TNF and rheumatoid arthritis: The efficacy and safety of abatacept, a selective T-cell co-stimulation modulator, has been demonstrated in patients with active rheumatoid arthritis (RA) and an inadequate response to methotrexate1 and/or anti-tumour necrosis factor (TNF) agents.2 In the Abatacept Trial in Treatment of Anti-TNF Inadequate Responders (ATTAIN) trial, patients with an inadequate response to anti-TNF agents were required to undergo a washout of their anti-TNF therapy before initiating abatacept.