Receptor mediated gene delivery relies on carrier molecules to facilitate plasmid DNA internalization into target cells resulting in transient expression of the encoded protein. The asialoglycoprotein receptor (ASGP-R) has been the subject of numerous investigations that have proven the feasibility of receptor mediated gene deliver to hepatocytes both in vitro and in vivo. These studies emphasize that the biodistribution, intracellular routing, and stability of exogenous DNA and transcribed mRNA each contribute to the overall level and duration of gene expression in vivo. Several of these parameters are directly influenced by the carrier molecule structure which must condense DNA into small particles, present ligands for receptor recognition and insure DNA transport to the nucleus.
The aim of this proposal is to optimize low molecular weight glycopeptides for hepatic gene delivery. The proposed glycopeptides will be composed of a single complex oligosaccharide ligand covalently attached at a defined site to a synthetic peptide anchor. Substitution of oligosaccharides and peptide anchors will result in homogenous carrier molecules capable of defining structure activity relationships. Glycopeptides with ASGP-R binding affinities (K/d) ranging from uM to nM will be used to assess performance in transfecting hepatocytes. Anchor peptides that systematically vary sequence will be used to optimize the condensation of plasmid DNA into defined particles. Fusogenic and nuclear localizing peptides will be tested for their ability to augment carrier function. Glycopeptide structures will be correlated with physical formulation data and in vitro and in vivo hepatic transfection models to arrive at optimal carrier properties. The development of rationally designed low molecular weight glycopeptide carriers for ASGP-R mediated gene delivery will lead to the formulation of soluble DNA:carrier complexes of defined particle size, blood stability, pharmacokinetics and biodistribution resulting in enhanced gene expression. These are important factors towards developing a safe and effective receptor mediated gene delivery system for in vivo use in humans.
