To evaluate the safety of a plasmid DNA-lipid complex, a series of good laboratory practice (GLP) safety studies were conducted with VCL-1005, a plasmid DNA expression vector containing both the human class I MHC HLA-B7 heavy-chain and the beta 2-microglobulin (beta 2m) light-chain genes formulated with the cationic lipid, DMRIE/DOPE. In mice, the repeated intravenous injection of VCL-1005 at plasmid DNA doses of 0.1, 1.0, or 10 micrograms for 14 days had only incidental effects on clinical chemistry and hematology, and did not result in any organ pathology. Repeated intrahepatic injections of VCL-1005 in mice did not result in significant liver histopathology or significant alterations in liver enzymes. In cynomolgus monkeys, the repeated intravenous administration of VCL-1005 at a cumulative dose of 720 micrograms of DNA had no effects on clinical chemistry, hematology, or organ pathology. Thus, systemic administration of a plasmid DNA expression vector containing the coding sequence for a foreign MHC class I molecule did not result in significant toxicity or a pathological immune response in animals. These results suggest that the direct transfer of VCL-1005, a plasmid DNA-lipid complex, could be used for the safe in vivo delivery of recombinant DNA for a cancer gene therapy trial.