Drug Interaction Report

MONITOR: Coadministration with olutasidenib may decrease the plasma concentrations of drugs that are substrates of CYP450 3A4. Based on in vitro studies, olutasidenib may increase clearance via induction of CYP450 3A4, resulting in decreased plasma concentrations of agents that are metabolized by the isoenzyme. Clinical and pharmacokinetic data are currently lacking.

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is required, clinical and laboratory monitoring may be appropriate whenever olutasidenib is added to or withdrawn from therapy.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

GENERALLY AVOID: Coadministration with grapefruit or grapefruit juice may increase the plasma concentrations of rilpivirine. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruit. In 15 study subjects given rilpivirine (150 mg once daily) with the potent CYP450 3A4 inhibitor ketoconazole (400 mg once daily), mean rilpivirine peak plasma concentration (Cmax), systemic exposure (AUC) and trough plasma concentration (Cmin) were increased by 30%, 49% and 76%, respectively. In 16 study subjects given a single 500 mg dose of a less potent CYP450 3A4 inhibitor chlorzoxazone two hours after rilpivirine (150 mg once daily), mean rilpivirine Cmax, AUC, and Cmin were increased by 17%, 25%, and 18%, respectively. Because grapefruit juice inhibits primarily intestinal rather than hepatic CYP450 3A4, the magnitude of interaction is greatest for those drugs that undergo significant presystemic metabolism by CYP450 3A4 (i.e., drugs with low oral bioavailability). 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. Pharmacokinetic interactions involving grapefruit juice are also subject to a high degree of interpatient variability, thus the extent to which a given patient may be affected is difficult to predict.

ADJUST DOSING INTERVAL: The administration of rilpivirine in a fasting state may decrease its oral absorption. Under fasted conditions, the systemic exposure to rilpivirine was 40% lower compared to normal or high-fat caloric meals (533 to 928 Kcal). The systemic exposure was 50% lower when rilpivirine was taken with a protein-rich nutritional beverage.

MANAGEMENT: Coadministration of grapefruit or grapefruit juice with rilpivirine should preferably be avoided. For optimal absorption, it is recommended to take rilpivirine on a regular schedule with a meal.

ADJUST DOSING INTERVAL: Coadministration with a high-fat meal may increase the plasma concentrations of olutasidenib. According to the product labeling, administration of a single 150 mg dose with a high-fat meal (approximately 800 to 1000 calories, with approximately 50% of those calories from fat) increased olutasidenib peak plasma concentration (Cmax) and systemic exposure (AUC) by 191% and 83%, respectively, in healthy subjects.

MANAGEMENT: Olutasidenib should be administered at about the same time each day, on an empty stomach at least 1 hour before or 2 hours after a meal.

Food enhances the oral absorption and bioavailability of tenofovir, the active entity of tenofovir disoproxil fumarate. According to the product labeling, administration of the drug following a high-fat meal increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of tenofovir by approximately 14% and 40%, respectively, compared to administration in the fasting state. However, administration with a light meal did not significantly affect the pharmacokinetics of tenofovir compared to administration in the fasting state. Food delays the time to reach tenofovir Cmax by approximately 1 hour. Tenofovir disoproxil fumarate may be administered without regard to meals.