A Study to Evaluate the Efficacy and Safety of KarXT for the Treatment of Schizophrenia in Adolescents (EMERGENT TEEN)

Inclusion Criteria: * Diagnosis of schizophrenia as defined by the The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition,Text Revision (DSM-5-TR) criteria, confirmed by the Kiddie Schedule for Affective Disorders and Schizophrenia-Present and Lifetime version (K-SADS-PL) and experiencing symptoms of psychosis at screening (Visit 1). * PANSS total score of at least 70 at screening (Visit 1) and randomization (Visit 2). * Participant has a CGI-S score of ≥ 4 at screening (Visit 1) and randomization (Visit 2). Exclusion Criteria: * Any primary DSM-5-TR disorder other than schizophrenia within 12 months before screening. * History or presence of clinically significant cardiovascular, pulmonary, hepatic impairment, renal, hematologic, GI, endocrine, immunologic, dermatologic, neurologic, or oncologic disease or any other condition that, in the opinion of the investigator, would jeopardize the safety of the participant or the validity of the study results. * All grades of hepatic impairment (mild \[Child-Pugh Class A\], moderate \[Child-Pugh Class B\], and severe \[Child-Pugh Class C\]). Participants with known intellectual disability defined as an IQ less than 70; or, either clinical evidence or known social or school history indicative of intellectual disability. * Any neurological disorder, except for Tourette's Syndrome. * Participants who have either a systolic blood pressure (sBP) or diastolic blood pressure (dBP) meeting criteria for stage 2 HTN, regardless of the presence or absence of symptoms. * Other protocol-defined Inclusion/Exclusion criteria apply.