A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Efficacy of ABBV-3373 in Participants With Moderate to Severe Rheumatoid Arthritis (RA)

A Randomized, Double-Blind, Double-Dummy, Active Controlled Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Efficacy of ABBV-3373 in Subjects With Moderate to Severe Rheumatoid Arthritis

This study will assess the safety, tolerability, and efficacy of ABBV-3373 in participants with moderately to severely active rheumatoid arthritis (RA) on background methotrexate (MTX) compared with adalimumab.

This study consists of a 12-week double-blind active-controlled phase and a 12 week double-blind extension period.

In the active-controlled period of the first 12 weeks of treatment, participants are randomized to receive either ABBV-3373 100 mg intravenously (IV) every other week (EOW) or adalimumab 80 mg subcutaneously (SC) EOW according to a 2:1 ratio.

At Week 12, the administration of ABBV-3373 was to stop to assess the durability of the observed clinical effects up to 24 weeks. Participants randomized to ABBV-3373 were to receive placebo injections, whereas participants randomized into the adalimumab arm were to continue their 80 mg dosing.

Inclusion Criteria:

• Participant has the clinical diagnosis of RA for > 3 months based on the 1987 American College of Rheumatology (ACR) classification criteria or 2010 ACR/European League against Rheumatism (EULAR) criteria.
• Participant meets the following disease activity criteria: >= 4 swollen joints (based on 28 joint count) and >= 4 tender joints (based on 28 joint count) at Screening and Baseline visits and disease activity score (28 joints) (DAS28) C-reactive protein (CRP) >= 3.2 at Screening.
• Participant has an incomplete response to methotrexate. Participants must have been on oral or parental MTX therapy >= 3 months and on a stable prescription of 15 to 25 mg/week (or >= 10 mg/week in participants intolerant of MTX at doses >= 15 mg/week) for >= 4 weeks prior to the first dose of study drug. Participant must be expected to be able to continue on stable dose of MTX for the duration of study participation.

Exclusion Criteria:

• Participants previously exposed to adalimumab or other anti-tumor necrosis factor (TNF) biologics.
• Participants previously exposed to non-anti-TNF biologics or targeted synthetic disease-modifying antirheumatic drugs (DMARDs) for RA, with exception of participants exposed for less than 3 months and terminated not due to lack of efficacy or intolerability.