Background It is unknown which maintenance therapy is the most effective option for patients admitted for an acute severe ulcerative colitis (ASUC) episode responding to intravenous steroids.

Methods We conducted a multicentre, parallel-group, open-label randomised controlled trial among 23 French centres in thiopurine and biologics-naïve adults admitted for ASUC responding to intravenous steroids. Eligible patients were randomly assigned to receive infliximab (IFX) and azathioprine (AZA) with a 7-day steroid tapering scheme (IFX+AZA arm) or AZA and conventional standardised steroid tapering regimen (AZA arm). The primary composite endpoint was treatment failure at week 52, defined as the absence of steroid-free clinical remission, the absence of endoscopic response, the use of a prohibited treatment for relapse, severe adverse event leading to treatment interruption, colectomy or death. Multiple imputation for missing data was performed.

Findings Among the 64 patients randomised (Lichtiger score 13.5±2.0; median age of 34.5 (P25–P75 26.3–50.3) years, median C reactive protein of 29.0 (12.8–96.8) mg/L at baseline): 32 were assigned to the IFX+AZA arm and 32 to the AZA arm. In the ITT population, treatment failure at week 52 was observed in 22/27 (81.5%) in the AZA arm and 16/30 (53.3%) in the IFX+AZA arm (risk ratio 3.85, 95% CI (1.15 to 12.88), p=0.03). 29 adverse events were severe, including 13 disease exacerbations, 6 severe infections without any difference between both arms.

Interpretation Combination therapy with IFX+AZA was more effective at 1 year than AZA alone to avoid treatment failure in patients with ASUC responding to intravenous steroids.

Trial registration number NCT02425852.