title: Preclinical characterization of the novel HCV NS3 protease inhibitor GS-9256.
abstract: GS-9256 is an inhibitor of HCV NS3 protease with a macrocyclic structure and novel phosphinic acid pharmacophore.
  
  
  
  Key preclinical properties of GS-9256 including in vitro antiviral activity, cross-resistance and pharmacokinetic properties were investigated in non-human species.
  
  
  
  In genotype (GT) 1b Huh-luc cells with a replicon encoding luciferase, GS-9256 had a mean 50% effective concentration (EC50) value of 20.0 nM, with minimal cytotoxicity. Antiviral activity was similar in a number of additional GT1b and GT1a replicon cell lines. Similar potency was observed in chimeric replicons encoding the NS3 protease of GT1 clinical isolates. GS-9256 was less active in GT2a replicon cells (14.2-fold increase in EC50). Additive to synergistic in vitro antiviral activity was observed when GS-9256 was combined with other agents including interferon-α, ribavirin, NS5B polymerase inhibitors GS-6620 and tegobuvir, as well as the NS5A inhibitor ledipasvir. GS-9256 retained wild-type activity against all tested NS5B and NS5A inhibitor resistance mutations. GS-9256 was metabolically stable in microsomes and hepatocytes of tested species, including rodents, dogs and humans. GS-9256 had high bioavailability in mice (near 100%) and moderate bioavailability in rats (14%), dogs (21%) and monkeys (14%). Elimination half-lives were approximately 2 h in mice, 0.6 h in rats, 5 h in dogs and 4 h in monkey. A study in bile duct-cannulated rats indicated that the major route of elimination is through biliary excretion of unmetabolized GS-9256.
  
  
  
  GS-9256 showed a favourable preclinical profile supportive of clinical development for the treatment of chronic HCV infection in GT1 patients.
authors.affiliation: Department of Biology, Gilead Sciences, Foster City, CA, USA.
authors.forename: Huiling
authors.initials: H
authors.lastname: Yang
authors.affiliation: Department of Drug Metabolism, Gilead Sciences, Foster City, CA, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Drug Metabolism, Gilead Sciences, Foster City, CA, USA.
authors.forename: Yujin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Drug Metabolism, Gilead Sciences, Foster City, CA, USA.
authors.forename: Gerry
authors.initials: G
authors.lastname: Rhodes
authors.affiliation: Department of Biology, Gilead Sciences, Foster City, CA, USA.
authors.forename: Margaret
authors.initials: M
authors.lastname: Robinson
authors.affiliation: Department of Biology, Gilead Sciences, Foster City, CA, USA.
authors.forename: Guofeng
authors.initials: G
authors.lastname: Cheng
authors.affiliation: Department of Biology, Gilead Sciences, Foster City, CA, USA.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Qi
authors.affiliation: Department of Biology, Gilead Sciences, Foster City, CA, USA.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Mo
authors.affiliation: Department of Biology, Gilead Sciences, Foster City, CA, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Tian
authors.affiliation: Department of Formulation and Process Development, Gilead Sciences, Foster City, CA, USA.
authors.forename: Rowchanak
authors.initials: R
authors.lastname: Pakdaman
authors.affiliation: Department of Medicinal Chemistry, Gilead Sciences, Foster City, CA, USA.
authors.forename: X Christopher
authors.initials: XC
authors.lastname: Sheng
authors.affiliation: Department of Medicinal Chemistry, Gilead Sciences, Foster City, CA, USA.
authors.forename: Choung U
authors.initials: CU
authors.lastname: Kim
authors.affiliation: Department of Biology, Gilead Sciences, Foster City, CA, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Delaney
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D001682:Biological Availability; D002460:Cell Line; D002478:Cells, Cultured; D004285:Dogs; D004353:Drug Evaluation, Preclinical; D024882:Drug Resistance, Viral; D016174:Hepacivirus / Q000187:drug effects* / Q000201:enzymology; D006526:Hepatitis C / Q000188:drug therapy / Q000821:virology; D006801:Humans; D008252:Macaca fascicularis; D051379:Mice; D010456:Peptides, Cyclic / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D010721:Phosphinic Acids / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D051381:Rats; D017361:Viral Nonstructural Proteins / Q000037:antagonists & inhibitors*; D014779:Virus Replication / Q000187:drug effects; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D000998:Antiviral Agents; D010456:Peptides, Cyclic; D010721:Phosphinic Acids; D011480:Protease Inhibitors; D017361:Viral Nonstructural Proteins; C571665:GS-9256; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases