A single-center, parallel group study evaluated the drug interaction between BIC/FTC/TAF and estradiol in trans women with HIV (n=25) versus trans women without HIV taking estradiol (n= 15) and no antiretroviral treatment. Participants were taking at least 2 mg/day of oral 17-beta estradiol plus an anti-androgen therapy. Estradiol Cmax (IQR) and Tmax (IQR) for the antiretroviral group were 357.5 pmol/L (257, 512.25) and 1.5 hours (2, 2.75), respectively and 262 pmol/L (151.5, 312) (p=0.115) and 4 hours (2, 7) (p=0.130) for controls. AUC were not different between groups: 5827 mg.h/L (4488, 8352) for the antiretroviral group and 4808 mg.h/L (2952, 6281) for controls (p=0.235). Overall, 64% had estradiol (4h within the target of 200-750 pmol/L [80% among women on antiretroviral treatment and 53% among those not on antiretroviral treatment (p=0.229). This study showed that estradiol concentrations were similar between trans women on bictegravir/F/TAF and controls suggesting a low risk of drug interactions between feminizing hormone therapy and bictegravir/F/TAF.

Serum oestradiol concentrations were determined in trans women with HIV taking feminizing hormone therapy (FHT) and unboosted integrase strand transfer inhibitor-based ART (n=8) versus trans women without HIV taking FHT (n=7). Among participants, the median oral oestradiol dose was 4 mg (range 2-6 mg). Six trans women with HIV were taking bictegravir/emtricitabine/tenofovir alafenamide and two were taking dolutegravir/abacavir/lamivudine. All oestradiol concentrations were not significantly different between groups. Eleven (73%) participants had target oestradiol concentrations in the range 200-735 pmol/L at C4h (75% among women with HIV, 71% among those without HIV). However, further research is needed with larger sample sizes to fully understand the impact of HIV and ART on FHT in trans women with HIV.