Dose-finding Study of New Tolvaptan Formulation in Subjects With ADPKD

Group 1 will have 12 subjects enrolled in a 3-period, randomized, crossover to compare multiple doses of a 90-30 mg split-dose of the tolvaptan IR formulation, a 120 mg once daily (QD) dose of the tolvaptan MR formulation, and, in an incomplete block randomization, multiple doses of either 20 mg QD, 60 mg QD, or 20 mg twice daily (BID) tolvaptan MR formulation. All dose regimens will be administered for 7 days. Placebo doses will be administered in order to mask QD vs BID treatments. Group 2 will have 12 subjects enrolled in a 3-period, randomized, crossover to compare multiple oral doses of the tolvaptan MR formulation administered for 7 days as 20 mg QD, 60 mg QD, and 20 mg BID. Placebo capsules will be administered in order to mask QD vs BID treatments. Subjects will have in-clinic assessments on 12 days to obtain 24-hour PK and PD data. Subjects will visit the clinic from the afternoon of Day -1 through the morning of Day 1. They will return at the end of each dosing period for a similar inpatient period (ie, from the afternoon of Day 6 through the morning of Day 8, from the afternoon of Day 13 through the morning of Day 15, from the afternoon of Day 20 through the morning of Day 22). Except for the first dose of each period and the doses taken in the clinic on the last day of each regimen and the afternoon of Days 6, 13 and 20, all other doses will be taken by the subject as an outpatient.