Background: The efficacy and safety of anakinra, a recombinant human interleukin 1 (IL1) receptor antagonist used in rheumatoid arthritis, has been documented in five randomised controlled studies. However, long term post-marketing efficacy data are lacking.
Objective: To evaluate the efficacy, safety, and drug survival of anakinra in clinical practice.
Methods: All patients with rheumatoid arthritis who started anakinra in six hospitals between May 2002 and February 2004 were included in a two year prospective, in part retrospective, cohort study. Efficacy was assessed using the 28 joint disease activity score (DAS28) and the EULAR response criteria. Safety was evaluated using the common toxicity criteria. Drug survival and prognostic factors were analysed using Kaplan-Meier and Cox proportional hazard analyses.
Results: After three months, 55% of the patients (n = 146) showed a response (43% moderate, 12% good). A subset of patients continuing anakinra after 18 months had a sustained clinical response compared with patients who switched to other disease modifying antirheumatic drug treatment (DAS28 improvement, 2.46 v 1.79). Drug survival was 78%, 54%, and 14% after three, six, and 24 months, respectively. The reason for discontinuation was lack of efficacy in 78% and adverse events in 22%. Except for higher drug survival in women (odds ratio = 0.51, 95% confidence interval, 0.27 to 0.97), no prognostic factors were found. Adverse events were reported 206 times in 111 patients, the most common being injection site reactions (36%). Serious adverse events occurred in 12% of the patients, with one classified as related.
Conclusions: The short term efficacy and safety profile of anakinra are comparable to those found in randomised clinical studies. However, the drug survival of anakinra after two years is low, mostly because of lack of efficacy.