This open-label extension study will allow subjects who have completed either the 3242K1-2000-WW or 3242K1-2001-JA study to receive up to an additional 48 weeks of ATN-103 treatment and will provide data on the long-term safety and tolerability of ATN-103 in subjects with rheumatoid arthritis.

Inclusion Criteria:

• Subjects must have completed study 3242K1-2000-WW or 3242K1-2001-JA and have had no events that, in the opinion of the investigator, would preclude entry or participation in this study.

Exclusion Criteria:

• Pregnant or nursing women.
• Any major illness/condition or evidence of an unstable clinical condition (eg, renal, hepatic, cardiovascular, hematological, gastrointestinal, endocrine, pulmonary, immunologic [eg, Felty syndrome, human immunodeficiency virus (HIV) infection], infectious, neurological, or cerebral psychiatric disease, or evidence of demyelinating disease) that, in the investigator's judgment, will substantially increase the risk associated with the subject's developing an adverse event (AE) or serious adverse event (SAE) during the study, or preclude the evaluation of the subject's response.