A Study of Brexpiprazole in Patients With Major Depressive Disorder

Inclusion Criteria: * Outpatients, or inpatients at the time of informed consent whose treatment status can be successfully shifted to outpatient status before enrollment in the antidepressant treatment period * Male and female patients ≥ 20 to \< 65 years of age (at the time of informed consent) * Patients who have a level of comprehension sufficient to allow them to give written informed consent to all of the observation/examination/evaluation items specified in the protocol, and who can understand the contents of the trial * Patients with a DSM-5 classification-based diagnosis of "major depressive disorder, single episode" or "major depressive disorder, recurrent episode," and whose current episode has persisted for at least 8 weeks Exclusion Criteria: * Women who are pregnant or breastfeeding or who have positive pregnancy test (urine) results at screening * Sexually active male subjects or sexually active female subjects of childbearing potential, who will not agree to practice 2 different methods of birth control or to remain abstinent during the trial and for 30 days after the final IMP administration. For birth control, 2 of the following methods must be used: vasectomy, tubal ligation, vaginal diaphragm, intra-uterine contraceptive device (IUD), oral contraceptives, or condom with spermicide. * Patients with a treatment history showing that all antidepressants (including those not used for the current major depressive episode) cannot be tolerated * Patients with a history of electroconvulsive therapy * Patients with a diagnosis of any of the following diseases according to DSM-5 1. Neurocognitive disorders 2. Schizophrenia spectrum and other psychotic disorders 3. Bipolar and related disorders 4. Feeding and eating disorders 5. Obsessive-compulsive disorder 6. Panic disorder 7. Posttraumatic stress disorder