Drug Interactions between larotrectinib and trabectedin

GENERALLY AVOID: Coadministration with grapefruit juice may increase the plasma concentrations of trabectedin. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit.

GENERALLY AVOID: Coadministration of trabectedin with other agents known to induce hepatotoxicity such as alcohol may potentiate the risk of liver injury. Reversible, acute increases in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) have occurred frequently in patients treated with trabectedin alone or with pegylated liposomal doxorubicin in clinical trials. In one U.S. trial with 378 patients, grade 3 or 4 elevated liver function tests (defined as elevations in ALT, AST, total bilirubin, or alkaline phosphatase) were reported in 35% of patients receiving trabectedin. ALT or AST elevations greater than eight times the upper limit of normal (ULN) occurred in 18% of patients, and drug-induced liver injury (defined as concurrent elevations in ALT or AST more than three times ULN, alkaline phosphatase less than two times ULN, and total bilirubin at least two times ULN) occurred in 1.3% of patients.

MANAGEMENT: Consumption of grapefruit or grapefruit juice during treatment with trabectedin should be avoided. Excessive use of alcohol is also not recommended. Patients should be advised to seek medical attention if they experience potential signs and symptoms of hepatotoxicity such as fever, rash, itching, anorexia, nausea, vomiting, fatigue, malaise, right upper quadrant pain, dark urine, pale stools, and jaundice. Monitoring of alkaline phosphatase, bilirubin, AST, and ALT should occur regularly during trabectedin treatment in accordance with the product labeling, or as often as necessary when clinical symptoms develop. Trabectedin must not be used in patients with elevated bilirubin at the time of initiation of cycle. Elevated liver function tests should be managed with treatment interruption, dosage reduction, or permanent discontinuation depending on the severity and duration of abnormality.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of larotrectinib. The proposed mechanism is inhibition of CYP450 3A4-mediated metabolism of larotrectinib by certain compounds present in grapefruit. When a single 100 mg dose of larotrectinib was coadministered with itraconazole, a potent CYP450 3A4 inhibitor, larotrectinib peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 2.8- and 4.3-fold, respectively, compared to administration of larotrectinib alone. The interaction has not been studied with grapefruit juice. 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 larotrectinib may increase the risk of adverse effects such as neurotoxicity (delirium, dysarthria, dizziness, gait disturbance, paraesthesia, encephalopathy, memory impairment, tremor) and hepatotoxicity (elevations in liver transaminases).

Food does not alter the pharmacokinetics of larotrectinib to a clinically significant extent. When a single 100 mg dose of larotrectinib was administered with a high-fat meal (approximately 900 calories; 58 g carbohydrate, 56 g fat, 43 g protein) in healthy study subjects, larotrectinib peak plasma concentration (Cmax) was reduced by 35% while systemic exposure (AUC) was similar compared to administration in the fasted state.

MANAGEMENT: Larotrectinib may be taken with or without food. Patients should avoid the consumption of grapefruit and grapefruit juice during treatment.