This trial is conducted in Europe. The aim of this clinical trial is to investigate the safety and tolerability of the drug Anti-IL-20 in subjects with rheumatoid arthritis.

Inclusion Criteria:

• Informed consent obtained before any trial-related activities
• A diagnosis of rheumatoid arthritis made at least 3 months prior to screening
• Active rheumatoid arthritis, characterised by a DAS28 equal or above 3.2
• Methotrexate treatment (stable dose, equal or below 25 mg/week) for at least 4 weeks prior to study start (subjects receiving stable doses of oral corticosteroids, and/or non-steroidal anti-inflammatory drugs and/or acetaminophen and/or opioids according to prescribed recommended doses can be included)
• Male subjects and female subjects of non-child bearing potential

Exclusion Criteria:

• Body mass index (BMI) less than 18.5 or above 35.0 kg/m2
• Subjects with chronic inflammatory autoimmune disease other than rheumatoid arthritis
• History of or current inflammatory joint disease other than rheumatoid arthritis
• Chronic or ongoing infectious disease requiring systemic anti-infectious treatment within 2 weeks prior to study start
• Past or current malignancy (as judged by the investigator)
• Clinically significant cardiac or cardiovascular disease
• Positive for human immunodeficiency virus (HIV), hepatitis or tuberculosis
• Blood donation or blood loss of more than 0.45L within 2 months prior to study start, or longer if required by local regulations
• Breast-feeding women