We synthesized a polymeric prodrug of prostaglandin E-1, (PGE(1)) using galaclosylated poly-(L-glutamic acid) (Gal-PLGA) as a biodegradable and targetable carrier to the liver parenchymal cells. PLGA was reacted with ethylenediamine followed by coupling with 2-imino-2-methoxyethyl-1-thiogalactosides to obtain Gal-PLGA. PGE(1) was activated with N,N'-carbonyldiimidazole (CDI) then the PGE(1) ester obtained was attached to Gal-PLGA. After intravenous injection in mice at a dose of 1 mg/kg PGE(1) conjugates with Gal-PLGA (PGE(1)-PLGA-Gal) labeled with [In-111] or [H-3]PGE(1) rapidly accumulated in the liver up to 65 and 50% of the dose respectively. The hepatic uptake of [In-111]PGE(1)-PLGA-Gal was remarkably inhibited by the co-administration of Gal-BSA indicating that the PGE(1) conjugates were taken up by the liver via the asialoglycoprotein receptor-mediated endocytosis. These findings suggest that PGE(1) can be effectively targeted to the liver parenchymal cells by covalently conjugating with Gal-PLGA. (C) 1997 Elsevier Science B.V.