Comparison of drug survival and clinical outcome in patients with ankylosing spondylitis treated with etanercept or adalimumab.

Objective: To compare rates of drug survival and clinical response during 2 years of follow-up in ankylosing spondylitis (AS) patients treated with etanercept or adalimumab in routine care.Method: Biological-naive consecutive AS patients treated with etanercept (n=163) or adalimumab (n=82) were followed. Treatment discontinuation was due to inefficacy, adverse events, loss to follow-up, planning a pregnancy, or uveitis. Disease activity was assessed by the Ankylosing Spondylitis Disease Activity Score using C-reactive protein (ASDAS-CRP). Moderate disease activity was defined as an ASDAS-CRP < 2.1.Results: Twenty-seven patients (32.9%) treated with adalimumab and 30 (18.4%) with etanercept discontinued treatment. Cox regression analysis demonstrated a significant difference in survival rate between discontinuation of the drug in adalimumab patients compared with etanercept patients [hazard ratio (HR) 2.1, 95% confidence interval (CI) 1.3-4.5, p=0.005; corrected for confounding factors: HR 2.5, 95% CI 1.3-4.5, p=0.006]. There was no significant difference at 2years of follow-up between the adalimumab- and the etanercept-treated patients in meansd ASDAS-CRP (1.9 +/- 1.1 and 2.0 +/- 0.9, respectively, p=0.624), and 23 out of 34 (67.6%) compared to 71 out of 117 (60.7%) reached ASDAS-CRP moderate disease activity (odds ratio 0.738, 95% CI 0.329-1.657, p=0.530).Conclusion: No significant difference was found between AS patients treated with etanercept and those treated with adalimumab in mean ASDAS-CRP and reaching ASDAS-CRP minimal disease activity at 2year follow-up. Drug survival rate was higher in etanercept- compared to adalimumab-treated patients. However, this should be interpreted cautiously as the risk of allocation bias cannot be excluded.