Targeted delivery of oligodeoxynucleotides to parenchymal liver cells in vivo

Anti-sense oligodeoxynucleotides (ODNs) hold great promise for correcting t he biosynthesis of clinically relevant proteins. The potential of ODNs for modulating liver-specific genes might be increased by preventing untimely e limination and by improving the local bioavailability of ODNs in the target tissue. In the present study we have assessed whether the local ODN concen tration can be enhanced by the targeted delivery of ODNs through conjugatio n to a ligand for the parenchymal liver cell-specific asialoglycoprotein re ceptor. A capped ODN (miscellaneous 20-mer sequence) was derivatized with a ligand with high affinity for this receptor, N-2-[N-2-(N-2, N-6-bis{N-[p-( beta-D-galactopyranosyloxy) anilino] thiocarbamyl)-L-lysyl)-N-6-(N-{p-[beta -D-galactopyranosyloxy)anilino)thiocarbamyl {beta-D-galactopyranosyloxy}ani lino)thiocarbamyl]-L-lysine (L(3)G(4)) (K-d 6.5 +/- 0.2 nM, mean +/- S.D.). Both the uptake studies in vitro and the confocal laser scan microscopy st udies demonstrated that L(3)G(4)-ODN was far more efficiently bound to and taken up by parenchymal liver cells than underivatized ODN. Studies in vivo in rats showed that hepatic uptake could be greatly enhanced from 19+/-1% to 77+/-6% of the injected dose after glyco-conjugation. Importantly, speci fic ODN accumulation of ODN into parenchymal liver cells was improved almos t 60-fold after derivatization with L(3)G(4), and could be attributed to th e asialoglycoprotein receptor. In conclusion, the scavenger receptor-mediat ed elimination pathway for miscellaneous ODN sequences can be circumvented by direct conjugation to a synthetic tag for the asialoglycoprotein recepto r. In this manner a crucial requisite is met towards the application of ODN s in vivo to modulate the biosynthesis of parenchymal liver cell-specific g enes such as those for apolipoprotein (a), cholesterol ester transfer prote in and viral proteins.