Abstract Objective There is increasing evidence that tumor necrosis factor α (TNFα) is centrally involved in the pathogenesis of ankylosing spondylitis (AS) and other spondylarthritides. This study was designed to investigate the efficacy of anti‐TNFα therapy with etanercept, a 75‐kd receptor fusion protein, in active AS. Methods This multicenter trial had 2 phases: an initial placebo‐controlled period of 6 weeks' duration and an observational phase lasting 24 weeks. Thirty patients with active AS were included. They were randomized into 2 groups, which received either etanercept (25 mg twice weekly) (n = 14) or placebo (n = 16) for 6 weeks. Then both groups were treated with etanercept. Nonsteroidal antiinflammatory drug (NSAID) treatment could be continued, but disease‐modifying antirheumatic drugs (DMARDs) and steroids had to be withdrawn prior to the study. All patients received etanercept for a total of 12 weeks and were followed up for at least 24 weeks. The Bath AS Disease Activity Index (BASDAI), Bath AS Functional Index, Bath AS Metrology Index, pain level on a numeric rating scale, quality of life by the Short Form 36, and C‐reactive protein (CRP) level were assessed. The primary outcome parameter was a ≥50% improvement in the BASDAI. Results Treatment with etanercept resulted in at least a 50% regression of disease activity in 57% of these patients at week 6, versus 6% of the placebo‐treated patients ( P = 0.004). After the placebo‐treated patients switched to etanercept, 56% improved. The mean ± SD BASDAI improved from 6.5 ± 1.2 at baseline to 3.5 ± 1.9 at week 6 in the etanercept group, with no improvement in the placebo group ( P = 0.003 between groups). Similarly, pain, function, mobility, and quality of life improved with etanercept but not with placebo at week 6 ( P &lt; 0.05). Mean CRP levels decreased significantly with etanercept but not with placebo ( P = 0.001). There was ongoing improvement in all parameters in both groups until week 12 and week 18, respectively (i.e., throughout the period of etanercept treatment). Disease relapses occurred a mean ± SD of 6.2 ± 3.0 weeks after cessation of etanercept. No severe adverse events, including major infections, were observed during the trial. Conclusion This study shows that on a short‐term basis (3 months), treatment with etanercept is clearly efficacious in patients with active AS who are receiving NSAID therapy but not DMARDs or steroids. After cessation of therapy, almost all patients experienced a relapse within a few weeks. Thus, it seems probable that etanercept must be administered continuously in most AS patients to achieve permanent inhibition of the inflammatory process.

Six‐month results of a double‐blind, placebo‐controlled trial of etanercept treatment in patients with active ankylosing spondylitis