Design, synthesis, and evaluation of non-steroidal farnesoid X receptor (FXR) antagonist

A series of substituted-isoxazole derivatives was prepared as candidate farnesoid X receptor (FXR) antagonists, based on our previously proposed ligand superfamily concept. Structure-activity relationship studies indicated that the shape and the structural bulkiness of the substituent at the 5-position of the isoxazole ring affected FXR-antagonistic activity. Compounds 15 g (5-substituent: 2-naphthyl) and 15 h (5-substituent: 4-biphenyl) were identified as potent antagonists with higher selectivity for FXR over Progesterone Receptor than the naturally occurring FXR antagonist GS. The 5-substituent is also a critical determinant of the characteristic corepressor recruitment profile of this class of FXR antagonists, though distinct mechanisms appear to be involved: 15 h stabilizes the corepressor-nuclear receptor interaction, while 15 g inhibits coactivator recruitment.