Phase IIIB Subcutaneous Missed Dose Study

A Phase IIIb, Multi-Center, Randomized, Withdrawal Study to Evaluate the Immunogenicity and Safety of Subcutaneous Administered Abatacept in Adults With Active Rheumatoid Arthritis

The purpose of the study is to determine whether subcutaneous abatacept administered to patients with rheumatoid arthritis is associated with increased immunogenicity or increased safety events upon withdrawal and reintroduction.

Inclusion Criteria:

• Clinical diagnosis of Rheumatoid Arthritis
• Disease Activity Score (DAS)28-C-Reactive Protein (CRP) score ≥ 3.2 and ≤5.1
• On background methotrexate at least 3 months (≥10mg weekly)
• Must be able to self injection or allow a care giver to do it for them
• Discontinue all Biologics and Disease-Modifying Anti-rheumatic Drugs (DMARDs) except for methotrexate

Exclusion Criteria:

• Participants who had prior exposure to abatacept or CTLA-4 Ig
• Received treatment with rituximab.
• Participants who have received treatment with leflunomide within 1 year of screening
• Participants who have received treatment with immunoadsorption columns (such as Prosorba columns), mycophenolate mofetil (Cellcept®), cyclosporine A or other calcineurin inhibitors, or D-Penicillamine.