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CROI 2015: Partners PrEP Demo project: Near Elimination of HIV Transmission with ART and PrEP

, by Emily Newman

BETA is attending and reporting from the 2015 Conference on Retroviruses and Opportunistic Infections this week in Seattle from February 23 to 26—bringing you the latest news, updates, and research on HIV treatment and prevention.

Impressive results from the Partners PrEP demonstration project were presented at CROI on Tuesday. Jared Baeten, MD, PhD, from the University of Washington, presented findings from an open-label multi-national study showing that PrEP can be used successfully as a “bridge” to antiretroviral therapy (ART) in serodiscordant couples.

Not all people living with HIV are able to, or want, to start ART immediately—placing their sexual partners at higher risk of transmission. “Staged” use of PrEP can therefore be employed as a bridge—to protect the HIV-negative partner before (or if, ever) their HIV-positive partner achieves viral suppression.

The demonstration project enrolled 1,013 heterosexual serodiscordant couples in Uganda and Kenya that were classified as “higher risk,” with risk factors (such as younger age, reporting condomless sex in the last month, or higher viral loads in the HIV-positive partner) that might make transmission more likely.

The treatment strategy they used—providing PrEP to the HIV-negative partner only until the HIV-positive partner had been on ART for six months, permitting time to achieve viral suppression—proved successful.

They observed an estimated 96% reduction in HIV incidence as of January 2015 (the study is ongoing).

Enrolling participants in the study without any intervention to provide a control group for the study would have been unethical. So, in order to estimate an expected HIV incidence rate and number of infections, Baeten’s team used a simulation model and data from previous studies of serodiscordant couples to determine that 5.2% of participants (39.7 HIV infections) that might have become infected without ART and PrEP.

The difference between the HIV infection risk expected in an untreated population and that actually observed, reported Baeten, was “highly statistically significant.”

Thus far, their team has only had two individuals test positive for HIV—both had started PrEP but reported lapses in use. Neither individual had detectable tenofovir levels in their plasma samples taken when they tested positive.

Baeten pointed to the importance of PrEP, especially, in contributing to their significant findings.

“We were able to demonstrate that PrEP as a bridge to ART is not only feasible in this high risk population, but highly effective in preventing HIV transmission.”

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