Drug Interaction Report

GENERALLY AVOID: Coadministration of pexidartinib with strong CYP450 3A4 inhibitors and/or uridine diphosphate glucuronosyltransferase (UGT) inhibitors may significantly increase the plasma concentrations and the incidence and severity of adverse effects of pexidartinib, including potentially fatal hepatotoxicity. The proposed mechanism is inhibition of CYP450 3A4 and/or UGT, the primary isoenzymes responsible for the metabolic clearance of pexidartinib. Concomitant administration of itraconazole, a strong CYP450 3A4 inhibitor, increased pexidartinib peak plasma concentration (Cmax) and systemic exposure (AUC) by 48% and 70%, respectively. Coadministration with probenecid, a UGT inhibitor, increased pexidartinib Cmax and AUC by 5% and 60%, respectively.

MANAGEMENT: The use of pexidartinib with strong CYP450 3A4 inhibitors and/or UGT inhibitors should generally be avoided. If concomitant use is required, the dose of pexidartinib should be reduced according to the manufacturer's recommendations. If concomitant use of a strong CYP450 3A4 inhibitor or UGT inhibitor is discontinued, the dose of pexidartinib may be increased, after 3 plasma half-lives of the strong CYP450 3A4 inhibitor or UGT inhibitor, to the dose that was used prior to starting the strong CYP450 3A4 inhibitor or UGT inhibitor.

ADJUST DOSING INTERVAL: The presence of food may increase the absorption and toxicity of pexidartinib. Administration of pexidartinib with a high-fat meal increased peak plasma concentration (Cmax) and systemic exposure (AUC) by 100% and prolonged the time to reach peak plasma concentration (Tmax) by 2.5 hours.

GENERALLY AVOID: Grapefruit or grapefruit juice may increase the plasma concentration and risk of adverse effects of pexidartinib, including potentially fatal hepatotoxicity. The mechanism is inhibition of CYP450 3A4-mediated metabolism of pexidartinib by certain compounds present in grapefruits. Concomitant administration of itraconazole, a strong CYP450 3A4 inhibitor, increased pexidartinib peak plasma concentration (Cmax) and systemic exposure (AUC) by 48% and 70%, respectively.

MANAGEMENT: Pexidartinib should be administered on an empty stomach, at least one hour before or two hours after a meal or snack. Consumption of grapefruit or grapefruit juice should generally be avoided during pexidartinib therapy. If concomitant use is unavoidable, the dose of pexidartinib should be reduced according to the manufacturer's recommendations. If concomitant use of grapefruit or grapefruit juice is discontinued, the dose of pexidartinib may be increased (after 3 plasma half-lives of a strong CYP450 3A4 inhibitor) to the dose that was used prior to consumption of grapefruit or grapefruit juice.

ADJUST DOSING INTERVAL: Food significantly enhances the oral bioavailability of telaprevir. When given with a meal containing 533 kcal and 21 g fat, telaprevir systemic exposure (AUC) increased by 237% compared to administration under fasting conditions. The type of meal also affects the exposure to telaprevir. Relative to fasting, telaprevir AUC increased by approximately 117% with a low-fat meal (249 kcal; 3.6 g fat) and 330% with a high-fat meal (928 kcal; 56 g fat). In Phase 3 clinical trials, telaprevir doses were administered within 30 minutes of completing a meal or snack containing approximately 20 grams of fat.

MANAGEMENT: Telaprevir should be administered with food containing approximately 20 grams of fat. Patients should be advised that the fat content of the meal or snack is critical to the absorption of telaprevir. Food taken with telaprevir should be ingested within 30 minutes prior to each dose. Examples of some foods that could be taken with telaprevir include: bagel with cream cheese; half cup of nuts; 3 tablespoons of peanut butter; 1 cup of ice cream; 2 ounces of American or cheddar cheese; 2 ounces of potato chips; or half cup of trail mix.