HLA-Haploidentical Donors Seem to be Not Inferior to HLA-Identical Sibling Donors for Hematopoietic Stem Cell Transplantation of Patients with Paroxysmal Nocturnal Hemoglobinuria (PNH)?

Background PNH is an acquired clonal disorder of the hemopoietic stem cells for which the only curative treatment is allogeneic hematopietic stem cell transplantation (allo-HSCT). But allo-HSCT is challenging for those who have no HLA-matched donors.Several recent studies have shown that haploidentical HSCT for patients with hematological malignancy can achieved comparable outcomes with HLA-identical sibling transplantation . There are very few reports on the use of haploidentical HSCT for PNH . Is haploidentical HSCT a valid alternative option for patients with PNH?

Methods 19 PNH patients received allo-HSCT between Dec 2007 and Oct 2015 at our institution. 12 donors were HLA-haploidentical and 7 were HLA-matched siblings. The patients were aged 8 to 54 years (median 28 years) . Of the 12 haploidentical donors, 6 were siblings, 2 fathers,2 mothers,1 son and 1 daughter. 12 patients with haploidentical donors received a myeloablative conditioning regimen consisting of busulfan, cyclophosphamide and ATG (anti-thymocyte globulin), 7 patients with identical siblings were given a reduced intensity conditioning. G-CSF-mobilized bone marrow and peripheral blood stem cells were transplanted as graft. Prophylaxis for graft-versus-host disease (GVHD) consisting of cyclosporine or tacrolimus + short-term methotrexate + mycophenolate mofetil was used for 12 patients with haploidentical donors, and cyclosporine + short-term methotrexate for 7 with identical siblings.

Results All 19 patients were engrafted successfully. The median time of neutrophils (ANC) reached to 0.5×10⁹/L and platelets (PLT) reached to 20×10⁹/L was 12 days and 15 days in haploidentical group , and that to identical group was 11 days and 13 days ,respectively. There were 2 patients developed grade Ⅱ acute GVHD in haploidentical group while 1 patients with grade Ⅳ aGVHD in identical group . Limited chronic GVHD was observed in 2/12 patients in haploidentical group and 1/7 patients in identical group. After a median follow-up time of 22.0 (range 4.0-42.0) months, the 3-year OS probability was 77.8±13.9% and 85.7±13.2% for haploidentical and identical group,respectively (P=0.03). 2 patients died of treatment-related mortality in haploidentical group, including severe pulmonary infection (n=1) and transplant-associated thrombotic microangiopathy (n=1) ,and 1 died of severe aGVHD in identical group. No patients were documented to have a recurrence of a PNH clone after HSCT in both groups.

Conclusion This report seemed that long-term outcomes of HLA- haploidentical HSCT in patients with PNH were comparable to that of HLA- matched donor at our institution . Haploidentical HSCT should be considered as a valid alternative option for PNH patients without HLA- matched donors .