With a deployable HIV vaccine still years away, the U.S. Centers for Disease Control and Prevention on Wednesday recommended that Americans at high risk of contracting the virus that causes AIDS take a daily pill that’s been shown to prevent infection. The comprehensive, guide posted online and intended for physicians signaled clear federal support of a preventive measure known as pre-exposure prophylaxis, or PrEP.
It also sent a clear message that “prevention is part of getting this epidemic under control,” said Dr. Deborah Donnell of Fred Hutchinson Cancer Research Center’s Vaccine and Infectious Disease Division.
“In our heart of hearts, everybody believes that,” said Donnell, who leads the HIV Prevention Trials Network’s Statistical Data Management Center . “But there’s always somebody who stands up and says we don’t have the resources.”
The pill, called Truvada, contains two antiretroviral medicines that are also used, in combination with other drugs, to treat HIV. Numerous studies have shown those who take the daily pill consistently have about a 90 percent lower risk of getting HIV than those who don’t.
Donnell and other researchers, meanwhile, are already working on the next hurdle: testing a longer-acting, injectable drug that would overcome one of the pill’s major drawbacks: If it is not taken every day, the level of medicine in the bloodstream may not be enough to block infection.
The HIV Prevention Trials Network plans trials of two injectables in the next two years in the United States, South America and Africa. Besides aiming for a longer acting drug, researchers want to use an agent that is not already used to treat HIV to lessen the risk that resistance would develop should a person take the treatment intermittently and become infected. Although alternate medications can be used to treat HIV in the United States, Truvada is the backbone of treatment in sub-Saharan Africa and other developing countries.
The network is a collaborative effort funded by the National Institute of Allergy and Infectious Diseases, a division of the NIH. Besides Donnell, other principle investigators are at the University of North Carolina, Columbia University and Johns Hopkins.
Donnell was the statistician for the Partners PrEP Study Team, led by University of Washington researchers, to study the use of PrEP among heterosexual couples in which one partner is infected and one partner is not. The findings of that trial, published in the New England Journal of Medicine in 2012, were instrumental in winning U.S. Food and Drug Administration approval of Truvada as a prophylaxis.
In addition to working on trials of injectable PrEP drugs, the HIV Prevention Trials Network is now involved in a study on how to ensure that the daily pill is used effectively in communities at highest risk of contracting HIV.
The CDC guidelines recommend that PrEP be considered for people who are “at substantial risk for an HIV infection,” including gay men who don’t use condoms, intravenous drug users who share needles or heterosexual men or women who don’t regularly use condoms during sex with partners who inject drugs or have bisexual male partners.
The group at highest risk in the United States is black men who have sex with men. A study out of Atlanta presented at the Conference on Retroviral Infections in Boston in March showed that a staggering one in 10 young gay or bisexual African-American men become infected with HIV each year. Donnell and fellow researchers in the HIV Prevention Trials Network are doing a pilot project for delivering Truvada to this community at three sites in the United States. In addition to the drug itself, the trial will look at the effectiveness of a coordinated care package that includes social workers and nurse practitioners and looks at issues of access, adherence and recognizing risks.
“The question we’ll be asking is, ‘if we provide it, will they come,’” Donnell said. “We’re trying to figure out what are the issues in this person’s life, and can we help them with that and through that—get them to a place where they are interested in PrEP and help them be successful.”
A group of 68 leading HIV/AIDS and health organizations issued a strong statement of support for PrEP as an important HIV prevention strategy. But PrEP also has critics. Some argue that, used properly, condoms already provide significant protection against HIV infection, and that PrEP is both expensive (a daily dose costs about $10,000 a year, though it is usually covered by insurance) and possibly riskier, considering that some people won’t remember to take pills daily. The CDC guidelines stress the continued importance of condoms as HIV prevention and point out that condoms provide protection against gonorrhea, chlamydia, hepatitis and other sexually transmitted diseases, which PrEP does not.
Internationally, the debate comes down to resources: Does an economically strapped, developing country spend its limited resources on medications to treat HIV or to prevent it, particularly when studies show that treating HIV can lower virus levels enough to prevent its transmission?
“The desirable answer is we do both,” said Donnell. “But in resource-constrained settings, which are basically everywhere, it’s very difficult for ministries of health to make these kinds of choices.”
Donnell sees PrEP as particularly important for what researchers call vulnerable populations, such as young women in sub-Saharan Africa where the gender power dynamics are such that they may be at risk for HIV and not have a lot of control over it. She also talked about how PrEP could provide protection during what an African colleague calls “seasons of risk”—years where they are sexually active with more partners and years when they are not.
But even if a longer-last drug emerges from trials, people would need to return every four months for an injection, which means that adherence could still be a problem.
“The holy grail is vaccines,” said Donnell. “We have daily pills that work, and an injectable would be somewhere in between. It’s clearly a step in the right direction.”
Mary Engel is a former staff writer at Fred Hutchinson Cancer Center. Previously, she covered medicine and health policy for the Los Angeles Times, where she was part of a team that won a Pulitzer Prize for Public Service. She was also a fellow at the Knight Science Journalism Program at MIT. Follow her on Twitter @Engel140.