A Pharmacokinetic Evaluation of Tenofovir/Emtricitabine as HIV Pre-Exposure Prophylaxis in Transgender Women

Inclusion Criteria: * Evidence of a personally signed and dated informed consent document indicating that the participant has been informed of all pertinent aspects of the study. * Participants who are willing and able to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures. * Self identify as a transgender woman. * Receiving estradiol (oral/sublingual tablets or transdermal patches) with oral spironolactone for at least 3 months prior to study entry. * Serum estradiol level \>100 pg/mL. * Non-reactive 4th or 5th generation screening test for HIV. * Adults (19 years or older). * Able to read and speak English to ensure appropriate ability to obtain informed consent. Exclusion Criteria: * Participants will not be included in the study if one, or more, of the following criteria are met: * Use of drugs known to be contraindicated with TDF, FTC, estradiol, or spironolactone within 30 days of study entry. The study team will review all concomitant medications at screening based on the US Department of Health and Human Services drug interaction table and the drug product labeling. * Use of injectable estradiol (valerate or cypionate). * Presence of any active condition or clinically significant disease that, in the investigator's opinion, would compromise the subject's safety or outcome of the study, including qualifying for non-occupational post-HIV exposure prophylaxis. * Signs or symptoms of acute HIV infection within the last 30 days. * Laboratory values obtained within 30 days prior to study entry: * Creatinine clearance (CrCl) less than 60 mL/min as estimated by the Cockcroft-Gault equation. * Positive hepatitis B surface antigen and/or hepatitis C antibody. * Alanine transaminase (ALT), Aspartate transaminase (AST) or alkaline phosphatase \> 5x the upper limit of normal (ULN). * Hemoglobin \<10 g/dL. * Platelets \<50,000/mm3.