Doxycycline Prophylaxis for Prevention of Sexually Transmitted Infections (foXXxy doxy)

May 12, 2026 updated by: Westat

Doxycycline Prophylaxis for Prevention of Sexually Transmitted Infections Among Adolescent and Young Adult Females in the United States

The goal of this open-label, randomized trial is to assess the efficacy of doxycycline prophylaxis in reducing incidences of bacterial sexually transmitted infections (STIs) among adolescent and young adult females while also evaluating acceptability and antimicrobial resistance in order to inform public health policy.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

Participants will be randomized to receive on-demand doxycycline post-exposure prophylaxis (doxyPEP), weekly doxycycline, or standard of care (SOC) and will be followed quarterly to assess the impact of doxycycline use on the quarterly incidence of STIs (gonorrhea [GC], chlamydia [CT], and early syphilis), and within the doxycycline arms adherence and acceptability of weekly versus on-demand dosing.

Approximately 760 females will be randomized 1:1:1 to (1) on-demand doxyPEP (doxycycline 200 mg as soon as possible and within 72 hours after any condomless oral, vaginal, and/or anal sex), (2) weekly doxycycline (doxycycline 200 mg weekly regardless of sexual activity), or (3) SOC (quarterly STI testing/treatment and sexual health counseling). Participants will complete quarterly study visits over the course of 1 year during which they will receive STI testing (GC, CT, and syphilis), complete surveys, undergo safety monitoring, provide specimens for objective markers of doxycycline adherence and other laboratory assessments, and provide specimens (vaginal and rectal swabs [participant self-collected or staff-collected if the participant prefers]) for future testing, such as microbiome analysis. Resistance testing will be conducted on Staphylococcus (S.) aureus and Neisseria (N.) gonorrhoeae isolates to evaluate for doxycycline and tetracycline resistance, respectively. Participants will also complete weekly assessments of sexual activity and doxycycline adherence via the HealthMpowerment (HMP) application (app).

Study Type

Interventional

Enrollment (Estimated)

760

Phase

  • Phase 4

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • United States
    • California
      • Los Angeles, California, United States, 90095
        • Not yet recruiting
        • UCLA Care
        • Contact:
        • Principal Investigator:
          • Cherie Blaire
      • San Francisco, California, United States, 94102
        • Recruiting
        • San Francisco Department of Public Health
        • Principal Investigator:
          • Albert Liu
        • Contact:
    • District of Columbia
      • Washington D.C., District of Columbia, United States, 20010
        • Recruiting
        • Children's National Medical Center
        • Principal Investigator:
          • Natella Rakhmanina
        • Contact:
    • Florida
      • Tampa, Florida, United States, 33612
        • Recruiting
        • University of Florida
        • Contact:
        • Principal Investigator:
          • Patricia Emmanuel
    • Georgia
      • Atlanta, Georgia, United States, 30303
        • Not yet recruiting
        • Ponce de Leon
        • Contact:
        • Principal Investigator:
          • Anandi Sheth
    • Illinois
      • Chicago, Illinois, United States, 60612
        • Recruiting
        • University Illinois Chicago
        • Contact:
        • Principal Investigator:
          • Kelly Bojan
    • Louisiana
      • New Orleans, Louisiana, United States, 70112
        • Not yet recruiting
        • Tulane University
        • Principal Investigator:
          • Tina Simpson
        • Contact:
    • Maryland
      • Baltimore, Maryland, United States, 21287
        • Not yet recruiting
        • Johns Hopkins University
        • Principal Investigator:
          • Allison Agwu, MD
        • Contact:
    • New York
      • New York, New York, United States, 10027
        • Not yet recruiting
        • Harlem Prevention Center
        • Contact:
        • Principal Investigator:
          • Yael Hirsch-Movermann
    • North Carolina
      • Chapel Hill, North Carolina, United States, 27599
        • Not yet recruiting
        • Chapel Hill
        • Contact:
        • Principal Investigator:
          • Lina Rosengren-Hovee
    • Pennsylvania
      • Philadelphia, Pennsylvania, United States, 19104
        • Not yet recruiting
        • Penn Prevention
        • Contact:
        • Principal Investigator:
          • Arianne Morrison
    • Tennessee
      • Memphis, Tennessee, United States, 38015
        • Recruiting
        • St. Jude Children's Research Hospital
        • Contact:
        • Principal Investigator:
          • Aditya Gaur
    • Texas
      • Houston, Texas, United States, 77030
        • Recruiting
        • Baylor College of Medicine
        • Contact:
        • Principal Investigator:
          • Mary Paul

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child
  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age 13-29 years, inclusive;
  • Self-reports GC, CT, and/or early syphilis diagnosis in the 12 months prior to screening;
  • Self-reports condomless (oral, vaginal, and/or anal) intercourse at least once in the 30 days prior to screening
  • Is at least 45 kilograms (99.2 pounds) in weight
  • Fluent in English (able to read, speak, and understand English);
  • Willing to undergo all required study procedures; and
  • Willing to provide written informed consent to participate in the study.

