Clinical Drug-Drug Interaction Studies to Evaluate the Effects of a P-Glycoprotein Inhibitor, CYP3A Inhibitors, and a CYP3A Inducer on the Pharmacokinetics of Naldemedine in Healthy Subjects

BACKGROUND: Naldemedine is a peripherally acting μ-opioid receptor antagonist that is indicated to treat opioid-induced constipation. OBJECTIVES: To assess the potential for drug-drug interactions between a single oral dose of naldemedine and the oral P-glycoprotein inhibitor cyclosporine, cytochrome P450 (CYP) 3A inhibitors itraconazole and fluconazole, and CYP3A inducer rifampin. METHODS: Three Phase 1, open-label studies were conducted in healthy subjects. In the P-glycoprotein inhibitor study, subjects received naldemedine 0.4 mg alone or coadministered with cyclosporine 600 mg. In the CYP3A inhibitors study, subjects in separate cohorts received naldemedine 0.2 mg alone or with itraconazole or fluconazole. In the CYP3A inducer study, subjects received naldemedine 0.2 mg alone or with rifampin 600 mg. Geometric mean ratios and 90 % confidence intervals were used to evaluate the effects of coadministered drugs on naldemedine maximum plasma concentration (C(max)) and the area under the concentration-time curve (AUC). Safety assessments included occurrence of adverse events (AEs), laboratory parameters, vital signs, and electrocardiography results. RESULTS: A total of 56 subjects were enrolled (n = 14 in each cohort). Cyclosporine increased naldemedine AUC(0–inf) 1.78-fold and C(max) 1.45-fold. Itraconazole and fluconazole increased naldemedine AUC(0–inf) 2.91-fold and 1.90-fold, and C(max) 1.12-fold and 1.38-fold, respectively. Rifampin decreased naldemedine AUC(0–inf) by 83% and C(max) by 38%. Across studies, AEs were generally mild. Laboratory, vital sign, or electrocardiogram assessments produced no clinically significant findings. CONCLUSIONS: Coadministration of naldemedine with a P-glycoprotein inhibitor or a strong/moderate CYP3A inhibitor increases naldemedine exposure; coadministration with a strong CYP3A inducer decreases its exposure. Coadministration of naldemedine with cyclosporine, itraconazole, fluconazole, or rifampin was generally safe and well tolerated.