The investigators propose an open-label, steady-state study of TFV and FTC PK in blood and colon tissue in healthy TGW on feminizing hormones to be compared to healthy cis men, all at risk for HIV infection. Research participants will already have received eight days of TDF/FTC dosing. Evaluating TDF and FTC PK at steady-state is important as it reduces inter-individual variability since the rate of phosphorylation of TFV and FTC is highly variable, resulting in highly variable TFV-DP and Emtricitabine-Triphosphate (FTC-TP) PK among individuals in the first day and during rise to steady-state.
