SB-681323 is a p38 MAP-kinase inhibitor that has potential uses in inflammatory conditions such as RA. Previous p38 MAP-kinase inhibitors have been hindered in development by liver toxicity. Methotrexate (common treatment for RA patients) also has potential liver toxicity. This study was an enabling study to determine the safety of co-administration of the two compounds with respect to liver function

Inclusion Criteria:

• Male or female. Females must be of non-child-bearing capacity
• BMI 19 - 30 kg/m2 (inclusive)
• Diagnosis of RA according to the revised 1987 criteria of the American College of Rheumatology (ACR)
• Negative urine drugs of abuse screen, breath alcohol tests, hepatitis B and C, and HIV tests.
• Liver function tests within normal limits
• Must be on a stable dose of methotrexate (2.5 - 25 mg/week) for >8 weeks prior to enrolment and which will not be changed during the course of this study.
• Must be on stable folate supplements for >8 weeks prior to enrolment with normal red cell folate levels at enrollment.

Exclusion Criteria:

• History of alcohol &/or drug abuse
• Abnormal ECGs at screening
• Liver disease, uncontrolled hypertension, diabetes mellitus, psoriasis, history of peptic ulcer disease
• The patient is using glucocorticoid at doses >10mg/day.
• The patient is using sulphasalazine at a dose >3g/day.
• The patient is using hydroxychloroquine at a dose >400mg/day.
• The patient is on treatment regimen of DMARDs other than MTX plus one or both of sulphasalazine and hydrochloroquine (e.g. leflunomide)
• The patient dose of NSAIDs, COX-2 inhibitors or glucocorticoids change at any time during 2 weeks prior to enrolment until the end of the clinical phase of the study