A Study to Investigate the Safety and Efficacy of ABBV-105 Alone or in Combination With Upadacitinib (ABBV-599 Combination) in Participants With Active Rheumatoid Arthritis

* Diagnosis of rheumatoid arthritis (RA) for ≥ 3 months based on the 2010 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) classification criteria for RA * Participant meets the following minimum disease activity criteria: * ≥ 6 swollen joints (based on 66 joint counts) and ≥ 6 tender joints (based on 68 joint counts) at Screening and Baseline Visits * High-sensitivity C-reactive protein (hsCRP) ≥ 3 mg/L (central lab) at Screening Visit * Participants must have been treated for ≥ 3 months with ≥ 1 biologic disease-modifying anti-rheumatic drug (bDMARD) therapy but continue to exhibit active RA or had to discontinue due to intolerability or toxicity, irrespective of treatment duration * Participants must have been receiving conventional synthetic disease-modifying anti-rheumatic drug (csDMARD) therapy ≥ 3 months and on a stable dose for ≥ 4 weeks prior to the first dose of study drug * Participants must have discontinued all bDMARDs prior to the first dose of study drug

\- Participant has prior exposure to any Janus Kinase (JAK) inhibitor for greater than 2 weeks (including but not limited to upadacitinib, tofacitinib, baricitinib, and filgotinib). A washout period of ≥ 30 days is required for any JAK inhibitor prior to the first dose of study drug.