The primary purpose of this study is to assess the efficacy in treating patients with Major Depressive Disorder of one or more doses of Lu AA24530 relative to placebo

According to the World Health Organisation, Major Depressive Disorder is the leading cause of disability and the 4th leading contributor to the global burden of disease. There are unmet medical needs in the treatment of depressive disorders in terms of insufficient effectiveness and unpleasant side-effects of current therapies. The overall prognosis of the disorder is positive for the majority of patients, but as many as 30% of patients will develop a chronic and treatment-resistant depression. In the study, patients with depression are treated for 6 weeks. Assessments of efficacy and safety are taking place every week for the first 4 weeks and again after 6 weeks of treatment.

Inclusion Criteria:

• Major Depressive Episode that has lasted at least 3 months
• Moderate to severe depression

Exclusion Criteria:

• Any current psychiatric disorder established as the principal diagnosis other than MDD as defined in the DSM-IV-TR and as assessed with the Mini-International Neuropsychiatric Interview (MINI)
• Current or past history of: manic or hypomanic episode, schizophrenia or any other psychotic disorder, including major depression with psychotic features, mental retardation, organic mental disorders, or mental disorders due to a general medical condition as defined in the DSM-IV-TR
• Major Depressive Episode that has been unresponsive to two adequate courses of antidepressant treatment, each of at least 6 weeks duration
• Electroconvulsive therapy within 6 months prior to Baseline
• Ongoing formal cognitive or behavioural therapy, systematic psychotherapy, or plans to initiate such therapy during the study
• Clinically significant unstable illness, for example, hepatic or renal insufficiency, or a cardiovascular, pulmonary, gastrointestinal, endocrine, neurological, infectious, neoplastic, or metabolic disturbance
• The patient is pregnant or breast-feeding