A combination of poloxamers increases gene expression of plasmid DNA in skeletal muscle

Intramuscular administration of plasmid DNA is a promising strategy to expr ess therapeutic genes, however, if is limited by a relatively low level of gene expression. We report here that a non-ionic carrier, SP1017, composed of two amphiphilic block copolymers, pluronics L61 and F127, also known as poloxamers, significantly increases intramuscular expression of plasmid DNA . Two reporter genes, luciferase and beta-galactosidase, and one therapeuti c gene, erythropoietin, were injected intramuscularly with and without SP10 17 into C57Bl/6 and Balb/C mice and Sprague-Dawley rats. SP1017 increased g ene expression by about 10-fold and maintained higher gene expression compa red with naked DNA. Comparison of SP1017 with polyvinyl pyrrolidone (PVP) s howed that SP1017 exhibited a significantly higher efficacy and its optimal dose was 500-fold lower. Experiments with beta-galactosidase using X-gal s taining suggested that SP1017 considerably increased plasmid DNA diffusion through the tissue. SP1017 also improved expression of the erythropoietin g ene leading to an increase in its systemic level and hematocrits. Previous toxicity studies have suggested that SP1017 has over a 1000-fold safety mar gin. Poloxamers used in SP1017 are listed in the US Pharmacopeia as inactiv e excipients and are widely used in a variety of clinical applications. We believe that the described system constitutes a simple and efficient gene t ransfer method to achieve local or systemic production of therapeutic prote ins.