Pharmacokinetics, Pharmacodynamics, and Tolerability of Opicapone in Healthy Chinese and Caucasian Subjects: An Open-Label, Single-Center, Phase 1 Study

Introduction This study evaluated the pharmacokinetics (PK) and pharmacodynamics (PD) of single and multiple doses of opicapone (OPC) in healthy Chinese and Caucasian subjects. Methods In this open-label, single-center, phase 1 study, eligible Chinese subjects received one of three OPC doses (25, 50, or 100 mg), and Caucasian subjects received either 25 or 50 mg of OPC. All subjects were administered a single dose of OPC, whereas subjects in the 50-mg OPC group continued to receive once-daily doses of 50 mg OPC for 10 days. The primary endpoint was to evaluate and compare the plasma concentrations and PK parameters of OPC and its main metabolite, and erythrocyte-soluble catechol-O-methyltransferase (S-COMT) activity in Chinese subjects with that of Caucasian subjects. The secondary endpoint was to evaluate the safety of OPC in Chinese subjects. The estimated results for geometric mean ratios (GMRs) were evaluated with the standard bioequivalence (BE) limits between 80% and 125% to evaluate the ethnic differences. All statistical analyses were performed using SAS version 9.4. Results In total, 70 subjects (45 Chinese, 25 Caucasian) were enrolled; the majority of them were male (85.7%). The plasma exposure of both OPC and BIA 9-1103 increased in an approximately dose-proportional manner in both populations. Maximum S-COMT inhibition ranged from 79% to 95% after a single dose and was about 94% after a 10-day once-daily regimen in both populations. The point estimates of GMRs (Chinese/Caucasian) and 90% CI, except C-max in 25-mg and 50-mg OPC groups, for PK and PD parameters were within 80% to 125%. Furthermore, no new risks or safety concerns associated with OPC were identified, indicating a tolerable safety profile in healthy Chinese subjects. Conclusion Ethnicity had no significant impact on PK and PD parameters after single or multiple doses of OPC, and OPC was safe and tolerable in healthy Chinese subjects.