While anti-TNF agents have been shown in large randomized controlled trials (RCTs) to be effective at improving the signs and symptoms of RA, and preventing damage as identified on radiography, between 30 and 40 % of patients in clinical trials and real-world practice settings develop an inadequate response to anti-TNF agents, either due to a primary lack of response or secondary treatment failure due to drug resistance or intolerance [3–6]. This evidence concerns the gene TNF and rheumatoid arthritis.