Evaluating Effectiveness and Safety of Flumatinib for Chronic Phase Chronic Myeloid Leukemia in (CML-CP) without Optimal Response (Warning, Failure) to Imatinib or/and Dasatinib

Abstract

Introduction Flumatinib is a novel second-generation BCR-ABL1 targeted kinase inhibitors (TKI) with better efficacy and safety than first generation TKIs in first-line treatment of chronic myeloid leukemia in chronic phase (CML-CP). In the previous phase III study, newly diagnosed CML-CP patients receiving flumatinib achieved higher treatment responses and safety than imatinib. When it comes to the patients not achieving the optimal response to TKIs, flumatinib is potentially a better option, nonetheless the robust evidence is unavailable. This study reports the effectiveness and safety of switching to flumatinib in patients who have not achieved the optimal molecular response to imatinib or/and dasatinib. Methods This prospective, multicentre study enrolled Philadelphia Chromosome-Positive (Ph+) CML-CP patients aged ≥18 years and who failed to achieve the optimal response with imatinib or/and dasatinib between March 2021 to October 2022. All patients were treated with flumatinib 600 mg once a day and followed up to 24 months. The primary endpoint of the study was rate of major molecular response (MMR) at 12 months as defined by European LeukemiaNet 2020 recommendations (BCR-ABL1 transcript level ≤0.1% in peripheral blood on RT-PCR assay on International Scale [IS]) and safety was the secondary endpoint assessed with CTCAE 4.03 version. In addition, the optimal molecular response in either the warning or failure patients was evaluated at 3, 6 and 12 months respectively, after switching to flumatinib, and the difference in effectiveness was also analyzed from the available mutation subtypes. Results Overall, 94 patients with Ph+ CML-CP were included in the study. The median (range) age of the patients were 53 (19.0-84.0) years old and 61.7% of the patients were males. A total of 38 (40.4%) patients reported warning response from the previous TKIs whereas 56 (59.6%) of patients reported treatment failure to the previous TKIs. Seventy-seven (81.9%) patients have been treated with one TKI, either imatinib or dasatinib, and 17 (18.1%) have been treated with both prior to the study. Overall, 25 (54%) patients achieved MMR at 12-months follow-up compared to the baseline (Figure 1). The rates of optimal molecular response at 3- and 6-months were also improved compared to the baseline. The optimal molecular response was 76(88%) at 3 months, and 52(73%) at 6 months. Subgroup analysis with previous response to TKIs revealed that flumatinib improved the rates of optimal molecular response in both warning and failure groups. Switching to flumatinib from imatinib or/and dasatinib have been reported with an enhanced optimal molecular response in patients who experienced warning compared with those who had treatment failure after the TKIs with 38 (100%) vs 38 (79%), 29 (91%) vs 23 (59%) and 15 (68%) vs 10 (42%) at 3-, 6- and 12-months respectively (Figure 2). Similarly, the rates of optimal molecular response were improved in patients without mutations compared to those having mutations, 65 (90%) vs 9 (75%) at 3 months, 46 (77%) vs 5 (56%) at 6 months and 23 (59%) vs 1 (20%) at 12 months respectively. The most common adverse events (AEs) were diarrhea in 17 (18%), rash in 11 (12%), bloating in 11 (12%), and thrombocytopenia in 11 (12%) patients. Common hematological AEs of grade 3/4 were thrombocytopenia in 7 (7%), anemia in 3 (3%) and leucopenia in 1 (1%) patients. Conclusion For Ph+ CML-CP patients without the optimal molecular response in previous imatinib or/and dasatinib, flumatinib is a better alternative to the existing treatments. In addition, if the patients were switched to flumatinib earlier, the optimal response was achieved faster. The grade 3/4 AEs were mainly hematologically related, whereas the gastrointestinal events were mostly of grade 1-2.