Nelson JC, et al. - Researchers performed this study to examine the efficacy of brexpiprazole on the core symptoms of major depressive disorder (MDD) adjunct to antidepressant treatment (ADT), defined using Montgomery-Åsberg Depression Rating Scale (MADRS) items. As an adjunct to ADT, brexpiprazole produced a statistically significant and clinically meaningful improvement in the core symptoms of MDD. Brexpiprazole was believed to exert its effects in MDD by treating the core symptoms of the disease.