University of Utah doctors are part of a clinical trial testing a new type of drug to treat genital herpes.

The new drug, ASP2151, by Astellas Pharmaceuticals, works differently from drugs now used to treat Herpes Simplex Virus. ASP2151 inhibits a viral process called helicase-primase, which is needed to unravel DNA as the virus replicates. The existing drugs, acyclovir, valacyclovir and famciclovir, typically have limited effect — "about one-third reduction on symptoms with no effect whatsoever on the interval to the next outbreak," said Dr. John D. Kriesel, an infectious disease expert at University Hospital.

An estimated 20 percent of the adult population has genital herpes, about half of them without symptoms. As many as 10 percent of the total have very problematic disease, Kriesel said.

The new drug "appears to be very potent in preclinical studies, so we're enthusiastic about how it might perform in human patients in this clinical trial."

There's no guarantee, though, he added, because sometimes drugs that look good in animal testing "have flopped" when tried in humans.

Some studies have also suggested that the new drug provides a longer interval before recurrence. Current drugs have no effect on recurrence. ASP2151 also seems to have some effect on resistant virus. Although few people have resistant virus — primarily patients who are immunocompromised or have cancer — they have been hard to treat with existing medications. "It would be nice to see more improvement," Kriesel said.

The nationwide clinical trial will involve 650 patients, and the U. hopes to enroll 20 to 60.

A blood test will be used to confirm that would-be participants have genital herpes. Enrollees must be at least 18 and have had four or more outbreaks in the past year. Exclusions include being immunocompromised or having significant underlying medical condition. Participants will be paid for time and travel. Two-thirds of enrollees will receive the active study medication, one-sixth will receive placebo and one-sixth valacyclovir, assigned randomly.

To learn more, call 801-587-3831.

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