The primary objective of this study is to evaluate if baseline levels of T cell associated biomarkers predict efficacy of abatacept during 24 weeks of treatment in patients with moderate to severe active Rheumatoid Arthritis (RA) who have had an inadequate response to conventional disease modifying anti-rheumatic drugs (cDMARDs)

Inclusion Criteria:

• Male or non-pregnant, non-nursing female
• Age 18 years or greater
• Body weight less than or equal to 120 kg
• Classification of Rheumatoid Arthritis according to the 1987 ACR criteria or 2010 ACR/EULAR criteria
• Symptoms of Rheumatoid Arthritis present for at least 3 months and less that 10 years prior to Screening.
• Clinical Disease Activity Index (CDAI) greater than or equal to 16, corresponding to moderate to severe disease activity.
• Patients taking oral DMARDs must be on stable doses of DMARDs for at least 4 weeks prior to Abatacept initiation
• Treatment within the past year with either methotrexate, leflunomide, hydroxychloroquine and/or sulfasalazine for greater than or equal to 8 weeks.
• Patients who have received one prior Tumor necrosis factor (TNF) inhibitor must have discontinued etanercept, infliximab, adalimumab, certolizumab, or golimumab for at least 6 months prior to screening.
• Patients taking oral corticosteroids, the dose must be less than or equal to 5mg per day (prednisone or equivalent)
• Females of child bearing potential and males with female partners of child bearing potential may participate in this study only if using a reliable means of contraception

Exclusion Criteria:

• Previous treatment with Abatacept (Orencia)

• Previous treatment with rituximab, tocilizumab, tofacitinib, sarilumab, or anakinra

• Previous treatment with IV immunoglobulin, plasmapheresis, or alkylating agents such as cyclophosphamide

• Intraarticular or parenteral corticosteroids within 4 weeks of screening

• Rheumatic autoimmune disease other than Rheumatoid Arthritis, including Systemic Lupus Erythematosus, primary Sjogren syndrome, spondyloarthritis, systemic sclerosis, dermatomyositis, mixed connective tissue disease, or vasculitis

• Non-rheumatic auto-immune disease including inflammatory bowel disease, psoriasis, multiple sclerosis

• Recurrent or chronic bacterial, viral, fungal, mycobacterial, or other infections including Human immunodeficiency virus (HIV), Hepatitis B, Hepatitis C, latent tuberculosis (TB) (TB not adequately treated)

• Primary or secondary immunodeficiency

• Current, uncontrolled renal, gastrointestinal, endocrine, pulmonary, cardiac, or neurologic disease

• History of malignancy within 10 years prior to screening, except for appropriately treated carcinoma in situ of the cervix or non-melanoma skin carcinoma

• History of alcohol, drug, or chemical abuse within 1 year prior to screening

• Laboratory exclusion criteria at screening including:

  1. estimated glomerular filtration rate (eGFR) <30ml/min
  2. Alanine aminotransferase (ALT) or Aspartate aminotransferase (AST) >1.5 times upper limit of normal

• Major surgery (including joint surgery) within 8 weeks prior to screening or planned major surgery during the study

• Immunization with a live/attenuated vaccine within 4 weeks prior to screening

• Pregnant or nursing women, or women of child bearing potential who plan to become pregnant prior to 14 weeks after the last dose of abatacept treatment

• Patients of reproductive potential not willing to use an effective method of contraception

• Prisoners, or subjects who are compulsory detained

From time of study drug administration to end of study (week 24 or safety follow-up visit, if needed), up to 39 weeks