Novel stable, concentrated, biologically active and ready-to-use lipid-comprising drug delivery complexes and methods for their production are described. The complexes of the invention comprise a drug, at least one lipid species, optionally at least one polycation, and at least one targeting factor. The at least one lipid species may comprise a pegylated lipid. The complexes of the invention may provoke lower levels of inflammatory cytokines such as tumor necrosis factor-α (TNF-α). The method described herein provides for the large scale production of lipid-comprising drug delivery systems useful for gene therapy and other applications.