title: NS5A Sequence Heterogeneity and Mechanisms of Daclatasvir Resistance in Hepatitis C Virus Genotype 4 Infection.
abstract: BACKGROUND
  Daclatasvir is an NS5A inhibitor approved for treatment of infection due to hepatitis C virus (HCV) genotypes (GTs) 1-4. To support daclatasvir use in HCV genotype 4 infection, we examined a diverse genotype 4-infected population for HCV genotype 4 subtype prevalence, NS5A polymorphisms at residues associated with daclatasvir resistance (positions 28, 30, 31, or 93), and their effects on daclatasvir activity in vitro and clinically.
  
  
  METHODS
  We performed phylogenetic analysis of genotype 4 NS5A sequences from 186 clinical trial patients and 43 sequences from the European HCV database, and susceptibility analyses of NS5A polymorphisms and patient-derived NS5A sequences by using genotype 4 NS5A hybrid genotype 2a replicons.
  
  
  RESULTS
  The clinical trial patients represented 14 genotype 4 subtypes; most prevalent were genotype 4a (55%) and genotype 4d (27%). Daclatasvir 50% effective concentrations for 10 patient-derived NS5A sequences representing diverse phylogenetic clusters were ≤0.080 nM. Most baseline sequences had ≥1 NS5A polymorphism at residues associated with daclatasvir resistance; however, only 3 patients (1.6%) had polymorphisms conferring ≥1000-fold daclatasvir resistance in vitro. Among 46 patients enrolled in daclatasvir trials, all 20 with baseline resistance polymorphisms achieved a sustained virologic response.
  
  
  CONCLUSIONS
  Circulating genotype 4 subtypes are genetically diverse. Polymorphisms conferring high-level daclatasvir resistance in vitro are uncommon before therapy, and clinical data suggest that genotype 4 subtype and baseline polymorphisms have minimal impact on responses to daclatasvir-containing regimens.
authors.affiliation: Bristol-Myers Squibb, Wallingford, Connecticut.
authors.forename: Nannan
authors.initials: N
authors.lastname: Zhou
authors.affiliation: Bristol-Myers Squibb, Wallingford, Connecticut.
authors.forename: Dennis
authors.initials: D
authors.lastname: Hernandez
authors.affiliation: Bristol-Myers Squibb, Wallingford, Connecticut.
authors.forename: Joseph
authors.initials: J
authors.lastname: Ueland
authors.affiliation: Bristol-Myers Squibb, Wallingford, Connecticut.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Yang
authors.affiliation: Bristol-Myers Squibb, Wallingford, Connecticut.
authors.forename: Fei
authors.initials: F
authors.lastname: Yu
authors.affiliation: Bristol-Myers Squibb, Princeton, New Jersey.
authors.forename: Karen
authors.initials: K
authors.lastname: Sims
authors.affiliation: Bristol-Myers Squibb, Princeton, New Jersey.
authors.forename: Philip D
authors.initials: PD
authors.lastname: Yin
authors.affiliation: Bristol-Myers Squibb, Wallingford, Connecticut.
authors.forename: Fiona
authors.initials: F
authors.lastname: McPhee
mesh_terms: D019943:Amino Acid Substitution; D002219:Carbamates; D024882:Drug Resistance, Viral; D015967:Gene Expression Regulation, Viral / Q000502:physiology; D005838:Genotype; D014943:Global Health; D016174:Hepacivirus / Q000145:classification* / Q000187:drug effects / Q000235:genetics*; D006526:Hepatitis C / Q000188:drug therapy / Q000453:epidemiology / Q000821:virology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology* / Q000627:therapeutic use; D010802:Phylogeny; D011110:Polymorphism, Genetic; D011759:Pyrrolidines; D014633:Valine / Q000031:analogs & derivatives; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase
chemical_list: D002219:Carbamates; D007093:Imidazoles; D011759:Pyrrolidines; D014633:Valine; D017361:Viral Nonstructural Proteins; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase; C549273:daclatasvir
keywords: HCV; NS5A; daclatasvir; polymorphism; resistance