Study of Safety & Tolerability of OPC-34712 as Adjunctive Therapy in Treatment of Adult Patients With Major Depressive Disorder

Inclusion Criteria:

- Male or female subjects between 18 and 65 years of age, with a diagnosis of a single
or recurrent, non-psychotic episode of major depressive disorder, as defined by
DSM-IV-TR criteria and confirmed by the Mini International Neuropsychiatric Interview
(M.I.N.I.) which is equal to or greater than 8 weeks in duration.

- Subjects must currently be taking allowable antidepressant therapy at an adequate
dose for a minimum of six weeks by the end of the screening period (ie at the time of
the Baseline visit).

- Subjects must report a history for the current depressive episode of an inadequate
response to at least one and no more than four 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, eating disorder (including anorexia
nervosa or bulimia), obsessive compulsive disorder, panic disorder, post-traumatic
stress disorder.

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