Evaluation of Efficacy and Safety of Milsaperidone as Adjunctive Therapy in Patients With Major Depressive Disorder

Inclusion Criteria: * 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) Exclusion Criteria: * 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