Lyoprotectant Optimization for the Freeze-Drying of Receptor-Targeted Trojan Horse Liposomes for Plasmid DNA Delivery

Trojan horse liposomes (THLs) are a form of ligand-targeted nanomedicine, where a plasmid DNA is encapsulated in the interior of a 100-150 nm pegylated liposome, and the tips of a fraction of the surface pegylated strands are covalently linked to a receptor-specific monoclonal antibody (MAb) via a thio-ether linkage. The goal of this work was to develop a lyophilization methodology that enables retention of the structure and function of the THLs following the freeze-drying/hydration process. THL fusion and leakage of plasmid DNA were observed with several lyoprotectants, including trehalose, hyaluronic acid, gamma-cyclodextrin, or sulfobutylether-beta-cyclodextrin. However, the use of hydroxypropyl-gamma-cyclodextrin, at a 40:1 wt/wt ratio relative to the THL phospholipid, eliminated liposome fusion and produced high retention of encapsulated plasmid DNA and THL-mediated gene expression after lyophilization followed by hydration. The freeze-dried THL cake was amorphous without cavitation, and the diameters and functional properties of the THLs were preserved following hydration of cakes stored for at least six months. Intravenous administration of the hydrated freeze-dried THLs in the Rhesus monkey demonstrated the safety of the formulation. Blood plasmid DNA was measured with a quantitative polymerase chain reaction method, which enabled a pharmacokinetics analysis of the blood clearance of the THL-encapsulated plasmid DNA in the primate. The work shows that optimization of the lyoprotectant enables long-term storage of the MAb-targeted DNA encapsulated liposomes in the freeze-dried state.