title: A novel oligodeoxynucleotide inhibitor of thrombin. I. In vitro metabolic stability in plasma and serum.
abstract: OBJECTIVE
  To determine the degradation rates and pathways of GS-522, a potent oligodeoxynucleotide (GGTTGGTGTGGTTGG) inhibitor of thrombin, in serum and plasma.
  
  
  METHODS
  A stability-indicating, anion-exchange HPLC method was developed and used to determine concentrations of GS-522 and metabolites.
  
  
  RESULTS
  In monkey plasma at 2 microM or below, the degradation of GS-522 can be fit to a first-order exponential with a kpobs approximately 0.01 min-1. At 3 microM and above the degradation process deviates from a monoexponential decay profile. An initial fast degradation process is followed by a slower phase with an observed rate constant equal to that observed at 2 microM and below. In monkey serum, the KM and Vmax are 8.4 microM and 0.87 microM min-1, respectively.
  
  
  CONCLUSIONS
  The kinetics are consistent with an equilibrium binding of GS-522 to prothrombin in plasma (Kd = 50 nM) which saturates at GS-522 concentrations > 2 microM. Compared to a scrambled sequence (GGTGGTGGTTGTGGT), with no defined tertiary structure, GS-522 is 4-fold more stable in serum. The metabolic profile in plasma is consistent with a 3'-exonuclease catalyzed hydrolysis of GS-522.
authors.affiliation: Gilead Sciences, Inc., Foster City, California 94404, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Shaw
authors.forename: J A
authors.initials: JA
authors.lastname: Fishback
authors.forename: K C
authors.initials: KC
authors.lastname: Cundy
authors.forename: W A
authors.initials: WA
authors.lastname: Lee
mesh_terms: D052157:Aptamers, Nucleotide; D001483:Base Sequence; D004305:Dose-Response Relationship, Drug; D004355:Drug Stability; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000378:metabolism* / Q000494:pharmacology*; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D013917:Thrombin / Q000187:drug effects*
chemical_list: D052157:Aptamers, Nucleotide; D009841:Oligonucleotides; D004364:Pharmaceutical Preparations; C081676:thrombin aptamer; D013917:Thrombin