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No Interactions Between Hormone Therapy
and PrEP in Transgender Women or Men
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2022 CROI, February 12-16 and 22-24, 2022
Mark Mascolini
A study of 172 transgender people found no clinically meaningful bidirectional effects between PrEP with tenofovir disoproxil/emtricitabine (TDF/FTC) and gender-affirming hormone therapy [1].
Researchers from the University of California, San Diego and other US centers noted that drug-drug interactions are not expected between gender-affirming hormone therapy and TDF/FTC PrEP because the agents involved pursue different metabolic pathways. But bidirectional effects between hormone therapy and PrEP in transgender people remain poorly defined because study groups have been small and included few transgender men, evaluation periods were short, and results were mixed.
To address these shortcomings, the US investigators planned to explore bidirectional effects of hormone therapy and TDF/FTC PrEP in a big group of transgender people over 3 months. The parent study involved 256 transgender people using individualized Texting for Adherence Building (iTAB) with or without brief motivational interviews through 48 weeks to encourage PrEP adherence [2]. This parallel two-arm randomized controlled trial-iTAB plus Motivational Interviewing for PrEP Adherence in Transgender Individuals (ImPrEPT)-included a 172-person hormone substudy that measured tenofovir diphosphate (TFV-DP, the active form of TDF) in dried blood spots and hormones in serum at weeks 0 and 12. At weeks 0 and 24, participants completed surveys about desired hormone effects and satisfaction with hormone therapy.
For this analysis, transgender women and nonbinary individuals assigned male at birth were called transgender women (TGW), while transgender men and nonbinary individuals assigned female at birth were called transgender men (TGM). Researchers included TGW and TGM in the analysis if they were taking a stable estrogen- or testosterone-containing regimen. The investigators removed people from the analysis if they reported not taking PrEP or if TFV-DP concentrations were undetectable.
Among people in the hormone concentration analysis, age averaged 32.7 years, 14% were black, 44% white, and 31% Latinx. In 49 TGW using a stable estrogen regimen, estradiol concentrations did not vary significantly between weeks 0 and 12 among people taking PrEP (185.2 vs 221.8 pg/mL, P = 0.53). Among 39 TGM taking stable testosterone, serum concentrations of testosterone fell marginally lower between weeks 0 and 12 in people using PrEP (373.2 vs 274.3 ng/mL, P = 0.052). The researchers believe that small change is unlikely to be clinically meaningful.
At a week-12 analysis of 112 TGW, TFV-DP concentrations did not differ significantly between TGW not taking hormone therapy and those taking hormones (1885.8 vs 1589.5 fmol/punch, P = 0.26). Nor did 12-week TFV-DP concentrations differ significantly between TGM not taking hormone therapy and those using hormones (TGM n = 60, 1682 vs 1961 fmol/punch, P = 0.49).
Body image satisfaction did not vary significantly from week 0 to week 24 in 112 TGW or the 60 TGM. Similarly, self-reports of satisfaction with the impact of hormone therapy on gender transition did not change significantly from week 0 to week 24 in TGW or TGM.
The ImPrEPT investigators summarized their main findings indicating no clinically meaningful bidirectional interactions between TDF/FTC PrEP and hormone therapy in transgender people:
- After 12 weeks of daily reported PrEP use by transgender individuals, those taking or not taking hormone therapy had similar TFV-DP levels in dried blood spots.
- TDF/FTC PrEP did not affect serum estradiol concentrations.
- TGM taking TDF/FTC had marginally lower serum testosterone concentrations, but the impact of TDF/FTC was judged unlikely to be clinically meaningful.
- People taking PrEP perceived no PrEP impact on hormone therapy.
The researchers plan to pursue this research in people using tenofovir alafenamide (TAF)/FTC PrEP.
References
1. Blumenthal J, Goyal R, Burke L, et al. The bidirectional effects of hormone therapy and PrEP in transgender individuals. 2022 CROI, February 12-16 and 22-24, 2022. Abstract 84.
2. Morris S, Jain S, Blumenthal J, et al. RCT of iTAB plus motivational interviewing for PrEP adherence in transgender people. 2022 CROI, February 12-16 and 22-24, 2022. Abstract 851.
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