The presence or absence of antibodies to infliximab or adalimumab determines the outcome of switching to etanercept.

Objective: The aim of this study was to test the hypothesis that the reason for non-response (caused by immunogenicity or not) to a first tumour necrosis factor (TNF) inhibitor defines whether a second TNF inhibitor will be effective.

Methods: This cohort study consisted of 292 consecutive patients with rheumatoid arthritis (RA), all treated with etanercept. A total of 89 patients (30%) were treated previously with infliximab or adalimumab ('switchers'), and the remaining 203 (70%) were anti-TNF naive. All switchers were divided into two groups: with and without antibodies against the previous biological. Differences in clinical response to etanercept between switchers with and without antibodies and patients who were anti-TNF naive were assessed after 28 weeks of treatment using changes in Disease Activity Score in 28 joints (DAS28).

Results: After 28 weeks of treatment, response to etanercept did not differ between patients who were anti-TNF naive and switchers with anti-drug antibodies (ΔDAS28=2.1 ± 1.3 vs ΔDAS28=2.0 ± 1.3; p = 0.743). In contrast, switchers without anti-drug antibodies had a diminished response to etanercept treatment compared to patients who were TNF naive (ΔDAS28 =1.2±1.3 vs ΔDAS28 = 2.1 ± 1.3; p = 0.001) and switchers with antibodies (ΔDAS28 =1.2±1.3 vs ΔDAS28 = 2.0 ± 1.3; p = 0.017).

Conclusion: Patients with RA with an immunogenic response against a first TNF-blocking agent had a better clinical response to a subsequent TNF blocker compared to patients with RA without anti-drug antibodies. Hence, determining immunogenicity can be helpful in deciding in which patient switching could be beneficial and can be part of a personalised treatment regimen.