Drugs for HIV prevention: topical and systemic PrEP

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Connie Celum, MD, MPH, professor of medicine and global health at the University of Washington, took the plenary stage Wednesday morning at the 18th Conference on Retroviruses and Opportunistic Infections (CROI) to provide an overview on progress to date on topical and systemic pre-exposure prophylaxis (PrEP), where antiretroviral drugs are used to protect an individual prior to possible HIV exposure to reduce the likelihood of infection.  She reviewed the now well-know results of the CAPRISA and iPrEx studies and also highlighted trials currently in progress.

In 2012 we will have important results about PrEP in injection drug users and in HIV discordant heterosexual couples.  By 2013 we will have important results from other trials including the so-called VOICE trial which will compare topical and oral PrEP.  Notwithstanding all this clinical trial activity, there will be important questions that will remain unanswered, Celum said.  There will be no data on the impact on topical or oral PrEP in pregnant and breastfeeding women, adolescents, and persons with chronic hepatitis B.  There will not be information on the efficacy of tenofovir gel for anal sex in men or women. There will not be long-term adherence information or information about the efficacy of intermittent as opposed to daily use of these interventions.

Critical work remains to be done on different PrEP delivery platforms, Celum said, including vaginal film, vaginal rings and long-term injectibles.  A vaginal ring using the drug dapivirine is scheduled to enter Phase III trials in mid- 2011.

There are many implementation challenges including who to target, where to deliver this intervention, and how to attain high access and coverage to realize a population level public health impact, Celum said. Two abstract presentations at this conference highlight level of effectiveness, drug and delivery costs, and effective targeting as the key ingredients in determining cost-effectiveness.

Celum noted that it is critical to reframe the discussion from prevention versus treatment to prevention and treatment.  She outlined a combination, or high-impact, prevention strategy that would include: HIV testing; risk reduction counseling including couples counseling and partner reduction strategies; antiretroviral therapy for HIV-infected persons; medical male circumcision; and topical and oral PrEP.

Celum reminded the audience that access and adherence to PrEP are the key determinants and are ultimately more important than the effectiveness of the product itself.

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