NR1H4 and primary biliary cholangitis: Obeticholic acid (OCA) is a first-in-class selective FXR agonist with approximately 100-fold greater potency than its natural bile acid homologue14, and is currently approved in combination with ursodeoxycholic acid (UDCA) in adults with an inadequate response to UDCA, or as monotherapy in adults unable to tolerate UDCA for the treatment of primary biliary cholangitis (PBC)15,16.