Drug Interactions between Viekira XR and zanubrutinib

GENERALLY AVOID: Grapefruit and/or grapefruit juice may increase the plasma concentrations of zanubrutinib. 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 zanubrutinib was coadministered with the potent CYP450 3A4 inhibitor itraconazole (200 mg once daily), zanubrutinib peak plasma concentration (Cmax) and systemic exposure (AUC) increased 157% and 278%, respectively, in healthy volunteers. Data evaluating coadministration of zanubrutinib, in patients with B-cell lymphoma, and several other known CYP450 3A4 inhibitors have been reported. When zanubrutinib was coadministered with another CYP450 3A4 inhibitor, clarithromycin (250 mg twice daily), zanubrutinib Cmax and AUC increased 101% and 92%, respectively. The moderate CYP450 3A4 inhibitor diltiazem (180 mg once daily) increased both zanubrutinib Cmax and AUC increased by 62%. Another moderate CYP450 3A4 inhibitor, fluconazole (400 mg once daily), increased zanubrutinib Cmax and AUC 81% and 88%, respectively. Clinical data for less potent inhibitors are not available. In general, the effects of grapefruit products are concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit (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 zanubrutinib exposure may potentiate the risk of toxicities such as hemorrhage, infection, cytopenias, malignancies, and serious cardiac arrhythmias, primarily atrial fibrillation and atrial flutter.

Food does not affect the oral bioavailability of zanubrutinib. No clinically significant differences in zanubrutinib Cmax or AUC were observed following administration of a high-fat meal (approximately 1000 calories; 50% from fat) in healthy subjects.

MANAGEMENT: Zanubrutinib may be administered with or without food. Patients should avoid consumption of grapefruit, grapefruit juice, Seville oranges (a citrus relative of the grapefruit), and Seville orange juice during treatment with zanubrutinib. Close clinical monitoring for development of zanubrutinib-related toxicities, dosage adjustments, and/or withholding treatment in accordance with product labeling is advised. Additional consultation with individual package labeling, as well as relevant institutional protocols, may be advisable for further guidance.

ADJUST DOSING INTERVAL: Administration with food may modestly affect the bioavailability of ritonavir from the various available formulations. When the oral solution was given under nonfasting conditions, peak ritonavir concentrations decreased 23% and the extent of absorption decreased 7% relative to fasting conditions. Dilution of the oral solution (within one hour of dosing) with 240 mL of chocolate milk or a nutritional supplement (Advera or Ensure) did not significantly affect the extent and rate of ritonavir absorption. When a single 100 mg dose of the tablet was administered with a high-fat meal (907 kcal; 52% fat, 15% protein, 33% carbohydrates), approximately 20% decreases in mean peak concentration (Cmax) and systemic exposure (AUC) were observed relative to administration after fasting. Similar decreases in Cmax and AUC were reported when the tablet was administered with a moderate-fat meal. In contrast, the extent of absorption of ritonavir from the soft gelatin capsule formulation was 13% higher when administered with a meal (615 KCal; 14.5% fat, 9% protein, and 76% carbohydrate) relative to fasting.

MANAGEMENT: Ritonavir should be taken with meals to enhance gastrointestinal tolerability.

ADJUST DOSING INTERVAL: Food enhances the oral bioavailability of ombitasvir, paritaprevir, ritonavir, and dasabuvir. Relative to fasting conditions, administration of ombitasvir, paritaprevir, ritonavir, and dasabuvir with a moderate-fat meal (approximately 600 Kcal; 20% to 30% calories from fat) increased the mean systemic exposure (AUC) by 82%, 211%, 49%, and 30%, respectively. Relative to fasting conditions, administration of ombitasvir, paritaprevir, ritonavir, and dasabuvir with a high-fat meal (approximately 900 Kcal; with 60% calories from fat) increased the mean AUC by 76%, 180%, 44%, and 22%, respectively.

MANAGEMENT: Ombitasvir/paritaprevir/ritonavir plus dasabuvir should always be administered with a meal. The fat or calorie content does not matter.