The purpose of this study is to determine the efficacy and safety of milsaperidone compared to placebo as adjunctive therapy in patients with Major Depressive Disorder
Male or female patient 18 to 65 years of age, inclusive;
Meets DSM-5-TR criteria for MDD
Currently having an inadequate response to antidepressant therapy as confirmed by the Investigator using the Antidepressant Treatment Response Questionnaire (ATRQ)
Within the patients lifetime, has a confirmed DSM-5-TR psychiatric diagnosis other than MDD
Within 6 months of Screening, has a confirmed DSM-5-TR psychiatric diagnosis other than MDD
Within 12 months of Screening, has had any other psychiatric condition (other than MDD) that has been the main focus of treatment