Study to Evaluate Safety and Tolerability of FK949E in Patients With Major Depressive Disorder

Inclusion Criteria: * Diagnosis of major depressive disorder according to the DSM-IV-TR (Text Revision of the Diagnostic and Statistical Manual of Mental Disorders version-4) * Female patients of childbearing potential with a negative serum pregnancy test result and who were willing and able to use a reliable method of birth control during the study * Patients who could understand and comply with the requirements of the study, as judged by the investigator/sub-investigator Exclusion Criteria: * A current or past history of a DSM-IV-TR Axis I disorder other than major depressive disorder within 6 months prior to the study * Diagnosis of a DSM-IV-TR Axis II disorder that was considered to have a major impact on the patient's current psychiatric status * A history of substance or alcohol abuse or dependence excluding caffeine and nicotine * Patients who were unable to abstain from drugs that induce or inhibit the drug-metabolizing enzyme CYP3A4 from 14 days prior to the start of study drug administration and throughout the study period * Pregnant or lactating women * Patients showing evidence or signs of renal or hepatic failure, serious heart disease, cerebrovascular disease, viral hepatitis B or C, or acquired immunodeficiency syndrome (AIDS) (carrier) * A clinical finding that in the opinion of the investigator/sub-investigator could be negatively affected by the study or that would affect the study results (e.g., hypertension, unstable angina) * Conditions that could affect absorption and metabolism of the study medication (e.g., malabsorption syndrome, liver disease) * A current diagnosis of malignant tumor unless in remission for at least 5 years (except basal or squamous cell skin carcinoma) * A current or past diagnosis of transient ischemic attack (TIA) * A history of seizure disorder, except for febrile convulsions * Application of electroconvulsive therapy within 90 days prior to the start of study drug administration * Use of a depot antipsychotic injection and inability to be off the drug for a period of twice the dosing interval prior to the start of study drug administration and throughout the study period * Patients could require psychotherapy (other than supportive psychotherapy) during the study period, unless psychotherapy had been ongoing for a minimum of 90 days prior to the start of study drug administration * A score of ≥ 3 on the HAM-D17 Item (suicide) or a suicide attempt within the past 6 months, and those judged to be at serious suicidal or homicidal risk in the opinion of the investigator/sub-investigator * A current or past history of diabetes mellitus\* or glycated hemoglobin (HbA1c) of ≥ 6.5% at screening within 2 months before the start of study drug administration (\*refer to the guidelines for monitoring blood glucose levels in patients treated with atypical antipsychotics) * A white blood cell count (WBC) of ≤ 3,000/mm3 at screening assessment * Elevation of aspartate aminotransferase (AST) or alanine aminotransferase (ALT) values at screening assessment (grade 2 or higher according to the "Criteria for Classification of the Grade of Adverse Drug Reactions to Pharmaceutical Products" (Pharmaceutical Affairs Bureau Safety Division's Notification No. 80 issued on 29 June 1992)) * A known history of hypersensitivity to quetiapine or to any other component in the FK949E tablets at the time of providing written informed consent * Treatment with quetiapine for depressive symptoms or bipolar disorder (mania) at the time of providing written informed consent * Participation in another clinical study or post-marketing study within 12 weeks prior to the start of study drug administration