(HealthDay News) – The efficacy of prophylactic treatment with the antiretroviral combination of tenofovir and emtricitabine (TDF-FTC) seems to vary in different populations, according to three studies published online July 11 in the New England Journal of Medicine.

Jared M Baeten, MD, PhD, from the University of Washington in Seattle, and colleagues conducted a randomized trial involving 4,747 HIV-1 serodiscordant heterosexual couples in Kenya and Uganda. The seronegative partners were randomized to receive once-daily TDF (1,584 couples); TDF-FTC (1,579 couples); or placebo (1,584 couples). The researchers observed a similar, significant relative reduction in the incidence of HIV-1 in the TDF group (67%) and the TDF-FTC group (75%), compared with placebo.

In a second study, Lut Van Damme, MD, from FHI 360 in Research Triangle Park, NC, and colleagues assessed preexposure prophylaxis with antiretroviral drugs in a trial involving 2,120 HIV-negative women in Kenya, South Africa, and Tanzania, randomized to receive TDF-FTC or placebo once daily. The researchers found that the HIV incidence rate was 4.7 per 100 person-years in the TDF-FTC group and 5 per 100 person-years in the placebo group, for an estimated hazard ratio of 0.94 (P=0.81). In a third study, Michael C. Thigpen, MD, from the US Centers for Disease Control and Prevention in Atlanta, and colleagues found that daily TDF-FTC prophylaxis prevented HIV infection in a cohort of 1,219 HIV-seronegative heterosexual men and women in Botswana, with an efficacy of 62.2% for TDF-FTC (P=0.03).

“Daily oral TDF-FTC, given in the context of other prevention services, prevented HIV infection among heterosexual men and women,” Thigpen and colleagues conclude.

Gilead Sciences donated the study medications for all three studies; several authors from all three studies disclosed financial ties to pharmaceutical companies, including Gilead.

Abstract – Baeten

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Abstract – Van Damme

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Abstract – Thigpen

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