A Study to Compare the Response to Treatment With Abatacept vs Adalimumab, on Background Methotrexate, in Adults With Early, Seropositive, and Shared Epitope-positive Rheumatoid Arthritis and an Inadequate Response to Methotrexate

Inclusion Criteria:

• Early rheumatoid arthritis (RA), defined as symptoms of RA that started ≤ 12 monthsprior to screening and satisfied the American College of Rheumatology/EuropeanLeague Against Rheumatism (ACR/EULAR) 2010 criteria for the classification of RA atsome point during the 12-month period

• Naïve to any targeted (biologic or nonbiologic) disease-modifying antirheumaticdrugs (DMARDs), conventional synthetic DMARDs other than methotrexate (MTX), orinvestigational therapies for RA

• Treated with MTX for at least 12 weeks, with a stable dose of oral or parenteral MTXfor at least 4 weeks prior to randomization

• Anti-cyclic citrullinated peptide-2 (Anti-CCP-2) test that is > 3× the upper limitof normal and are positive for rheumatoid factor (RF) according to central labtesting during screening

• At least a Disease Activity Score 28-joint count calculated using C-reactive protein (DAS28-CRP) ≥ 3.2 at screening

• At least 3 tender and at least 3 swollen joints at screening and at randomization

Exclusion Criteria:

• Women who are breastfeeding

• Autoimmune disease other than RA (e.g., psoriasis, systemic lupus erythematosus [SLE], vasculitis, seronegative spondyloarthritis, inflammatory bowel disease,Sjogren's syndrome) or currently active fibromyalgia

• History of or current inflammatory joint disease other than RA (e.g., psoriaticarthritis, gout, reactive arthritis, Lyme disease)

• At risk for tuberculosis

• Recent acute infection

• History of chronic or recurrent bacterial infection (e.g., chronic pyelonephritis,osteomyelitis, bronchiectasis)

• History of infection of a joint prosthesis or artificial joint

• History of systemic fungal infections (such as histoplasmosis, blastomycosis, orcoccidiomycosis)

• History of primary immunodeficiency

• Current clinical findings or a history of a demyelinating disorder

• 5 or more joints cannot be assessed for tenderness or swelling

Other protocol-defined inclusion/exclusion criteria apply