Background and objective: Tumor necrosis factor (TNF) antagonists, including etanercept (a soluble TNF receptor) and infliximab (an anti-TNF monoclonal antibody) are used in the treatment of patients with rheumatoid arthritis (RA). The purpose of this study was to evaluate the effectiveness and safety of 50 mg etanercept weekly in subjects with RA who have failed infliximab therapy.
Methods: This phase 4, multicenter, open-label, single-arm, 16-week observational study enrolled subjects who had experienced primary (failure to achieve an initial response) or secondary (failure to maintain an initial response) infliximab failures. Effectiveness was measured using European League Against Rheumatism (EULAR) and American College of Rheumatology (ACR) response criteria and laboratory assessments were used to evaluate levels of inflammation, lymphotoxin alpha, drug concentrations, and antibodies to infliximab. Safety endpoints included incidence of serious adverse events.
Clinical trial registration: This trial was registered under U.S. National Institutes of Health ClinicalTrials.gov identifier NCT00099554.
Results: At week 16, over half (62%; 95% CI = 55, 69) of all subjects in the trial achieved a good or moderate EULAR response (DAS28) with etanercept. Using ACR criteria, after 16 weeks of etanercept therapy, 45% (95% CI = 38, 52) of all subjects had achieved an ACR20 response. Benefits were noted in tender and swollen joint counts, subject and physician global assessments, joint pain, and the Health Assessment Questionnaire. Outcomes were similar between subjects with primary and secondary infliximab failures. Levels of lymphotoxin alpha did not appear to affect response to etanercept. Potential limitations included the lack of a washout period, short duration of the trial, and the number of subjects who did not receive all doses of etanercept.
Conclusion: In this open-label, uncontrolled study, subjects with moderate to severe RA who failed to respond or who lost their initial response to infliximab safely benefited from receiving etanercept.