Pharmacokinetics, biodistribution, and stability of capped oligodeoxynucleotide phosphorothioates in mice.

Several end-modified oligodeoxynucleotide phosphorothioates (S-oligonucleotides) were studied for their pharmacokinetics, biodistribution, excretion, and metabolic stability in vivo after intravenous administration in mice. The overall tissue distribution and excretion patterns of these S-oligonucleotides were found to be independent of 5' or 3' end modification studied. However, the 3' end modification proved to be of considerable importance with respect to metabolic stability of the oligonucleotide. In the case of uncapped and 5'-capped S-oligonucleotide, only 50% of intact oligonucleotide was recovered out of the total bioavailable concentration in liver and kidney. In contrast, in the case of 3'-capped oligonucleotides almost all bioavailable concentrations of 3'-capped oligonucleotide was found to be intact in kidney and liver at 24 hr after administration. These results demonstrate that superior pharmaceutical potential can be created by 3'-end modification of oligonucleotide phosphorothioates.