[Efficacy and safety of gilteritinib-based combination therapy bridging allo-HSCT in relapsed or refractory acute myeloid leukemia patients with positive FLT3-ITD mutation].

ABSTRACT

Objective: This study aims to evaluate the safety and effectiveness of gilteritinib (Gilt) -based combination therapy bridging allo-HSCT for FLT3-ITD(+) R/R AML. Additionally, it aims to assess the impact of Gilt maintenance therapy on the prognosis of patients after allo-HSCT. Methods: The clinical data of 26 patients with FLT3-ITD(+) R/R AML treated at the First Affiliated Hospital of Soochow University from August 2019 to January 2023 were retrospectively analyzed. The analysis included an assessment of the composite complete remission rate (CRc), overall survival (OS) time, disease-free survival (DFS) time, and adverse events experienced by all enrolled patients. Results: A total of 26 patients with FLT3-ITD(+) R/R AML were enrolled, including 14 men and 12 women with a median age of 38 (18-65) years. A total of 18 cases were refractory, and eight cases were relapsed. The curative effect evaluation conducted between 14 and 21 days showed that the complete remission (CR) rate was 26.9% (7/26), the CR with hematology incomplete recovery was 57.7% (15/26), and the partial response (PR) rate was 7.7% (2/26). The CRc was 84.6% (22/26), and the minimal residual disease (MRD) negativity rate was 65.4%. The 12 month cumulative OS rate for all patients was 79.0%, and the 24 month cumulative OS rate was 72.0%. The median OS time was not determined. The median follow-up time was 16.0 months. Among the patients who responded to treatment, the 12 month cumulative DFS rate was 78.0%, and the 24 month cumulative DFS rate was 71.0%. The median DFS time was not determined. Patients who received allo-HSCT had a median OS time that was significantly longer than those who did not receive allo-HSCT (3.3 months, 95%CI 2.2-4.3 months, P=0.005). The median OS time of patients with or without Gilt maintenance therapy after allo-HSCT was not determined, but the OS time of patients with Gilt maintenance therapy after allo-HSCT treatment was longer than that of patients without Gilt maintenance therapy after allo-HSCT treatment (P=0.019). The FLT3-ITD mutation clearance rate in this study was 38.5%, and the median OS time of patients with FLT3-ITD mutation clearance was not determined but was significantly longer than the median OS of patients without FLT3-ITD mutation clearance (15.0 months; P=0.018). The most common grade 3 and above hematological adverse events of Gilt-based combination therapy included leukopenia (76.9%), neutropenia (76.9%), febrile neutropenia (61.5%), thrombocytopenia (69.2%), and anemia (57.7%). One patient developed differentiation syndrome during oral Gilt maintenance therapy after allo-HSCT treatment, but his condition improved after treatment. Conclusion: The Gilt-based combination therapy is highly effective in treating FLT3-ITD(+) R/R AML. It demonstrates a high CRc, MRD negativity rate, and rapid onset, leading to a significant improvement in patients' survival. Furthermore, the clearance rate of FLT3-ITD mutation is notably high. Additionally, implementing bridging allo-HSCT and Gilt maintenance therapy after allo-HSCT treatment has considerably enhances patients' survival. Closely monitoring and managing any adverse event that may occur during treatment are crucial.