IPrEx Findings Hold in Extension Study

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Science Speaks is in Atlanta, Georgia this week and will be live-blogging from the 20th CROI — Conference on Retroviruses and Opportunistic Infections from Sunday to Wednesday, covering breaking developments from investigators on cure research, new antiretroviral agents, hepatitis, tuberculosis and treatment as prevention.

ATLANTA, GA — Robert Grant from University of California at San Francisco shared the results of a follow-up study of the so called IPrEx OLE (open label extension) which began in June 2011. IPrEX found a 44 percent reduction in the risk of HIV acquisition for study participants who took the drug 4 times a week and a 99 percent reduction for those who took the drug daily. Some 7 months after the IPrEX trial ended in November 2010, HIV uninfected trial participants from either arm of the trial were offered the opportunity to receive PREP and participate in IPrEX OLE.

The aim of the extension study was to provide information about how gaps in access to pre-exposure prophylaxis (PrEP) medications affect HIV seroconversion rates and to evaluate the durability of the study results.  The extension study also provides insights about how open access to PrEP affects choice of prevention strategies, adherence and sexual practices.

After completion of the trial, 1529 men who have sex with men who remained HIV negative elected to enroll in IPrEX OLE. Generally those that elected to enroll were more likely to be older and to engage in more high-risk behavior.  Those who enrolled and came from the active arm of IPREX—received drug instead of placebo—were more likely to be individuals who had detectable drug in their blood during the trial.

Would PrEP delay infections, but not stop them so that additional infections would become evident after PREP was stopped?  There was no evidence of this.  There were 78 new HIV infections during the so-called gap period, and excess infection where not seen in men who had been in the drug arm of the original trial.  In fact there was lower HIV incidence among those who had been on drug rather than placebo. The HIV incidence rate was comparable to the rates of HIV acquisition seen in the placebo arm of the original trial.  Risk factors for HIV acquisition were receptive anal intercourse without condoms, younger individuals and those with herpes infection. Overall HIV incidence continues to be high among this group when PrEP is not available. Despite high overall infection rates, the study found that risk level is not constant with most participants moving in and out of high risk periods.

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