Bone marrow transplantation from a haploidentical donor was effective with excellent overall survival (OS) and low rates of graft vs host disease (GVHD) among patients with relapsed/refractory severe aplastic anemia, according to the results of a phase 2 trial published in Lancet Haematology.

“In clinical practice, this could now be considered a standard approach for salvage transplantation across populations,” the authors wrote.

Aplastic anemia that does not respond to immunosuppressive therapy is treated with bone marrow transplantation, but a suitable donor is frequently not available for under-represented minorities. The aim of this trial was to evaluate the outcomes of transplantation in relapsed/refractory severe anemia with the use of a haploidentical donor.

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The multicenter, single-arm, phase 2 BMT CTN 1502 trial treated 31 patients with relapsed/refractory severe aplastic anemia with haploidentical bone marrow transplant after reduced-intensity conditioning and post-conditioning cyclophosphamide-based GVHD prophylaxis. GVHD prophylaxis also included mycophenolate mofetil followed by tacrolimus. The target yield of donor bone marrow was 4×108 nucleated marrow cells per kilogram of recipient ideal bodyweight and a recommended minimum yield of 2.5×108 nucleated marrow cells per kg of recipient ideal bodyweight.

The primary endpoint of the study was 1-year OS and secondary endpoints included proportion of patients alive and engrafted, recovery of neutrophil and platelets, graft failure, and acute and chronic GVHD.

At baseline, the median age was 24.9 and 39% of patients were female. The cohort included 42% of patients who were non-White, including 23% who were non-Hispanic Black, 16% who were Asian or Pacific Islander, 13% who were Hispanic White, and 3% who were more than 1 race. There were 6% of patients with unknown race and 39% who were non-Hispanic White.

With a median follow-up of 24.3 months, the OS was 81% and 77% of patients were alive and engrafted at 1 year. There were 13% of patients who developed primary graft failure, 3% with secondary graft failure, and 6% of deaths not due to graft failure.

A second transplant was performed for the 16% of patients who developed graft failure, with all but 1 patient experiencing associated complications that lead to death.

Neutrophil recovery was achieved by 94% of patients within a median time of 17 days. There were 77% of patients who achieved platelet recovery within 100 days, with a median time to recovery of 23 days.

There were 16% of patients who developed acute GVHD, all of which were grade 2. Chronic GVHD occurred among 26% of patients at 1 year, nearly all of which were mild, and all patients with 2-year follow-up data were off therapy.

The authors concluded, “this study provides strong evidence for use of post-transplantation cyclophosphamide-based GVHD prophylaxis for patients with severe aplastic anemia when a haploidentical donor is used.”


DeZern AE, Eapen M, Wu J, et al. Haploidentical bone marrow transplantation in patients with relapsed or refractory severe aplastic anaemia in the USA (BMT CTN 1502): a multicentre, single-arm, phase 2 trial. Lancet Haematol. Published online July 27, 2022. doi: 10.1016/S2352-3026(22)00206-X