Different profile of efficacy of thiopurines in ulcerative colitis and Crohn's disease

Background: Thiopurines are effective drugs in treating ulcerative colitis (UC) and Crohn's disease (CD) even if studies that specifically investigate these drugs' profile of efficacy in UC compared with CD are scarce. Our aim was to compare the profile of efficacy of thiopurines in patients with UC and CD. Methods: We perfomed a longitudinal observational study evaluating steroid-free clinical remission (CR) and mucosal healing (MH) in all patients with UC and CD who would complete 2 years of maintenance treatment with thiopurines. In patients with UC, CR and MH were assessed before starting treatment and 2 years later using the Mayo score (CR Mayo score <2; MH Mayo subscore ≤1). In patients with CD, CR and MH were assessed at the same time points using the Crohn's disease activity index (CR Crohn's disease activity index < 150) and the Simplified Endoscopic Score for Crohn's Disease (MH Simplified Endoscopic Score for Crohn's Disease < 2). The efficacy of thiopurines was assessed through intention-to-treat and per-protocol analyses. Results: The study included 205 steroid-dependent patients (104 UC; 101 CD), 140 of whom (70 UC; 70 CD) completed the 2-year observation period. Steroid-free CR was recorded in 43 patients with UC and 37 with CD (intention-to-treat: 41% versus 36%; P 0.6; per-protocol: 61% versus 53%; P 0.4); MH was obtained in 38 patients with UC and 17 with CD (intention-to-treat: 36% versus 16%; P < 0.01; odds ratio, 2.9; per-protocol: 54% versus 25%; P < 0.01; odds ratio, 3.7). Conclusions: Thiopurines are effective in maintaining steroid-free CR in both UC and CD although they show a better profile of efficacy in terms of MH in cases of UC.