Phase 2, Efficacy and Safety Study of ACP-204 in Lewy Body Dementia Psychosis

Inclusion Criteria: * Male or female ≥55 years to \<85 years of age at the Screening visit living in the community or, if permitted by local regulations, in an institutionalized setting * Can provide written informed consent. If the subject is deemed not competent to provide informed consent, the following requirements for consent must be met: 1. The subject's LAR must provide written informed consent. 2. The subject must provide written (if capable) informed assent per local regulations. * Meets either the clinical criteria for Parkinson's disease with dementia as defined by the Movement Disorder Society's Task Force or the revised clinical criteria for probable dementia with Lewy bodies (DLB) by consensus criteria (Fourth consensus report of the DLB Consortium). * Meets the revised criteria for psychosis in major or mild neurocognitive disorder established by the International Psychogeriatrics Association Exclusion Criteria: * Is in hospice, is receiving end-of-life palliative care, or is bedridden * Has psychotic symptoms that are primarily attributable to delirium, substance abuse, or a medical or psychiatric condition (e.g. schizophrenia, bipolar disorder, delusional disorder) other than dementia * Is actively suicidal at Visit 1 (Screening) or Visit 2 (Baseline) * Has a history or current evidence of a serious and/or significant unstable cardiovascular, respiratory, endocrine, gastrointestinal, renal, hepatic, hematologic, immunologic, genitourinary, psychiatric or neurologic (including stroke, chronic seizures, or clinically significant head injury) abnormality or disease or other medical disorder, including cancer or malignancies that could interfere with subject's ability to complete the study or comply with study procedures * Has other clinically significant CNS abnormalities that are most likely contributing to the dementia or findings on MRI or CT