Drug Interaction Report

CONTRAINDICATED: Coadministration with potent inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of venetoclax, which is primarily metabolized by the isoenzyme. In a study of 11 previously treated non-Hodgkin lymphoma patients, when the potent CYP450 3A4 inhibitor, P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) inhibitor ketoconazole (400 mg daily for 7 days) was coadministered with venetoclax (50 mg single dose), venetoclax peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 2.3-fold and 6.4-fold, respectively. Likewise, concomitant use of the P-gp and potent CYP450 3A4 inhibitor posaconazole (300 mg) with venetoclax 50 mg or 100 mg daily for 7 days increased the venetoclax Cmax by 1.61-fold and 1.86-fold, respectively, and AUC by 1.9-fold and 2.44-fold, respectively, compared with venetoclax (400 mg daily) alone. Increased venetoclax exposure may potentiate the risk of tumor lysis syndrome, particularly at initiation of therapy and during the dosage ramp-up phase, as well as other adverse effects such as diarrhea, nausea, vomiting, neutropenia, anemia, and thrombocytopenia.

MANAGEMENT: In patients with chronic lymphocytic leukemia or small lymphocytic lymphoma (CLL/SLL), the concomitant use of potent CYP450 3A4 inhibitors is contraindicated during the initiation and dosage ramp-up phase of venetoclax. The manufacturer also advises against use of potent CYP450 3A4 inhibitors once the dosage ramp-up phase is completed and the steady daily dose phase of venetoclax therapy begins. However, if concomitant therapy with a potent CYP450 3A4 inhibitor other than posaconazole is considered necessary, the daily dose of venetoclax should be reduced to 100 mg or less. If a dose had already been modified for venetoclax-related adverse reactions/toxicities in accordance with product labeling, some authorities suggest the dose should be further reduced by 75%. If concomitant use with posaconazole is required during the steady daily dose phase of therapy, the manufacturer advises the venetoclax dosage be reduced to 70 mg.

In patients with acute myeloid leukemia (AML), the dose of venetoclax should be reduced when coadministered with potent CYP450 3A4 inhibitors. This adjustment applies throughout both the initiation and dosage ramp-up phases, as well as the ongoing steady daily dose phase of therapy. During the initiation and ramp-up phases, the recommended schedule from the manufacturer is 10 mg on day 1, 20 mg on day 2, 50 mg on day 3, and 100 mg on day 4. Following completion of the ramp-up phase, a maintenance dose of 100 mg or less per day is advised for the steady daily dose phase. Some authorities suggest reducing the dose by at least 75% if adjustments have already been made due to venetoclax-related adverse reactions or toxicities. However, in cases where concurrent use with posaconazole is necessary, certain authorities propose a similar initiation and ramp-up phase dosing regimen of venetoclax from days 1 to 3 , followed by 70 mg on day 4, and continuing into the steady daily dose phase of therapy.

All patients, regardless of indication, should be closely monitored for signs and symptoms of venetoclax-induced adverse effects/toxicities. In addition, the dosage used prior to initiating the potent CYP450 3A4 inhibitor may be resumed 2 to 3 days after discontinuation of the inhibitor.

ADJUST DOSING INTERVAL: Food enhances the oral bioavailability of venetoclax. Relative to fasting conditions, venetoclax systemic exposure (AUC) increased by approximately 3.4-fold when administered with a low-fat meal (approximately 512 kilocalories, 25% calories from fat) and by 5.1- to 5.3-fold when administered with a high-fat meal (approximately 753 kilocalories, 55% calories from fat).

GENERALLY AVOID: Grapefruit, grapefruit juice, Seville oranges, and starfruit may increase the plasma concentrations of venetoclax, which is primarily metabolized by the CYP450 3A4 isoenzyme. 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 with potent CYP450 3A4 inhibitors. In a study of 11 previously treated non-Hodgkin lymphoma patients, when the potent CYP450 3A4 inhibitor, P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) inhibitor ketoconazole (400 mg daily for 7 days) was coadministered with venetoclax (50 mg single dose), venetoclax peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 2.3-fold and 6.4-fold, respectively. Physiologically based pharmacokinetic modeling estimates that the moderate CYP450 3A4 inhibitors diltiazem and erythromycin may increase the Cmax and AUC of venetoclax by between 1.4- to 2- fold and 2- to 4.9-fold, respectively, while the weak CYP450 3A4 inhibitors fluoxetine and fluvoxamine appear to have no significant effect on its Cmax or AUC. 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 venetoclax exposure may potentiate the risk of tumor lysis syndrome, particularly at initiation of therapy and during the dosage ramp-up phase, as well as other adverse effects such as diarrhea, nausea, vomiting, neutropenia, anemia, and thrombocytopenia.

MANAGEMENT: Venetoclax should be administered with a meal and water at approximately the same time each day. Patients should avoid consumption of grapefruit products, Seville oranges, and starfruit during treatment with venetoclax.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of lonafarnib. 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 50 mg oral dose of lonafarnib was administered following pretreatment with the potent CYP450 3A4 inhibitor ketoconazole (200 mg once daily for 5 days) in healthy study subjects, lonafarnib peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 270% and 425%, respectively, compared to lonafarnib administered alone. 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 lonafarnib may increase the risk and/or severity of adverse effects such as nausea, vomiting, diarrhea, anorexia, electrolyte disturbances, liver enzyme elevations, myelosuppression, infection, and hypertension.

ADJUST DOSING INTERVAL: Food does not have clinically relevant effects on the oral bioavailability of lonafarnib. When a single 75 mg oral dose of lonafarnib was administered with a high-fat meal (952 calories; approximately 43% from fat) in healthy subjects, lonafarnib Cmax and AUC decreased by 55% and 29%, respectively, compared to administration under fasted conditions. When administered with a low-fat meal (421 calories; approximately 12% from fat), lonafarnib Cmax decreased by 25% and AUC decreased by 21% relative to fasting. However, administration with food may help improve gastrointestinal tolerance to lonafarnib, which may commonly cause nausea, vomiting, diarrhea, and abdominal pain.

MANAGEMENT: Lonafarnib should be administered with the morning and evening meals and an adequate amount of water. Patients should avoid consumption of grapefruit or grapefruit juice and Seville oranges (also known as bitter or sour oranges).during treatment with lonafarnib.