A Study Comparing Biologics + Methotrexate With Biologics + Tacrolimus in Patients With Rheumatoid Arthritis (RA)

Inclusion Criteria: * Subjects with rheumatoid arthritis (RA) diagnosed by the 2010 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR). * Subjects who have been treated with combination therapy of one of biologic agent (adalimumab, tocilizumab, or abatacept) + methotrexate (MTX) over 2 months prior to Visit 1. * Disease Activity Score (DAS28) erythrocyte sedimentation rate (ESR) ≥ 3.2 at screening and baseline. * Subject agrees not to participate in another interventional study while participating in the present study. Exclusion Criteria: * Subjects with a past history of allergic reaction to Investigational Product or Comparative Drug used in this study. * Subjects who were given tacrolimus (TAC) within three months before participation in this study. * Subjects who have been treated with combination therapy of one of biologic agent (adalimumab, tocilizumab, or abatacept) + MTX exceeds 3 months at Baseline. * Subjects who were already taking 20 mg of MTX at Screening Period. * Subjects who were given the prohibited concomitant medications prior to randomization. * Subjects with a medical history of clinically significant blood, gastrointestinal, endocrine, lung, nerve, or brain diseases at screening. * Subjects with a medical history of clinically significant liver, kidney, or heart diseases: * Liver disease: Aspartate Aminotransferase (AST) and Alanine aminotransferase (ALT) \> 3 × upper limit of normal (ULN) at screening, viral infection, nonviral infection, and liver cirrhosis; * Kidney disease: serum creatinine \> 2.0 mg/dL at screening; * Heart disease: heart failure of ≥ The New York Heart Association class 3, arrhythmia or ischemic heart disease requiring treatment, and QTc interval \> 450 ms on Electrocardiogram (ECG) at screening; * Subjects with a history of uncontrolled diabetes (glycosylated hemoglobin \> 8.5%). * Subjects with hyperkalemia or serum potassium level \> ULN of site reference ranges at screening. * Subjects with severe respiratory disease or chronic generalized infectious disease. * Subject who have a history of chronic infection or severe or life-threatening infection within 24 weeks before the baseline visit. * Subject who are known to be infected by Human Immunodeficiency Virus, Hepatitis B, or Hepatitis C. * Subject has a history of active tuberculosis or latent tuberculosis infection without treatment. * Subject with mental disorder uncontrolled by drugs. * Subject with chronic diarrhea, ulcerative stomatitis, gastric ulcer, or ulcerative colitis. * Subject with genetic disorders including galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabsorption. * Subject with maculopathy, retinal disorders, or clinically significant eye diseases that may lead to visual disorder. * Subject with bone marrow disorder, leukopenia, and blood cell disorder such as severe anemia and thrombocytopenia. * Subject with a history of major surgery within 12-weeks before screening. * Subject who were diagnosed with malignant tumors within 5 years before screening or who need treatment for malignant tumors diagnosed in the past. * Patients with basal cell and squamous cell carcinomas of the skin or carcinoma in situ of the cervix uteri that has been excised and cured, may be included on the study at the discretion of the investigator. * Female subject who is positive for the serum pregnancy test at Visit 1 among a woman of childbearing potential (WOCBP) (menopausal is defined as amenorrhea for at least one year) or not surgically sterile, or is not willing to use appropriate contraception during the study. Female subject trying to become pregnant or is currently pregnant or breast feeding. * Male subject who donates sperm during the treatment period and for at least 30 days whichever is longer after the final study drug administration. * Male subject with a pregnant or breastfeeding partner(s) who do not agree to remain abstinent or use a condom for the duration of the pregnancy, or for the time partner is breastfeeding, throughout the study period and for 30 days whichever is longer after the final study drug administration.