Study to Evaluate Adverse Events and Change in Disease Activity in Participants Between 18 to 75 Years of Age Treated With Subcutaneous (SC) Injections of ABBV-154 for Moderately to Severely Active Rheumatoid Arthritis (RA)

Rheumatoid Arthritis (RA) is an inflammatory disease of the joints causing pain, stiffness, swelling and loss of joint function. This study evaluates how safe and effective ABBV-154 is in participants treated for moderately to severely active RA. Adverse events and change in the disease activity will be assessed. ABBV-154 is an investigational drug being evaluated for the treatment of RA. Study doctors place the participants in 1 of 5 treatment groups or arms, each arm receiving a different treatment. There is a 1 in 5 chance that participants will be assigned to placebo. Participants 18-75 years of age with moderate to severe RA will be enrolled. Around 425 participants will be enrolled in the study in approximately 270 sites worldwide. The study is comprised of a 12-week placebo-controlled period, a double-blind long-term extension (LTE) period 1 of 66 weeks, a LTE period 2 of 104 weeks and a follow-up visit 70 days after the last dose of the study drug. In the LTE period 1, participants in the placebo group will be re-randomized to receive ABBV-154 in 2 different doses SC every other week (eow). Other participants will remain on their previous dose and dosing regimen of ABBV-154. There may be higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular visits during the study at a hospital or clinic. The effect of the treatment will be checked by medical assessments, blood tests, checking for side effects and completing questionnaires.