Extended iPrEx study looks at long-term safety, behavior change and medication adherence

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In a conference call convened by AVAC Tuesday, government representatives, scientists and advocates discussed the particulars of the Pre-Exposure Prophylaxis Initiative (iPrEx) open label study set to launch at some trial sites in March 2011.

The study continues on the infrastructure of the original iPrEx study trial, which determined that daily oral dosing of Truvada among high-risk men who have sex with men (MSM) indicated a 44 percent reduction in the incidence of HIV, with efficacy strongly correlating to adherence. The study has 11 trial sites in Lima and Iquitos in Peru; Guayaquil in Ecuador; San Francisco and Boston in the U.S.; Sao Paulo and Rio de Janeiro in Brazil; Cape Town in South Africa and Chiang Mai in Thailand.

“An open label extension or ‘rollover’ of the iPrEx study will provide all HIV-negative iPrEx participants who wish to enroll in this phase with access to tenofovir/emtricitabine [Truvada] for HIV prevention for 72 weeks,” according to the iPrEx website. The study aims to gather additional information about how to improve adherence to the daily regimen, whether adherence will increase now that the regimen has shown partial efficacy in preventing HIV infection, and whether risk-taking behavior will increase as well. Unlike the original study, the iPrEx rollover study participants who choose to participate will all knowingly receive the Truvada daily pill, and all participants will be advised of the efficacy and safety of pre-exposure prophylaxis (PrEP) learned in the first iPrEx study.

The rollover will also get more safety data, and try to assess how well the treatment can be administered in “real world” clinical settings, said Susan Buchbinder, MD, of the San Francisco Department of Public Health and an iPrEx investigator who participated in the AVAC call. For instance, researchers will try stretching doctor visits out to once every three months (more realistic in a clinical setting than the monthly visits that occurred in the study) to see what happens to adherence to the medication. Since all participants will be taking the active drug in this round of iPrEx, incidence of rare safety events will be monitored and studied as well.

“In the original iPrEx study we saw much greater efficacy among those who took the drug regularly,” Buchbinder said. “Can we actually help more people to take the medication regularly? We also want to get feedback – why is it difficult to take Truvada on a daily basis? Can we also help people to reduce their risk of HIV exposure while taking the daily pill?” Participants in the rollover study will also receive a package of HIV prevention interventions to include HIV risk reduction counseling, condoms and STI management.

Buchbinder also said that some preliminary discussions have occurred about launching a demonstration project, “To get information on how and for whom can we offer PrEP in the real world clinical setting,” she said.

“We don’t want demonstration projects designed so they are incredibly extensive and hard to do in resource-constrained environments,” but extensive enough to use as an effective global health tool, said Chris Collins of amfAR, the Foundation for AIDS Research. “Let’s move forward with demonstration projects without delay, but make sure we have a diversity of participation,” to include young African American gay men and others at high risk, to determine how PrEP can be delivered to these key populations, he said. 

iPrEx rollover study results are expected in early 2013. More information on the iPrEx rollover study can be found on the global iPrEx website.

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