Late Breaker: Daily Oral PrEP for HIV-Negative MSM Shows Encouraging Results

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Vienna – The CAPRISA trial results are not the only good news to come out of the International AIDS Conference. At a late breaker session on Friday, Lisa A. Grohskopf from the CDC presented preliminary findings and analysis of the phase II clinical safety trial of tenofovir disoproxil fumarate (TDF) used as pre-exposure prophylaxis (PrEP) among HIV-negative, at-risk MSM in three U.S. cities. Global Center Advisory Committee chair, Ken Mayer, MD, led the study at the Boston site at Fenway Health. The other sites were the San Francisco Health Department and the AIDS Research Consortium of Atlanta.

Investigators looked at whether tenofovir was safe and well tolerated. The study administered oral tenofovir versus a placebo with 400 HIV-1 negative MSM in Atlanta, San Francisco and Boston. All study participants had reported anal sex with another man in the past year.

Half of the men were randomized to take a pill right away (half of which received tenofovir and half a placebo), and the other 200 men had nine months of observation without pills, and then were given pills (half tenofovir, half a placebo) for the remaining 15 months.

There were a total of seven HIV infections during the trial. One was identified as an acute infection that was not detected at enrollment. Three infections occurred in men in the observation arm during the observation phase, and the other three infections occurred in men taking the placebo.

Were the men taking the medication behaving riskier than the men off pills? Did risk increase or decrease when they started taking the tenofovir? Preliminary results show that there was no evidence of increased risk behavior. In fact, overall everyone tended to less risky behavior.

Although some people living with HIV taking tenofovir regimens can experience kidney dysfunction and bone demineralization, after a two-year follow up, investigators found no significant side effects experienced among the trial participants, all of whom were HIV-negative.

In short, the study found that tenofovir for PrEP was safe, well-tolerated and that participation in a PrEP study did not seem to promote increased behavioral disinhibition.

This important safety study and the CAPRISA trial will be cited frequently as the treatment-as-prevention discussion moves forward and more trial results become available over the next few years.

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