Experimental Drug Shows Promise for Genital Herpes
But larger, longer trials are needed, experts say
Even with that daily treatment, there is still viral shedding and the drugs cut HSV transmission by only about half, said Dr. Anna Wald, lead researcher on the new study.
"Clearly, we'd like to do better," said Wald, a professor of allergy and infectious disease at the University of Washington, in Seattle.
Acyclovir, the oldest of the existing drugs, was developed in the 1980s. All three medications had a big impact on managing genital herpes when they came out, said Dr. Lawrence Stanberry, an infectious disease expert at Columbia University Medical Center/NewYork-Presbyterian Hospital, in New York City.
Stanberry agreed, however, that the drugs fall short when it comes to preventing HSV transmission. Plus, he said, doctors are seeing some viral resistance to acyclovir in patients with compromised immune systems, such as people with HIV.
The ultimate hope is to develop drugs that eliminate dormant HSV from the nerve cells, said Stanberry, who was not involved in the new study.
"But we don't have anything like that," he said. "And [pritelivir] is not it either."
"[But] it's exciting that there's a new class of drugs," Stanberry said. "This has the potential to improve treatment."
The study, funded by German drug maker AiCuris, included 156 adults with HSV-2 infections. They were randomly assigned to one of five groups. One group received placebo pills, while the other four took different doses of pritelivir.
Over 28 days, patients on the highest drug dose (75 milligrams a day) showed the biggest effects. They had viral shedding on only 2 percent of those days, versus almost 17 percent in the placebo group. Another group, which received a once-a-week 400 mg dose, also showed a significant drop in viral shedding.
That's important, Stanberry said, because if a once-weekly drug dose were effective, that would make treatment more convenient.
There were no significant side effects from the medication, according to the researchers. But, Ward said, the study was small and short-term, so the safety question needs more investigation.
Further clinical trials of the drug are on hold right now. Last May, the U.S. Food and Drug Administration suspended the work after research in monkeys showed some unexpected blood and skin abnormalities.
It's not clear why, Ward said. "We haven't seen those effects in humans," she said.