Doxycycline Prophylaxis for Prevention of Sexually Transmitted Infections

Phase 4

Suspended

• Conditions: Gonorrhea; Chlamydia; Syphilis; Sexually Transmitted Infections (STIs)
• Interventions: Drug: Doxycycline hyclate delayed released 200 mg; Drug: Doxycycline hyclate delayed released 200 mg weekly

• Registration Number: NCT06738407
• Lead Sponsor: Westat

Brief Summary

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.

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 Timeline

• Study First Submitted: 2024-12-12
• Study First Submitted QC: 2024-12-12
• Status Verified: 2025-03
• Study First Posted: 2025-03-25
• Last Update Submitted: 2025-03-26
• Last Update Posted: 2025-04-01
• Study Start: 2025-05-15
• Primary Completion: 2027-06-30
• Study Completion: 2028-06-30

Recruitment & Eligibility

• Status: SUSPENDED
• Sex: Female
• Target Recruitment: 760

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;
• Reports 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 & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
On-demand doxyPEP	Doxycycline hyclate delayed released 200 mg	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.
Weekly doxycycline	Doxycycline hyclate delayed released 200 mg weekly	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.

Primary Outcome Measures

Name	Time	Method
Combined incidence of GC, CT, and/or early syphilis infection	One (1) year	To evaluate the 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 newly positive or fourfold rise in RPR titers) per quarter, by arm.

Secondary Outcome Measures

Name	Time	Method
Individual incidence diagnoses of GC, CT, and early syphilis infection	One (1) year	To evaluate individual incidence diagnoses of GC, CT, and early syphilis infection by laboratory-based diagnosis (defined as positive GC or CT on NAAT or newly positive or fourfold rise in RPR titers) per quarter, by arm.

Trial Locations

Locations (11)

Penn Prevention; 🇺🇸 Philadelphia, Pennsylvania, United States

St. Jude Children's Research Hospital; 🇺🇸 Memphis, Tennessee, United States

Baylor College of Medicine; 🇺🇸 Houston, Texas, United States

UCLA Care; 🇺🇸 Los Angeles, California, United States

Children's National Medical Center; 🇺🇸 Washington, District of Columbia, United States

Ponce de Leon; 🇺🇸 Atlanta, Georgia, United States

University Illinois Chicago; 🇺🇸 Chicago, Illinois, United States

Tulane University; 🇺🇸 New Orleans, Louisiana, United States

Callen-Lorde Community Health Center; 🇺🇸 New York, New York, United States

Harlem Prevention Center; 🇺🇸 New York, New York, United States

Chapel Hill; 🇺🇸 Chapel Hill, North Carolina, United States