Drug Interaction Report

MONITOR: Coadministration with inhibitors of P-glycoprotein (P-gp) and/or breast cancer resistance protein (BCRP) may increase the plasma concentrations of talazoparib, which has been shown in vitro to be a substrate of both efflux membrane transporters. In clinical studies, administration of talazoparib with the P-gp inhibitors amiodarone, carvedilol, clarithromycin, itraconazole, and verapamil resulted in an approximate 45% increase in talazoparib exposure and an increase in the rate of talazoparib dose reduction. In contrast, coadministration with the P-gp inhibitors azithromycin, atorvastatin, diltiazem, felodipine, fluvoxamine, and quercetin increased talazoparib exposure by just 8%. The effect of BCRP inhibitors on the pharmacokinetics of talazoparib has not been studied.

MANAGEMENT: No initial dosage adjustment is recommended by the manufacturer when talazoparib is coadministered with inhibitors of BCRP and/or P-gp other than amiodarone, carvedilol, clarithromycin, itraconazole, or verapamil. However, patients should be closely monitored for adverse effects such as myelosuppression and myelodysplastic syndrome/acute myeloid leukemia, and dosage adjustments made or treatment withheld as needed in accordance with the product labeling.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of futibatinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. 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. Increased exposure to futibatinib may increase the risk of adverse effects such as retinal pigment epithelial detachment, dry eye/corneal keratitis, pyrexia, hyperphosphatemia and soft tissue mineralization, palmar-plantar erythrodysesthesia syndrome, fatigue, nail toxicity, urinary tract infection, constipation, diarrhea, dry mouth, increased liver function tests (ALT and AST), stomatitis, abdominal pain, ascites, bile duct obstruction, and musculoskeletal pain.

MANAGEMENT: Patients should be advised to avoid consumption of grapefruit or grapefruit juice during treatment with futibatinib.