CONFIGURATIONS OF DIASTEREOMERIC HYDROXYETHYLENE ISOSTERES STRONGLY AFFECT BIOLOGICAL-ACTIVITIES OF A SERIES OF SPECIFIC INHIBITORS OF HUMAN-IMMUNODEFICIENCY-VIRUS PROTEINASE

Human immunodeficiency virus (HIV) proteinase (PR) represents an impor tant target for antiviral chemotherapy. We present an analysis of inhi bitory activities of a series of pseudopeptide inhibitors of HIV-1 PR. All inhibitors were N-protected tetrapeptides with the scissile bond replaced by a nonhydrolysable hydroxyethylene or hydroxyethylamine iso stere. To elucidate subtle structural requirements of the PR binding c left, we synthesised inhibitors with four combinations of configuratio ns at the asymmetric carbons of the isostere. Compounds were tested in vitro using purified recombinant enzyme and a chromogenic peptide sub strate. The differences in inhibition constants between individual dia stereoisomers reached three orders of magnitude. The most active hydro xyethylene-containing inhibitor possessed the 2R,4S,5S configuration a t the isostere. Inhibitor activity was also tested in mammalian cell c ulture by analysing reduction of viral polyprotein processing and viru s infectivity. The results obtained in tissue culture were generally i n agreement with the in vitro data, giving a similar order of potency for the individual diastereoisomers. The most active compounds complet ely blocked production of infectious virus. A simulation method for in teraction was employed to build a model of the inhibitors in the PR ac tive site, to identify the interactions responsible for the difference s in activities of individual stereoisomers, and to estimate the relat ive contribution of individual structural features to the overall inhi bitory activity.