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iPrEx OLE shows PrEP efficacy, adherence
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New results from the iPrEx open-label extension trial indicate that pre-exposure prophylaxis offered a high degree of protection against HIV infection among men who have sex with men and transgender women, and its use did not lead to risky sexual behavior. Pre-exposure prophylaxis was effective even among those who missed daily doses of the drug.
The trial results, presented at AIDS 2014, appear to bolster recent CDC and WHO guidelines recommending the expansion of pre-exposure prophylaxis (PrEP) as an additional method of curtailing new HIV infections in high-risk populations.
“Findings from iPrEx OLE are particularly important in relation to emerging guidelines recommending expanded use of PrEP,” iPrEx protocol chair Robert Grant, MD, MPH, an investigator at the Gladstone Institutes, said in a press release. “The project provides critical insight into what happens as PrEP transitions from clinical trials to clinical practice. It is particularly compelling to see such strong interest in PrEP among young gay and bisexual men, who are increasingly impacted by HIV.”
Robert Grant
A total of 1,603 HIV uninfected participants (average age, 28 years) at 11 sites in four continents were enrolled in the 72-week open-label extension (OLE) study, all of whom participated in the original iPrEx randomized controlled trial conducted in 2010. Of these participants, 76% opted to receive the combination treatment of emtricitabine plus tenofovir disoproxil fumarate (Truvada, Gilead). The remainder elected to stay in the study but did not receive prophylactic treatment. Participants’ use of PrEP was measured in dried blood spots — a technique developed at the University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences.
According to the researchers, the most common reasons participants gave for choosing not to receive PrEP included concerns about side effects (49%), the inconvenience of a daily pill (24%) and preference for other methods to prevent HIV infection (14%).
As for the efficacy of PrEP, HIV incidence was 4.7/100 person-years (95% CI, 2.8-7.2) among those in whom the drug was not detected in dried blood spots. However, among those who took two to three tablets per week, the incidence was 0.6/100 person-years (95% CI, 0-2.5) — translating to a 90% reduced risk for HIV infection. There were no infections among those who took more than four tablets per week (P<.0001).
“Daily dosing of PrEP is recommended because it helps foster the habit of consistent PrEP use and increases drug levels in the body, providing the best safety cushion for individuals who occasionally miss doses,” Grant said. “At the same time, these results demonstrate that PrEP remains highly effective, even in real-world circumstances in which adherence may not be perfect.”
However, those who were at highest risk for infection were more likely to choose PrEP and use it more effectively — that is, taking more than four tablets per week. According to the researchers, receptive anal intercourse without condoms was associated with PrEP uptake (P=.001).
“Encouragingly, these results indicate that people at higher risk may be more likely to seek out and to benefit from the protection that PrEP provides,” study researcher Kenneth Mayer, MD, medical research director of the Fenway Institute in Boston, said in the release.
Additionally, the researchers found no evidence of risk compensation among PrEP users. The proportion of PrEP recipients who reported risky behavior decreased from 33% to 25% (P<.01) during the study period.
According to Jim Pickett, director of prevention and advocacy and gay men’s health at AIDS Foundation of Chicago, the iPrEx OLE results further demonstrate the benefits associated with PrEP, but barriers to its use must be addressed.
“This study provides still more evidence that gay and bisexual men and transgender women want access to this safe and highly effective form of HIV prevention,” he said in the press release. “Moving forward, we must increase awareness of PrEP among all who could benefit from it, and overcome critical barriers to PrEP access, including misinformation, lack of provider training and insufficient coverage via health insurance and other payor programs.”
For more information:
Grant RM. #TUAC0105LB. Presented at: 20th International AIDS Conference. July 20-25, 2014; Melbourne, Australia.
Disclosure: The researchers report no relevant financial disclosures.