Phosphorothioate Antisense Oligonucleotide Cantide Pharmacokinetic Studies

Cantide is a 20-mer antisense phosphorothioate oligonucleotide that inhibits telomerase catalytic subunit hTERT, the evaluation on proliferation of tumour cells in vitro and in vivo treatment of HepG2 tumor xerografts showed that cantide had promising antitumor activity.In order to study the pharmacokinetic properties, cantide, the phosphorothioate internal standard were prepared and purified. Cantide and the internal standard had approximately equal percentage of base composition.Cantide was quantitated by capillary electrophoresis instrument using two solid-phase extractions. In the present study, six standard curves were generated with the internal standard concentration hold at 25.0 mg/L.The precision of the process was ascertained by measurement of cantide concentration in water solution, plasma, tissues, urea, feces. Percentage relative errors of lower than 15% reflect that the influence of solid-phase extractions or injection-induced effects can be neglected.The overall yields of cantide recovered from biological fluids and tissue and feces were determined at different concentrations, and also compared the initial concentration to the extracted concentration of cantide. The observation that the ratio of cantide to the internal standard remained unchanged after the extraction demonstrated that cantide and the internal standard was extracted equivalently and allows quantitation of cantide levels in biological fluids and tissue and feces based on the initial added concentration of the internal standard.Mice received with a 50mg/kg i.v. injection of cantide. The results showed theproperties of pharmacokinetics was coincided with a two-compartment model with first order equation. The pharmacokinetic parameters derived from these analyses. The pharmacokinetic parameters showed that cantide was cleared rapidly from plasma.The concentration of cantide was determined in liver and kidney at different time point by CGE. Kidney concentrations peaked at 2 h, and peak concentration was 107. 0 +24. 0 mg/g. Liver concentration reached the highest at 8h, and the concentration was 22.10+3.39 mg/g. The kidney accumulated the greater fraction of dose than liver, but liver concentration changed slowly. The relationships between tissue distribution and plasma kinetics showed the metabolism was not the primary mechanism of plasma clearance, distribution of cantide into tissues was the predominant driving force in plasma clearance.Based on determination of the excretion of cantide in mice, urinary excretion represented the major pathway of elimination, the kinds of the excreted oligonucleotides was basically same at different duration over 24 h.The results of the metabolites in mice derived from CGE analysis. Metabolic rates in plasma and liver and kidney showed the percentage of intact drug as function of time. In plasma, cantide did not degrade basically within 3 min after a dose, it had at least four nucleotide deleted as early as 8 min after administration. Metabolism was significantly-slower in the liver and significantly rapid in the kidney. In the liver and kidney, the kinds of chain-shorted metabolites of parent compound were basically same from 1 h to 24 h after administration.