Daily oral tenofovir-based preexposure prophylaxis (PrEP) for HIV also seemed to provide the additional benefit of decreasing the risk for acquiring herpes simplex virus 2 (HSV-2) in heterosexual men and women, researchers found.
Findings from the the Partners PrEP trial, which involved 4,747 heterosexual couples, showed that taking daily medication including tenofovir (Viread) was found to cut the risk of acquiring HIV by up to 75%, according to Connie Celum, MD, MPH, of the University of Washington, and colleagues.
An additional subgroup analysis conducted among 1,498 participants who were HSV-2 negative at baseline and who also had a final study sample available for testing showed tenofovir also reduced the risk of HSV-2.
Overall, 131 patients had an incident HSV-2, including 79 patients in the tenofovir PrEP group (5.6 per 100 person-years) and 52 patients in the placebo group (7.7 per 100 person-years). Compared with placebo, the hazard ratio for HSV-2 acquisition with daily oral PrEP was 0.70 (95% CI: 0.49-0.99; P=0.047). The absolute risk reduction was 2.1 per 100 person-years.
Among the 1,044 couples where the HIV-positive partner was also HSV-2-positive, HSV-2 incidence in the uninfected partners was 10.1 and 7.0 per 100 person-years in the placebo and PrEP groups, respectively.
In this subset of patients with documented exposure to HSV-2, the hazard ratio for PrEP was 0.67 (95% CI: 0.46-0.98; P=0.038), and the absolute risk reduction was 3.1 per 100 person-years.
Tenovir-based PrEP had a 33% protective effective against HSV-2 in those with documented exposure, according to the researchers. Adherence to daily PrEP therapy was high, with pill counts suggesting that 96% of medication dispensed was taken, they added.
This finding is consistent with a 2010 study involving tenovir gel that showed a 51% protective effect against HSV-2, and previous laboratory studies that showed tenovir inhibits HSV-2, according to background information in the study.
Possible study limitations included inability to stratify randomized patients by HSV-2 status and inability to exclude patients with HSV-2 infections at baseline.
Disclosure: The study was funded by the Bill & Melinda Gates Foundation.