Transgender women can now feel confident taking PrEP without fear that it might impact their hormone levels. That's the news that came out of the 22nd International AIDS Conference in Amsterdam this past summer, as a recent study proves the pre-exposure prophylaxis HIV-prevention strategy does not impact feminizing hormone levels in trans women.
"These results provide reassurance that you can use PrEP without fear that it will decrease hormones to a suboptimal level," said Akarin Hiransuthikul of the Thai Red Cross AIDS Research Center during a conference press briefing.
The new iFACT study was jointly conducted by several major world health organizations in Thailand, and was prompted when prior research showed blood concentrations of PrEP drugs in trans women were lower than expected. Another previous study, presented at last year's International AIDS Society Conference on HIV Science, found that some trans women living with HIV are hesitant to use antiretroviral therapy, or if they do, don't take it as prescribed, over concerns about drug interactions with their hormone therapy. That led researchers to worry HIV-negative trans women might have the similar fears around PrEP use.
As NAM's AIDSMap reports, researchers were also concerned that the decrease in drug levels might occur because feminizing hormones reduce PrEP levels, or because trans women had poorer adherence due to worries about drug interactions. Previous research suggests transgender people of both sexes will prioritize gender affirming hormone therapy over HIV prevention and treatment.
The iFACT study enrolled 20 HIV-negative transgender women in Thailand who still had intact testicles and had not received injectable hormones within the previous six months. At the start of the study, participants then began a feminizing hormone therapy regimen of estradiol valerate (2 milligrams/day), a form of the female hormone estrogen, plus the androgen blocker cyproterone acetate (25 milligrams/day). Hiransuthikul stressed that feminizing hormone regimens vary in different countries and these results are only applicable to this particular regimen.
At week three, the women started taking Truvada, the brand name for the only pill currently approved by the FDA for use as PrEP. Truvada contains the drugs tenofovir and emtricitabine. At week five, the participants stopped the hormone regimen so the researchers could compare PrEP drug levels on and off hormones, and then resumed taking the hormones in week eight. The women continued on both hormone therapy and PrEP through week 15.
The study showed that concurrent use of hormone therapy and Truvada as PrEP did not affect hormone levels. Comparing levels at week three (before starting PrEP) and week five (while on PrEP), the researchers saw no significant differences in estradiol levels. No changes in testosterone levels occurred, either. With these findings, they concluded that PrEP did not significantly affect levels of feminizing hormones.
However, in looking at the effect the feminizing hormones had on PrEP drugs, researchers did discover that total tenofovir exposure was about 13 percent lower in the presence of estradiol. (The study did not measure emtricitabine levels.)
This difference was statistically significant, but Hiransuthikul emphasized that even with this reduction, the tenofovir level remained above the target level shown to confer protection. The drug still retains the ability to prevent HIV at this level. It is not known whether this difference in blood levels correlates with tenofovir levels in rectal tissue, where HIV exposure typically occurs among Thai trans women.
After analyzing previous studies, the researchers also discovered that although PrEP appears to work well for cisgender women, previous data shows they may need to take PrEP more consistently than cisgender men to achieve a similar level of protection. This suggests female hormones in general may impact drug levels, and stricter adherence is needed for both trans and cis women.
Still, the important takeaway is that trans women -- who are one of the most marginalized and vulnerable populations in terms of HIV -- can safely continue their hormone therapy and protect their health with PrEP.