Drug Interactions between fedratinib and pemigatinib

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of pemigatinib, which is primarily metabolized by CYP450 3A4 in vitro. 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. When itraconazole, a potent CYP450 3A4 inhibitor, was administered following a single oral pemigatinib dose of 4.5 mg, pemigatinib peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 17% and 88%, respectively. Concomitant use of moderate CYP450 3A4 inhibitors is predicted to increase pemigatinib exposure by approximately 50% to 80%. 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 pemigatinib may increase the incidence and severity of serious adverse reactions such as hyperphosphatemia (which can cause precipitation of calcium-phosphate crystals over time that can lead to hypocalcemia, soft tissue mineralization such as cutaneous calcification and calcinosis, secondary hyperparathyroidism, anemia, muscle cramps, seizures, QT prolongation, and arrhythmias), serous retinal detachment (which may cause symptoms such as blurred vision, visual floaters, or photopsia), palmar-plantar erythrodysesthesia syndrome (hand-foot syndrome), arthralgia, stomatitis, diarrhea, nausea, vomiting, and constipation.

Pemigatinib pharmacokinetics were not significantly affected by coadministration of a high-fat, high-calorie meal (approximately 1000 calories; 500 to 600 calories from fat).

MANAGEMENT: Pemigatinib may be administered with or without food. Patients should avoid consumption of grapefruit, grapefruit juice, or supplements that contain grapefruit extract during treatment with pemigatinib.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of fedratinib. 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. When a single 300 mg oral dose of fedratinib (0.75 times the recommended dose) was coadministered with 200 mg twice daily ketoconazole, a potent CYP450 3A4 inhibitor, fedratinib total systemic exposure (AUC(inf)) increased by approximately 3-fold. Using physiologically based pharmacokinetic (PBPK) simulations, coadministration of fedratinib 400 mg once daily and ketoconazole 400 mg once daily is predicted to increase fedratinib AUC at steady state by 2-fold. Coadministration with the moderate CYP450 3A4 inhibitors, erythromycin (500 mg three times daily) or diltiazem (120 mg twice daily), is predicted to increase fedratinib AUC by approximately 1.5- to 2-fold following single-dose administration and by approximately 1.2-fold at steady state. 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 fedratinib exposure may potentiate the risk of adverse reactions such as nausea, vomiting, diarrhea, anemia, thrombocytopenia, neutropenia, encephalopathy (including Wernicke's), liver (ALT, AST) and pancreatic (amylase, lipase) enzyme elevations, increased blood creatinine, and secondary malignancies.

Food does not affect the oral bioavailability of fedratinib to a clinically significant extent. Administration of a single 500 mg dose (1.25 times the recommended dose) with a low-fat, low-calorie meal (162 calories; 6% from fat, 78% from carbohydrate, 16% from protein) or a high-fat, high-calorie meal (815 calories; 52% from fat, 33% from carbohydrate, 15% from protein) increased fedratinib peak plasma concentration (Cmax) and systemic exposure (AUC) by up to 14% and 24%, respectively.

MANAGEMENT: Fedratinib may be taken with or without food. However, administration with a high-fat meal may help reduce the incidence of nausea and vomiting. Patients should avoid consumption of grapefruit and grapefruit juice during treatment with fedratinib.

The recommended maximum number of medicines in the 'multikinase inhibitors' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'multikinase inhibitors' category:

• fedratinib
• pemigatinib

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.