Drug Interaction Report

MONITOR: Coadministration with sotorasib may decrease the plasma concentrations of drugs that are substrates of the CYP450 3A4 isoenzyme. The proposed mechanism is increased metabolic clearance due to induction of CYP450 3A4 by sotorasib. When midazolam, a sensitive CYP450 3A4 substrate, was coadministered with sotorasib, midazolam peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by 48% and 53%, respectively. These results suggest moderate induction of CYP450 3A4 by sotorasib.

MANAGEMENT: Caution is advised when sotorasib is used concomitantly with drugs that are substrates of CYP450 3A4, particularly sensitive substrates or those with a narrow therapeutic range. The prescribing information recommends avoiding coadministration of sotorasib with CYP450 3A4 substrates for which minimal concentration changes may lead to therapeutic failure. If coadministration is required, dosage adjustments as well as clinical and laboratory monitoring may be appropriate whenever sotorasib is added to or withdrawn from therapy. The prescribing information for concomitant medications should be consulted to assess the benefits versus risks of coadministration of a moderate CYP450 3A4 inducer like sotorasib and for any dosage adjustments that may be required.

Grapefruit juice may delay the gastrointestinal absorption of clarithromycin but does not appear to affect the overall extent of absorption or inhibit the metabolism of clarithromycin. The mechanism of interaction is unknown but may be related to competition for intestinal CYP450 3A4 and/or absorptive sites. In an open-label, randomized, crossover study consisting of 12 healthy subjects, coadministration with grapefruit juice increased the time to reach peak plasma concentration (Tmax) of both clarithromycin and 14-hydroxyclarithromycin (the active metabolite) by 80% and 104%, respectively, compared to water. Other pharmacokinetic parameters were not significantly altered. This interaction is unlikely to be of clinical significance.

Food does not appear to have a clinically significant effect on the oral bioavailability of sotorasib. When a 960 mg dose of sotorasib was administered to study patients with a high-fat, high-calorie meal (approximately 800 to 1000 calories; 150, 250, and 500 to 600 calories from protein, carbohydrate, and fat, respectively), sotorasib peak plasma concentration (Cmax) did not change while systemic exposure (AUC 0-24 hours) increased by 25% compared to administration under fasted conditions. Sotorasib can be administered with or without food at approximately the same time each day.