Treat-to-target in spondyloarthritis: implications for clinical trial designs.

Spondyloarthritis (SpA) is a chronic inflammatory disease involving the spine and peripheral joints, and extra-articular manifestations such as uveitis, psoriasis and bowel inflammation. The treatment goals for SpA are maintenance of physical function, control of disease activity and prevention of radiographic progression. However, unlike the well-established treat-to-target (T2T) guidance in rheumatoid arthritis, the T2T concept for treating SpA is still immature. Clinical evidence of T2T in SpA is still lacking. To develop evidence of T2T in SpA, several research agendas need to be accomplished. Firstly, a well-accepted measureable treatment target needs to be defined through expert consensus. Secondly, a T2T treatment algorithm for monitoring disease activity and adjusting therapies needs to be generated. Finally, well-designed comparative clinical trials to compare this T2T strategy with the current standard of treatment should be conducted to demonstrate long-term benefits and risks. In SpA clinical trials, T2T comparative studies should have a clear disease definition for enrollment of patients with ankylosing spondylitis (AS), psoriatic arthritis, axial SpA or non-radiographic axial SpA. Endpoints should be assessment with AS International Working Group criteria for 20% improvement (ASAS20), ASAS40, and the Ankylosing Spondylitis Disease Activity Score (ASDAS) with inactive and moderate disease activity at month 3. Long-term efficacy endpoints such as the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) of radiographic progression and magnetic resonance imaging (MRI) score at 2 years are encouraged. More sensitive assessment tools to detect structural damage and new bone formation, such as low-radiation computerized tomography (CT), are promising.