Principles of electroporation for gene therapy

Abstract

Gene therapies can compensate for missing or mutated proteins, directly treat cancer, act as cancer or infectious disease vaccines, or modulate protein expression. For any type of gene therapy, the dose of expressed protein should be appropriate to correct the disease. Therapeutic development is often hampered by the concept that an optimal therapy is one with the highest and longest transgene expression coupled with the inability to predict the ultimate expression levels and duration of the therapeutic protein. Gene therapy methods can be loosely described as biological or nonbiological. All gene therapies achieving regulatory approval to date are biological gene therapies delivered by engineered viruses. Nonbiological transfer by chemical and physical means removes the need for a biological vector and improves the safety profile. Several nonbiological delivery methods, including electroporation, have been developed to enhance gene delivery. In electroporation or electropermeabilization, controlled electric pulses produce temporary permeabilized areas in a cell's membrane to allow molecular transfer. Electrotransfer has been used to transport a variety of molecules ranging from ions to drugs to nucleic acids across the plasma membrane and into cells. Electrotransfer also allows molecular transfer in vivo to many tissue types. After satisfactory preclinical studies developing gene therapies using this delivery method, several therapeutic applications have reached Phase II clinical trials. This chapter overviews the steps necessary to develop a gene therapy using electrotransfer, including vector design, electric pulse choice, and electrode optimization. In addition, the complexity of the tissue target must be considered for successful development of an electrotransfer-based gene therapy.