Dr. Richard Heller: Gene electrotransfer: an effective tool for delivering plasmid DNA encoding therapeutic agents for multiple applications

Richard Heller

Depart. of Medical Engineering, Univ. of South Florida, Tampa, FL, USA

Gene electrotransfer: an effective tool for delivering plasmid DNA encoding therapeutic agents for multiple applications

Gene therapy has the potential to be utilized as an effective therapeutic approach for a variety of disorders. While there have been some major advances, there are still many issues that need to be resolved. One of the critical aspects to advance the field of gene transfer is controlled delivery to the appropriate target. Non-viral gene delivery systems including the use of physical delivery approaches have seen tremendous growth and success. Our group has explored the use of electroporation (gene electrotransfer; (GET)) and have developed several protocols for a variety of tissues. The focus has been to find the correct parameters that deliver the transgene in a manner that yields a reproducible expression pattern with minimal to no adverse effects. Expression of the transgene can be controlled by manipulating the delivery parameters. This control of the expression profile is a key element in developing successful therapeutic applications. Effective protocols to deliver plasmid DNA encoding IL-12 (pIL-12) directly into tumors with reduced or no adverse events were developed utilizing gene electrotransfer (GET)1. We have demonstrated that obtaining the correct expression of plasmid IL-12 delivered intratumorally can increase immune cell infiltration and induce a local as well as systemic response2. We have further explored combining this approach with checkpoint inhibitors such as anti-PD-1 and anti-PDL13. This combination resulted in higher responses to distant lesions in a peritoneal metastatic melanoma model in mice. This was one therapeutic application that demonstrated that the control of the expression profile is a key element in developing successful therapeutic applications. We have explored utilizing this approach for other potential therapeutic applications. One of these areas has been to enhance delivery of plasmid DNA to the skin. We have recently established that the addition of moderate heat (43oC) in combination with GET can significantly enhance delivery4. We further evaluated the combination of moderate heating and GET for delivering a DNA vaccine against Hepatitis B Virus. Guinea pigs were injected intradermally with a plasmid encoding Hepatitis B viral surface antigen followed by GET with or without moderate heating. After a prime/boost vaccination, αHBSAg serum titers indicated a 12-fold increase in antibody levels up to 30 weeks post-vaccination in those animals receiving GET combined with moderate heating compared to GET alone5. In addition, a single dose vaccination generated titers significantly higher than injection of plasmid DNA alone. We also investigated delivering a plasmid encoding Human Factor IX as a protein replacement therapy for treating Hemophilia B. A guinea pig model was also used for this work and elevated Factor IX protein serum levels were detected6. In addition to DNA vaccine delivery and protein replacement, GET has also been tested as a potential therapeutic approach for accelerating wound healing or for inducing reperfusion of ischemic tissue. The immunotherapy approach for cancer has now been successfully tested in multiple clinical trials. Work is ongoing to obtain the data to translate to the clinic the other therapeutic approaches utilizing skin as the target.

Selected references

• Daud, A.I., DeConti, R.C. Andrews, S., Urbas, P., Riker, A.L., Sondak, V.K., Munster, P.N., Sullivan, D.M., Ugen, K.E., Messina, J.L., and Heller, R. Phase I trial of interleukin-12 plasmid in patients with metastatic melanoma. Journal Clinical Oncology, 26(36): 5896–5903, 2008
• Shirley, S., Lundberg, C., Li, F., Burcus, N. and Heller, R. Controlled Gene Delivery Enhances Therapeutic Outcome for cancer Immune Therapy. Current Gene Therapy 15:32-43, 2015
• Shi, G, Edelblute, C., Arpag, S, Lundberg, C and Heller R. IL-12 gene electrotransfer triggers a change in immune response within mouse tumors. Cancers 10:498, 2018
• Donate, A, Bulysheva, A, Edelblute, C, Jung, D, Malik, MA, Guo, S, Burcus, N, Schoenbach, K and Heller R. Thermal assisted in vivo gene electrotransfer. Current Gene Therapy 16(2):83-89, 2016
• Edelblute, CM, Mangiamele, C and Heller, R. Moderate heat-assisted gene electrotransfer for cutaneous delivery of a DNA vaccine against Hepatitis B virus. Human Gene Therapy 32(21-22):1360-1369
• Edelblute, CM, Mangiamele, C and Heller, R. Moderate heat-assisted gene electrotransfer for Factor IX protein replacement therapy in the skin. Pharmaceutics 13(11):908, 2021