Drug Interaction Report

MONITOR: Coadministration with potent inducers of CYP450 3A4 may decrease the plasma concentrations of asciminib. Asciminib is primarily metabolized by CYP450 3A4-mediated oxidation and uridine diphosphate glucuronosyl transferase (UGT) 2B7- and 2B17-mediated glucuronidation. When a single 40 mg dose of asciminib was coadministered with rifampin, a potent CYP450 3A4 inducer, asciminib peak plasma concentration (Cmax) increased by 9% while its systemic exposure (AUC) decreased by 14.9%. According to physiologically-based pharmacokinetic (PBPK) models, coadministration of asciminib 80 mg once daily and rifampin is predicted to reduce asciminib Cmax and AUC by 23% and 52%, respectively, while coadministration of asciminib 200 mg twice daily and rifampin is predicted to reduce asciminib Cmax and AUC by 47% and 63%, respectively. In addition, when two or more medications with similar adverse effect profiles are given concurrently, the likelihood of experiencing these adverse reactions may be increased. For example, coadministration with other agents that can prolong the QT interval (e.g., apalutamide, encorafenib, enzalutamide) may result in additive effects and an increased risk of ventricular arrhythmias like torsade de pointes.

MANAGEMENT: Caution is advised when asciminib is prescribed with potent CYP450 3A4 inducers such as carbamazepine, phenobarbital, phenytoin, and St. John's wort. According to some authorities, dose adjustment of asciminib is not required. If the CYP450 3A4 inducer also carries a risk of prolonging the QT interval, then obtaining more frequent electrocardiograms (ECGs) to monitor the QT interval may be advisable. Patients should be counseled to seek immediate medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, syncope, palpitations, irregular heartbeat, and/or shortness of breath. The prescribing information for the concomitant potent CYP450 3A4 inducers should be consulted for specific recommendations.

GENERALLY AVOID: Concurrent use of rifampin in patients who ingest alcohol daily may result in an increased incidence of hepatotoxicity. The increase in hepatotoxicity may be due to an additive risk as both alcohol and rifampin are individually associated with this adverse reaction. However, the exact mechanism has not been established.

ADJUST DOSING INTERVAL: Administration with food may reduce oral rifampin absorption, increasing the risk of therapeutic failure or resistance. In a randomized, four-period crossover phase I study of 14 healthy male and female volunteers, the pharmacokinetics of single dose rifampin 600 mg were evaluated under fasting conditions and with a high-fat meal. Researchers observed that administration of rifampin with a high-fat meal reduced rifampin peak plasma concentration (Cmax) by 36%, nearly doubled the time to reach peak plasma concentration (Tmax) but reduced overall exposure (AUC) by only 6%.

MANAGEMENT: The manufacturer of oral forms of rifampin recommends administration on an empty stomach, 30 minutes before or 2 hours after meals. Patients should be encouraged to avoid alcohol or strictly limit their intake. Patients who use alcohol and rifampin concurrently or have a history of alcohol use disorder may require additional monitoring of their liver function during treatment with rifampin.

ADJUST DOSING INTERVAL: Food may reduce the oral bioavailability of asciminib. When a single 40 mg dose of asciminib was administered with a low-fat meal (400 calories; 25% fat) in healthy volunteers, asciminib peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by 35% and 30%, respectively, compared to asciminib administered in the fasted state. Administration with a high-fat meal (1000 calories; 50% fat) decreased the Cmax and AUC of asciminib by 68% and 62%, respectively.

MANAGEMENT: To ensure adequate asciminib exposures, food consumption should be avoided for at least 2 hours before and 1 hour after taking asciminib.