2-Amino-5-arylbenzoxazole derivatives as potent inhibitors of fatty acid amide hydrolase (FAAH)

2,5-Disubstituted benzoxazole derivatives were evaluated for their ability to inhibit hFAAH. Structure-activity studies indicated that an isoindoline group at the 2-position of the benzoxazole ring gave rise to particularly potent inhibitors. Further refinement resulted in compounds, such as 50, with low nanomolar potencies against hFAAH. Preliminary biochemical experiments revealed that model benzoxazole FAAH inhibitors inhibited the enzyme in a manner consistent with a reversible mechanism. Additionally, the species dependency of FAAH inhibition was measured. Of the species tested, inhibition of rabbit FAAH, but not rat and guinea pig FAAH, appeared to show close alignment to human FAAH. These results may suggest similarities between the active sites of the FAAH enzyme for these two species, and may also suggest that rabbit could be a viable species with which to conduct preclinical testing with benzoxazole FAAH inhibitors.