Genetic predictors of response to anti-tumor necrosis factor drugs in rheumatoid arthritis

The introduction of anti-tumor necrosis factor (anti-TNF) agents has dramatically improved the outlook for many patients with rheumatoid arthritis (RA). However, 30% of patients fail to respond to treatment for unknown reasons. While research has identified clinical markers of response, including baseline disease activity, disability and the concurrent use of disease modifying therapy, these account for only a small proportion of the variation in treatment response. A number of groups, therefore, have started to investigate genetic markers of response to anti-TNF therapies. To date, many of these studies have been small, underpowered and have largely been restricted to the analysis of candidate genes. The only replicated and validated genetic predictor of anti-TNF response is the 308G> A SNP in the TNF promoter region, but the amount of variation in response accounted for by this marker is modest. It is unknown whether variation in treatment response is determined by several genes each with a small effect size or small numbers of genes with large effect sizes but what is certain is the need for a non-hypothesis driven approach in order to identify further genetic markers of anti-TNF response. The identification of genetic predictors of response to anti-TNF therapies would enable clinicians to tailor treatment of these expensive and potentially harmful agents to patients most likely to benefit from them.