P202 TRITIATED ANTISENSE OLIGONUCELOTIDES – RADIOSYNTHESIS AND PHARMACOKINETIC INVESTIGATIONS

Stephen Harris , Pharmaron UK Ltd, Rushden, United Kingdom
Kathryn Webbley , Pharmaron UK Ltd, Rushden, United Kingdom
Claire Henson , Pharmaron UK Ltd, Rushden, United Kingdom
Stephanie Geoffroy , Pharmaron UK Ltd, Rushden, United Kingdom
Stuart G Wood , Pharmaron UK Ltd, Rushden, United Kingdom
Ray Cooke , Pharmaron UK Ltd, Rushden, United Kingdom
Adrian Waring , Pharmaron UK Ltd, Rushden, United Kingdom
Jon Bloom , Pharmaron UK Ltd, Cardiff, United Kingdom
Vernon Wilson , Pharmaron UK Ltd, Cardiff, United Kingdom
Calvin Hawes , Pharmaron UK Ltd, Cardiff, United Kingdom
Darren Price , Pharmaron UK Ltd, Cardiff, United Kingdom
Jack Haffenden , Pharmaron UK Ltd, Cardiff, United Kingdom
The potential therapeutic applications for oligonucleotides are enormous, ranging over hypertension, cardiovascular disease, parasitic infections, and cancer, however the effectiveness of a therapeutic agent depends on the pharmacokinetics, tissue disposition, stability, elimination and safety profile. The successful prediction of human ADME properties is therefore an essential stage in the development of marketable antisense therapeutics. The aim of this project was to investigate the use of radiolabeled oligonucleotides for ADME studies. In order to label the phosphorothioate oligonucleotide we used a synthesis method which entailed labeling a nucleotide, converting it into a phosphoramidite and carrying out an oligo-synthesis. Following intravenous administration of the [3H]-labeled material to male albino rats concentration of radioactivity in blood quickly declined, however the data indicated a long elimination phase. The AUC0-672h and AUC0- were 39.2 and 48.0 µg equiv.hr/mL respectively indicating that the period of exposure to [3H]-labeled oligonucleotide and derived radioactive material was greater than the initial sampling period. A mean total of 16.4 % and 10.3 % dose was recovered in urine and faeces 0-336 hours respectively, however the majority of the radioactivity, 72.1%, remained in the carcass at 336 hours. QWBA data showed radioactivity was widely distributed and elimination from the majority of tissues was slow. The data obtained in this study demonstrated that good quality pharmacokinetic and tissue distribution data can be obtained following radiolabeling of oligonucleotides with tritium. The properties of the tritium label (high activity, short path length) provide quantification of tissue concentrations with excellent spatial resolution. The tritium label also facilitates the isolation, quantification and identification of breakdown products using metabolite profiling and identification techniques.