Objective: To demonstrate that administration of 7500 Trichuris suis ova [TSO] every second week over 24 weeks would reduce the intestinal inflammation in moderate ulcerative colitis.

Methods: A single-centre, randomised, double-blinded, placebo-controlled, phase 2b clinical trial of 7500 Trichuris suis ova every 2 weeks for 24 weeks compared with placebo in moderate activity of ulcerative colitis [Mayo score 6-10] were performed. Primary outcome: clinical remission; secondary outcomes: clinical response at 24 weeks, complete corticosteroid-free clinical remission, endoscopic remission, symptomatic remission at 12 and 24 weeks, and partial Mayo score over time.

Results: In all, 119 patients were randomised to Trichuris suis ova [n = 60] or placebo [n = 59]. At Week 24, clinical remission was achieved in 30% of Trichuris suis ova-treated vs 34% of placebo-treated (risk ratio [RR] = 0.89; 95% confidence interval [CI]: 0.52-1.50; p = 0.80, intention to treat). No difference was found in clinical response in any of the clinical response subgroups. However, in patients who did not need treatment with corticosteroids during the trial, a temporary effect of TSO was seen in the analysis of symptomatic remission at Week 12 [p = 0.01] and the partial Mayo score at Week 14 and Week 18 [p < 0.05 and p = 0.02].

Conclusions: Compared with placebo, Trichuris suis ova administration was not superior in achieving clinical remission at Week 24 in ulcerative colitis or in achieving clinical Mayo score reduction, complete corticosteroid-free clinical remission, or endoscopic remission. However, Trichuris suis ova treatment induced symptomatic temporary remission at Week 12.