A Study Comparing Upadacitinib (ABT-494) to Placebo in Adults With Rheumatoid Arthritis on a Stable Dose of Conventional Synthetic Disease-Modifying Antirheumatic Drugs (csDMARDs) Who Have an Inadequate Response to csDMARDs Alone

* Adult male or female, at least 18 years old. * Diagnosis of rheumatoid arthritis (RA) for greater than or equal to 3 months. * Subjects have been receiving conventional synthetic DMARD (csDMARD) therapy for greater than or equal to 3 months and on a stable dose for greater than or equal to 4 weeks prior to the first dose of study drug. The following csDMARDs are allowed: methotrexate (MTX), sulfasalazine, hydroxychloroquine, chloroquine, and leflunomide. * Meets the following minimum disease activity criteria: greater than or equal to 6 swollen joints (based on 66 joint counts) and greater than or equal to 6 tender joints (based on 68 joint counts) at Screening and Baseline Visits. * Subjects with prior exposure to at most one biologic DMARD (bDMARD) may be enrolled (up to 20% of study population) if they have documented evidence of intolerance to bDMARDs or limited exposure (less than 3 months) and have satisfied required washout periods.

* Prior exposure to any Janus kinase (JAK) inhibitor (including but not limited to tofacitinib, baricitinib, and filgotinib). * History of inflammatory joint disease other than RA. History of secondary Sjogren's Syndrome is permitted. * Subjects who are considered inadequate responders to bDMARD therapy as determined by the Investigator.