A Clinical Study That Will Assess the Effect of SEP-363856 and Prior Antipsychotic (PA) Standard of Care on Glucose and Regulation of Insulin in Patients With Schizophrenia

Inclusion Criteria: (this list is not all inclusive) * Male or female subjects between 18 and 65 years of age, inclusive at time of consent. * Subject meets Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria for a primary diagnosis of schizophrenia as established by clinical interview, using the DSM-5 as a reference and confirmed using the Structured Clinical Interview for DSM-5, Clinical Trials Version \[SCID-CT\]). * Subject must have a CGI-S score ≤ 4 (normal to moderately ill) at Screening * Subject must have a PANSS total score ≤ 80 at Screening and a score of ≤ 4 on the following PANSS items at Screening: P7 (hostility) and G8 (uncooperativeness) * Subjects' antipsychotic medication at screening must have had no dose change (minor dose adjustments for tolerability purposes are permitted) for at least eight weeks prior to the Screening visit. Exclusion Criteria: (this list is not all inclusive) \-- Subject has a DSM-5 diagnosis or presence of symptoms consistent with a DSM-5 diagnosis other than schizophrenia or intellectual disability (IQ \< 70). * Subject has attempted suicide within 12 months prior to Screening. * Subject answers "yes" to "Suicidal Ideation" Items 4 (active suicidal ideation with some intent to act, without specific plan) or Item 5 (active suicidal ideation with specific plan and intent) on the C-SSRS at Screening (ie. in the past 1 month) or at any subsequent C-SSRS assessment prior to dosing (ie, since last visit). * Subject is at risk of harming him/herself or others according to the Investigator's judgment.