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

This is an open-label, fixed sequence, multiple dose design. Following screening evaluations, subjects will check-in to the clinical research unit. After confirmation of continuation criteria, subjects will undergo an oral glucose tolerance test (oGTT), mixed meal tolerance test (MMTT) and spirulina breath test (GEBT). After these assessments are completed, subjects will have their prior antipsychotic (PA) or any other medication with psychotropic propensity washed out (dependent on their antipsychotic elimination half-life). Subjects will undergo SEP-363856 titration schedule, followed by the oGTT, MMTT and GEBT tests during the SEP-363856 Stable Dose Period. Subjects will be stabilized on their prior antipsychotic, discharged from the clinical research unit, and return to the unit for the follow-up visit 7 + 2 days after discharge.