Structure-Modifying Capacity of Anti-Tumour Necrosis Factor-α Therapy in Ankylosing Spondylitis

Spondylarthropathies (SpA) present mainly with spondylitis, pauciarticular peripheral arthritis and enthesopathy. Ankylosing spondylitis (AS) is the prototype disease in this concept. Other entities include reactive arthritis, arthritis in patients with inflammatory bowel disease, some forms of psoriatic arthritis and undifferentiated SpA.

NSAIDs are the classical cornerstone of medical therapy in patients with SpA. The effect of these drugs on disease progression, more specifically the ankylosis, is uncertain. Sulfasalazine can be combined with NSAIDs, particularly if peripheral arthritis symptoms persist. However, this combination therapy is not effective for the spondylitis symptoms. Indeed, AS is one of the rheumatic diseases for which no real disease-modifying antirheumatic treatment is available.

Challenges in chronic autoimmune arthritis have changed dramatically, especially since biotechnological compounds became available. These compounds allow for a specific intervention in the immune cascade underlying the disease. Tumour necrosis factor (TNF)-α antagonists (monoclonal antibodies such as infliximab, or soluble receptors such as etanercept) are the first representative drugs in this category. Open-label studies have shown the efficacy of these new targeted drugs, which has been confirmed by controlled studies, at least in the short term. Improvements in several clinical parameters, function, quality of life, biological parameters, histopathological synovial characteristics and magnetic resonance imaging, have all been observed. As a result of these favourable results, anti-TNFα therapy has been approved for the treatment of AS and should be considered for patients with severe axial symptoms and elevated serological markers of inflammatory activity who have responded inadequately to conventional nonsteroidal therapy.

There is evidence that this new therapeutic approach has a disease- and even structure-modifying effect in SpA. In this context, structure modification should not only be seen as inhibition of bone and cartilage destruction but more broadly as modulation of tissue histology.

Some questions remain unanswered, such as the long-term efficacy and safety of anti-TNFα therapy, the extent of structural benefit and the cost effectiveness. However, despite these concerns, anti-TNFα therapy represents a major therapeutic advancement in the treatment of AS.