title: Stabilized plasmid-lipid particles containing PEG-diacylglycerols exhibit extended circulation lifetimes and tumor selective gene expression.
abstract: Stabilized plasmid lipid particles (SPLP) consist of a single copy of DNA surrounded by a lipid bilayer. The particles are small ( approximately 100 nm), stable, monodisperse and have a low surface charge. A diffusible polyethylene glycol (PEG) coating attached to a lipid anchor is critical to the SPLP's functionality. The PEG-lipid exchanges out of the bilayer at a rate determined by the size of the lipid anchor. Here we show that SPLP can be prepared using a series of PEG-diacylglycerol lipids (PEG-S-DAGs). SPLP were prepared incorporating PEG-dimyristoylglycerol (C14), PEG-dipalmitoylglycerol (C16) or PEG-distearoylglycerol (C18) and the rate of PEG-lipid diffusion from the bi-layer determined using a FRET assay. SPLP pharmacokinetics confirm a correlation between the stability of the PEG-lipid component and circulation lifetime. PEG-S-DAGs with longer lipid anchors yield more stable SPLP particles with longer circulation half-lives yielding an increase in tumor delivery and gene expression. PEG-distearoylglycerol (C18) containing SPLP bypass so-called 'first pass' organs, including the lung, and elicit levels of gene expression in distal tumor tissue 100- to 1000-fold greater than that observed in any other tissue. The incorporation of PEG-S-DAG in SPLP confirms that small size, low surface charge and extended circulation lifetimes are prerequisite to the accumulation and tumor selective expression of plasmid DNA following systemic administration.
authors.affiliation: Protiva Biotherapeutics Inc., 100-3480 Gilmore Way, Burnaby, BC, Canada V5G 4Y1.
authors.forename: E
authors.initials: E
authors.lastname: Ambegia
authors.forename: S
authors.initials: S
authors.lastname: Ansell
authors.forename: P
authors.initials: P
authors.lastname: Cullis
authors.forename: J
authors.initials: J
authors.lastname: Heyes
authors.forename: L
authors.initials: L
authors.lastname: Palmer
authors.forename: I
authors.initials: I
authors.lastname: MacLachlan
mesh_terms: D004075:Diglycerides; D016503:Drug Delivery Systems; D018014:Gene Transfer Techniques; D008081:Liposomes / Q000493:pharmacokinetics; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism; D010957:Plasmids; D011092:Polyethylene Glycols
chemical_list: D004075:Diglycerides; D008081:Liposomes; D011092:Polyethylene Glycols