LAUSR

Transgender persons have an increased vulnerability to HIV infection yet have not been well-represented in past clinical trials for pre-exposure prophylaxis (PrEP). Because of this, there are few data available to understand whether gender-affirming hormone concentrations are influenced by PrEP agents in transgender men (TM) and transgender women (TW).The objective of this study was to compare gender-affirming hormone concentrations with vs. without emtricitabine-tenofovir disoproxil fumarate (F/TDF). TM and TW without HIV, ages 15-24 years, were enrolled for one month of directly observed daily F/TDF. Participants were required to be receiving a stable hormone dose (estradiol or testosterone) for at least one month or three consecutive doses, whichever was longer, prior to enrollment and willing to continue this same dose. Intensive PK sampling for gender-affirming hormones was collected prior to and 2-3 weeks after daily F/TDF. Serum estradiol and total testosterone were determined by LC-MS/MS; free testosterone by equilibrium dialysis. Maximum concentrations (Cmax) and area under the curve (AUCtau) were log-transformed and compared between baseline and on F/TDF using geometric mean ratios (GMRs) with 95% confidence intervals (CIs). Twenty-five TW and 24 TM were enrolled (median ages: 20 and 21 years, respectively). In TW, estradiol Cmax (GMR [95% CI]: 0.85 [0.65- 1.11]) and AUCtau (GMR [95% CI]: 0.87 [0.73-1.03]) were comparable on F/TDF vs. baseline. In TM, similar comparability was observed for PrEP vs. baseline including total testosterone Cmax (GMR [95% CI]: 0.91 [0.80-1.03]) and AUCtau (GMR [95% CI]: 0.91 [0.81-1.04]) and free testosterone Cmax (GMR [95% CI]: 0.89 [0.74-1.07]) and AUCtau (GMR [95% CI]: 0.88 [0.74-1.03]). Estradiol and testosterone exposures in young TW and TM did not significantly differ on F/TDF vs. baseline. These findings should reassure patients and providers that F/TDF can be used as PrEP without concern for altering gender-affirming hormone pharmacokinetics.