The purpose of the study is to assess whether treatment with SR58611A can prevent relapse of depressive symptoms in patients with major depressive disorder. Relapse will be assessed using the MADRS scale.Patients who demonstrate improvement in depressive symptoms at the end of the initial 12-week open-label treatment period with SR58611A are randomized to continue SR58611A or switch to placebo under double blind conditions for up to 52 weeks of additional treatment. The secondary objective is to evaluate the safety of SR58611A in patients with MDD.

Inclusion Criteria:

• Patients diagnosed with Major Depressive Disorder, Recurrent according to DSM-IV-TR criteria Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) and assessed with the Mini International Neuropsychiatric Interview (MINI)
• Total score on the Montgomery and Asberg Depression Rating Scale (MADRS) > 28
• At W12 (V7), patients will be randomized into the double-blind treatment phase if they have MADRS total score < 12

Exclusion Criteria:

• Patients with a significant risk of suicide.
• Patients whose current depressive episode is diagnosed with psychotic features, catatonic features, seasonal pattern or post-partum onset.
• Patients with a current depressive episode secondary to a general medical disorder.
• Patients with a lifetime history or presence of bipolar disorder, psychotic disorder, panic disorder and antisocial personality disorder.
• Patients with severe or unstable concomitant medical conditions
• Patients with clinically significant abnormal laboratory value at screening
• The investigator will evaluate whether there are other reasons why a patient may not participate