Maintenance treatment with gilteritinib suppresses post-transplant relapse in relapse/refractory FLT3-mutated acute myeloid leukemia.

The FLT3 inhibitor, gilteritinib, has been widely used in patients with relapsed or refractory (R/R) FLT3-mutated acute myeloid leukemia (AML), but its tolerability and effectiveness after allogeneic hematopoietic stem cell transplantation (HSCT) are not well known outside of clinical trials.Therefore, we performed nation-wide surveillance in Japan. We used data from the national registry for patients transplanted including R/R FLT3-mutated AML patients treated with gilteritinib before and/or after HSCT. Post-HSCT administration dose and safety were summarized, and outcomes, including relapse-free survival (RFS) were investigated. We also used the historical cohort of HSCT before the approval of gilteritinib. Among R/R FLT3-mutated AML patients, 120 were treated with gilteritinib before and/or after allo-HSCT, and maintenance treatment was performed in 55 patients. The median initiation day was Day 47 after allo-HSCT (range 23-379) with a median starting dose of 80 mg (range 40-120 mg), and serious adverse events leading to gilteritinib dose reduction or temporary discontinuation were observed in 52.7% of these cases. The 3-year RFS was 46.8% and patients treated with post-HSCT gilteritinib had significantly better RFS (58.8%) than those without it (36.4%) (p < 0.001). Survival data in the historical cohort were similar to that of those who did not resume gilteritinib. In the subgroup analysis, post-HSCT gilteritinib showed an RFS benefit in cord blood transplantation (CBT; 79.4% vs. 26.1%, p < 0.001), but not in bone marrow or peripheral blood stem cell transplantation. This Japanese real-world study supports the tolerability and effectiveness of post-HSCT gilteritinib in R/R FLT3-mutated AML.