Phosphonate inhibitors of West Nile virus NS2B/NS3 protease.

West Nile virus (WNV) is a member of the flavivirus genus belonging to the Flaviviridae family. The viral serine protease NS2B/NS3 has been considered an attractive target for the development of anti-WNV agents. Although several NS2B/NS3 protease inhibitors have been described so far, most of them are reversible inhibitors. Herein, we present a series of α-aminoalkylphosphonate diphenyl esters and their peptidyl derivatives as potent inhibitors of the NS2B/NS3 protease. The most potent inhibitor identified was Cbz-Lys-Arg-(4-GuPhe)P (OPh)2 displaying Ki and k2 /Ki values of 0.4 µM and 28 265 M-1 s-1 , respectively, with no significant inhibition of trypsin, cathepsin G, and HAT protease.