TNF and rheumatoid arthritis: To date, three anti-tumour necrosis factor (TNF) biological agents have been approved for the treatment of rheumatoid arthritis (RA), namely etanercept.1 Collectively these drugs have become one of the most effective methods of treating RA, with nearly half of all treated patients achieving an American College of Rheumatology 20% (ACR20) improvement level or higher.