Primary sclerosing cholangitis (PSC) is a chronic cholestatic disease with no effective medical therapy. A homologue of ursodeoxycholic acid, 24-norursodeoxycholic acid (norUDCA), was previously shown to be effective in mouse models of cholestatic and fibrotic liver diseases, prompting a randomized, placebo-controlled trial to evaluate its efficacy and safety for PSC. In the study, conducted in 38 centres from 12 countries, 161 patients with PSC were randomized to receive placebo or one of three doses (500 mg, 1,000 mg or 1,500 mg per day) of norUDCA for 12 weeks. The primary efficacy endpoint was the relative change in serum alkaline phosphatase (ALP) levels between baseline and final visit. A significant dose-dependent decrease in ALP levels was seen in response to all treatments with norUDCA. Importantly, the safety profile of norUDCA was similar to placebo, justifying further trials in PSC.