The purpose of this study is to investigate the safety and tolerability of the new medication ASK8007, and to study whether it has a beneficial effect on joint inflammation in patients with rheumatoid arthritis.

Inclusion Criteria:

• meet the American Rheumatism Association (ARA) 1987 revised criteria for the classification of RA (also referred to as the American College of Rheumatology [ACR] criteria);
• being treated with an adequate dose (to the discretion of the local physicians) of either MTX or leflunomide (LEF)or sulfasalazine (SS2) for at least 4 months prior to baseline of which the last 6 weeks before baseline were at a stable dose;
• have active poly-arthritis (i.e. active rheumatoid arthritis as defined in detail in the protocol)

Exclusion Criteria:

• have been treated with any registered or non-registered investigational drug in the context of a clinical intervention study during the last 3 months before baseline;
• have been treated with TNFα-blockers within a certain period of time (defined for each medication) before baseline;
• have been treated with any DMARD other than MTX, LEF or SS2 during the last month before baseline;
• documented evidence for the presence of clinically severe, unstable, or uncontrollable renal, hepatic, respiratory, hematological, genitourinary, cardiovascular, endocrine, neurological, psychiatric, or other medical illness which would, in the opinion of the investigator, put the patient at safety risk or mask measures of efficacy.