The products of biotechnology, recombinant proteins, monoclonal antibodies, antisense, RNA interference, or non-viral gene transfer, cannot be developed as pharmaceuticals for the brain, unless these molecules are re-formulated to enable transport across the blood-brain barrier (BBB). Large molecule drugs, and plasmid DNA, can be delivered across the BBB with receptor-specific molecular Trojan horses. Trojan horse BBB delivery systems, coupled with one of 3 different technology platforms (fusion proteins, avidin-biotin, or Trojan horse liposomes), can enable the BBB transport of virtually any large molecule drug or plasmid DNA.