Withdrawal of medical therapies in axial spondyloarthritis: what would be the optimal trial design?

Remission or low disease activity is achievable in patients with axial spondyloarthritis (SpA), and remission has been defined as one of the main targets in treating patients with axial SpA. However, it is unclear what actions should be taken once remission has occurred. Very little data are available concerning the effect of TNF inhibitors (TNFi) dosage adjustment or on withdrawal strategies in patients with axial SpA and/or in patients with ankylosing spondylitis (AS). Most issues relating to withdrawal of treatment in patients who are in remission cannot be addressed with traditional randomised placebo-controlled trials (RCT). Facing these challenges, there is a need for conducting trials with an innovative trial design to reflect real-life practice. Possible strategies upon remission include continuation, dose reduction or withdrawal of the effective therapy. Future scenarios should recognise heterogeneity in patients with axial SpA, which makes it questionable whether different trial designs will be applicable for the whole group of axial SpA. Several questions should be addressed before conducting a trial to study remission in patients with axial SpA: definition of remission (clinical and/or imaging remission), duration of remission as a defining inclusion criterion, predictors of remission, definition of subgroups (e.g. TNFi naïve patients or patients who will most likely remain in remission), when to restart and finally dose-adjustment after restart of the therapy.