Hematopoietic Cell Transplantation from an HLA-Mismatched Familial Donor Is Feasible Without Ex Vivo-T Cell Depletion after Reduced-Intensity Conditioning with Busulfan, Fludarabine, and Antithymocyte Globulin

To extend the use of allogeneic hematopoietic cell transplantation (HCT) to patients without an HLA-matched donor, we investigated HCT from a related donor with 1 fully mismatched HLA-haplotype after conditioning with busulfan in reduced-dose, fludarabine, and antithymocyte globulin. Hematopoietic cells were collected from the donors via leukapheresis after mobilization and infused without further manipulation. Cyclosporin and methotrexate were administered for graft-versus-host disease (GVHD) prophylaxis. Posttransplant engraftment, GVHD, and transplantation-related mortality (TRM) were recorded. Thirty-one patients (age range: 16-69 years) with high-risk acute leukemia/myelodysplastic syndrome (n = 25) or bone marrow failure (n = 6) were enrolled. The donors were either mothers (n = 14), offspring (n = 9), or siblings (n = 8) of these patients. Excluding 3 patients who died or relapsed with leukemia within 3 weeks after HCT, all the remaining 28 patients engrafted with neutrophils (>500/μL) at a median of 16.5 days. Twenty-two of 24 evaluated patients achieved complete donor chimerism (≥95%) 2 weeks after HCT and none experienced graft failure subsequently. The cumulative incidences of grade 2-4 acute GVHD (aGVHD) and moderate-severe chronic GVHD (cGVHD) were 19% (95% confidence interval [CI], 9%-40%) and 20% (95% CI, 10%-41%), respectively. After a median follow-up of 18.2 months (range: 6.3-52.1), 18 patients remained alive (53%). Four patients died without recurrence/progression of underlying diseases giving a TRM of 13% (95% CI, 5%-33%). HCT from an HLA-mismatched family member is feasible without ex vivo T cell depletion when reduced-intensity conditioning containing anti-hymocyte globulin is performed.