This is a Phase 3, randomized, double-blind, placebo-controlled, parallel group study to evaluate the safety and efficacy of KarXT in male and female subjects who are aged 55 to 90 years and have mild to severe Alzheimer's Disease (AD) with moderate to severe psychosis related to AD. The primary objective of the study is to evaluate the efficacy of KarXT compared with placebo in the treatment of subjects with psychosis associated with AD as measured by the Neuropsychiatric Inventory-Clinician (NPI-C): Hallucinations and Delusions (H+D) score.