Post-marketing surveillance of quizartinib for relapsed or refractory FLT3-ITD-positive acute myeloid leukemia in Japan

Quizartinib is an oral, once-daily, highly potent and selective second-generation, type II FMS-like tyrosine kinase 3 (FLT3) inhibitor, approved for the treatment of newly diagnosed and relapsed/refractory (R/R) FLT3-internal tandem duplication (ITD)-positive acute myeloid leukemia (AML). This descriptive, observational post-marketing surveillance (PMS) investigated the safety of quizartinib in patients with R/R FLT3-ITD-positive AML who initiated quizartinib between October 2019 and December 2021 in Japan. The safety analysis dataset included 126 patients (mean age 60.4 years) who consented to data publication. Eighty patients (63.5%) had previously received another FLT3 inhibitor. The median treatment duration was 71.0 days. Adverse drug reactions (ADRs) occurred in 68 patients (54.0%); grade ≥ 3 and serious ADRs occurred in 44 (34.9%) and 20 (15.9%) patients, respectively. QT interval prolongation occurred in 18/124 patients (14.5%), and the first event typically occurred < 30 days, but sometimes ≥ 150 days, after quizartinib initiation; none of these patients experienced clinical symptoms associated with the ADR. This PMS showed that the safety profile of quizartinib in routine clinical practice in Japanese patients with R/R FLT3-ITD-positive AML did not differ from the known safety profile of quizartinib. QT interval prolongation was manageable with current risk minimization measures.