CY/TBI-800 as a pretransplant regimen for allogeneic bone marrow transplantation for severe aplastic anemia using HLA-haploidentical family donors.

Allogeneic BMT is the treatment of choice for patients with SAA who have an HLA-identical sibling donor. The results, however, have been relatively poor for transplants from partially matched family donors or unrelated donors because of the high incidence of graft rejection and/or GVHD. Six multiply transfused patients received a novel conditioning regimen of CY 200 mg/kg and TBI 800 cGy prior to receiving marrow from their HLA-haploidentical family donors. Three recipient-donor pairs were mismatched for one HLA locus, one for two loci and two for three loci. A combination of MTX and CsA was used for GVHD prophylaxis. Engraftment was noted in all six patients. Acute GVHD occurred in four patients, two each for grade I and II, respectively. One patient, who was ABO-compatible with her donor had delayed onset of pure red cell aplasia (PRCA) which completely recovered 6 months after additional immunotherapy with prednisolone. There were two deaths; both occurred while patients were on treatment for GVHD. One was from systemic fungemia and the other probably from cytomegalovirus interstitial pneumonitis (CMV-IP). Four patients (66.7%) have been alive and disease-free for more than 8.2, 27.3, 38.4 and 47.2 months after BMT, respectively. The results suggest that CY/TBI-800 may be a simple and effective conditioning regimen for SAA patients receiving BMT from family members other than HLA-identical siblings.