Jp. Shaw et al., A NOVEL OLIGODEOXYNUCLEOTIDE INHIBITOR OF THROMBIN .1. IN-VITRO METABOLIC STABILITY IN PLASMA AND SERUM, Pharmaceutical research, 12(12), 1995, pp. 1937-1942
Purpose. To determine the degradation rates and pathways of GS-522, a
potent oligodeoxynucleotide (GGTTGGTGTGGTTGG) inhibitor of thrombin, i
n serum and plasma. Methods. A stability-indicating, anion-exchange HP
LC method was developed and used to determine concentrations of GS-522
and metabolites. Results. In monkey plasma at 2 mu M or below, the de
gradation of GS-522 can be fit to a first-order exponential with a k(o
bs)(p) similar to 0.01 min(-1). At 3 mu M and above the degradation pr
ocess deviates from a monoexponential decay profile. An initial fast d
egradation process is followed by a slower phase with an observed rate
constant equal to that observed at 2 mu M and below. In monkey serum,
the K-M and V-max are 8.4 mu M and 0.87 mu M min(-1), respectively. C
onclusions. The kinetics are consistent with an equilibrium binding of
GS-522 to prothrombin in plasma (K-d = 50 nM) which saturates at GS-5
22 concentrations > 2 mu M. Compared to a scrambled sequence (GGTGGTGG
TTGTGGT), with no defined tertiary structure, GS-522 is 4-fold more st
able in serum. The metabolic profile in plasma is consistent with a 3'
-exonuclease catalyzed hydrolysis of GS-522.