Genital Herpes Drug Shows Promise

Genital herpes may have met its match, a new industry-sponsored study led by University of Washington researchers suggests.

Called pritelivir, the drug is a product of the pharmaceutical company AiCuris, which backed the new study published in the New England Journal of Medicine.

According to the researchers, an estimated one in six Americans between ages 14-49 have herpes, with the most recurrent type being that caused by herpes simplex virus 2, or HSV-2. In most cases, symptoms are either mild or absent, meaning infected individuals may be unaware of their status and their potential to spread the virus. When symptoms do flare up, however, they can result in pain and sores in the genitals and lips.

The new drug is the first in a new class that inhibits HSV by targeting the virus's so-called helicase-primase enzyme complex. Other treatments - including Famvir, Valtrex and Zovirax - work by hampering viral replication by inhibiting an enzyme known as HSV DNA polymerase. However, while treatments currently in existence are able to shorten outbreaks, reduce transmission and prevent recurrences, a cure has yet to be found.

In the study, 156 patients with a genital HSV-2 infection received either a placebo or four dosage regimens of pritelivir. All patients were then asked to keep a diary in which they recorded any signs or symptoms and swab their genital areas each day. The swabs then underwent testing in order to determine whether the virus was shedding, and if so, how much.

Of the four different regimens, the one in which participants were given an initial dose of 300 milligrams followed by 75 mg each day resulted in the fewest number of days with genital lesion. The dose also resulted in an 87 percent reduction in days of viral shedding when compared to those taking the placebo. In addition, there was far less virus present during breakthrough shedding in those taking pritelivir, the researchers found.

"These data suggest this drug may be a potent treatment for HSV-2," said Dr. Anna Wald, lead author and professor of medicine, epidemiology and laboratory medicine at the University of Washington. "That's exciting because we have not had a new drug for herpes for three decades. In addition, our approach of using viral shedding as an endpoint clearly defined the dose that should be used in future studies."

However, while side effects were reportedly mild, additional clinical studies are on hold while health officials investigate a toxicology study in which monkeys receiving doses 70-900 times higher than a 75 mg dose in humans developed blood and skin abnormalities.