Site-specific delivery of oligonucleotides to hepatocytes after systemic administration

We previously complexed ODN with galactosylated poly(L-lysine) (Gal-PLL) to enhance its site specifiic delivery to hepatocytes. To avoid the use of polycations, in this study we conjugated galactosylated poly(ethylene glycol) (Gal-PEG (MW of PEG: 3486 +/- 500 Da)) to ODN via an acid-labile ester linkage-of beta-thiopropionate. Following tail vein injection into rats, Gal-PEG-P-33-ODN rapidly cleared from the circulation and 60.2% of the injected dose accumulated in the liver at 30 min postinjection, which was significantly higher than that deposited after. injection of P-33-ODNs. The plasma concentration versus time profile of Gal-PEG-P-33-ODN was biphasic, with 4.38 +/- 0.36 min as t(1/2) of distribution and 118.61 +/- 1 22.06 min as t(1/2) of elimination. Prior administration of excess Gal-BSA decreased the hepatic uptake of Gal-PEG-P-33-ODN from 60.2% to 35.9%, suggesting galactose triggers the asialoglycoprotein receptor-mediated endocytosis of Gal-PEG-P-33-ODN by hepatocytes. A large proportion of the injected Gal-PEG ODN was taken up by the hepatocytes as evidenced by determination of radioactivity in the digested liver cells upon liver perfusion and separation by centrifugation on a Nycodenz gradient. In conclusion, Gal-PEG-ODN conjugate may be used for treating a variety of liver diseases.