Vical has been awarded grant funding from the National Institute of Allergy and Infectious Diseases division of the NIH to develop a plasmid DNA-based vaccine to inhibit recurring lesions in patients latently infected with herpes simplex virus type 2 (HSV-2). The program advanced to a Phase 1/2 trial in December 2013 on strong preclinical results, including a reproducible statistically significant reduction in viral lesion occurrence in guinea pigs latently infected with HSV-2. The plasmid DNA encoding the HSV-2 antigens was formulated with Vaxfectin®, Vical's proprietary cationic lipid adjuvant.
Genital herpes is a recurrent, lifelong viral infection. HSV-2 is the most common cause of recurrent genital herpes in the United States. Approximately one in six persons aged 14 to 49 in the United States have genital HSV infection, with a rate of 1 million new infections per year.
Most persons infected with HSV-2 have not been diagnosed. Many such persons have mild or unrecognized infections but shed virus intermittently in the genital tract. Many genital herpes infections are transmitted by persons unaware that they have the infection or who are asymptomatic when transmission occurs. HSV-2 is a lifelong infection and results in pain and discomfort during outbreaks. It is associated with considerable psychological and psychiatric morbidity, resulting in a significant impact to the quality of life of the individual. It poses a risk for immunocompromised individuals, where outbreaks are longer-lasting and more severe.
The current standard of care is the use of antiviral drugs designed to specifically inhibit viral replication after the initial infection and recurrent lesions arising from the latent infection. Antiviral drugs only treat the symptoms of the viral infections, however, and they do not prevent the infection from occurring nor do they reduce the frequency of recurrent lesions arising from latent infection. A therapeutic vaccine could inhibit recurrent lesions and prevent further transmission.