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 major
depressive 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 inadequate
response 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 prior
to receiving study drug.

- Subjects who report an inadequate response to more than three adequate trials of
antidepressant treatments during current depressive episode at a therapeutic dose for
an adequate duration.

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

- Subjects with a clinically significant current Axis II (DSM-IV-TR) diagnosis of
borderline, antisocial, paranoid, schizoid, schizotypal or histrionic personality
disorder.