Drug Interaction Report

MONITOR: Coadministration with a moderate CYP450 3A4 inducer may decrease the systemic exposure (AUC) of lurbinectedin, which is metabolized by the isoenzyme in vitro. In a clinical drug interaction study, coadministration of bosentan, a moderate CYP450 3A4 inducer, decreased the AUC of total lurbinectedin by 20% and unbound lurbinectedin by 19%. According to the lurbinectedin prescribing information, these changes are not considered clinically relevant.

MANAGEMENT: Clinical and laboratory monitoring is advised whenever a moderate CYP450 3A4 inducer is added to or withdrawn from lurbinectedin therapy.

GENERALLY AVOID: Grapefruit and Seville oranges may increase the plasma concentrations of lurbinectedin. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit and Seville oranges. Inhibition of hepatic CYP450 3A4 may also contribute. The interaction has not been studied with grapefruit or Seville oranges, but pharmacokinetic data are available for potent and moderate CYP450 3A4 inhibitors. In a clinical drug interaction study, coadministration of itraconazole, a potent CYP450 3A4 inhibitor, increased the systemic exposure (AUC) of total lurbinectedin by 2.7-fold and unbound lurbinectedin by 2.4-fold. In a Phase 1 study, coadministration of aprepitant, a moderate CYP450 3A4 inhibitor, decreased lurbinectedin plasma clearance by 33% compared to lurbinectedin alone. In general, the effect of grapefruit and Seville oranges is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice and Seville oranges (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 may increase the incidence and severity of adverse reactions of lurbinectedin, such as myelosuppression and hepatotoxicity.

MANAGEMENT: Patients should avoid consumption of grapefruit, grapefruit juice, and Seville oranges during treatment with lurbinectedin.

ADJUST DOSING INTERVAL: Food increases the systemic exposure to both telotristat ethyl and its active metabolite, telotristat. Following administration of a single 500 mg dose of telotristat ethyl (twice the recommended dose) with a high-fat meal, telotristat ethyl peak plasma concentration (Cmax) and systemic exposure (AUC) were 112% and 264% higher, respectively, compared to administration under fasted conditions. The Cmax and AUC values for telotristat were also increased by 47% and 33%, respectively. The in vitro inhibitory potency of telotristat towards tryptophan hydroxylase has been shown to be approximately 29 times higher than that of the parent drug.

MANAGEMENT: Telotristat ethyl should be administered with food.