Study of the Safety and Efficacy of OPC-34712 as Adjunctive Therapy in the Treatment of Adults With Major Depressive Disorder

Inclusion Criteria:

• Male or female subjects between 18 and 65 years of age, with diagnosis of majordepressive disorder, as defined by DSM-IV-TR criteria

• The current depressive episode must be equal to or greater than 8 weeks in duration

• Subjects must report a history for the current depressive episode of an inadequateresponse to at least one and no more than three adequate antidepressant treatments.

Exclusion Criteria:

• Females who are breast-feeding and/or who have a positive pregnancy test result priorto receiving study drug.

• Subjects who report an inadequate response to more than three adequate trials ofantidepressant treatments during current depressive episode at a therapeutic dose foran adequate duration.

• Subjects with a current Axis I (DSM-IV-TR) diagnosis of: Delirium, dementia,amnesticor other cognitive disorder Schizophrenia, schizoaffective disorder, or otherpsychotic disorder Bipolar I or II disorder

• Subjects with a clinically significant current Axis II (DSM-IV-TR) diagnosis ofborderline, antisocial, paranoid, schizoid, schizotypal or histrionic personalitydisorder.