A Clinical Trial to Evaluate the Efficacy and Safety of SEP-363856 in Acutely Psychotic People With Schizophrenia, Followed by an Open-label Extension Phase

Inclusion Criteria: 1. Must be fully informed of and understand the objectives, procedures, and possible benefits and risks of the study, and give written informed consent prior to performing any study related activities. If the subject is considered a minor according to local regulations at the time of collection of the informed consent, written consent will be obtained from a legally acceptable representative (guardian) in addition to that obtained from the subject. 2. Male or female between 18 to 65 years of age (inclusive) at the time of consent. 3. Must meet DSM 5 criteria for schizophrenia as established by clinical interview at Screening 4. Must have a CGI S score ≥ 4 (moderately ill) at Screening and Baseline. 5. Must have a PANSS total score ≥ 80 and a PANSS item score ≥ 4 (moderate) on 2 or more of the following PANSS items: delusions (P1), conceptual disorganization (P2), hallucinations (P3), and unusual thought content (G9) at Screening and Baseline. 6. Must have an acute exacerbation of psychotic symptoms (no longer than 2 months prior to providing informed consent for this study). The acute exacerbation should include: a. Marked deterioration of functioning in one or more areas, such as occupational, social, or personal care or hygiene. 7. In the opinion of the Investigator, subjects must be generally healthy based on Screening medical history, physical examination (PE), vital signs, ECG, and clinical laboratory values (hematology, chemistry, and urinalysis). Exclusion Criteria: 1. Have a DSM 5 diagnosis or presence of symptoms consistent with a DSM 5 diagnosis other than schizophrenia. Exclusionary disorders include but are not limited to alcohol use disorder (within past 12 months), substance (other than nicotine or caffeine) use disorder within past 12 months, or lifetime history of significant substance abuse that, in the opinion of the Investigator, may have had a significant and potentially permanent impact on the brain or other body systems, major depressive disorder, bipolar I or II disorder, schizoaffective disorder, obsessive compulsive disorder, and posttraumatic stress disorder. Symptoms of mild to moderate mood dysphoria or anxiety are allowed so long as these symptoms have not been a focus of primary treatment 2. At significant risk of harming self, others, or objects based on Investigator's judgment. 3. Have any clinically significant unstable medical condition or any clinically significant chronic disease that in the opinion of the Investigator, would limit the subject's ability to complete and/or participate in the study. 4. Female subjects who are pregnant or lactating. 5. Have any clinically significant abnormal laboratory value(s) at Screening (hematology, chemistry, and urinalysis) as determined by the Investigator.