title: Binding kinetics, potency, and selectivity of the hepatitis C virus NS3 protease inhibitors GS-9256 and vedroprevir.
abstract: BACKGROUND
  GS-9256 and vedroprevir are inhibitors of the hepatitis C virus NS3 protease enzyme, an important drug target. The potency, selectivity, and binding kinetics of the two compounds were determined using in vitro biochemical assays.
  
  
  METHODS
  Potency of the compounds against NS3 protease and selectivity against a panel of mammalian proteases were determined through steady-state enzyme kinetics. Binding kinetics were determined using stopped-flow techniques. Dissociation rates were measured using dilution methods.
  
  
  RESULTS
  GS-9256 and vedroprevir had measured Ki values of 89 pM and 410 pM, respectively, against genotype 1b NS3 protease; Ki values were higher against genotype 2a (2.8 nM and 39 nM) and genotype 3 proteases (104 nM and 319 nM) for GS-9256 and vedroprevir, respectively. Selectivity of GS-9256 and vedroprevir was >10,000-fold against all tested off-target proteases. Association rate constants of 4×10(5)M(-1)s(-1) and 1×10(6)M(-1)s(-1), respectively, were measured, and dissociation rate constants of 4.8×10(-5)s(-1) and 2.6×10(-4)s(-1) were determined.
  
  
  CONCLUSIONS
  GS-9256 and vedroprevir are potent inhibitors of NS3 protease with high selectivity against off-target proteases. They have rapid association kinetics and slow dissociation kinetics.
  
  
  CONCLUSIONS
  The NS3 protease is a key drug target for the treatment of hepatitis C. The potency, selectivity, and binding kinetics of GS-9256 and vedroprevir constitute a biochemical profile that supports the evaluation of these compounds in combination with other direct-acting antivirals in clinical trials for hepatitis C.
authors.affiliation: Gilead Sciences, 333 Lakeside Drive, Foster City, CA 94404, USA.
authors.forename: Ona
authors.initials: O
authors.lastname: Barauskas
authors.affiliation: Gilead Sciences, 333 Lakeside Drive, Foster City, CA 94404, USA.
authors.forename: Amoreena C
authors.initials: AC
authors.lastname: Corsa
authors.affiliation: Gilead Sciences, 333 Lakeside Drive, Foster City, CA 94404, USA.
authors.forename: Ruth
authors.initials: R
authors.lastname: Wang
authors.affiliation: Gilead Sciences, 333 Lakeside Drive, Foster City, CA 94404, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Hluhanich
authors.affiliation: Gilead Sciences, 333 Lakeside Drive, Foster City, CA 94404, USA.
authors.forename: Debi
authors.initials: D
authors.lastname: Jin
authors.affiliation: Gilead Sciences, 333 Lakeside Drive, Foster City, CA 94404, USA.
authors.forename: Magdeleine
authors.initials: M
authors.lastname: Hung
authors.affiliation: Gilead Sciences, 333 Lakeside Drive, Foster City, CA 94404, USA.
authors.forename: Huiling
authors.initials: H
authors.lastname: Yang
authors.affiliation: Gilead Sciences, 333 Lakeside Drive, Foster City, CA 94404, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Delaney
authors.affiliation: Gilead Sciences, 333 Lakeside Drive, Foster City, CA 94404, USA. Electronic address: Brian.Schultz@gilead.com.
authors.forename: Brian E
authors.initials: BE
authors.lastname: Schultz
keywords: Binding kinetics; Hepatitis C virus; Inhibition; NS3 protease; Rate constant; Selectivity