Drug Interactions between docetaxel and mavorixafor

GENERALLY AVOID: Coadministration with inhibitors of CYP450 3A4, such as grapefruit juice, may significantly increase the plasma concentrations of docetaxel, which is a substrate of the isoenzyme. Current data suggest that consumption of large quantities of grapefruit juice inhibit both intestinal and hepatic CYP450 3A4 due to certain compounds present in grapefruit. In a pharmacokinetic study consisting of 7 cancer patients, mean dose-normalized docetaxel systemic exposure (AUC) increased by 2.2-fold and clearance decreased by 49% when intravenous docetaxel was given at a reduced dosage of 10 mg/m2 in combination with the potent CYP450 3A4 inhibitor ketoconazole (200 mg orally once daily for 3 days) compared to docetaxel administered alone at 100 mg/m2. In addition, a case report of a 52-year-old woman with esophageal squamous cell carcinoma receiving a twice weekly chemotherapy regimen including intravenous docetaxel (40 mg/m2) reported that docetaxel AUC increased by 65% compared with the AUC target of 1.96 mg*h/L and clearance decreased by 63%, with a 71% reduction in the patient's neutrophil count. In the absence of other CYP450 3A4 inhibitors, these effects were attributed to daily consumption of 250 mL of grapefruit juice, which the patient had been consuming for at least 3 months. Two weeks after the patient ceased the grapefruit juice, the docetaxel AUC was closer to the target value and the neutrophil count reduction was less than 35%.

MANAGEMENT: The use of docetaxel in combination with grapefruit and grapefruit juice should generally be avoided. If concomitant use is required, a reduced dosage of docetaxel should be considered, particularly if used with large amounts of grapefruit juice, and therapeutic drug monitoring of docetaxel considered per local treatment protocols. Patients should be closely monitored for the development of docetaxel toxicity such as myelosuppression, stomatitis, neurotoxicity (e.g., paraesthesia, dysesthesia, pain), myalgia, asthenia, fluid retention, nausea, vomiting, and diarrhea.

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.