Trial to Assess the Impact of PrEP to Tenofovir Gel on the Efficacy of Tenofovir-containing ART on Viral Suppression

The HIV/AIDS pandemic remains among the investigators greatest public health challenges. In the absence of an effective vaccine, focus has shifted to other prevention strategies such as pre-exposure prophylaxis. Tenofovir, with potent activity against retroviruses [1], was developed for oral use as Viread®, which is widely used for HIV treatment. The efficacy of Viread® has been demonstrated in treatment-experienced and naïve patients [2,3]. In antiretroviral-naive patients, the combination of tenofovir with lamivudine and efavirenz has been classified as a preferred regimen in the Department of Health and Human Services treatment guidelines[4], and has been adopted by the South African Department of health as the first line regimen in treatment-naïve HIV infected patients since April 2010. The durability of antiviral response, favourable resistance profile, once daily dosing, and excellent long term safety profile of tenofovir [5], makes this drug an attractive option in both treatment and prevention regimens and its long half-life [6], made it an ideal choice as the first antiretroviral drug to be formulated as a microbicide gel. The CAPRISA 004 study conducted in South Africa which tested the effectiveness and safety of 1% tenofovir gel showed that the use of tenofovir in a gel formulation reduced HIV acquisition by 39% overall, and by 54% in women with high gel adherence [7]. There have been concerns raised regarding the use of tenofovir in both PrEP and treatment regimens due to the potential for selection of viral mutations and development of resistance in patients who have become HIV-infected while on PrEP. There have been no studies conducted to determine whether using tenofovir in pre-exposure prophylaxis affects treatment outcomes in patients who later use tenofovir, which is part of the first line ART of South Africa. This study aims to determine whether prophylactic exposure to tenofovir gel alters the therapeutic response to a tenofovir containing antiretroviral regimen.