Drug Interaction Report

MONITOR: Coadministration with CYP450 3A4 inducers may decrease the plasma concentrations of tucatinib, which is primarily metabolized by CYP450 2C8 and to a lesser extent by CYP450 3A4. When rifampin (600 mg once daily), a potent CYP450 3A4 and moderate CYP450 2C8 inducer, was administered with a single tucatinib dose of 300 mg, tucatinib peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by 40% and 50%, respectively. No data are available for other, less potent CYP450 3A4 inducers.

MANAGEMENT: The potential for diminished pharmacologic effects of tucatinib should be considered during coadministration with CYP450 3A4 inducers. Alternative treatments may be required if an interaction is suspected.