title: Resistance of hepatitis C virus to NS3-4A protease inhibitors: mechanisms of drug resistance induced by R155Q, A156T, D168A and D168V mutations.
abstract: OBJECTIVE
  One of the main issues in the development of antiviral therapy is the emergence of drug-resistant viruses. In the case of hepatitis C virus (HCV), selection of drug-resistant mutants was evidenced by in vitro studies on protease inhibitors (PIs); for example, BILN-2061, VX-950 and SCH-6. Four mutations in the HCV protease (R155Q, A156T, D168A and D168V) have been identified in vitro in the HCV replicon system that confer resistance to BILN-2061 (a reference inhibitor). However, the molecular mechanism of drug resistance is still unknown. The aim of this study is to unravel, using an molecular modelling strategy, the structural basis of such molecular mechanism of HCV resistance to PIs. We focused on protease mutations conferring HCV resistance to BILN-2061 and described for the first time such mechanism at a molecular level.
  
  
  METHODS
  The structures of drug-resistant NS3 proteases were obtained by mutation of selected residues (R155Q, A156T, D168A and D168V) and the ternary complexes formed between NS3-4A and BILN-2061 were optimized using GenMol software (www.3dgenoscience.com; Genoscience, Marseille, France).
  
  
  RESULTS
  Two mechanisms were evidenced for viral resistance to BILN-2061. A 'direct' resistance mechanism is based on contacts between the mutated R155Q and A156T protease residues and its inhibitor. In the 'indirect' resistance mechanism, the mutated D168A/V residue is not in close contact with the drug itself but interacts with other residues connected to the drug.
  
  
  CONCLUSIONS
  These data provide new insights in the understanding of the mechanisms of HCV drug escape, and may allow predicting potential cross-resistance phenomenon with other PIs. This approach can be used as a basis for future rational PI drug design candidates.
authors.affiliation: Geoscience, Marseille, France. courcambeck@3dgenoscience.com
authors.forename: Jérôme
authors.initials: J
authors.lastname: Courcambeck
authors.forename: Mourad
authors.initials: M
authors.lastname: Bouzidi
authors.forename: Régis
authors.initials: R
authors.lastname: Perbost
authors.forename: Besma
authors.initials: B
authors.lastname: Jouirou
authors.forename: Nolwenn
authors.initials: N
authors.lastname: Amrani
authors.forename: Patrice
authors.initials: P
authors.lastname: Cacoub
authors.forename: Gérard
authors.initials: G
authors.lastname: Pèpe
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Sabatier
authors.forename: Philippe
authors.initials: P
authors.lastname: Halfon
mesh_terms: D001665:Binding Sites / Q000235:genetics; D002219:Carbamates / Q000737:chemistry / Q000494:pharmacology*; D024882:Drug Resistance, Viral; D016174:Hepacivirus / Q000187:drug effects* / Q000201:enzymology; D047028:Macrocyclic Compounds / Q000737:chemistry / Q000494:pharmacology*; D008958:Models, Molecular; D017354:Point Mutation; D011804:Quinolines / Q000737:chemistry / Q000494:pharmacology*; D012697:Serine Endopeptidases / Q000737:chemistry / Q000187:drug effects / Q000235:genetics; D013844:Thiazoles / Q000737:chemistry / Q000494:pharmacology*; D017361:Viral Nonstructural Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000187:drug effects / Q000235:genetics; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D002219:Carbamates; D047028:Macrocyclic Compounds; D011804:Quinolines; D012697:Serine Endopeptidases; D013844:Thiazoles; D017361:Viral Nonstructural Proteins; C479555:BILN 2061; C084422:NS3 protein, hepatitis C virus; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases