---
title: Assessment of Drug-drug Interactions Between Feminizing Hormone Therapy and Emtricitabine/Tenofovir Alafenamide Concomitantly for Pre-exposure Prophylaxis Among Transgender Women
nct_id: NCT04590417
overall_status: ACTIVE_NOT_RECRUITING
phase: NA
sponsor: Thai Red Cross AIDS Research Centre
study_type: INTERVENTIONAL
primary_condition: Drug Interaction
countries: Thailand
canonical_url: "https://parkinsonspathways.com/agent/trials/NCT04590417.md"
clinicaltrials_gov: "https://clinicaltrials.gov/study/NCT04590417"
ct_last_update_post_date: 2024-11-25
last_seen_at: "2026-05-12T06:02:27.885Z"
source: ClinicalTrials.gov (mirrored, no enrichment)
---
# Assessment of Drug-drug Interactions Between Feminizing Hormone Therapy and Emtricitabine/Tenofovir Alafenamide Concomitantly for Pre-exposure Prophylaxis Among Transgender Women

**Official Title:** Institute of HIV Research and Innovation (IHRI)

**NCT ID:** [NCT04590417](https://clinicaltrials.gov/study/NCT04590417)

## Key Facts

- **Status:** ACTIVE_NOT_RECRUITING
- **Phase:** NA
- **Study Type:** INTERVENTIONAL
- **Target Enrollment:** 20
- **Lead Sponsor:** Thai Red Cross AIDS Research Centre
- **Conditions:** Drug Interaction
- **Start Date:** 2022-01-24
- **Completion Date:** 2025-10-01
- **CT.gov Last Update:** 2024-11-25

## Brief Summary

Recent studies have showed that there were significant drug-drug interactions (DDI) from feminizing hormone therapy (FHT) towards emtricitabine/tenofovir disoproxil fumarate (F/TDF)-based pre-exposure prophylaxis (PrEP) among transgender women (TGW). New strategies for PrEP among TGW who use FHT are urgently needed. Because tenofovir alafenamide (TAF) can achieve higher intracellular TFV-DP levels with lower tenofovir plasma concentrations, it is promising that both plasma TFV and intracellular TFV-DP levels might not be significantly affected by FHT. The current study aims to determine the pharmacokinetics DDI between FHT and F/TAF-based PrEP among TGW.

## Detailed Description

Two full pharmacokinetic (PK) measurements will be performed. Samples collected will include: plasma for estradiol (E2), emtricitabine (FTC), tenofovir (TFV), and tenofovir alafenamide (TAF) measurement; and peripheral blood mononuclear cells (PBMC) for emtricitabine-triphosphate (FTC-TP) and tenofovir-diphosphate (TFV-DP) intracellular quantification.

## Eligibility

- **Minimum age:** 18 Years
- **Maximum age:** 40 Years
- **Sex:** MALE
- **Healthy Volunteers:** Yes

```
Inclusion Criteria:

1. Thai nationality
2. Age 18-40 years old
3. Transgender women
4. HIV-negative
5. Body mass index 18.5-24.9 kg/m2
6. Calculated creatinine clearance (CrCl) ≥60 mL/min, as estimated by the Cockcroft-Gault equation
7. Alanine aminotransferase (ALT) ≤2.5 x ULN
8. Signed the informed consent form

Exclusion Criteria:

1. Known history of allergy to hormonal component to be used in the study
2. Male-to-female transgender who underwent orchiectomy
3. Use of pre-exposure prophylaxis or post-exposure prophylaxis in the past 30 days
4. Use of injectable FHT in the past 3 months
5. Evidence of current hepatitis B virus infection (HBV) - i.e. hepatitis B surface antigen (HBsAg) positive
6. Evidence of current hepatitis C virus infection (HCV) - i.e. HCV antibody positive
7. Current use of any of the following:

   * Anticonvulsants: carbamazepine, felbamate, oxcarbazepine, phenytoin, phenobarbital, primidone or topiramate
   * Herbs: gingko biloba, St John's wort or milk thistle
   * Anti-infective agents: azole antifungals, macrolides, griseofulvin, protease inhibitors, rifampicin or rifabutin
8. Participant-reported active rectal infection requiring treatment
9. History of gastrointestinal tract surgery that alter gastrointestinal tract and/or drug absorption
10. Alcohol or drug use that, in the opinion of the investigator, would interfere with completion of study procedures
```

## Arms

- **20 HIV-negative TGW** (OTHER) — A single-arm prospective PK study of HIV-negative TGW taking FHT and daily PrEP.

## Interventions

- **Estradiol valerate 2 mg, cyproterone acetate 25 mg** (DRUG) — The entire study period will be approximately 1 year, which will include around 2 months of document preparation, 5 months of recruitment, 3 months of follow-up, and 2 months of data analysis.

## Primary Outcomes

- **Changes in plasma estradiol levels** _(time frame: Measured at week 3 and week 9 of the study period)_
- **Changes in plasma PrEP levels** _(time frame: Week 9 through 12)_ — 1. Plasma TFV
2. Plasma FTC
3. Plasma TAF
- **Changes in intracellular PrEP levels** _(time frame: Week 9 through 12)_ — 1. PBMC TFV-DP levels
2. PBMC FTC-TP levels

## Secondary Outcomes

- **Changes in plasma testosterone levels** _(time frame: Week 3 through 9)_

## Locations (1)

- Institute of HIV Research and Innovation (IHRI), Bangkok, Pathumwan, Thailand

## Recent Field Changes (last 30 days)

- `status.overallStatus` — added _(2026-05-12)_
- `status.primaryCompletionDate` — added _(2026-05-12)_
- `status.completionDate` — added _(2026-05-12)_
- `status.lastUpdatePostDate` — added _(2026-05-12)_
- `design.phases` — added _(2026-05-12)_
- `design.enrollmentCount` — added _(2026-05-12)_
- `eligibility.criteria` — added _(2026-05-12)_
- `eligibility.minAge` — added _(2026-05-12)_
- `eligibility.maxAge` — added _(2026-05-12)_
- `eligibility.sex` — added _(2026-05-12)_
- `outcomes.primary` — added _(2026-05-12)_
- `outcomes.secondary` — added _(2026-05-12)_
- `armsInterventions.arms` — added _(2026-05-12)_
- `armsInterventions.interventions` — added _(2026-05-12)_
- `sponsor.lead` — added _(2026-05-12)_
- `results.hasResults` — added _(2026-05-12)_
- `locations.institute of hiv research and innovation (ihri)|bangkok|pathumwan|thailand` — added _(2026-05-12)_

---

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*Source data (authoritative): https://clinicaltrials.gov/study/NCT04590417*  
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