The aims of this study are to assess the efficacy and safety of tacrolimus in patients with active rheumatoid arthritis(RA). EULAR(European League Against Rheumatism) response at week 24 compared to baseline will be evaluated to assess the efficacy of Tacrolimus.

A Phase IV, Open labeled, Multi-Center Trial to Assess the Efficacy and Safety of Tacrolimus(Tacrobell®)in patients with active rheumatoid arthritis(RA).

Inclusion Criteria:

• Male or female aged ≥20years
• Signed and dated informed consent document indicating that the patient
• Women of childbearing potential must have a negative serum or urine pregnancy test at the screening visit. Except in the case of surgically sterile or amenorrhea for one year.
• Female patients must agree to use adequate contraception measures during the period of therapy which should be continued for 4 weeks.
• have RA and meet all of the following criteria; RA occurring ≥ 3months and less than 15 years and diagnosed based on 1987 ACR classification criteria for rheumatoid arthritis; Active RA patients with MTX and among them who has insufficiency response to DMARDs as defined DAS28>3.2 in active RA patient. Insufficiency response is defined despite MTX therapy for > 12 weeks, RA activity≥ more than moderate and confirmable during 12 weeks, sequence of taking MTX >7.5mg/week for more than 6 weeks; ESR≥28mm/h or CRP≥1.0mg/dl; Tender Joint Counts must be more than 6 and Swollen Joint Counts must be more than 3

Exclusion Criteria:

• Inflammatory joint diseases, Systematic inflammatory disease
• Prosthesis and had an event of infected in it.
• Medical history of chronic infection, moderate infection or possibly to life threatening or signs and symptoms of serious infection.
• Patients have received treatment with a live vaccine from baseline within 8 weeks.
• HBsAg positive and hepatitis C virus positive patient.
• Patients have a history of malignancy. (But, carcinoma in situ of the uterine cervix or basal cell carcinoma have been treated is allowed within 5years)
• Patients have cardiovascular disease or associated disease which is not controlled.
• uncontrollable blood sugar(HbA1C ≥8%) or required insulin.
• Patients with a history of operation on index knee joint which could have influence on the result and need to have surgery as determined by investigator.
• At screening, patients have laboratory result as defined by ; white blood cell(WBC) < 3,500/mm3, Absolute Neutrophil Count(ANC) < 1,500/mm3, Hemoglobin < 8.5g/dl, Platelet count(PLT) < 100,000/mm3, Serum creatinine >1.5*upper limit of normal or 2mg/dl, Total bilirubin > 2*upper limit of normal, aspartate aminotransferase(AST) > 2*upper limit of normal, alanine aminotransferase(ALT) > 2*upper limit of normal, alkaline phosphatase(ALP) > 2*upper limit of normal
• Patients on any other clinical trial or experimental treatment in the past 8weeks
• An impossible one who participates in clinical trial by investigator's decision