title: Structure-activity relationships of HCV NS3 protease inhibitors evaluated on the drug-resistant variants A156T and D168V.
abstract: BACKGROUND
  HCV infections are a serious threat to public health. An important drug target is the NS3 protease, for which several inhibitors are in clinical trials. Because of the high mutation rate of the virus, resistance against any HCV-specific drug is likely to become a substantial problem. Structure-activity data for the major resistant variants are therefore needed to guide future designs of protease inhibitors.
  
  
  METHODS
  The inhibitory potency of tripeptide NS3 protease inhibitors, with either a P2 proline or phenylglycine, in combination with different P3 and P1-P1' groups, was assessed in enzyme activity assays using the full-length NS3 protein with known resistance-conferring substitutions A156T or D168V. The results obtained from these variants were compared with the inhibition of the wild-type enzyme. Molecular modelling was used to rationalize the biochemical results.
  
  
  RESULTS
  Inhibitors combining the P2 proline and P1 (1R,2S)-1-amino-2-vinylcyclopropyl-carboxylic acid (vinylACCA) lost much of their potency on the resistant variants. Exchange of the P2 proline for phenylglycine yielded inhibitors that were equipotent on the wild-type and on the A156T and D168V variants. The same result was obtained from the combination of either the P2 residue with a norvaline or an aromatic scaffold in the P1 position.
  
  
  CONCLUSIONS
  The combination of a substituted P2 proline and P1 vinylACCA appears to be the main problem behind the observed resistance. Molecular modelling suggests an enforced change in binding conformation for the P2 proline-based inhibitors, whereas the phenylglycine-based inhibitors retained their wild-type binding conformation in the substituted forms of the enzyme.
authors.affiliation: Department of Medicinal Chemistry, Uppsala University, Sweden.
authors.forename: Pernilla
authors.initials: P
authors.lastname: Ortqvist
authors.forename: Aparna
authors.initials: A
authors.lastname: Vema
authors.forename: Angelica E
authors.initials: AE
authors.lastname: Ehrenberg
authors.forename: Göran
authors.initials: G
authors.lastname: Dahl
authors.forename: Robert
authors.initials: R
authors.lastname: Rönn
authors.forename: Eva
authors.initials: E
authors.lastname: Akerblom
authors.forename: Anders
authors.initials: A
authors.lastname: Karlén
authors.forename: U Helena
authors.initials: UH
authors.lastname: Danielson
authors.forename: Anja
authors.initials: A
authors.lastname: Sandström
mesh_terms: D024882:Drug Resistance, Viral; D016174:Hepacivirus / Q000187:drug effects* / Q000201:enzymology; D008958:Models, Molecular; D011480:Protease Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D013329:Structure-Activity Relationship; D017361:Viral Nonstructural Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D011480:Protease Inhibitors; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases