Gene therapy for the treatment of hemophilia B using PINC-formulated plasmid delivered to muscle with electroporation

Gene therapy, as a safe and efficacious treatment or prevention of diseases , is one of the next fundamental medical innovations. Direct injection of p lasmid into skeletal muscle is still a relatively inefficient and highly va riable method of gene transfer. However, published reports have shown that application of an electric field to the muscle immediately after plasmid in jection increases gene expression at least 2 orders of magnitude. Using thi s methodology, we have achieved potentially therapeutic circulating levels of human factor IX (hF.IX) in mice and dogs. A plasmid encoding hF.IX formu lated with a protective, interactive, noncondensing (PINC) polymer was inje cted into the skeletal muscle followed by administration of multiple electr ical pulses (electroporation). In mice long-term expression was achieved an d the ability to readminister formulated plasmid was demonstrated. In norma l dogs, expression of hF.IX reached 0.5-1.0% of normal levels. The transien t response in dogs was due to the development of antibodies against hF.IX. Elevated circulating creatine kinase levels and histological examination in dicated transient minor trauma associated with the procedure. These data sh ow that gene delivery using a plasmid formulated with a PINC polymer augmen ted with electroporation is scalable into large animal models and represent s a promising approach for treating patients with hemophilia B.