Efficacy and Safety Study of ABT-436 in Major Depressive Disorder

Inclusion Criteria:

- Has a primary Diagnostic and Statistical Manual of Mental Disorders-Fourth
Edition-Text Revision diagnosis of major depressive disorder without psychotic
features

- No current antidepressant treatment within 7 half-lives or 2 weeks, whichever is
longer, prior to Day minus 1.

- Can safely be treated on an outpatient basis.

- A condition of general good physical health.

- Surgically sterile, using a highly effective method of birth control or (if female)
at least 1 year post menopausal.

Exclusion Criteria:

- History of hypersensitivity, intolerance or adverse reaction to escitalopram that led
to discontinuation, or hypersensitivity to citalopram. History of serotonin
syndrome.

- Inadequate response to more than two different antidepressant medications during the
current major depressive episode.

- History of electroconvulsive therapy, vagal nerve stimulation or deep brain
stimulation.

- History of transcranial magnetic stimulation during the current major depressive
episode.

- Psychotherapy that has not been ongoing for at least 3 months prior to Day minus 1.