- Male or female participants, between 18 and 80 years of age, who have a diagnosis of moderately to severely active Rheumatoid arthritis for at least 6 months as defined by at least six swollen joints (66 joint count) and at least six tender joints (68 joint count) at Screening and Baseline (Day 1), and either an Erythrocyte sedimentation rate of >28 mm/hour OR a C-reactive protein (CRP) level >1.0 mg/dL (normal: <0.4 mg/dL) at Screening. Patients must currently be receiving methotrexate (MTX) therapy.