Recruiting

Doxycycline

Sponsor:

Emory University

Code:

NCT07215325

Conditions

Sexually Transmitted Infections (STI)

Eligibility Criteria

Sex: Male

Age: 18+

Healthy Volunteers: Accepted

Interventions

Doxycycline monohydrate 200 mg

Observation

Study Details

Brief summary:

This study is being done to test the effects of doxycycline on inflammation and the bacteria in the body in people with HIV and in people on HIV pre-exposure prophylaxis. This drug is approved by the Food and Drug Administration (FDA) for the treatment of bacterial infections.

The study team will investigate whether the drug has additional effects on inflammation or on the bacteria that live in the body.

Conditions

Sexually Transmitted Infections (STI)

Study ID

NCT07215325

Start date

Oct 13, 2025

Status verified date

Apr, 2026

Completion date

Apr 13, 2029

Anticipated

Primary completion date

Apr 13, 2029

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: Male

Age: 18+

Healthy Volunteers: Accepted

Inclusion Criteria:

  • Age >18 years
  • Assigned male sex at birth
  • Good general health as assessed by a clinician at the screening study visit
  • For people with HIV, on suppressive antiretroviral therapy for at least 6 months with the most recent viral load documented <50 copies/ml and the most recent cluster of differentiation 4 (CD4)>300cells/ul
  • For people without HIV, taking oral daily, oral on-demand, or injectable pre-exposure prophylaxis for at least 3 months at the time of enrollment, with plans to continue for the duration of the study
  • Additional criteria apply

Exclusion Criteria:

  • Severe/uncontrolled comorbidities that could influence immune outcomes (e.g., diabetes, hypertension, co-infections), as assessed by the investigator.
  • History of inflammatory bowel disease (IBD) or other inflammatory, infiltrative, infectious, or vascular condition involving the lower GI tract that, in the judgment of the investigators, may be worsened by study procedures or may significantly distort the anatomy of the distal large bowel.
  • Known allergy to doxycycline
  • Use of any antibiotics within 3 months before screening
  • Significant lab abnormalities at baseline visit for rectal biopsies,
  • Continued need for the following medications during the study:

1. Aspirin
2. Warfarin, heparin (LMW or unfractionated), platelet aggregation inhibitors, or fibrinolytic agents
3. Any form of rectally administered agent besides products (lubricants or douching) used for sexual intercourse
4. NSAIDS within 72 hours of rectal sampling procedures
  • Continued need for, or use during the 90 days before enrollment, of the following medications:

1. Systemic immunomodulatory agents
2. Supraphysiologic doses of corticosteroids, except for short-course corticosteroids <7 days duration at the discretion of the investigator. (Gender affirming hormone therapy is not exclusionary.)
3. Use of experimental medications, vaccines, or biologicals in the 12 months before enrollment

Study Design

Enrollment

200 participants

Anticipated

Allocation

Randomized

Intervention Model

Parallel Assignment

Primary purpose

Basic Science

Interventions and Outcome Measures

Arms

experimental: Doxycycline 200mg

Males with HIV infection on antiretroviral therapy or without HIV infection on HIV pre-exposure prophylaxis who are not taking doxy-PEP will be enrolled and randomized to take 12 weeks of doxycycline 200 mg by mouth three times weekly.

Blood and rectal mucosal samples will be collected before the initiation of doxycycline.

active comparator: Observation with biological sampling

Males with HIV infection on antiretroviral therapy or without HIV infection on HIV pre-exposure prophylaxis who are not taking doxy-PEP will receive standard of care and will undergo biological sampling.

Interventions

Doxycycline monohydrate 200 mg

Doxycycline monohydrate 200 mg (two 100 mg tablets) is used to treat or prevent infections that are strongly suspected to be caused by bacteria. Doxycycline monohydrate is an antimicrobial drug indicated for the treatment of bacterial infections, including sexually transmitted diseases. Centers for Disease Control and Prevention (CDC) recommends its use as post-exposure prophylaxis (PEP).

Blood and rectal mucosal samples will be collected before doxycycline is initiated. Participants will be instructed to take 200 mg of doxycycline by mouth every Monday, Wednesday, and Friday. Additional doses of doxycycline will be permitted on other days if sex without a condom occurs per CDC guidance. After 12 weeks of at least three-weekly doxycycline, blood and rectal mucosal samples will be collected for immunologic and microbiome/resistome assays.

Observation

Standard of care. Blood and rectal mucosal samples.

Primary outcome measure

  • Composite inflammation score [ Time Frame: Baseline and 12 weeks after the start of doxycycline administration ]

Central Contacts and Locations

Central contacts

Colleen Kelley, MD, MPH

404-712-1823kelley@emory.edu

Locations

Grady Health System (non-CRN)

Recruiting

Atlanta, Georgia, United States, 30322

Contacts

Colleen Kelley, MD, MPH

404-712-1823colleen.kelley@emory.edu

Hope Clinic

Recruiting

Atlanta, Georgia, United States, 30322

Contacts

Colleen Kelley, MD, MPH

404-712-1823colleen.kelley@emory.edu

More Information

Sponsor

Emory University

Last update posted

Apr 30, 2026

Last verified

Apr, 2026

Keywords

  • Doxycycline post-exposure prophylaxis (doxy-PEP)
  • Gut inflammation
  • Prevention
  • PEP
  • STI

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-10. This information was provided to ClinicalTrials.gov by Emory University on 2026-04-30.