Drug Interactions between abemaciclib and pexidartinib

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.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of abemaciclib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Inhibition of hepatic CYP450 3A4 may also contribute. The interaction has not been studied with grapefruit juice, but has been reported for other CYP450 3A4 inhibitors. According to the product labeling, abemaciclib systemic exposure (AUC) is predicted to increase by up to 16-fold when administered with the potent CYP450 3A4 inhibitor ketoconazole. Itraconazole, another potent inhibitor, is predicted to increase the relative potency-adjusted unbound AUC of abemaciclib plus its active metabolites by 2.2-fold. In cancer patients, administration of a single 50 mg dose of abemaciclib (one-third the approved recommended dose of 150 mg) with clarithromycin 500 mg twice daily increased the relative potency-adjusted unbound AUC of abemaciclib plus its active metabolites by 2.5-fold relative to abemaciclib administered alone. The moderate CYP450 3A4 inhibitors, diltiazem and verapamil, are predicted to increase the relative potency-adjusted unbound AUC of abemaciclib plus its active metabolites by 2.4-fold and 1.6-fold, respectively. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Increased exposure to abemaciclib may increase adverse effects such as nausea, vomiting, diarrhea, stomatitis, venous thromboembolism, hepatotoxicity, anemia, neutropenia, and thrombocytopenia.

Food has modest effects on the pharmacokinetics of abemaciclib. A high-fat, high-calorie meal (800 to 1000 calories; 150 calories from protein, 250 calories from carbohydrate, and 500 to 600 calories from fat) administered to healthy subjects increased the Cmax and AUC of abemaciclib plus its active metabolites by 26% and 9%, respectively.

MANAGEMENT: Abemaciclib may be administered with or without food. Patients should avoid consumption of grapefruit and grapefruit juice during treatment with abemaciclib.