Quizartinib + chemotherapy significantly improved overall survival compared to chemotherapy in patients with newly diagnosed FLT3-ITD positive acute myeloid leukemia.

The data were featured as part of the press program and presented during the Presidential Symposium (#S100) at the European Hematology Association (#EHA2022) Congress. AML is one of the most common leukemias in adults with an estimated five-year survival rate of approximately 30.5%. Of all newly diagnosed cases of AML, 25% carry the FLT3-ITD gene mutation, which is associated with particularly unfavorable prognosis including increased risk of relapse and shorter overall survival.

Quizartinib combined with standard induction and consolidation chemotherapy and then continued as a single agent demonstrated a 22.4% reduction in the risk of death compared to standard chemotherapy alone (HR = 0.776 [95% CI: 0.615-0.979; 2-sided p=.0324]) in patients with newly diagnosed FLT3-ITD positive AML. After a median follow-up of 39.2 months, median OS was more than double at 31.9 months for patients receiving quizartinib (95% CI: 21.0-NE) compared to 15.1 months for patients receiving chemotherapy (95% CI: 13.2-26.2).

The safety of quizartinib combined with intensive chemotherapy and as continuation monotherapy in QuANTUM-First was generally manageable , with no new safety signals observed. Rates of grade 3 or higher treatment emergent adverse events (TEAEs) were similar for both study groups and the most common grade 3 or higher TEAEs occurring in greater than 10% of patients were febrile neutropenia (43.4% quizartinib; 41.0% placebo), neutropenia (18% quizartinib; 8.6% placebo), hypokalemia (18.9% quizartinib; 16.4% placebo and pneumonia (11.7% quizartinib; 12.7% placebo). Rates of TEAEs associated with fatal outcomes were 11.3% for quizartinib versus 9.7% chemotherapy alone and were mainly due to infections.

QTcF greater than 500 ms occurred in 2.3% of patients receiving quizartinib and 0.8% of patients discontinued quizartinib due to QT prolongation. Ventricular arrhythmia events with quizartinib were uncommon. Two (0.8%) patients experienced cardiac arrest with recorded ventricular fibrillation on ECG (one with fatal outcome) both in the setting of severe hypokalemia.

The OS improvement with quizartinib was also supported by a sensitivity analysis censoring for the effect of allogenic hematopoietic stem cell transplant (HSCT) (HR = 0.752; [95% CI: 0.562-1.008]). Additional secondary and exploratory analyses provide further understanding and some supporting evidence for improved OS in patients receiving quizartinib combined with chemotherapy in the trial. The primary event-free survival (EFS) analysis (with induction treatment failure (ITF) defined as not achieving complete remission (CR) by day 42 of the last induction cycle), did not show a statistically significant difference between the two study arms; two pre-specified sensitivity analyses on EFS (the first one defining ITF as not achieving CR by the end of induction; the second one defining ITF as having not achieved composite complete remission (CRc) by the end of induction) showed HR = 0.818 [95% CI: 0.669, 0.999] and HR = 0.729 [95% CI: 0.592-0.897], respectively.

The CRc rate was numerically higher for patients receiving quizartinib compared to chemotherapy alone (71.6% versus 64.9%), and rates of CR were similar for the two study arms (54.9% and 55.4%). The median duration of CR was 38.6 months for quizartinib (95% CI: 21.9-NE) and 12.4 months for chemotherapy (95% CI: 8.8-22.7).The median relapse-free survival (RFS) for patients who achieved CR was 39.3 months for quizartinib and 13.6 months for placebo, representing a 38.7% relative risk reduction of relapse or death (HR = 0.613 [95% CI: 0.444-0.845]).