Well-Defined Multivalent Ligands for Hepatocytes Targeting via Asialoglycoprotein Receptor

Targeted delivery of therapeutic agents to hepatocytes is a particularly attractive strategy for the treatment of hepatocellular carcinoma and other liver diseases. The asialoglycoprotein receptor (ASGP-R) is abundantly expressed on hepatocytes and minimally found on extra-hepatic cells, making it an ideal entry gateway for hepatocyte-targeted therapy. Numerous multivalent ligands have been developed to target ASGP-R, among which well-defined multivalent ligands display especially high binding affinity to the receptor. Recently, several gene delivery systems based on such ligands for ASGP-R showed encouraging clinical results, drawing increasing interest in the scientific community and eventually promoting the improvement of current treatment for liver diseases. Here, we review ASGP-R targeting with a special emphasis on well-defined systems and properties such as the linker's length, hydrophilic hydrophobic balance of the linker, and the spatial geometry of the scaffold. The present manuscript provides important guidelines for the design of multivalent ligands for ASGP-R.