NR1H4 and primary biliary cholangitis: Some of them are very potent FXR-interacting agents with sub-μM or even nM level IC50 values, such as 6-ECDCA/INT-747, the first FXR agonist approved by the U.S. FDA in 2016 for the treatment of primary biliary cholangitis, GW4064, feraxamine, MFA-1 and WAY-362450 (Figure 1), etc. To date, aside from the success of 6-ECDCA/INT-747, only a limited number of these agonists have however been studied in humans.