Outcome of children with acute leukemia given HLA-haploidentical HSCT after αβ T-cell and B-cell depletion

Allogeneic hematopoietic stem cell transplantation (HSCT) from an HLA-haploidentical relative (haplo-HSCT) is a suitable option for children with acute leukemia (AL) either relapsed or at high-risk of treatment failure. We developed a novel method of graft manipulation based on negative depletion of αβ T and B cells and conducted a prospective trial evaluating the outcome of children with AL transplanted with this approach (ClinicalTrial.gov identifier: NCT01810120). Eighty AL children, transplanted between September 2011 and September 2014, were enrolled in the trial. All children were given a fully myeloablative preparative regimen. Anti-T lymphocyte globulin from day -5 to -3 was used for preventing graft rejection and graft-versus-host disease (GvHD); no patient received any post-transplantation GvHD prophylaxis. Two children experienced primary graft failure. The cumulative incidence (CI) of skin-only, grade I-II acute GvHD was 30%; no patient developed extensive chronic GvHD. Four patients died, the CI of non-relapse mortality being 5%, while 19 relapsed, resulting into a 24% CI of relapse. With a median follow-up of 46 months for surviving patients, the 5-year probability of chronic GvHD-free, relapse-free survival (GRFS) is 71%. Total body irradiation-containing preparative regimen was the only variable favorably influencing relapse incidence and GRFS. The outcomes of these 80 patients are comparable to those of 41 and 51 children given transplantation from an HLA-identical sibling or a 10/10 allelic-matched unrelated donor in the same period. These data indicate that haplo-HSCT after αβ T- and B-cell depletion represents a competitive alternative for children with AL in need of urgent allograft.