The Safety and Efficacy of Brexpiprazole as Adjunctive Therapy in the Treatment of Major Depressive Disorder

Screening phase: It can last up to 28 days and will begin when informed consent is signed. The screening phase will serve the following purposes: 1) To review the inclusion and exclusion criteria; 2) To allow for appropriate washout of prohibited medications; 3) To establish a pretreatment baseline of critical outcome measures. Single-blind Prospective Treatment Phase (Phase A): It lasts 8 weeks; the purpose of the Phase A is to select the MDD subjects with incomplete response to ADT. Randomized Double-blind Treatment Phase (Phase B): It lasts 6 weeks; the purpose of Phase B is to compare the efficacy and safety of Brexpiprazole as adjunctive therapy in the treatment of MDD patients with incomplete response to ADT. Continued Treatment Phase after Phase A (Phase A+): It lasts 6 weeks; the purpose of Phase A+ is to continue treatment for subjects with complete response to ADT and not satisfying the criteria for Phase B. Follow-up Phase: It lasts 4 weeks and only applies to the subjects from Phase B; the purpose of Follow-up Phase is to collect the safety information after the last dose of IMP.