A vaginal gel that sharply reduces a woman’s risk of infection with the AIDS virus is even more effective against genital herpes, a much more common risk for young American women, a new study has found.
In an unexpected bonus, the researchers also noted that it reduced herpes by 51 percent. In the trial, the gel was used within a few hours before and after sex. Another trial now going on is testing whether using it daily is more effective.
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The study, by researchers from the National Institutes of Health, Gilead Sciences Inc. and universities in Belgium and Italy, suggests that the microbicide gel, which was originally developed to fight AIDS in Africa, could lower the incidence of herpes in many women.
“This could be incredibly helpful,” said Dr. Jeanne Marrazzo, a herpes expert from the University of Washington’s medical school. “Protection that a woman can control is the holy grail in this field. It’s hard for me to believe that something that protects against both H.I.V. and herpes wouldn’t be appealing to a lot of young American women.”
An executive at Gilead, the company that makes tenofovir, the anti-AIDS drug that is the gel’s active ingredient, said the company was debating whether to spend the millions of dollars needed to get the gel approved for the American market. Even if the company pressed ahead immediately, “it would be three to four years before we were ready to submit data” to the Food and Drug Administration, Norbert W. Bischofberger, Gilead’s chief scientific officer, said.
Genital herpes is far more common than AIDS. The World Health Organization estimates that 20 percent of all sexually active adults have it. In the United States, the Centers for Disease Control and Prevention estimates that 21 percent of sexually active women have it, including 16 percent of all white women and 48 percent of all black women.
While not fatal, the infection can be very painful, ruining sexual pleasure. The blisters it causes, which resemble the cold sores caused on the lips by a related virus, can also be an entryway for more dangerous pathogens, including H.I.V. and syphilis.
It can be transmitted when neither partner has sores, and even using a condom is effective in preventing infection only half the time, said Dr. Anna Wald, a herpes specialist at the University of Washington’s school of public health, because — unlike AIDS — it can be transmitted by skin-to-skin contact, not just in semen or vaginal fluid.
And although it can often be controlled with another drug, acyclovir, herpes is not curable.
The new study, published online by Cell Host and Microbes this week, explains the surprise result of a much-heralded 2010 clinical trial done in South Africa.
That trial, run by Caprisa, an AIDS research center in Durban, showed for the first time that tenofovir gel protected women against H.I.V. It also showed that the roughly 450 women in the survey who did not have herpes were even better protected against it than they were against the AIDS virus.
Over all, the gel reduced H.I.V. infections by 39 percent. That announcement was greeted with a standing ovation by scientists at the international AIDS Conference in Vienna last year because it was the first weapon that women at risk of AIDS could use without a man’s knowledge.
In an unexpected bonus, the researchers also noted that it reduced herpes by 51 percent.
The new study, involving lab experiments, was done to explain why the trial worked, said Dr. Salim Abdool Karim, a professor of epidemiology at the University of KwaZulu-Natal in South Africa and Columbia University and one of the Caprisa trial leaders.
“We were very pleasantly surprised to see such a potent effect,” he said. “However, until now, we had only a hypothesis for the mechanism of action — no clear-cut data.”
The new study showed that when tenofovir enters human tissue it is converted into a form that disrupts an enzyme that herpes needs to make copies of itself.
In laboratory cultures of tonsil and cervical tissue, it lowered herpes viral levels by as much as 99 percent. It also prolonged the lives of mice that were given massive skin infections of herpes.
Taken as a pill, tenofovir inhibits H.I.V. but not herpes. Getting it into the vaginal wall is apparently crucial to its success.
Tissue concentrations of the drug are up to 100 times higher with a gel than with a pill, said Leonid Margolis, chief of intercellular interactions at the National Institute of Child Health and Human Development and an author of the study.
While the final gel trial was done in South Africa because AIDS rates there are so high, earlier safety and acceptability tests were done in several countries, including the United States. American heterosexual couples did not find the gel unpleasant; nor did South African couples, Dr. Karim said. (Gay men having anal sex have complained that it was too watery, so new formulations are in the works.)
“I’m confident American women would accept it,” Dr. Wald said.
In the Caprisa trial, the gel was used within a few hours before and after sex. Another trial now going on is testing whether using it daily is more effective.
The gel may be even more effective against herpes than the 51 percent figure reached in the Caprisa study. Among the subset of women who said they used it consistently and who gave back enough empty gel applicator tubes to confirm they were telling the truth, the protection rate against H.I.V. was 54 percent and the protection rate against herpes was 62 percent, Dr. Karim said.
http://www.nytimes.com/2011/10/21/health/research/21herpes.html?_r=3
