Successful Short Term Treatment of Patients with Severe Undifferentiated Spondyloarthritis with the Anti-tumor Necrosis Factor-alpha Fusion Receptor Protein Etanercept

Objective: Anti-tumor necrosis factor-a (TNF-alpha) therapy has been successfully used in patients with active ankylosing spondylitis (AS) and other subtypes of spondyloarthritis (SpA). Treatment options for patients with severe forms of undifferentiated spondyloarthritis (uSpA), a rather frequent SpA subset, are limited. In this open study we examined the efficacy of the TNF-alpha receptor fusion protein etanercept in patients with uSpA.

Methods: Ten patients classified to have uSpA according to modified European Spondylarthropathy Study Group criteria in a severe and active stage of disease were included in the study and received etanercept in a dosage of 25 mg two times a week for 12 weeks, followed by an observation period of 12 weeks. The following outcome variables were used: Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Functional Index (BASFI), pain on a numerical rating scale, disability by the Funktionsfragebogen Hannover (FFbH), a validated questionnaire to assess functional disability, and quality of life (Medical Outcome Study Short Form-36, SF-36). The primary outcome variable was defined as >or= 50% improvement of the BASDAI.

Results: Treatment with etanercept resulted in a >or= 50% regression of disease activity in 60% (95% CI 31-83%) of the patients. The mean BASDAI at baseline of 6.1 (range 3.7-9.2) dropped significantly to 3.5 at Week 12 (0.8-8.7; p = 0.01). Function, spinal pain, peripheral arthritis, enthesitis, quality of life, and acute phase reactants improved similarly. The FFbH improved from 62.8% to 69.7%. After cessation of anti-TNF therapy, 4 out of 8 patients relapsed after an average of 4.5 weeks (range 3-6). Two patients went into longstanding remission. No severe adverse events or major infections were observed.

Conclusion: This study strongly suggests that treatment with etanercept has short term efficacy in patients with active and severe uSpA. Since it is known that 30-50% of uSpA patients develop AS over time, it will be important to study whether this can be prevented by anti-TNF-alpha therapy.