Study to Investigate the Efficacy, Safety, and Tolerability of FBL-MTX in Patients With Rheumatoid Arthritis

The goal of this clinical trial is to evaluate the efficacy of FBL-MTX administered by subcutaneous route in Rheumatoid Arthritis patients. Participants will be screened within 28 days prior to treatment period, to confirm that they meet the selection criteria for the study. Treatment period: The treatment period will consist of eight sequential study visits, separated by a 2-week interval. * DMARD-naïve Patients: Patients will be administered an initial dose of FBL-MTX of 1 mg, by SC route. Subsequent doses will be titrated according to clinical response at intervals of 4 weeks, for 12 weeks. Maximum dosage will be 2.5 mg, every 2 weeks. * Patients with an Inadequate Response or Intolerance to Oral MTX: Patients will be administered an initial dose of FBL-MTX 2.5 mg, by SC route. Subsequent doses will be titrated according to clinical response at intervals of 4 weeks, for 12 weeks. Maximum dosage will be 2.5 mg, every two weeks.