The primary objective of this study is to compare the efficacy and safety of 3 dose levels of oral ERB-041 administered daily for 12 weeks versus placebo in subjects with active rheumatoid arthritis who have had a suboptimal response to therapy with stable doses of methotrexate (MTX).

Inclusion Criteria:

• Clinical diagnosis of active rheumatoid arthritis for at least 6 months and on a stable dose of methotrexate for at least 12 weeks
• Rheumatoid arthritis onset after 16 years of age

Exclusion Criteria:

• Any significant health problem other than rheumatoid arthritis
• History of male or female reproductive system cancer
• Clinically significant laboratory abnormalities