Oral and topical pre-exposure prophylaxes are successful in preventing the transmission of human immunodeficiency virus via sexual intercourse, according to a presentation at the 13th European AIDS Conference of the European AIDS Clinical Society (EACS). Established in 1991, the EACS is a leading scientific society composed of clinicians that aims to educate, train and compose guidelines for those clinicians in Europe treating patients with HIV and AIDS.
The results of recent studies were reviewed at the conference by Dr Charles Lacey, professor of genitourinary medicine at the Hull York Medical School at the University of York in the United Kingdom. Lacey reviewed the results from five studies and noted that effect sizes ranged from 31% to 96% in preventing transmission.
One of the larger studies, the Partners PrEP study, followed serodiscordant couples (N=4,758) from Africa for 36 months. The study aimed to determine the efficacy of tenofovir and emtricitabine(Drug information on emtricitabine)/tenofovir in protecting the couple’s HIV-negative partner. For comparison purposes, the study included a placebo arm. As part of the study, all participant couples received comprehensive HIV prevention services in addition to the treatment modality.
The researchers found reduced HIV incidence rates among both treatment arms as compared to the placebo arm. For tenofovir and emtricitabine/tenofovir, the incidence rates were 0.74/100 person-years and 0.53/100 person-years, respectively, while the placebo group had an incidence rate of 1.92/100 person-years. Lacey explained that the research indicated a slight advantage in efficacy in men for emtricitabine/tenofovir over tenofovir; however, Lacey cautioned that the study was not designed to fully explore gender differences.
Interestingly, the researchers from the TDF2 study came to similar conclusions, Lacey reported. This study looked at daily oral emtricitabine/tenofovir versus placebo among higher-risk heterosexually active young adults in Botswan who were not in stable partnerships. Lacey reported that the analysis showed an overall protective efficacy of about 63%. Although the study was not powered to show gender differences, when the researchers conducted analysis by gender, they found the protective effect for men and not for women.
According to Lacey, research is emerging indicating that tenofovir vaginal gel also is effective. For instance, the Centre for AIDS Programme for Research in South Africa trial found an overall 39% reduction in acquiring HIV for women who used the gel. The reduction was highest (54%) among those women with the best adherence. In this trial, the gel was used before and after sex.
In a statement to the press, Dr Charles Kelly, professor of oral immunology at King’s College London, United Kingdom, noted that antiretroviral drugs are going to make good microbicides. “For women, it looks as though the best option at the moment is topically applied microbicides. I guess for men that may be the case, but clearly the oral PrEP is working,” he said.
Reference:
Keller DM. Many trials indicate benefit of HIV preexposure prophylaxis. Accessed October 24, 2011.
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