor for patients. Therefore, haploidentical donors should be considered for patients lacking a suitable donor. Our pilot study evaluated whether HSCT with posttransplantation cyclophosphamide (PTCy) is an effective treatment for WAS. METHODS: Haploidentical family donors were selected as donor sources for a total of five patients without a suitable donor between March 2015 and March 2017. A modified transplant protocol using PTCy (50 mg/kg/day on days +3 and +4) was performed, including busulfan (16 mg/kg), fludarabine (150 mg/m2 ), and rabbit antihuman thymocyte globulin (7.5 mg/kg). RESULTS: The median time for neutrophil recovery over 1,000 × 103 /mm3 was 15 days (range, 12-18 days), and that for keeping platelets counts over 50,000/mm3 was 27.5 days (range, 20-35 days). The median follow-up was 2.1 years (range, 1.4-2.5 years). Two patients developed grade I acute graft-versus-host disease (GVHD), and one patient had limited chronic GVHD. All five patients are alive and independent of platelet infusion with 100% donor chimerism. CONCLUSION: Our pilot study suggests that HSCT with modified PTCy is a safe and effective treatment for WAS, which needs further clinical practice and research.