Drug Interaction Report

Coadministration with mild or moderate inhibitors of CYP450 3A4 is not expected to have clinically significant effects on the pharmacokinetics of quizartinib or its major circulating active metabolite, AC886. According to the prescribing information, quizartinib is primarily metabolized via oxidation by CYP450 3A4/5 in vitro, and AC886 is formed and metabolized by CYP450 3A4/5. Following coadministration of a single 53 mg dose of quizartinib with ketoconazole, a potent CYP450 3A4 inhibitor, quizartinib peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 17% and 94%, respectively, while the Cmax and AUC of AC886 decreased by 60% and 94%, respectively. By contrast, clinically significant changes in the Cmax and AUC of quizartinib and AC886 were not observed following coadministration of single-dose quizartinib with fluconazole, a moderate CYP450 3A4 inhibitor. Therefore, no dosage adjustments are recommended when quizartinib is coadministered with mild and moderate CYP450 3A4 inhibitors.

ADJUST DOSING INTERVAL: Food may reduce the oral absorption and bioavailability of zafirlukast. In two separate studies, one using a high-fat and the other a high-protein meal, administration of zafirlukast with food reduced the mean bioavailability by approximately 40%.

MANAGEMENT: To ensure maximal oral absorption, zafirlukast should be administered at least 1 hour before or 2 hours after meals.