Obeticholic Acid in Bile Acid Diarrhoea

Bile acid diarrhoea (BAD) is an under-recognised but common condition of chronic watery diarrhoea. BAD may be secondary to ileal disease affecting the reabsorption and the enterohepatic circulation of bile acids (bile acid malabsorption) or can be an idiopathic, primary BAD (PBAD). In work published in 2009, we described a new mechanism to explain this syndrome of primary BAD. Blood levels of the hormone fibroblast growth factor 19 (FGF19) are reduced in primary and secondary BAD, producing impaired feedback inhibition of bile acid synthesis, leading to excess faecal bile acids, which then produce diarrhoea by stimulating colonic secretion. FGF19 is synthesised in the ileum and we have shown transcription is markedly induced by farnesoid X receptor(FXR) agonists such as chenodeoxycholic acid, an abundant natural bile acid. More potent FXR agonists are logical diagnostic and therapeutic agents for this condition, and obeticholic acid (OCA), which is 100x more potent than chenodeoxycholic acid, has recently been developed. It has been used in phase II studies in primary biliary cirrhosis and in non-alcoholic steatohepatitis where a relatively common side-effect was constipation. We aim to investigate the effects of OCA in patients with primary and secondary BAD to determine whether FGF19 is able to be stimulated in these conditions. We will compare these responses to those in control patients with chronic diarrhoea but without evidence of BAD. It is possible in BAD that the defect in FGF19 levels is due to an inability to respond to FXR stimulation (particularly likely in secondary BAD after ileal resection). Patients with primary BAD may be able to respond and benefit from an increase in FGF19 levels. This study aims to obtain pilot data on the effects of OCA on FGF19, other markers of bile acid metabolism and patient symptoms including diarrhoea. These are early phase II, proof of concept studies.