A Study to Evaluate the Efficacy and Safety of KarXT for the Treatment of Manic Episodes in Bipolar-I Disorder

The purpose of this study is to evaluate the efficacy and safety of KarXT for the treatment of manic episodes in Bipolar-I Disorder

This is a Phase 3, randomized, double-blind, placebo-controlled, multicenter, inpatient study in subjects with bipolar disorder experiencing an acute episode of mania or mania with mixed features. The primary objective of the study is to evaluate the efficacy of KarXT compared to placebo in treating symptoms of mania during a 3-week inpatient period. The duration of the study including screening, the double-blind inpatient treatment period and safety-follow-up is no more than seven weeks.

Inclusion Criteria * Participants must have a primary diagnosis of Bipolar-I disorder established by a comprehensive psychiatric evaluation. * Participants must be experiencing an acute episode or relapse of mania or mania with mixed features (≤ 3 weeks). * Participants must require hospitalization for the acute exacerbation or relapse of mania. * Participants must have all psychotropic medications washed out in no more than 14 days prior to the first dose of the study drug. * Participants must have a Young Mania Rating Scale (YMRS) score of ≥ 20 at Screening and at Baseline. * Participants must have a Clinical Global Impressions-Bipolar (CGI-BP) ≥ 4 at Screening and at Baseline. Exclusion Criteria: * Participants must not have any primary Diagnostic and Statistical Manual of Mental Disorders (5th Edition, Text Revision) (DSM-5-TR) disorder, other than BP-I with mania or mania with mixed features within 12 months before screening, including BP-I with depression (for previous 3 months only), BP-II disorder, borderline personality disorder, major depressive disorder, and primary psychotic disorder, with the exception of mild anxiety disorders. * Participants must not have a primary diagnosis of BP-I with rapid cycling (≥ 4 distinct mood episodes in one year). * Participants must not have a DSM-5-TR diagnosis of moderate to severe substance use disorder (except tobacco use disorder) within the 12 months before screening, or current use as determined by urine toxicology screen or alcohol test. * Participants must not be at risk for suicidal behavior at screening or the baseline visit as determined by the Investigator's clinical assessment and the Columbia-Suicide Severity Rating Scale (C-SSRS). * Participants must not have a history of irritable bowel syndrome (with or without constipation) or serious constipation requiring treatment within the last 6 months. * Participants must not have a history or high risk of urinary retention, gastric retention, or untreated narrow-angle glaucoma. * Other protocol-defined Inclusion/Exclusion criteria apply.