A randomized, three-period crossover, open-label, phase I trial assessed coadministration of doravirine/lamivudine/tenofovir disoproxil fumarate (100/300/100 mg single dose) and estradiol (4 mg twice daily for one day) and spironolactone (200 mg twice daily for one day) in healthy transgender women (n=6). Geometric mean ratios for doravirine AUC, Cmax and C24 were similar (decreased by 3%, 7% and 3%, respectively). However, tenofovir AUC, Cmax and C24 moderately increased by 19%, 38% and 14%, respectively. Estradiol AUClast, Cmax , and C24 increased by 10%, 12% and 13%, respectively, but AUCinf decreased by 3%. Whereas most 90% confidence intervals did not meet the bioequivalence bounds of 80%-125%, the point estimates fell within the intervals. Log-transformed doravirine, tenofovir, and estradiol pharmacokinetic parameters computed with and without co-administration were not statistically different (p>0.05). There were no serious adverse events. Visual inspection of plasma concentration-time profiles for total testosterone mean concentrations over 96 h suggested coadministration of DOR/3TC/TDF with estradiol and spironolactone produced lower mean total testosterone concentrations than with estradiol and spironolactone alone, however, both curves were generally similar to each other. Clinically significant interactions between DOR/3TC/TDF and feminizing hormones should not be expected. Concomitant estradiol and spironolactone slightly reduced doravirine exposure whereas moderate increases were seen for tenofovir, which is not expected to impact clinical efficacy. DOR/3TC/TDF is not anticipated to significantly impact plasma estradiol and total testosterone levels. Coadministration of DOR/3TC/TDF, estradiol, and spironolactone appeared to be safe and well- tolerated with no reported breakthrough masculinization.