Obeticholic acid improves hepatic bile acid excretion in patients with primary biliary cholangitis

Abstract Background & Aims Obeticholic acid (OCA) is an agonist of the nuclear bile acid receptor FXR, which regulates hepatic bile acid metabolism. We tested whether OCA treatment would influence hepatic transport of conjugated bile acids in patients with primary biliary cholangitis (PBC) who responded inadequately to treatment with ursodeoxycholic acid (UDCA). Patients & Methods Eight UDCA-treated PBC patients with alkaline phosphatase ≥ 1.5 ULN participated in a double-blind, placebo-controlled study. While continuing on UDCA, the patients were randomized to two 3-month crossover treatment periods with placebo and OCA, in random order, separated by one month washout without study treatment. After each of the two treatment periods, we determined rate constants for transport of conjugated bile acids between blood, hepatocytes, biliary canaliculi and bile ducts by positron emission tomography (PET) of the liver using the conjugated bile acid tracer [N-methyl- 11 C]cholylsarcosine (11C-CSar), and the hepatic blood perfusion using indocyanine green. Results Compared to placebo, OCA increased the hepatic blood perfusion by median 11% (p = 0.045), the unidirectional uptake clearance of 11C-CSar from blood into hepatocytes by median 11% (p = 0.01), and the rate constant for secretion of 11C-CSar from hepatocytes into biliary canaliculi by median 73% (p = 0.03). This resulted in an OCA-induced decrease in hepatocyte residence time of 11C-CSar by median 30% (p = 0.01), from group median 11 min to 8 min. Conclusions This study of UDCA-treated PBC patients showed that, compared to placebo, OCA increased the transport of the conjugated bile acid tracer 11C-CSar, and thus endogenous conjugated bile acids, from hepatocytes into biliary canaliculi. Thereby OCA reduced the time hepatocytes are exposed to potentially cytotoxic bile acids.