Drug Interactions between fezolinetant and pacritinib

GENERALLY AVOID: Theoretically, coadministration with grapefruit juice may increase the plasma concentrations of pacritinib, which is primarily metabolized by CYP450 3A4. 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 the potent CYP450 3A4 inhibitor, clarithromycin. In a clinical drug interaction study, a single dose of pacritinib (400 mg) was administered following treatment with clarithromycin (500 mg twice daily for 5 days). The peak plasma concentration (Cmax) and systemic exposure (AUC) of pacritinib increased by 30% and 80%, respectively, compared to pacritinib administered alone. Longer treatment with clarithromycin that results in maximal CYP450 3A4 inhibition may increase pacritinib exposure even higher. 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 pacritinib may increase the risk of adverse effects such as diarrhea, thrombocytopenia, infection, and QT prolongation.

Pacritinib pharmacokinetics were not significantly affected when administered with a high-fat meal.

MANAGEMENT: Although clinical data are lacking, it may be advisable to avoid consumption of grapefruit or grapefruit juice during treatment with pacritinib. Pacritinib may be administered with or without food.

CONTRAINDICATED: Coadministration with inhibitors of CYP450 1A2 such as caffeine may significantly increase the plasma concentrations of fezolinetant, which is primarily metabolized by the isoenzyme. The interaction has not been studied with caffeine but has been reported for other CYP450 1A2 inhibitors. Consumption of caffeine-containing food or beverages (e.g., chocolate, coffee, cola drinks, energy drinks, tea) could result in an interaction with fezolinetant. In clinical drug interaction studies, fezolinetant was coadministered with fluvoxamine, mexiletine, and cimetidine (potent, moderate, and weak CYP450 1A2 inhibitors, respectively). Fezolinetant peak plasma concentration (Cmax) increased by 80%, 40%, and 30%, respectively, while its systemic exposure (AUC) increased by 840%, 360%, and 100%, respectively.

MANAGEMENT: Concomitant use of fezolinetant with CYP450 1A2 inhibitors such as caffeine, including caffeine-containing food or beverages, is considered contraindicated.