Exclusion Criteria:

  • Is male;
  • Is pregnant, breastfeeding, or planning to become pregnant in the next 12 months;
  • Documented history of tetracycline allergy or self-reports an allergy to tetracyclines;
  • Current or anticipated use of a medication (e.g., barbiturates, phenytoin, lithium, carbamazepine, systemic retinoids, warfarin) with a contraindicated interaction to doxycycline ;
  • Current or planned use of doxycycline for a prolonged period (> 2 weeks) in the 30 days prior to enrollment, including current prescription for doxycycline for STI prophylaxis;
  • Prolonged antibiotic use (> 2 weeks) within the last 30 days prior to enrollment;
  • Co-enrollment in any other concurrent interventional research or studies that may interfere with this study, such as an STI prevention trial, unless approved by Protocol Team in writing;
  • Does not have consistent access (or anticipated weekly access for 52 weeks of survey completion) to smartphone that can access the HMP app; or
  • Any other medical condition, medical/behavioral intervention, or other conditions that, in the opinion of the clinical site Project Lead (PL)/Investigator of Record (IoR) or designee, could interfere with adherence to study procedures or compromise interpretation of study results.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Weekly doxycycline
Participants will take by mouth doxycycline 200 mg weekly regardless of sexual activity in addition to standard of care STI testing/treatment and sexual health counseling.
Drug: Doxycycline hyclate delayed released 200 mg weekly
200 mg of doxycycline taken by mouth weekly regardless of sexual activity along with STI screening and sexual health counseling
Experimental: On-demand doxyPEP
Participants will take by mouth doxycycline 200 mg as soon as possible and within 72 hours after any condomless oral, vaginal, and/or anal sex in addition to standard of care STI testing/treatment and sexual health counseling.
Drug: Doxycycline hyclate delayed released 200 mg
200 mg of doxycycline taken by mouth as soon as possible and within 72 hours after any condomless oral, vaginal, and/or anal sex along with STI screening and sexual health counseling
Other: Quarterly STI testing/treatment and sexual health counseling
Participants will be followed per standard of care with quarterly STI testing/treatment and sexual health counseling.
Other: Per standard of care with quarterly STI testing/treatment and sexual health counseling
Quarterly STI testing/treatment and sexual health counseling

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Combined incidence of GC, CT, and/or early syphilis infection
Time Frame: One (1) year
Overall combined incidence of GC, CT, and/or early syphilis infection by laboratory-based diagnosis (defined as positive GC or CT on nucleic acid amplification test [NAAT] or first positive rapid plasma reagin [RPR] with positive treponemal-specific antibody [Ab] or a new 4-fold rise in RPR titers) over the duration of follow-up.
One (1) year

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Individual incidence diagnoses of GC, CT, and early syphilis infection
Time Frame: One (1) year
Individual incidence diagnoses of GC, CT, and early syphilis infection by laboratory-based diagnosis (defined as positive GC or CT on NAAT or first positive RPR with positive treponemal-specific Ab or a new 4-fold rise in RPR titers) per quarter, by arm.
One (1) year

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
First occurrence of a bacterial STI
Time Frame: One (1) year
First occurrence of a bacterial STI (GC, CT, and/or early syphilis) after study enrollment, based on testing during each quarterly follow-up visit or documented testing occurring at an outside clinical site, by arm.
One (1) year
Proportion GC isolates that are detected as tetracycline-resistant
Time Frame: One (1) year
Proportion of GC isolates that are detected as tetracycline-resistant during follow-up, by arm.
One (1) year
Proportion S. aureus isolates that are detected as doxycycline-resistant
Time Frame: One (1) year
Proportion of S. aureus isolates that are detected as doxycycline-resistant at 24 and 48 weeks, by arm.
One (1) year
Adherence to doxycycline
Time Frame: One (1) year
Adherence to on-demand doxyPEP and weekly doxycycline assessed with objective doxycycline plasma, and/or DBS concentrations matched with expected detection of once-weekly dosing or based on self-reported sexual behavior, by arm.
One (1) year
Adherence to doxycycline - self report
Time Frame: 1 year
Adherence to on-demand doxyPEP and weekly doxycycline assessed with self- reported proportion of sexual exposures within the prior 12 weeks when on-demand doxyPEP and weekly doxycycline was used, by arm.
1 year
Acceptability and optimism
Time Frame: One (1) year
Acceptability and optimism, using Likert scales, by arm.
One (1) year

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Westat

Collaborators

National Institute on Drug Abuse (NIDA)
National Institute of Allergy and Infectious Diseases (NIAID)
Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
National Institute of Mental Health (NIMH)
Florida State University
The Office of the Director, National Institutes of Health (NIH)

Investigators

  • Study Chair: Cherie Blaire, MD, PhD, University of California, Los Angeles
  • Study Chair: Jenell Stewart, DO, MPH, Hennepin Healthcare

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

February 27, 2026

Primary Completion (Estimated)

June 15, 2028

Study Completion (Estimated)

June 15, 2028

Study Registration Dates

First Submitted

December 12, 2024

First Submitted That Met QC Criteria

December 12, 2024

First Posted (Actual)

December 17, 2024

Study Record Updates

Last Update Posted (Actual)

May 15, 2026

Last Update Submitted That Met QC Criteria

May 12, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • ATN173/HPTN 115
  • UM2HD111076 (U.S. NIH Grant/Contract)
  • UM2HD111102 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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