Background: Bile acid diarrhoea is an underdiagnosed disease estimated to affect 1-2% of the general population. Case reports indicate that the glucagon-like peptide 1 receptor agonist liraglutide might be an effective treatment for bile acid diarrhoea. We aimed to investigate the safety and efficacy of liraglutide for the treatment of bile acid diarrhoea.

Methods: We conducted a randomised, double-blind, active-comparator, double-dummy, non-inferiority clinical trial at the Center for Clinical Metabolic Research at Copenhagen University Hospital-Herlev and Gentofte, Hellerup, Denmark. Patients aged 18-75 years with 75selenium-homotaurocholic acid test (SeHCAT)-verified moderate-to-severe primary bile acid diarrhoea were randomly assigned (1:1) to receive liraglutide (one daily subcutaneous injection uptitrated from 0·6-1·8 mg per day over 3 weeks) or colesevelam (three capsules of 625 mg twice daily), the standard of care, for 6 weeks following one run-in week with no treatment. The primary endpoint was the proportion of participants experiencing a reduction in daily stool frequency of 25% or greater after 6 weeks. Data from all participants were included in the analysis of the primary outcome. The non-inferiority limit was set to 15% in favour of colesevelam. This trial is registered with EudraCT (2018-003575-34) and is completed.

Findings: Between April 1, 2019, and Jan 31, 2021, 52 patients were enrolled; 26 were assigned to liraglutide and 26 to colesevelam. 20 (77%) of 26 participants on liraglutide and 13 (50%) of 26 on colesevelam experienced a 25% or greater reduction in stool frequency, corresponding to a significant risk difference of -27% in favour of liraglutide (one-sided 95% CI -100 to -6). Liraglutide was therefore superior to colesevelam in reducing daily stool frequency. Mild nausea with a duration of 10-21 days was reported by six participants in the liraglutide group and by one participant in the colesevelam group. No other adverse events were reported.

Interpretation: The superiority of liraglutide compared with colesevelam in reducing stool frequency suggests consideration of liraglutide as a potential new treatment modality for bile acid diarrhoea, although larger confirmatory trials powered for superiority are warranted.

Funding: Novo Nordisk, Novo Nordisk Foundation, Foundation for the Advancement of Medical Science under The A.P. Møller and Chastine Mc-Kinney Møller Foundation.