New Genital Herpes Drug Proves More Promising Than Existing Treatment in Clinical Trial

As what may be one of the most promising treatments for the herpes simplex virus 2 (HSV-2) in two decades, pritelivir, has demonstrated in a recent trial that it provides greater viral suppression than the present standard treatment, valacyclovir.

In the study, conducted by a research team led by Anna Wald, MD, medical director of virology research at the University of Washington, Fred Hutchinson Cancer Research Center in Seattle, patients who took pritelivir not only experienced less HSV shedding than those who took valacyclovir (2.4% vs. 5.3%), but they also had fewer lesions (1.9% vs. 3.9%), less pain, and fewer treatment-emergent adverse events (62% vs. 69%).

Pritelivir, which is still in the relatively early stages of development, is particularly attractive to patients with HSV-2 (otherwise known as genital herpes) because it not only limits their symptoms, but also appears to reduce the likelihood of passing the infection on to a susceptible partner. Of note: pritelivir did not completely eliminate viral shedding; practitioners and patients must remember that the protection is only partial. Given that many infected individuals often do not show signs of infection but still shed viral cells intermittently, “management of genital HSV should address the chronic nature of the disease rather than focusing solely on treatment of acute episodes of genital lesions,” a CDC spokesperson also noted. The spokesperson added that HSV-2 infections tend to have “much more frequent” recurrences and shedding.

In the double-blind study, Dr. Wald and her team studied 91 adults—who reported having had between four and nine annual genital HSV-2 recurrences—randomized into two groups. One group received pritelivir for 28 days, followed by a 28-day “washout” period, and then received valacyclovir for 28 days. The second group received valacyclovir first, and then the 28-day washout period, followed by pritelivir.

The study was terminated before all subjects had completed the entire treatment period for both drugs due to the US Food and Drug Administration (FDA) putting a hold on the drug’s clinical use because of skin and blood abnormalities that had presented in a concurrent animal trial. Dr. Wald noted that there have been no serious side effects in humans so far, and German drug maker AiCuris is working with the FDA to partially lift the hold so that patients who are resistant to drugs in the “standard treatment family,”—which includes the drugs acyclovir, famciclovir, and valacyclovir—could participate in a new clinical trial. At the time of termination, 56 patients had completed both treatments.

Dr. Wald and her team emphasized the importance of being able to go back to the general population with further trials, noting that it is very important to develop new drugs for this incredibly common infection. (HSV-2 affects approximately one in every six adults between the ages of 14 and 49 in the United States.) The virus can also be transmitted to newborns, and can cause serious illness and even death; it can also create serious and painful lesions in patients with suppressed immune systems. Furthermore, HSV-2 infections can actually increase the risk of getting or transmitting HIV.

As researchers are testing and developing new treatments for herpes infections, the US Preventive Services Task Force (USPSTF) has called for less routine testing for the infection because “the potential harms of screening outweigh the benefits.” Because “blood test screening for genital herpes is highly inaccurate and there is no cure, so screening, early identification and treatment are unlikely to affect the course of the disease.” With this in mind, novel effective treatments for the infection are that much more important to ensure the population remains safe. Currently, the CDC states that 1 in 6 individuals aged 14 to 49 years are infected with genital herpes in the United States.