Drug Interaction Report

ADJUST DOSE: Coadministration of protein-bound sirolimus intravenous suspension with moderate or weak inhibitors of CYP450 3A4 may increase the systemic exposure to sirolimus, which is primarily metabolized by the isoenzyme and also a substrate of the P-glycoprotein (P-gp) efflux transporter. No formal studies evaluating the drug interaction potential of protein-bound sirolimus have been conducted. However, significant increases in systemic exposure have been reported for oral sirolimus coadministered with moderate dual inhibitors of CYP450 3A4 and P-gp such as diltiazem, erythromycin and verapamil, all of which are also substrates of CYP450 3A4 and P-gp. When 10 mg of sirolimus oral solution was administered with 120 mg of diltiazem in 18 healthy volunteers, sirolimus peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 1.4- and 1.6-fold, respectively. Sirolimus did not affect the pharmacokinetics of either diltiazem or its metabolites, desacetyldiltiazem and desmethyldiltiazem. When sirolimus oral solution 2 mg once a day was coadministered with erythromycin ethylsuccinate 800 mg every 8 hours to steady state in 24 healthy volunteers, sirolimus Cmax and AUC increased by 4.4- and 4.2-fold, respectively, while erythromycin Cmax and AUC increased by 1.6- and 1.7-fold, respectively. Likewise, when sirolimus oral solution 2 mg once a day was coadministered with verapamil 180 mg every 12 hours to steady state in 25 healthy volunteers, sirolimus Cmax and AUC increased by 2.3- and 2.2-fold, respectively, while Cmax and AUC of the pharmacologically active S(-) enantiomer of verapamil both increased by 1.5-fold. Increased exposures to sirolimus may increase the risk of adverse effects such stomatitis, nausea, diarrhea, vomiting, myelosuppression, infections, hypokalemia, hyperglycemia, interstitial lung disease, edema, rash, alopecia, and hemorrhage.

MANAGEMENT: When administered concomitantly with moderate or weak CYP450 3A4 inhibitors, the manufacturer recommends reducing the dosage of protein-bound sirolimus intravenous suspension to 56 mg/m2. Clinical response and toxicities should be closely monitored, and the dosage of protein-bound sirolimus further adjusted as necessary. In addition, patients may also require monitoring for potentially increased effects of concomitant CYP450 3A4 inhibitors, as many are also substrates of CYP450 3A4 and/or P-gp and may be impacted by sirolimus. The prescribing information for concomitant medications should be consulted.

GENERALLY AVOID: Grapefruit products may significantly increase the plasma concentrations and effects of mavorixafor, which is primarily metabolized by the isoenzyme CYP450 3A4. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. A study examining mavorixafor in combination with the strong CYP450 3A4 and P-glycoprotein inhibitor, itraconazole, suggests an increase in mavorixafor's systemic exposure (AUC) of approximately 2-fold. Clinical data with grapefruit products are not available. Pharmacokinetic interactions involving grapefruit are subject to a high degree of interpatient variability and can also be affected by the product and amount consumed; therefore, the extent to which a given patient may be affected is difficult to predict. Additionally, since mavorixafor is associated with concentration-dependent prolongation of the QT interval, increased levels may potentiate the risk of ventricular arrhythmias such as torsade de pointes and sudden death.

ADJUST DOSING INTERVAL: Food may significantly reduce the peak plasma concentration (Cmax) and systemic exposure (AUC) of mavorixafor. When a single-dose of mavorixafor (400 mg) was administered with a high-fat meal (1000 calories, 50% fat) to healthy subjects, the Cmax and AUC decreased by 66% and 55%, respectively. Similarly, when the same dose was given with a low-fat meal (500 calories, 25% fat) to healthy subjects, mavorixafor's Cmax and AUC decreased by 55% and 51%, respectively. Additionally, a single dose of mavorixafor (400 mg) administered with a low-fat meal to healthy subjects following an overnight fast resulted in a 14% higher Cmax and an 18% lower AUC than those obtained from subjects who fasted for an additional 4 hours after the dose.

MANAGEMENT: Mavorixafor should be taken on an empty stomach after an overnight fast, 30 minutes before food. Patients should be advised to avoid eating or drinking products containing grapefruit, as this could increase the risk of experiencing adverse effects from mavorixafor such as QT prolongation.

GENERALLY AVOID: Coadministration of protein-bound sirolimus intravenous suspension with grapefruit juice may increase the systemic exposure to sirolimus. The proposed mechanism is inhibition of CYP450 3A4-mediated metabolism of sirolimus by certain compounds present in grapefruit. However, grapefruit juice primarily inhibits CYP450 3A4-mediated first-pass metabolism in the gut wall and may have limited effects on medications that are not administered orally. No formal studies evaluating the drug interaction potential of protein-bound sirolimus have been conducted. 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.

MANAGEMENT: The manufacturer recommends avoiding grapefruit and grapefruit juice during treatment with protein-bound sirolimus.