Synthesis of antisense oligonucleotides conjugated to a multivalent carbohydrate cluster for cellular targeting

Carrier-mediated delivery holds great promise for significantly improving the cellular uptake and therefore the therapeutic efficacy of antisense oligonucleotides in vivo. A multivalent carbohydrate recognition motif for the asialoglycoprotein receptor has been designed for tissue- and cell-specific delivery of antisense drugs to parenchymal liver cells. To combine low molecular weight with high receptor affinity, the synthetic ligand contains three galactosyl residues attached to a cholane scaffold via epsilon-aminocapramide linkers. Three-dimensional structural calculations indicate that this unique design provides proper spacing and orientation of the three galactosyl residues to accomplish high affinity binding to the receptor. Covalent conjugation of the bulky carbohydrate cluster to oligonucleotides has been achieved by solid-phase synthesis using low-loaded macroporous resins and optimized synthesis protocols.