The promise of pre-exposure prophylaxis with antiretroviral drugs to prevent HIV transmission

Abstract

Public health experts are wrestling with how to translate recent scientific findings from pre-exposure prophylaxis (PrEP) effectiveness trials into real-world programmes. This review summarizes clinical trial findings on oral and topical PrEP, discusses how decision-makers can evaluate the place of PrEP within combination prevention and highlights anticipated developments that could be important in future HIV-prevention strategies. PrEP taken daily as oral tablets to create systemic protection has been found to be effective in the Pre-Exposure Prophylaxis Initiative (iPrEx), Partners' PrEP and TDF2 trials, but not in Fem-PrEP or the Vaginal and Oral Interventions to Control the Epidemic (VOICE) tenofovir arm. Tenofovir gel for topical protection was effective in CAPRISA 004 when used peri-coitally but not in VOICE with daily use. These findings underscore the importance of adherence to achieve adequate drug levels and the potential additive role of PrEP within combination prevention. Pivotal phase III trials are underway of the dapivirine ring, whereas phase I trials of injectable formulations show promise. Antiretroviral-based HIV-prevention programmes should be tailored to those most likely to be adherent, providing them with state-of-the-art counselling and support to achieve high adherence during the time period of use. Long-acting products, if found well tolerated and effective, could be ideal for overcoming adherence challenges.