New PrEP Studies Offer Hope, Caution

Newly released studies are offering more hope for the efficacy of the once-a-day HIV prevention pill, but also ringing a sour note of concern.
PrEP was approved by the FDA in 2012. It is the use of the drug Truvada. Taken daily, the anti-HIV drug was shown in early human studies to be, when taken daily, at least 92 percent effective in preventing someone from contracting HIV. Since then, some studies have placed that efficacy as high as 99 percent.
After it was approved, some high profile HIV activists expressed concerns the use of the drug would create super viruses; lead to significant spikes in other STIs as people on PrEP threw caution to the wind and ditched the condoms; and warned that the potent drug would cause serious side effects.
"We conclude that (Truvada) for PrEP for HIV infection favorably compares to aspirin in terms of user safety," the authors wrote. "While long-term studies are needed, providers should feel reassured about the safety of short- and medium-term PrEP for HIV infection with (Truvada)."
The second study found the results of the demonstration project for PrEP conducted in three U.S. cities. Those cities were Miami, San Francisco and Washington, DC. According to HIVandHepatitis.org, the study was published in the JAMA Internal Medicine website. It reported that of the nearly 600 participants — men who have sex with men or transwomen — none of the participants that showed blood levels consistent with four or more doses of the drug contracted HIV.
"The incidence of HIV acquisition was extremely low despite a high incidence of STIs in a large U.S. PrEP demonstration project," the authors wrote in the study. "Adherence was higher among those participants who reported more risk behaviors. Interventions that address racial and geographic disparities and housing instability may increase the impact of PrEP."
That adherence point is also key as it knocks down arguments by opponents of PrEP that people won't take their medications. The fear those opponents expressed is that low adherence would lead to infection and potentially resistance.
And while it is rare, a new study in the Journal of Infectious Diseases found that resistance to the anti-HIV drugs can occur when a person is infected during PrEP treatment.
"These results suggest that resistance selected by PrEP is rare but can occur both with PrEP initiation during acute seronegative HIV infection and in PrEP breakthrough infections and that FTC is associated with a greater frequency of resistance mutations than TDF," the authors wrote.
In that study which reviewed 121 blood samples of people in PrEP studies that had seroconverted, researchers found 26 individuals had blood levels consistent with PrEP use. Of those, five had developed resistance.
Also a study out from The Science Translational Medicine reports that sero-sorting, or refusing to have sex with a person of a differing HIV status, may be feeding the epidemic. Researchers reviewed 617 newly infected patients for the source of their virus and found, "Seventy-one percent of transmissions were from undiagnosed men, 6 percent from men who had initiated antiretroviral therapy (ART), 1 percent from men with no contact to care for at least 18 months, and 43 percent from those in their first year of infection." The authors estimated that 19 percent of those cases of infection could have been prevented with annual HIV testing and immediate start of anti-HIV drugs.