To assess the efficacy of etanercept in the treatment of early active nonsteroidal antiinflammatory drug (NSAID)-refractory nonradiographic axial spondyloarthritis (SpA).
The study population consisted of patients who met the Assessment of SpondyloArthritis international Society (ASAS) classification criteria for axial SpA but not the modified New York radiographic criteria for ankylosing spondylitis (as assessed by a radiologist at the central trial site), had a symptom duration of >3 months but <5 years, had a score of ≥4 on the Bath Ankylosing Spondylitis Disease Activity Index, and had been treated unsuccessfully with ≥2 NSAIDs. Patients were randomized to receive etanercept 50 mg/week or placebo and continued background NSAID treatment for 12 weeks (double-blind study); during the subsequent open-label period, all patients received etanercept 50 mg/week. The primary study end point was meeting the ASAS criteria for 40% improvement (ASAS40) at week 12. Magnetic resonance imaging (MRI) of the sacroiliac joints and spine was performed at baseline and week 12.
One hundred six patients were randomized to the etanercept group and 109 to the placebo group. Of the 215 patients, the mean ± SD age at baseline was 32.0 ± 7.8 years, 154 (72%) were HLA-B27 positive, and 174 (81%) had MRI-confirmed sacroiliitis. At 12 weeks, the proportion of patients with improvement according to the ASAS40 was significantly higher in the etanercept group than in the placebo group (34 of 105 [32%] versus 17 of 108 [16%]; P = 0.006). Patients who received etanercept exhibited a greater reduction in MRI-based scores for sacroiliac joint inflammation (-46.9% versus -10.9%; P < 0.001) and spinal inflammation (-45.4% versus -33.4%; P = 0.04) compared with placebo-treated patients at week 12. Post hoc analyses suggested a possible association between higher baseline C-reactive protein levels or MRI sacroiliac joint inflammation scores and higher rates of ASAS40 response to etanercept. At week 24, patients in the placebo group who had switched to etanercept at 12 weeks exhibited improvement similar to that observed in patients who had received etanercept for 24 weeks.
In patients with nonradiographic axial SpA, etanercept treatment was associated with rapid, significant improvement in symptomatic disease activity, function, and systemic and skeletal inflammation over 12 weeks; clinical/functional improvement was sustained over 24 weeks.