Inclusion Criteria:
* Diagnosed with rheumatoid arthritis (RA) based on either the 1987-revised American College of Rheumatology (ACR) classification criteria or the 2010 American College of Rheumatology/European League against Rheumatism (ACR/EULAR) criteria for ≥ 3 months.
* Subjects must have been receiving oral or parenteral methotrexate (MTX) therapy ≥ 3 months and on a stable prescription of 7.5 to 25 mg/week for at least 4 weeks prior to initiating the study drug. Subjects should also be on a stable dose of folic acid (or equivalent) for at least 4 weeks prior to initiating the study drug. Subjects should continue with their stable doses of MTX and folic acid throughout the study
* Subjects have been treated with 1 or more anti-tumor necrosis factor (TNF) biologics (no maximum cap) for ≥ 3 months but continue to exhibit active RA, or had to discontinue due to intolerability or toxicity. In addition, subjects with prior exposure to non-anti-TNF biologic(s) (no maximum cap) (e.g., abatacept, rituximab, anakinra, or tocilizumab) are allowed.
* Have active RA as defined by the following minimum disease activity criteria: ≥ 6 swollen joints (based on 66 joint counts) at Screening and Baseline, ≥ 6 tender joints (based on 68 joint counts) at Screening and Baseline, high sensitivity C reactive protein (hs-CRP) \> Upper Limit of Normal (ULN) OR positive for both rheumatoid factor and anti-cyclic citrullinated peptide (anti-CCP) antibody.
Exclusion Criteria:
* Prior exposure to Janus Activated Kinase (JAK) inhibitor (e.g. tofacitinib, baricitinib)
* Pregnant or breastfeeding female
* Ongoing or active infection.
