ACP-204 in Adults With Alzheimer's Disease Psychosis

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).

Inclusion Criteria: * Is male or female and ≥55 and ≤95 years of age living in the community or in an institutionalized setting * Meets clinical criteria for possible or probable AD based on the 2011 National Institute on Aging-Alzheimer Association (NIA-AA) criteria * Meets the revised criteria for psychosis in major or mild neurocognitive disorder established by the International Psychogeriatrics Association (IPA) * Has either blood-based biomarker or documented evidence (e.g. positron emission tomography, cerebrospinal fluid biomarker) indicating amyloid plaque deposition and neuropathologic change consistent with AD * Has a prior magnetic resonance imaging or computed tomography scan of the brain that is consistent with the diagnosis of AD * Meets revised criteria for psychosis in major or mild neurocognitive disorder as per International Psychogeriatrics Association * MMSE score ≥6 and ≤24 * Psychotic symptoms for at least 2 months * Lives in a stable place of residence and there are no plans to change living arrangements * Has a designated study partner/caregiver * Able to complete all study visits with a study partner/caregiver * Must be on a stable dose of cholinesterase inhibitor or memantine, if applicable Exclusion Criteria: * Requires treatment with a medication prohibited by the protocol * Is in hospice and receiving end-of-life palliative care, or has become bedridden * Requires skilled nursing care * Psychotic symptoms that are primarily attributable to delirium, substance abuse, or a medical or psychiatric condition other than dementia * Known history of cerebral amyloid angiopathy, epilepsy, central nervous system neoplasm, or unexplained syncope * Atrial fibrillation * Symptomatic orthostatic hypotension * Protocol-defined exclusionary clinical laboratory findings * Treatment with anti-tau therapy or donanemab within 2 months prior to Screening Additional inclusion/exclusion criteria apply. Subjects will be evaluated at screening to ensure that all criteria for study participation are met.