Microbicides for HIV prevention: reality or hope?

PURPOSE OF REVIEW This review discusses recent developments within the field of microbicide development and considers whether there are grounds to be hopeful that it will be possible to develop a microbicide for the prevention of HIV infection. RECENT FINDINGS Phase 2B/3 effectiveness studies of surfactant and polyanion vaginal microbicides have demonstrated modest or no effect against HIV infection and in the case of nonoxynol-9 and cellulose sulfate the potential to increase the risk of HIV acquisition. However, newer antiretroviral microbicide candidates, such as tenofovir, have shown good safety and significant efficacy in animal models and human tissue explant systems and are currently being evaluated in human effectiveness studies. New formulation platforms, such as vaginal rings, are being developed to optimize product acceptability and adherence, and far greater scrutiny of candidate microbicides is happening at both the preclinical and early clinical phase of development. SUMMARY Drug development is an inherently high-risk activity and many promising candidates are discarded due to safety issues or lack of efficacy. Lessons learned over the last two decades have helped to improve the microbicide development pathway and provide hope that it will be possible to develop a safe and effective microbicide for HIV prevention.