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

Inclusion Criteria: * Male or non-pregnant female subjects with moderate-to-severe active RA, age ≥ 18 years, Body Mass Index \> 35 kg/m2. * Diagnosis of RA according to the 2010 classification criteria of the American College of Rheumatology/ European Alliance of Associations for Rheumatology, formerly known as European League Against Rheumatism, (ACR/EULAR), with a Total Score ≥ 6/10. * At least moderately active disease, as defined by DAS28-CRP \>3.2 at Screening and Baseline, including: * Tender joint count (TJC) ≥ 4 * Swollen joint count (SJC) ≥ 4 * C Reactive protein (CRP) ≥ 5 mg/L * Documented history of positive RA factor and/or cyclic citrullinated peptide antibody test. * Chest X-ray performed in the previous 3 months not suggestive of tuberculosis. * If under nonsteroidal anti-inflammatory drugs (NSAIDs), must be able to be on a stable regimen from at least 2 weeks before baseline up to end-of-study. * If under an oral corticosteroid (≤ 10 mg per day of prednisone or equivalent), must be able to be on a stable regimen from at least 4 weeks before baseline up to EoS. * Eligible to start treatment with an immunomodulator. * No evidence of clinically significant active infection. Exclusion Criteria: * Positive Interferon-Gamma Release Assay (IGRA) test result. * Creatinine clearance \< 60 mL/min.