KINETICS OF PHOSPHOROTHIOATE OLIGONUCLEOTIDE METABOLISM IN BIOLOGICAL-FLUIDS

The in vitro stability and metabolism of GEM(R)91, a 25mer phosphoroth ioate antisense oligonucleotide complementary to the gag mRNA region o f HIV-1, was investigated using capillary electrophoresis (CE), The in vitro degradation of the parent compound at 37 degrees C was followed over the course of 120 h in human plasma, A CE method using laser-ind uced fluorescence detection was able to detect 5'-end intact metabolit es including the parent compound extracted from biological fluids, Bec ause the primary metabolic pathway is believed to be via 3'-exonucleas e activity, the results of this study were compared with the stability of the compound in a solution containing 3'-exonuclease, The numerica l solution of sequential first-order reactions was used to obtain kine tic parameters, Exonuclease digestion of the parent compound, as measu red using an automated CE-UV instrument, yielded striking similarities between the two in vitro systems as well as between in vitro and in v ivo systems.