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 plasmid into skeletal muscle is still a relatively inefficient and highly variable method of gene transfer. However, published reports have shown that application of an electric field to the muscle immediately after plasmid injection increases gene expression at least 2 orders of magnitude. Using this methodology, we have achieved potentially therapeutic circulating levels of human factor IX (hF.IX) in mice and dogs. A plasmid encoding hF.IX formulated with a protective, interactive, noncondensing (PINC) polymer was injected into the skeletal muscle followed by administration of multiple electrical pulses (electroporation). In mice long-term expression was achieved and the ability to readminister formulated plasmid was demonstrated. In normal dogs, expression of hF.IX reached 0.5–1.0% of normal levels. The transient response in dogs was due to the development of antibodies against hF.IX. Elevated circulating creatine kinase levels and histological examination indicated transient minor trauma associated with the procedure. These data show that gene delivery using a plasmid formulated with a PINC polymer augmented with electroporation is scalable into large animal models and represents a promising approach for treating patients with hemophilia B.