Sexually Transmitted Infections (STI)Phase 4NCT07215325
Got Doxy- 'Flipping the Script' on STI PEP
A Phase 4 study testing Doxycycline monohydrate 200 mg and Observation in people with Sexually Transmitted Infections (STI), run by Emory University at 2 sites in United States.
Trial 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. Read more about this study
- Who is it for?
- Ages 18 years and older, men onlyHealthy volunteers can take part
- Conditions the study is for
- Sexually Transmitted Infections (STI)
- What is being tested?
- Doxycycline monohydrate 200 mg and Observation
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 200 participants
- Where
- 2 sitesUnited States
- Study dates
- 13 Oct 2025to 13 Apr 2029
- Phase
- Phase 4
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- Men only
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- 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
Who cannot join
- 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:
Show all 14Show fewer
- Aspirin
- Warfarin, heparin (LMW or unfractionated), platelet aggregation inhibitors, or fibrinolytic agents
- Any form of rectally administered agent besides products (lubricants or douching) used for sexual intercourse
- NSAIDS within 72 hours of rectal sampling procedures
- Continued need for, or use during the 90 days before enrollment, of the following medications:
- Systemic immunomodulatory agents
- 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.)
- Use of experimental medications, vaccines, or biologicals in the 12 months before enrollment
Trial locations and contacts
2 sites in 1 country. Contact the study team or a site near you to ask about taking part.
United States2 sites, 2 recruiting
- Recruiting
Grady Health System (non-CRN)
Atlanta, Georgia, 30322
Colleen Kelley, MD, MPH, 404-712-1823, colleen.kelley@emory.edu
- Recruiting
Hope Clinic
Atlanta, Georgia, 30322
Colleen Kelley, MD, MPH, 404-712-1823, colleen.kelley@emory.edu
About this study
Official title: The Effects of Doxycycline on Inflammation and the Microbiome: 'Flipping the Script' on STI PEP
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.
Read the detailed description
This project aims to determine the potential anti-inflammatory and microbiome effects of doxycycline when used as post-exposure prophylaxis (Doxy PEP) for sexually transmitted infections (STIs).
This study is important in the field of research because it allows the investigators to define the systemic and gut anti-inflammatory, microbiome, and resistome effects of doxycycline when used as post-exposure prophylaxis (Doxy PEP) for sexually transmitted infections. The study population that this study seeks to enroll consists of healthy people assigned male at birth, with and without HIV, who are willing to undergo study procedures.
Study procedures will include the collection of medical history, as well as biological specimen sampling, such as blood and rectal tissue biopsies.
The duration of this clinical trial for study participants will be approximately 12 weeks. This will include five in-person visits lasting about 45 minutes to 1 hour (including two biopsy visits).
This study will utilize data specimen banking for future research.
- Conditions
- Sexually Transmitted Infections (STI)
- Being tested
- Doxycycline monohydrate 200 mg, Observation
- Keywords
- Doxycycline post-exposure prophylaxis (doxy-PEP), Gut inflammation, Prevention, PEP, STI
- Medical subject headings
- Sexually Transmitted Diseases
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Doxycycline monohydrate 200 mgDrug
Also called Doxycycline
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.
ObservationOther
Also called Standard of Care
Standard of care. Blood and rectal mucosal samples.
| Study group | Role | What they receive |
|---|---|---|
| Doxycycline 200mg | Experimental | 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. Receives: Drug: Doxycycline monohydrate 200 mg |
| Observation with biological sampling | Active comparator | 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. Receives: Other: Observation |
What is being measured
The primary outcome is the main question the study is designed to answer.
Composite inflammation score
A composite inflammation score in the blood and rectal secretions before and after doxy-PEP will be calculated for each participant: +1 point for each proinflammatory cytokine (IP-10, IL-1β, tumor necrosis factor (TNF-α), Monocyte chemoattractant protein-1 (MCP-1), IL-17A, IL-6, interferon (IFN-γ), IL-12p70, IL-8) that was in the top quartile concentration and -1 point for each anti-inflammatory cytokine (IL-4, IL-10), T-cell growth factor (TGF-β1) that was in the top quartile concentration for a maximum score of 9 and minimum score of -3.
Measured: Baseline and 12 weeks after the start of doxycycline administration
Secondary outcomes (2)
Tetracycline (TCN) Gene Abundance
TCN gene-level abundance will be normalized using reads per kilobase per genome equivalent (RPKG), calculated from filtered contigs and estimated genome equivalents (MicrobeCensus). RPKG values will be summed by resistance class, sub-class (e.g., inactivation, target modification, efflux), and by host assignment (pathogen vs. commensal). Group differences in mean TCN RPKG values will be evaluated using non-parametric permutation tests.
Measured: Baseline and 12 weeks after the start of doxycycline administration
Estimated mass of antimicrobial resistance (AMR) Genes
To benchmark normalized abundance, the mass of AMR genes will be estimated using spike-in controls (ZymoBIOMICS). This will provide a quantitative measure of the total AMR gene burden per sample. Group differences in total AMR gene mass will be tested using non-parametric permutation tests.
Measured: Baseline and 12 weeks after the start of doxycycline administration
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted10 Oct 2025
- Study start13 Oct 2025
- Primary completion13 Apr 2029 (estimated)
- Study completion13 Apr 2029 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Sexually Transmitted Infections (STI)Studies of the same condition, open and under way.
