Methods and analysis The ASTUTE trial is a multicentre, parallel-group, placebo-controlled, pragmatic RCT with a treatment run-in (TRI). In the TRI, eligible participants will receive open-label adalimumab for 16 weeks. At 16 weeks, participants will be assessed, and only those classified as having a therapeutic response will be randomised. The study schema is shown in figure 1. The target population is adults with active or controlled ANIU.