Targeted delivery of oligodeoxynucleotides to parenchymal liver cells in vivo

Abstract

Anti-sense oligodeoxynucleotides (ODNs) hold great promise for correcting the biosynthesis of clinically relevant proteins. The potential of ODNs for modulating liver-specific genes might be increased by preventing untimely elimination and by improving the local bioavailability of ODNs in the target tissue. In the present study we have assessed whether the local ODN concentration can be enhanced by the targeted delivery of ODNs through conjugation to a ligand for the parenchymal liver cell-specific asialoglycoprotein receptor. A capped ODN (miscellaneous 20-mer sequence) was derivatized with a ligand with high affinity for this receptor, N2-[N2-(N2,N6-bis{N-[p-(β-D-galactopyranosyloxy) anilino] thiocarbamyl} - L - lysyl) - N6 - (N - {p - [β-D -galactopyranosyloxy] anilino} thiocarbamyl) - L - lysyl] - N6 - [N - (p -{β-ᴅ-galactopyranosyloxy}anilino)thiocarbamyl]-ʟ-lysine (L3G4) (Kd 6.5±0.2 nM, mean±S.D.). Both the uptake studies in vitro and the confocal laser scan microscopy studies demonstrated that L3G4-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 glycoconjugation. Importantly, specific ODN accumulation of ODN into parenchymal liver cells was improved almost 60-fold after derivatization with L3G4, and could be attributed to the asialoglycoprotein receptor. In conclusion, the scavenger receptor-mediated elimination pathway for miscellaneous ODN sequences can be circumvented by direct conjugation to a synthetic tag for the asialoglycoprotein receptor. In this manner a crucial requisite is met towards the application of ODNs in vivo to modulate the biosynthesis of parenchymal liver cell-specific genes such as those for apolipoprotein (a), cholesterol ester transfer protein and viral proteins.