The purpose of this research is to find out how effective and safe SB-681323 will be in the treatment of RA when it is added to standard anti-rheumatic treatments.

Inclusion Criteria:

• Females cannot be pregnant or lactating.
• Must use defined contraceptive methods if of child-bearing potential.
• BMI range: 18.5-35.0 kg/m2.
• Diagnosis of RA (rheumatoid arthritis) according to revised 1987 American College of Rheumatology (ACR) criteria.
• If other RA-medication is used: Disease-Modifying Anti-Rheumatic Drug (DMARDS) must be stable for at least 8 weeks before first trial visit.
• If other oral anti-RA therapies are used, these must have been stable at least 4 weeks before first trial visit.
• If Methotrexate medication is used as RA-therapy, Folate supplement must be taken with stable red cell folate levels.
• Must give informed consent.
• Must abstain from alcohol during the trial participation.

Exclusion Criteria:

• Non-responder on biological RA treatment.
• Has a positive alcohol screen.
• Any history of liver disease.
• Positive Hepatitis B surface antigen or Hepatitis C antibody result within 3 months of screening.
• Have any significant disease that places the subject at unacceptable risk as a participant in this trial.
• Acute infection.
• History of active tuberculosis.
• History of repeated or chronic infection.
• History of malignancy.
• History of HIV or other immunosuppressive diseases.
• Participated in a clinical trial within the last 3 months for non-biological therapies and 6 months for biological therapies.
• Uncontrolled diabetes or psoriasis.