Objective Interleukin-13 (IL-13) has been implicated as a key driver of UC. This trial evaluates the efficacy and safety of tralokinumab, an IL-13-neutralising antibody, as add-on therapy in adults with moderate-to-severe UC despite standard treatments.

Design Non-hospitalised adults with UC (total Mayo score ≥6) were randomised to receive tralokinumab 300 mg or placebo subcutaneously every 2 weeks for 12 weeks. The primary end point was the rate of clinical response at week 8. Secondary efficacy end points included clinical remission and mucosal healing rates at week 8 and changes in total Mayo score, total modified Riley score, partial Mayo score and disease activity markers.

Results Clinical response rate was 38% (21/56) for tralokinumab vs 33% (18/55) for placebo (p=0.406). Clinical remission rate was 18% (10/56) vs 6% (3/55) (p=0.033) and mucosal healing rate was 32% (18/56) vs 20% (11/55) (p=0.104) for tralokinumab vs placebo. Changes to week 8 in total Mayo score and total modified Riley score were similar for tralokinumab and placebo (least-squares mean difference between groups: −0.49 (p=0.394) and 0.25 (p=0.449), respectively). Partial Mayo score at week 4 was lower with tralokinumab than placebo (least-squares mean difference between groups: −0.90 (p=0.041)). No consistent patterns were observed for disease activity markers. Tralokinumab had an acceptable safety profile.

Conclusions Add-on therapy with tralokinumab did not significantly improve clinical response. However, the higher clinical remission rate with tralokinumab than placebo suggests that tralokinumab may benefit some patients with UC. Tralokinumab was well tolerated.

Trial registration number ClinicalTrials.gov number: NCT01482884.