Antiretrovirals for Prevention: Panacea or Pandora's Box

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The following post is by Kenneth Mayer, MD, in response to the recent CAPRISA 004 trial results presented at the International AIDS Conference in Vienna. He is the co-chair of the Global Center’s Scientific Advisory Committee and was recently elected to serve on the International AIDS Society (IAS) Governing Council.

Kenneth H. Mayer, MD, Professor of Medicine & Community Health at Brown University and Director of the Brown University AIDS Program

Treatment as prevention is a prominent theme at the 18th International AIDS Conference in Vienna, as is the remaining challenge of extending lifesaving treatment to millions of HIV-infected individuals in the developing world.

The CAPRISA 004 study from South Africa presented a critical finding – that the use of an antiretroviral (ARV)-containing gel leads to significant levels of protection for high-risk women against becoming HIV infected. The trial involved 889 South African women between the ages of 18 and 40, who were not infected with HIV but were sexually active and at high risk to become infected. (For study results, click here). The gel achieved close to 50 percent reduction in new HIV infections among the women who received the active gel compared to placebo gel. It also showed similar protection against HSV-2. What is particularly notable in the findings is that women who were highly adherent to using the gel before and after coitus had substantially higher levels of protection. Therefore, future ARV chemoprophylaxis interventions that better enhance product adherence will be particularly important.

The gel studied in this trial is not currently available, but oral medications containing tenofovir are. There are several studies underway in a variety of populations looking at whether oral chemoprophylaxis is an effective means of HIV prevention. Oral treatment results in the wide diffusion of the drug in the body, protecting all potential sites that might come into contact with the virus, but it can also lead to certain side effects.

By early 2011 the results of several studies on oral ARVs to prevent HIV infection will be available. If the results are positive, public health officials and governments worldwide will face a host of new dilemmas. For example, with the finite pool of funds available to purchase ARV drugs, how can they be most effectively used? Clearly, the first priority has to be to provide drugs to individuals who are already infected with HIV, especially those individuals who might otherwise get sick and die if they do not receive treatment in the near term. Moreover, there are several lines of evidence to suggest that people who go on treatment are less likely to transmit HIV to others, so there might be a prevention “dividend” to initiating antiretroviral therapy at earlier stages in the disease.

Even apart from the competing demands presented by those needing ARV therapy for treatment, the use of ARV drugs for prevention cannot be perceived as a panacea. There are significant costs, the potential for side effects, the need for careful clinical monitoring and concerns about risk compensation. Yet drugs offer the best opportunity to slow the epidemic by earlier treatment of infected people and by careful use of chemoprophylaxis for specific populations of at-risk individuals. For example, this could be a critical intervention for discordant couples and there are very high percentages of HIV serodiscordant couples in many high-prevalence African nations.

International AIDS conferences are a bellwether for major advances and challenges in the epidemic. The first of these conferences was held in Atlanta in 1985, at which time former U.S. Secretary of Health and Human Services Margaret Heckler promised an AIDS vaccine in five years. At the 1996 conference in Vancouver, the first group of concepts that supported the use of three individual ARV drugs, to effectively control HIV replication and extend the lives and health of HIV-infected persons, was demonstrated. One of the landmark conferences was held in Durban, South Africa, in 2000, because it shed a light that the death of a quarter to a third of the populations of several countries in sub-Saharan Africa was imminent without access to these life-saving, highly-effective ARV drugs. The recognition of the dire circumstances faced by people who did not have access to lifesaving medication compelled governments and foundations to develop programs that have saved millions of lives.

Many of us have been looking forward to the International AIDS Conference in Vienna to hear the results of the CAPRISA trial. Regrettably, this announcement occurs in the context of a worldwide economic recession that has slowed the scale-up of HIV treatment and prevention to persons in the developing world. Over the next few years, there will be a need for careful discourse among affected communities, advocates, clinicians, public health officials and funders in order to decide how to determine the best mix of the use of ARVs for both treatment and prevention. Clearly the advent of information suggesting benefits of ARV chemoprophylaxis should not do anything to jeopardize the access of people living with HIV to these lifesaving medications. Yet, at the same time, in the absence of a highly effective vaccine, using these medications wisely to mitigate the spread of this epidemic approaching its fourth decade of fury has to be carefully considered.

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