No single strategy for the prevention of HIV has emerged as consistently used and successful, so multiple strategies have been developed. PrEP involves delivering ARV medications to people before they are exposed to HIV, in order to prevent infection. The optimal method of delivering PrEP has not yet been determined. This study will examine the feasibility of delivering PrEP in three methods. Daily dosing involves receiving ARV medications every day; time-driven dosing involves receiving ARV medications twice weekly plus a post-exposure dose; and event-driven dosing involves receiving ARV medications before and after a potential exposure to HIV. The ARV medication that will be used in this study is a combination pill that contains emtricitabine and tenofovir disoproxil fumarate (FTC/TDF). Recent research studies have shown that, if taken consistently, a daily oral dose of FTC/TDF can reduce the risk of HIV infection.~This study will enroll HIV-uninfected men who have sex with men and transgender women (MSM/TGW) and women who have sex with men (WSM). Participation will last 34 weeks. All participants will be given a combination pill that contains FTC/TDF. For the first 5 weeks, all participants will come to the study clinic weekly to receive a single dose of FTC/TDF.~At Week 6, participants will be randomly assigned to one of three groups. In the daily dosing group, participants will take FTC/TDF once a day. In the time-dosing group, participants will take FTC/TDF twice per week and another dose after sexual intercourse (a post-exposure dose). In the event-dosing group, participants will take FTC/TDF before and after sexual intercourse. During this part of the study, participants will be given FTC/TDF to take on their own. Every week, from Week 6 to Week 29, study officials will call to ask questions about how many pills participants have taken and when they have had sexual intercourse. Participants will also complete computer-assisted self-interviews (CASIs).~Study visits will occur at enrollment, once a week for the first 5 weeks, and then once a month until Week 34. Assessment will include recording of medical history, completing an interview about sexual practices and background, and collection of blood, urine, and hair samples. Select study visits will include vaginal practices assessment (including use of lubricants and vaginal cleansing practices), family planning assessments (for women), and sex hormones assessments (for men).~Participants who acquire HIV infection during the study will discontinue study product. These participants will continue to be followed after enrollment at Weeks 4, 6, 10, 14, 18, 22, 26, 30, and every 12 weeks thereafter, as appropriate, until the last study participant completes follow-up at the study site. Participants whose first reactive HIV rapid test is at Week 34 who are later confirmed to be HIV infected will also be followed every 12 weeks after their Week 30 visit until the last study participant completes follow-up at the study site. Participants who acquire HIV infection during the study will undergo select protocol procedures and will receive counseling and referrals for HIV treatment.
Pre-exposure prophylaxis (PrEP) is a method of preventing HIV infection through the use of antiretroviral (ARV) medications before exposure to HIV. This study will examine the feasibility of different methods of dosing for a PrEP regimen. Three methods of delivery will be compared: daily, time-based, and event-based.