A phase II multicenter prospective study to evaluate the safety and efficacy of myeloablative-dose treosulfan plus fludarabine (FT14) conditioning regimen in allogeneic hematopoietic stem cell transplantation for AML patients aged 40-65 in first complete remission

Evidences supporting the use of myeloablative-dose Treosulfan combined with Fludarabine remain largely retrospective, with outdated prospective studies available. In this phase II multicenter prospective trial, we evaluated the safety and efficacy of FT14 conditioning regimen in patients with acute myeloid leukemia undergoing allogeneic stem cell transplantation in first complete remission.(EudraCT Number:2021-006515-28; Clinical trial number NCT07232953). The study was designed to provide a non-inferior alternative to standard busulfan-containing regimens, which would enable effective transplantation while minimizing toxicity. The primary objective was 1-year Leukemia-free survival (LFS). In total, 82 patients were enrolled in the study with a median follow up of 19.7 months; donor used were matched sibling in 22, matched unrelated 52 and mismatched unrelated in 8 cases, respectively. LFS at 180-day and 365-day were 87.8% and 81.7%, respectively. Cumulative incidence of relapse at 1 year after allo-HSCT was 14.9% with mean time to relapse of 5.6 months. Also, FT14 regimen provided an excellent safety with nearly absent NRM, no cases of septic death, and no cases of primary graft failure. Our study supports the use of FT14 as effective myeloablative conditioning regimen for AML patients aged 40-65 y in first complete remission, especially in patients for whom busulfan based conditioning regimens poses excessive toxic risks.