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 Among women who used tenofovir gel, the annual rate of infection
with the genital herpes virus, known as herpes simplex virus type 2
or HSV-2, was 10.2 percent versus a rate of 21 percent for women who
used a placebo gel.
If the gel were to be approved and manufactured, and "if a woman was
concerned about acquiring herpes simplex virus type 2, this would be
the best protection available," chief author Dr. Salim Abdool Karim
of the Centre for the AIDS Program of Research in South Africa told
Reuters Health.
"The problem is, right now it's not available. And taking tenofovir
tablets instead of the gel doesn't have the same benefit," he said.
"You see some protection with tablets, but the levels of protection
are much lower."
HSV-2 virus infects about one in five sexually active adults
worldwide, or about 417 million people aged 15 to 49 years old, the
study team writes in the New England Journal of Medicine. The virus
is the most common cause of genital ulcers, and in South Africa, the
estimated infection rate is 50 percent to 60 percent. Throughout
Sub-Saharan Africa the rate is thought to be as high as 80 percent
in women and 50 percent in men.
Condoms provide the best protection, but even that is limited
because the virus can be shed and acquired by other parts of the
groin not shielded by a condom, Abdool Karim said.
Oral tenofovir is used to prevent and treat HIV. The test of its
ability to protect against genital herpes was grafted onto an
existing study, which ultimately demonstrated that the gel reduced
the odds of getting HIV by 39 percent.
Among the 422 women enrolled in the herpes study, half were given
applicators with the drug-infused gel and the rest were given a
placebo gel. They were told to insert the gel within 12 hours before
they expected to have sex and as soon as possible within 12 hours
after sex. The women were tracked for an average of 18 months.
The study results indicate that topical tenofovir can reduce HSV-2
acquisition by almost half, said Dr. Connie Celum, director of the
International Clinical Research Center at the University of
Washington in Seattle, by email.
"This is significant, given the lack of other interventions to
reduce HSV-2 acquisition other than condoms," said Celum, who was
not connected with the study.
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The drug worked best among women who used the gel religiously. When
drug levels in the vagina were high, the annual rate of herpes-2
infection was less than 6 percent compared to almost 16 percent when
there was no detectable tenofovir in the vaginal fluid.
The study did not detail side effects, although an earlier report
available online says the drug can increase the risk of mild
diarrhea.
"Because it's in the gel formulation, it leads to very high levels
in the genital tract and very low levels in the blood, so very
little is absorbed and you get very limited side effects," Abdool
Karim said. "We did see a slight increase in mild diarrhea and it
wasn't statistically significant."
There was also concern that the gel might show adverse effects in
the kidneys and bones, he said, but "with the gel formation, we
didn't see either of those problems."
A key question is whether women will actually use it when the gel
gets to market.
"We've had a mixed bag of results in trying to get women to use
tenofovir gel for HIV protection," said Abdool Karim. "The main
concern has been many of these young individuals who are at highest
risk for herpes and HIV don't actually consider themselves at risk.
They don't appreciate their risk. It's the same for alcohol
consumption, dangerous driving or smoking or any of these things."
SOURCE: http://bit.ly/1DgJ5jF New England Journal of Medicine,
online August 5, 2015.
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