Jagged Little Pills - POZ unpacks PrEP

by Adam Graham-Silverman

Some drugs approved to treat HIV may also protect people not infected with HIV if taken before they engage in high-risk activities. Then why has it been so difficult to conduct the necessary studies to prove—or disprove—the theory?

It begins with a study published in 1994 that showed that retrovir (AZT) given to HIV-positive pregnant women before and during birth—and to the infants immediately after delivery—reduced the risk of HIV transmission to the child by 67%. Next came guidelines, issued by the Centers for Disease Control (CDC) in 1998, recommending post-exposure prophylaxis (PEP) for health care workers who were accidentally exposed to HIV, followed by PEP recommendations for sexual and injection-drug exposure, issued in 2005. Then, in 2006, the world got a glimpse of some intriguing data gleaned from studying HIV-negative monkeys who remained uninfected even after being “rectally challenged” with the HIV virus. They had been given a combination of Gilead Science’s tenofovir (Viread) and emtrictabine (Emtriva).

These studies raised a logical question: Could an HIV drug (or drugs) already on the market be used by people before being potentially exposed to the virus to reduce risk of HIV infections? Are we, in essence, sitting on a valuable addition to the prevention arsenal? The idea is known as PrEP—pre-exposure prophylaxis—and at first glance it seems to present one of the most promising fronts in prevention research. The implications are many. If ARVs like Viread and Emtriva proved effective in preventing (or reducing the risk of) HIV transmission in negative people, serodiscordant couples, gay or straight, could add another layer of reliable protection or quite possibly forgo the condoms in favor of pills. And heterosexual couples could conceive the old fashioned way, without risking passing on the virus to the HIV-negative partner—let alone the baby.

“There’s no reason to believe it won’t work,” says Mark Harrington, executive director of Treatment Action Group in New York City. “People are going to have unsafe sex no matter what, so we are trying to get as many prevention interventions as we can. We desperately need any tool we can get.”

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