Safety and Effectiveness of Tenofovir Gel in the Prevention of Human Immunodeficiency Virus (HIV-1) Infection in Women and the Effects of Tenofovir Gel on the Incidence of Herpes Simplex Virus (HSV-2) Infection

This is a phase III, multicenter trial to assess the safety and effectiveness of 1% tenofovir gel, administered vaginally by approximately 2900 sexually active women at high risk for sexually transmitted HIV. Approximately 2600 women aged 18-30 years old will be enrolled to achieve the required number of endpoints to show an effect on HIV-1 infection, while up to 300 additional women aged 31-40 years old will be enrolled to collect more safety information in this age group. This is an event driven study that plans to randomize seronegative women. Participants will be randomized to a 1:1 ratio to receive 1% tenofovir gel or placebo gel. Each will be asked to insert a dose of the assigned study product within 12 hours prior to a coital event and another dose as soon as possible within 12 hours after a coital event. Participants will be advised to use only two doses of gel in a 24 hour period. All women will be evaluated for the rates of adverse events and the rate of HIV seroconversion. In addition, the study will evaluate several secondary endpoints that bear directly on potential risks and benefits of vaginal tenofovir gel use.