Finding the Right Tenofovir/Emtricitabine Regimen for Pre-Exposure Prophylaxis (PrEP) in Transgender Women

Inclusion Criteria: * TGW and cis men (male at birth and not a TGW) * 18 to 65 years of age, inclusive on the date of screening * Provides informed consent for the study * Non-reactive HIV test results within four weeks of enrollment * An estimated calculated creatinine clearance (eCcr) of at least 70 mL/min * Agrees to use condoms for all sexual events during study participation. * Taking daily oral Truvada® (Tenofovir disoproxil fumarate (TDF) 300 mg/Emtricitabine (FTC) 200 mg) for at least one week at the time of study PK sampling visit * TGW have to be on an estradiol and have a serum total estradiol level \> 100 picograms(pg)/ml Exclusion Criteria: * Significant colorectal symptom(s) as determined by medical history or by participant self-report * Participant-reported symptoms and/or clinical or laboratory diagnosis of active rectal infection requiring treatment per current Centers for Disease Control (CDC) guidelines * A positive test for Herpes Simplex Virus -2 (HSV-2) (individuals with active lesions only) * Co-enrollment in any other HIV interventional research study (excluding behavioral only interventions) or prior enrollment in the active arm of a HIV vaccine trial. * Positive hepatitis B surface antigen (HBsAg) test * Interleukin therapy; medications with significant nephrotoxic potential, including but not limited to amphotericin B, aminoglycosides, cidofovir, foscarnet and systemic chemotherapy; medications that may inhibit or compete for elimination via active renal tubular secretion (including but not limited to probenecid); systemic immunomodulatory medications * Participants with a history of having a gastrectomy, colostomy, ileostomy, or any other procedure altering the gastrointestinal tract or drug absorption * Medications that prolong clotting time * Any other condition or prior therapy that, in the opinion of the investigator, would preclude informed consent, make study participation unsafe, make the individual unsuitable for the study or unable to comply with the study requirements.