This is a two-phased prospective switch study of 60 transgender individuals who are eligible for Truvada® (Emtricitabine/Tenofovir Disoproxil Fumarate) F/TDF PrEP and who are willing to switch to Descovy® (Emtricitabine/Tenofovir Alafenamide) F/TAF for 48 weeks. The purpose of the current study is to contribute safety and efficacy data to support the use of F/TAF in transgender/non-binary individuals. The current study leverages existing studies in trans/non-binary populations (e.g. CCTG 603; HRPP#161807) funded by the California HIV/AIDS Research Program (CHRP).

The dosage for Phase I is FTC 200 mg / TDF 300 mg. The dosage for Phase II is FTC 200 mg / TAF 25 mg. TDF/FTC is FDA approved for use as PrEP in adults and adolescents at risk for HIV-1. F/TAF has received approval by the FDA for use as PrEP as of October 3rd, 2019 except for those having receptive vaginal sex. The FDA has yet to approve F/TAF for use in those having receptive vaginal sex due to a lack of clinical research studies specific to the population. Participants will be advised that if they decide to have receptive vaginal sex while taking F/TAF, they should use another method of protection such as condoms.Eligibility criteria will be based on the CDC guidance for PrEP use in transgender persons. All participants must be confirmed HIV-negative (either by rapid test or Ag/Ab test), must have acceptable safety laboratory values, and must currently be taking or will initiate F/TDF by the Screening/Baseline visit. Participants will have a 12-week lead-in period prior to switching to F/TAF. At the Switch Visit, participants will be instructed to substitute F/TDF with F/TAF for PrEP for 48 weeks. Regular follow-up evaluations will occur at Weeks 12, 24, 36, and 48.

Participants will receive health education, clinical assessments, laboratory safety monitoring, STI and HIV screening, standard HIV risk reduction and adherence counseling, assessment of psychosocial barriers, and completion of a computer-based self-report survey that includes assessments of adherence and risk behaviors. Intracellular TFV-DP quantification will be performed in retrospect on batched, banked samples and additional banked specimens will be frozen for future use. Adherence by TFV-DP concentrations and self-reported measures will be used for the primary and secondary analyses of the study. Additional outcomes for the study will include changes in risk behavior and determinants of PrEP adherence.

This study will continue iTAB, a daily text message support system for adherence up until 12 weeks after F/TAF switch. As needed, the study will provide a) subject reimbursement to pay for unlimited text messaging and/or b) an appropriate cell phone if a subject does not have one. Daily dosing text message reminders will be sent for the duration of the study. Both reminder timing and content can be individualized. Participants have selected 15 personal reminders from a list of pre-determined reminders that cover various themes shown to be effective in improving adherence (e.g., social support, loss frame, health gain, etc.) as developed through focus groups and targeted group feedback. These messages can be modified and the patient can choose to create their own reminders if they prefer. These reminder times can vary for different days of the week to accommodate for changes in schedule (e.g., 8 M-F, and 10 AM on Sat/Sun). Once the time is identified, the text reminder system is automated. Patients will confirm medication taking via text responses to the personalized reminders.