title: In vitro selection of resistance to sofosbuvir in HCV replicons of genotype-1 to -6.
abstract: BACKGROUND
  Sofosbuvir is a nucleoside analogue inhibitor of the HCV NS5B polymerase approved for treatment of HCV-infected patients in combination with ribavirin or with other antivirals. It has activity against all genotypes of HCV. Resistance to sofosbuvir in genotype-1 and -2 HCV is conferred by the S282T substitution in NS5B.
  
  
  METHODS
  To begin to define the correlates of resistance to sofosbuvir in other genotypes, we performed selection experiments in cell culture using cell lines containing subgenomic replicons derived from genotypes-1b, -2a, -3a and -4a, or chimeric replicons in a genotype-1b background but encoding genotype-2b, -5a and -6a NS5B polymerase.
  
  
  RESULTS
  In every case, S282T was selected following passage in the presence of increasing concentrations of sofosbuvir for 10 to 15 weeks. When introduced as a site-directed mutant, S282T conferred reductions in sofosbuvir susceptibility of between 2.4 and 19.4-fold. Other substitutions observed during the selections had relatively less impact on susceptibility, such as N237S in genotype-6a (2.5-fold). Replication capacity was affected by the introduction of S282T in all genotypes to variable extents (3.2% to 22% of wild type).
  
  
  CONCLUSIONS
  These results confirm that S282T is the primary sofosbuvir resistance-associated substitution and that replication capacity is reduced when it is present in all genotypes of HCV.
authors.affiliation: Gilead Sciences, Foster City, CA, USA.
authors.forename: Simin
authors.initials: S
authors.lastname: Xu
authors.affiliation: Gilead Sciences, Foster City, CA, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Doehle
authors.affiliation: Gilead Sciences, Foster City, CA, USA.
authors.forename: Sonal
authors.initials: S
authors.lastname: Rajyaguru
authors.affiliation: Gilead Sciences, Foster City, CA, USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Han
authors.affiliation: Gilead Sciences, Foster City, CA, USA.
authors.forename: Ona
authors.initials: O
authors.lastname: Barauskas
authors.affiliation: Gilead Sciences, Foster City, CA, USA.
authors.forename: Joy
authors.initials: J
authors.lastname: Feng
authors.affiliation: Gilead Sciences, Foster City, CA, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Perry
authors.affiliation: Gilead Sciences, Foster City, CA, USA.
authors.forename: Hadas
authors.initials: H
authors.lastname: Dvory-Sobol
authors.affiliation: Gilead Sciences, Foster City, CA, USA.
authors.forename: Evguenia S
authors.initials: ES
authors.lastname: Svarovskaia
authors.affiliation: Gilead Sciences, Foster City, CA, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Miller
authors.affiliation: Gilead Sciences, Foster City, CA, USA.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Mo
mesh_terms: D019943:Amino Acid Substitution; D000998:Antiviral Agents / Q000494:pharmacology*; D002460:Cell Line; D024882:Drug Resistance, Viral; D016679:Genome, Viral; D005838:Genotype; D016174:Hepacivirus / Q000187:drug effects* / Q000235:genetics*; D006526:Hepatitis C / Q000188:drug therapy / Q000821:virology*; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D010641:Phenotype; D011487:Protein Conformation; D000069474:Sofosbuvir / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000235:genetics; D014779:Virus Replication
chemical_list: D000998:Antiviral Agents; D017361:Viral Nonstructural Proteins; D000069474:Sofosbuvir