['Reabsorption of bile acids from the intestine by ileal bile acid transporter is pivotal for the enterohepatic circulation of BAs and sterol homoeostasis.', 'To assess tolerability and study, bile acid metabolism in a phase 1 trial with the selective ileal bile acid transporter inhibitor A4250.', 'A randomised double-blind, single-ascending dose (SAD) and multiple-ascending-dose study consisting of five cohorts comprising 40 individuals with a single administration of A4250 (0.1, 0.3, 1, 3, or 10\xa0mg) or placebo and three cohorts comprising 24 individuals with a 1-week administration of A4250 (1 or 3\xa0mg once daily or 1.5\xa0mg twice daily) or placebo. For the multiple-ascending-dose study, bile acids were measured by HPLC-MS in plasma and faeces, and fibroblast growth factor 19 (FGF19) and 7α-hydroxy-4-cholesten-3-one (C4) were measured in plasma.', 'No serious adverse events occurred and all participants finished the trial per protocol. At the end of the multiple-ascending-dose study, plasma total bile acids and FGF19 decreased by 47% and 76%, respectively, at 3\xa0mg/day (P\xa0<\xa00.01), and by 15% and 16%, respectively, at 1.5\xa0mg twice daily (P\xa0<\xa00.05). Plasma C4 and faecal bile acids increased at all dose regimens, by 555%, 664%, 292% and 338%, 421%, 420%, respectively (P\xa0<\xa00.01-0.05). The primary bile acids cholic and chenodeoxycholic acids constituted the majority of faecal bile acids in the A4250-treated groups.'] Does the ileal bile acid transporter inhibitor A4250 decrease serum bile acids by interrupting the enterohepatic circulation?