A HEPATOCYTE-TARGETED CONJUGATE CAPABLE OF DELIVERING BIOLOGICALLY-ACTIVE COLCHICINE IN-VITRO

A derivative of colchicine was synthesized, in a manner that preserved its important structural features, and conjugated to an asialoglycopr otein. The conjugate was characterized by ultraviolet-visible spectrop hotometry and protein analysis. An average coupling ratio of 2 mol of colchicine per mole of asialoglycoprotein was achieved. The conjugate was stable to incubation in serum but was split into its separate comp onents under chemically reducing conditions. Incubation with cells in culture revealed that the conjugate had antiproliferative activity sim ilar to that of colchicine, but only in asialoglycoprotein receptor-co ntaining cells. There was no effect at all on asialoglycoprotein recep tor (-) cells. Furthermore, the antiproliferative effect of the conjug ate on receptor (+) cells was blocked by addition of a large molar exc ess of free asialoglycoprotein. Immunofluorescence microscopy revealed disruption of microtubules in cell cultures that were pretreated with the conjugate. These results indicate that a colchicine conjugate tha t is taken up specifically into cells by asialoglycoprotein receptors and released intracellularly in a biologically active form can be prep ared.