de Vries MK, van der Horst-Bruinsma IE, Nurmohamed MT et al.
VU University Medical Center, Amsterdam, The Netherlands.
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Editor’s note: Approximately 30% of patients with ankylosing spondylitis fail to respond to treatment with anti-tumor necrosis factor-
α (anti-TNF-
α) agents. One possible reason for this could be the development of antibodies to these drugs, and this is one reason why methotrexate is given concomitantly with infliximab. However, it is not clear whether anti-etanercept antibodies exert a similar effect. In the present study, the authors used a novel radioimmunoassay to measure levels of anti-etanercept antibodies in 53 consecutive patients who were treated with etanercept for ankylosing spondylitis. Serum etanercept levels were also measured and the assays were carried out after 3 months and 6 months of treatment.