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See Inside Scientific American Volume 311, Issue 1

New Microbicides Prevent HIV Infection in Women

New drugs for women are passing through key trials


HIV kills immune system cells.


SCIENCE SOURCE

Doctors now consider HIV infection to be a chronic disease rather than a death sentence because of the success of antiretroviral drugs (ARVs), which stop the infection's progression to AIDS. With that success in hand, the top priority is now prevention. The choices available to most of the world—abstinence, condoms and male circumcision—are not doing enough; more than 6,000 people contract HIV every day. And those methods are especially problematic for women, who, because of social and economic circumstances, often have less control over their options.

As an alternative for women, scientists are testing a new class of antiretroviral drugs, called ARV microbicides, that prevent HIV infection altogether. Researchers have fashioned the microbicides into an array of devices currently undergoing human trials. “These are extremely promising products,” says Robert Grant, an AIDS expert at the University of California, San Francisco. “I'm optimistic we can end HIV, but for too long we've been looking for the holy grail, a single product to prevent HIV. It's not one size fits all.” Here are three of the microbicide options in development today.

Stay-in-Place Ring
Placed in the vagina, this silicone ring releases the ARV drug dapivirine for one month. Dapivirine is a reverse transcriptase inhibitor: a drug that blocks HIV's replication from RNA to DNA, halting its takeover of human cells. More than 5,000 African women are testing the ring in two phase III clinical trials that will end in 2016. If safe and effective, it could become a two-in-one device: researchers are developing a dapivirine ring with birth control to prevent both HIV and pregnancy.

Gel for before Sex
Tenofovir gel, another reverse transcriptase inhibitor, comes in a tamponlike applicator that women use both before and after sexual intercourse.* The clear gel was the first microbicide to indicate significant reduction in HIV in humans in a large clinical trial; in the study, which had nearly 900 women participating, the gel reduced infection by 54 percent in women who used it consistently. Researchers are continuing to test its effectiveness at nine sites in South Africa. Those results are expected in early 2015.**

Gel for after Sex
Raltegravir gel could someday offer what the others do not: protection against HIV when applied after sex. Raltegravir stops HIV late in its life cycle, just before the virus integrates into the human chromosome. The Centers for Disease Control and Prevention evaluated the gel in macaques in March and found it highly effective in preventing infection up to three hours after exposure. If it passes future trials and becomes an option, it could give women a backup, especially in cases of sexual assault.

*Correction (6/25/14): This sentence was edited after print publication. It originally described the application of tenofovir gel only before sex. It is also applied after sex.

**Editor's Note (6/25/14): The estimated date for the study results given in the original print publication was late 2014. They have been subsequently revised.

 

This article was originally published with the title "How to Curb an Epidemic."

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