- More trials run by Emory UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 4
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Enrolment
- 200 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Emory University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Colleen Kelley, Emory University
- Investigators
- Colleen Kelley, MD, MPH, Principal investigator, Emory University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07215325
- Sponsor's protocol ID
- STUDY00009355
- Other IDs
- 1R01AI192319-01, 2025P009920
- Status last verified
- Apr 2026
- First submitted
- 3 Oct 2025
- Last updated
- 30 Apr 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: Individual participant data that underlie the results published for this study will be made available for sharing after de-identification.
Study at a glance
From the registry record, last updated by the sponsor on 30 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Effects of Doxycycline on Inflammation and the Microbiome: 'Flipping the Script' on STI PEP
- ClinicalTrials.gov ID
- NCT07215325
- Acronym / sponsor ID
- STUDY00009355
- Conditions
- Sexually Transmitted Infections (STI)
- Keywords
- Doxycycline post-exposure prophylaxis (doxy-PEP), Gut inflammation, Prevention, PEP, STI
- Phase
- Phase 4
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 200 participants (estimated)
- Lead sponsor
- Emory UniversityUniversity, hospital or other
- Collaborators
- National Institute of Allergy and Infectious Diseases (NIAID)
- Study start
- 13 Oct 2025 (actual)
- Primary completion
- 13 Apr 2029 (estimated)
- Study completion
- 13 Apr 2029 (estimated)
- First posted
- 10 Oct 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
This project aims to determine the potential anti-inflammatory and microbiome effects of doxycycline when used as post-exposure prophylaxis (Doxy PEP) for sexually transmitted infections (STIs).
This study is important in the field of research because it allows the investigators to define the systemic and gut anti-inflammatory, microbiome, and resistome effects of doxycycline when used as post-exposure prophylaxis (Doxy PEP) for sexually transmitted infections. The study population that this study seeks to enroll consists of healthy people assigned male at birth, with and without HIV, who are willing to undergo study procedures.
Study procedures will include the collection of medical history, as well as biological specimen sampling, such as blood and rectal tissue biopsies.
The duration of this clinical trial for study participants will be approximately 12 weeks. This will include five in-person visits lasting about 45 minutes to 1 hour (including two biopsy visits).
This study will utilize data specimen banking for future research.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Doxycycline 200mg | Experimental | Drug: Doxycycline monohydrate 200 mgMales 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. |
| Observation with biological sampling | Active comparator | Other: ObservationMales 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. |
Who may qualify
- Ages
- 18 years and older
- Sex
- Male only
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (6 listed)
- 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
Key exclusion criteria (14 listed)
- 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,
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Doxycycline monohydrate 200 mgAlso: DoxycyclineDoxycycline 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. | Drug | Doxycycline 200mg |
| ObservationAlso: Standard of CareStandard of care. Blood and rectal mucosal samples. | Other | Observation with biological sampling |
Primary outcome
Composite inflammation score
Time frame: Baseline and 12 weeks after the start of doxycycline administration
A composite inflammation score in the blood and rectal secretions before and after doxy-PEP will be calculated for each participant: +1 point for each proinflammatory cytokine (IP-10, IL-1β, tumor necrosis factor (TNF-α), Monocyte chemoattractant protein-1 (MCP-1), IL-17A, IL-6, interferon (IFN-γ), IL-12p70, IL-8) that was in the top quartile concentration and -1 point for each anti-inflammatory cytokine (IL-4, IL-10), T-cell growth factor (TGF-β1) that was in the top quartile concentration for a maximum score of 9 and minimum score of -3.
2 secondary outcomes
Tetracycline (TCN) Gene Abundance
Time frame: Baseline and 12 weeks after the start of doxycycline administration
Estimated mass of antimicrobial resistance (AMR) Genes
Time frame: Baseline and 12 weeks after the start of doxycycline administration
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 30 Apr 2026.
- Individual participant dataSharing planned: Yes. Individual participant data that underlie the results published for this study will be made available for sharing after de-identification.
Related trials for Sexually Transmitted Infections (STI)
Not yet recruitingPhase 2
Combination Bevacizumab and PRGN-2012 in Adults With Recurrent Respiratory Papillomatosis (RRP)
Respiratory Recurrent Papillomatosis (RRP), Human Papillomavirus (HPV)
Not yet recruitingPhase 1/2
Combining Neo-adjuvant ATR-inhibition With Nodal SBRT for Early-stage Resectable HPV+ OPSCCs
HPV Positive Oropharyngeal Squamous Cell Carcinoma, Squamous Cell Carcinoma
RecruitingObservational study
Leukapheresis to Obtain Plasma or Lymphocytes for Studies of HIV-infected Patients, Including Long-term Non-progressors
HIV
RecruitingPhase 1
Dasatinib for HIV-1 Reservoir Reduction
HIV Infections
RecruitingObservational study
Leukapheresis Procedures to Obtain Plasma and Lymphocytes for Research Studies on Antiretroviral Naive HIV-1 Research Participants
HIV
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Colleen Kelley, MD, MPH principal investigator
Emory University
2 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 4 study testing Doxycycline monohydrate 200 mg and Observation in people with Sexually Transmitted Infections (STI), run by Emory University at 2 sites in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 14 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 30 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 2 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 4 studies take place after a treatment is approved, to learn more about its long-term benefits and risks in everyday use.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Colleen Kelley, MD, MPH (404-712-1823, kelley@emory.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Composite inflammation score (time frame: Baseline and 12 weeks after the start of doxycycline administration). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 30 Apr 2026.