This is a master protocol for 3 independent, seamlessly enrolling, multicenter, randomized, double-blind, placebo-controlled, parallel-group studies in patients with ADP * Substudy 1 (Phase 2) will evaluate efficacy and dose response of ACP-204 30 and 60 mg vs placebo. This substudy will be initiated first. * Substudies 2A and 2B (both: Phase 3) will be confirmatory studies of either both doses (ACP-204 30 and 60 mg, respectively) or a single dose from Part 1 vs placebo. Substudies 2A and 2B will be performed independently of each other and will commence after enrollment of Part 1. All 3 substudies will be analyzed independently of each other. Each substudy individually will consist of a screening period (up to 49 days); a double-blind treatment period (6 weeks); a safety follow-up period (30 days) for patients not rolling over into an open-label extension study; and vital status follow-up (for patients who terminated their substudy early).