Patients will be male or female, 18 to 60 years of age, inclusive, outpatient or inpatient status, with diagnosis of major depressive episode (single or recurrent) by DSM-IV. The patients should also have HAMD-17 total score ≥ 20,a HAMD-17 Item 1(depressed mood) score ≥ 2 at enrollment in open-label preliminary phase.