Phenylimidazoles as potent and selective inhibitors of coagulation factor XIa with in vivo antithrombotic activity.

Novel inhibitors of FXIa containing an (S)-2-phenyl-1-(4-phenyl-1H-imidazol-2-yl)ethanamine core have been optimized to provide compound 16b, a potent, reversible inhibitor of FXIa (K-i = 0.3 nM) having in vivo antithrombotic efficacy in the rabbit AV-shunt thrombosis model (ID50 = 0.6 mg/kg + 1 mg kg(-1) h(-1)). Initial analog selection was informed by molecular modeling using compounds 11a and 11h overlaid onto the X-ray crystal structure of tetrahydroquinoline 3 complexed to FXIa. Further optimization was achieved by specific modifications derived from careful analysis of the X-ray crystal structure of the FXIa/11h complex. Compound 16b was well tolerated and enabled extensive pharmacologic evaluation of the FXIa mechanism up to the ID90 for thrombus inhibition.