Pharmacology and drug interactions with HIV PrEP in transgender persons receiving gender affirming hormone therapy.

INTRODUCTION: Transgender persons are at increased risk of HIV infection and would benefit from pre-exposure prophylaxis (PrEP) use. However, barriers to healthcare and a lack of data regarding PrEP efficacy among transgender persons limits use. A related issue is whether a drug-drug interaction (DDI) exists between gender affirming hormone therapy (GAHT) and PrEP. Recently, small pharmacokinetic studies were conducted to assess this interaction. AREAS COVERED: This review will assess the pharmacology of PrEP agents, existing data regarding potential DDIs between GAHT and PrEP, and hypothetical mechanisms for these DDIs. A summary will be provided on implications for PrEP use among transgender persons. EXPERT OPINION: Theoretically, DDIs are not expected between GAHT and PrEP. However, among transgender women (TGW) on GAHT, small studies identified a minor DDI between GAHT and tenofovir/emtricitabine (TFV/FTC), with TFV/FTC exposures ~12-27% lower among TGW vs. cisgender men. The mechanism of DDIs is unclear and requires further study. For perspective, median TFV/FTC concentrations were still within the range of median concentrations reported across controlled pharmacokinetic studies. TFV-disphosphate/FTC-triphosphate concentrations were similar between TGW and cisgender men. In summary, TDF/FTC likely reaches protective concentrations and should continue to be offered as PrEP for transgender persons.