A Study to Evaluate the Pharmacokinetics of VI-0521 Subjects With Renal Impairment

Overview

VI-0521, a fixed dose combination of immediate-release (IR) phentermine and controlled-release (CR) topiramate, is in Phase III clinical development as a potential therapy for obesity. In human, both phentermine and topiramate are primarily cleared by renal excretion. The contribution of hepatic metabolism to elimination of phentermine and topiramate is not significant. Obese patients, the proposed indicated population for future treatment with VI-0521, are likely to have renal impairment. Therefore, this study is important in understanding the effect of renal impairment on the pharmacokinetics of topiramate and phentermine in subjects with renal impairment compared to subjects with normal renal function.

This open-label, parallel-group, single dose, non-randomized study will be conducted at multiple sites in the United States in which up to 40 male and female subjects, 19-75 years of age (inclusive), with varying degrees of renal function may be enrolled and dosed to obtain at least 32 evaluable subjects (4 groups, 8 subjects per group). Subjects will report to the study site on the evening before treatment and will remain at the site until the 48-hour PK sample has been drawn (approximately 3 days). All subjects will be fasted overnight for a minimum of 8 hours before drug treatment in the morning. A single oral dose of the combination product VI-0521 (15 mg phentermine and 92 mg topiramate) will be administered with 240 mL of water at hour 0. Standard meals will be provided uniformly to all subjects at approximately 4 and 9 hours after dosing, and an evening snack will be provided approximately 12 - 13 hours after dosing. Blood samples for the determination of phentermine and topiramate concentrations in plasma will be collected at 0 (pre-dose), 1, 3, 4, 5, 6, 7, 8, 9, 10, 12, 16, 24, 36 and 48 hours post dosing. Subjects will be released from the study site following the 48-hour sample but will return to the site for PK sampling at 72, 96, 120, 144, 168 and 192 hours post dose. The severe renal impairment group will be given the option to stay at the site for the duration of the study.