Effects of Thiopurine Withdrawal on Vedolizumab-Treated Patients With Ulcerative Colitis: a Randomized Controlled Trial

Background and aims The impact of thiopurine de-escalation whilst on vedolizumab versus continuing thiopurine therapy in ulcerative colitis (UC) is unclear. We aimed to determine the effect of thiopurine withdrawal for patients with UC in remission on vedolizumab. Methods This multi-centre randomized controlled trial recruited UC patients on vedolizumab 300mg IV every 8 weeks and a thiopurine. Patients in steroid-free clinical remission for ≥6 months and endoscopic remission/improvement (Mayo endoscopic subscore[MES]≤1) were randomized 2:1 to withdraw or continue thiopurine. Primary outcome was comparing week 48 vedolizumab trough concentrations. Secondary outcomes were clinical relapse (partial Mayo score≥3 and fecal calprotectin>150μg/g or increase in MES≥1 from baseline), fecal calprotectin remission (<150μg/g), C-reactive protein remission (<5mg/L), centrally-read endoscopic remission (MES=0), histologic remission (Nancy index=0), histo-endoscopic remission and adverse events. Results In total, 62 patients were randomized to continue (n=20) or withdraw (n=42) thiopurine. At week 48, vedolizumab trough concentrations were not significantly different between continue and withdrawal groups (14.7μg/mL [IQR:12.3-18.5μg/mL] versus 15.9μg/mL [IQR:10.1-22.7μg/mL] respectively, P=0.36). The continue group had significantly higher fecal calprotectin remission (95.0% [19/20] versus 71.4% [30/42], P=0.03), histologic remission (80.0% [16/20] versus 48.6% [18/37], P=0.02) and histo-endoscopic remission (75.0% [15/20] versus 32.4% [12/37], P=0.002) than the withdrawal group. Histological activity (HR:15.5 [95%CI:1.6-146.5],P=0.02) and prior anti-TNF exposure (HR:6.5 [95%CI:1.3-33.8],P=0.03) predicted clinical relapse after thiopurine withdrawal. Conclusion Thiopurine withdrawal did not affect vedolizumab trough concentrations. However, it may increase fecal calprotectin, histologic and histo-endoscopic activity. Histological activity and prior anti-TNF exposure may predict disease relapse upon thiopurine withdrawal for patients using vedolizumab for UC; Australian and New Zealand Trial Registry, number ACTRN12618000812291.