A Study is to Assess Efficacy and Safety of Tacrolimus in Active Rheumatoid Arthritis Patients Who Showed Unsuccessful Response to Existing Disease Modifying Antirheumatic Drugs (DMARDs)

Inclusion Criteria: * Subjects who have rheumatoid arthritis for 6 months or longer based on American College of Rheumatology (ACR) diagnostic criteria * Subjects who used more than 1 Disease Modifying Antirheumatic Drug (DMARD) including MTX (methotrexate) for 6 months or longer * Subjects with ESR (erythrocyte sedimentation rate) ≥ 28mm/h or CRP (C-reactive protein)≥ 1.0 mg/dL * Subjects with ≥ 3 swollen joints out of 66 joints assessed * Subjects with ≥ 6 tender joints out of 68 joints assessed Exclusion Criteria: * Pregnant or nursing women, or subjects who plan to become pregnant within 6 months or whose screening test results show pregnancy cannot be ruled out * Subjects with previous experience of tacrolimus (excluding external preparations) * Subjects with renal dysfunction or with serum creatinin \> 1.4 mg/dL at screening * Following subjects with hepatic dysfunction: viral infection, non-viral infection, hepatic cirrhosis, and Serum Glutamic Oxaloacetic Transaminase / Serum Glutamic Pyruvic Transaminase (SGOT/SGPT) exceeding twice the upper limit of normal at screening * Subjects with pancreatitis, uncontrolled diabetes or complication(s) or with HbA1c \> 6.4% at screening * Subjects complicated with hyperkalemia or with serum potassium level \>5.5 mEq/L at screening * Subjects with history of heart disease (ischemic heart disease, arrhythmia requiring treatment, and heart failure), etc or complications * Subjects complicated with severe respiratory disease and infection * Subjects with history of malignant tumor or complication(s) (However, the subjects who are considered to have no risk of recurrence with malignant tumor untreated for 5 years or longer can enter the study. The subjects who succeeded in treatment for basal cell or squamous cell carcinoma of skin can also enter the study.) * Subjects who were treated with other investigational product(s) within 3 months before screening * Other subjects who are considered ineligible for the study by the investigator