Drug Interaction Report

Coadministration with inducers of CYP450 3A4 or dual P-glycoprotein (P-gp) and CYP450 3A4 inducers may decrease the plasma concentrations and effects of unconjugated monomethyl auristatin E (MMAE), the cytotoxic component of enfortumab vedotin. Enfortumab vedotin is an antibody-drug conjugate (ADC) that releases MMAE, via proteolytic cleavage. MMAE has been shown in vitro to be primarily metabolized by CYP450 3A4 as well as being a substrate of P-gp. According to physiologically-based pharmacokinetic (PBPK) modeling, concomitant use of enfortumab vedotin with rifampin, a dual P-gp and strong CYP450 3A4 inducer, is predicted to decrease unconjugated MMAE peak plasma concentration (Cmax) by 28% and systemic exposure (AUC) by 53%, with no change in ADC exposure. Some authorities suggest that the PBPK model may underestimate the full impact of rifampin on the Cmax of MMAE. The clinical significance of the interaction is unclear, since the intact ADC is required to bind to Nectin-4, an adhesion protein found on the surface of cells, which allows for internalization and cleavage by lysosomal proteases to enable intracellular delivery of MMAE. It is not known if, and to what extent, enfortumab vedotin may interact with less potent CYP450 3A4 inducers.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations and adverse effects of repotrectinib. According to prescribing information, repotrectinib is primarily metabolized by CYP450 3A4, and is also a substrate of P-gp 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 repotrectinib and grapefruit juice but has been reported for other CYP450 3A4 inhibitors. Drug interaction studies have shown that the administration of repotrectinib with itraconazole, a potent CYP450 3A4 and P-gp inhibitor, increased the peak plasma concentration (Cmax) and systemic exposure (AUC) of repotrectinib by 1.7-fold and 5.9-fold, respectively. 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 repotrectinib may increase the risk of adverse reactions such as dizziness, fatigue, cognitive disorders, ataxia, dysgeusia, peripheral neuropathy, muscular weakness, and dyspnea as well as more serious adverse effects such as interstitial lung disease/pneumonitis, liver transaminase elevations, myalgia with creatinine phosphokinase (CPK) elevation, hyperuricemia, and skeletal fractures.

MANAGEMENT: The manufacturer advises that concomitant use of repotrectinib with grapefruit, grapefruit juice, or supplements that contain grapefruit should be avoided.