Doxycycline for Sexually Transmitted Infections

Not yet recruiting at 1 trial location

Overseen By Colleen Kelley, MD, MPH

Age: 18+

Sex: Male

Trial Phase: Phase 4

Sponsor: Emory University

Must be taking: Antiretrovirals, PrEP

Must not be taking: Antibiotics, NSAIDs

Disqualifiers: Diabetes, Hypertension, IBD, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Prior Safety Data This treatment has passed at least one previous human trial

Compensation: Varies

Number of Visits: 6

Duration: 12 weeks

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial explores whether doxycycline, typically used to treat infections, can also reduce inflammation or affect bacteria in individuals with HIV or those on medication to prevent HIV. Participants will either take doxycycline or receive standard care. Men who have been on HIV medication or prevention for at least three months and are in good health may qualify for this trial. As a Phase 4 trial, this research aims to understand how the already FDA-approved doxycycline can benefit more patients.

Will I have to stop taking my current medications?

You may need to stop taking certain medications to join this trial. If you are using antibiotics, aspirin, blood thinners, or certain other medications, you might not be eligible. It's best to discuss your current medications with the study team to see if you can participate.

What is the safety track record for doxycycline?

Research has shown that doxycycline is generally safe and effective for preventing sexually transmitted infections (STIs). Specifically, taking 200 mg of doxycycline within 72 hours after sex can reduce infections like syphilis and chlamydia by over 70%. Studies involving men who have sex with men and transgender women demonstrated that the drug lowered the risk of these bacterial STIs.

The FDA has already approved doxycycline for treating bacterial infections, indicating its general safety. Some individuals might experience mild side effects such as nausea or sensitivity to sunlight, but these are usually manageable. Overall, evidence supports doxycycline as a safe option for preventing certain STIs. ^{1 2 3 4 5}

Why are researchers enthusiastic about this study treatment?

Researchers are excited about using doxycycline for sexually transmitted infections because it offers a potential preventative approach rather than just treating infections after they occur. Unlike standard treatments that typically focus on addressing infections once symptoms appear, doxycycline is being explored for its ability to reduce the risk of contracting STIs when taken regularly. This prophylactic approach is particularly promising for individuals at higher risk, such as those with HIV or on HIV pre-exposure prophylaxis, offering a proactive measure to enhance sexual health.

What is the effectiveness track record for doxycycline in treating bacterial infections?

Studies have shown that doxycycline can help prevent bacterial sexually transmitted infections (STIs). Specifically, taking 200 mg of doxycycline within 72 hours after sex reduced syphilis and chlamydia infections by more than 70% and also lowered the risk of gonorrhea. Another study found that using doxycycline as a preventive treatment after possible exposure reduced the overall occurrence of gonorrhea, chlamydia, and syphilis by two-thirds. In this trial, one group of participants will take 200 mg of doxycycline three times weekly for 12 weeks, while another group will receive standard care and undergo biological sampling. These findings suggest that doxycycline can be a powerful tool in preventing bacterial STIs, especially for people at high risk. ^{1 4 5 6 7}

Who Is on the Research Team?

Colleen Kelley, MD, MPH

Principal Investigator

Emory University

Are You a Good Fit for This Trial?

This trial is for individuals with HIV or those on HIV pre-exposure prophylaxis, to explore the effects of doxycycline on inflammation and body bacteria. Specific eligibility criteria are not provided.

Inclusion Criteria

Good general health as assessed by a clinician at the screening study visit

Additional criteria apply

I have been on HIV prevention medication for at least 3 months and plan to continue.

Exclusion Criteria

I haven't taken antibiotics in the last 3 months.

Significant lab abnormalities at baseline visit for rectal biopsies

Severe/uncontrolled comorbidities that could influence immune outcomes (e.g., diabetes, hypertension, co-infections), as assessed by the investigator

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

1 visit (in-person)

Treatment

Participants receive doxycycline 200 mg by mouth three times weekly for 12 weeks

12 weeks

5 visits (in-person, including 2 biopsy visits)

Follow-up

Participants are monitored for safety and effectiveness after treatment

4 weeks

What Are the Treatments Tested in This Trial?

Interventions

• Doxycycline

Trial Overview The study compares the impact of taking Doxycycline monohydrate (200 mg) against no intervention (observation) in reducing inflammation and altering body bacteria in people with HIV or on PrEP.

How Is the Trial Designed?

Group I: Doxycycline 200mg Experimental Treatment 1 Intervention

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.

Group II: Observation with biological sampling Active Control 1 Intervention

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.

Who Is Running the Clinical Trial?

Emory University

Lead Sponsor

Trials

1,735

Recruited

2,605,000+

National Institute of Allergy and Infectious Diseases (NIAID)

Collaborator

Trials

3,361

Recruited

5,516,000+

Citations

1. pubmed.ncbi.nlm.nih.gov pubmed.ncbi.nlm.nih.gov/40147465/

final results from the DoxyPEP multicentre, open-label, ... Doxy-PEP was effective in reducing bacterial STIs in this population of men who have sex with men and transgender women, including during an open-label ...

2. nature.com nature.com/articles/s41467-025-64261-w

Bacterial sexually transmitted infections and related ... In our study, gonorrhea accounted for 46% of all STI diagnoses preventable by doxyPEP among eligible PrEP recipients and 36% of preventable ...

3. cdc.gov cdc.gov/mmwr/volumes/73/rr/rr7302a1.htm

CDC Clinical Guidelines on the Use of Doxycycline .. ... 200 mg of doxycycline taken within 72 hours after sex has been shown to reduce syphilis and chlamydia infections by >70% and gonococcal infections by ...

4. sciencedirect.com sciencedirect.com/science/article/pii/S1201971224002571

Doxycycline prophylaxis for the prevention of sexually ... 200 mg doxycycline after sex significantly reduced the risk of chlamydia and syphilis. No serious adverse events were reported with the use of doxycycline ...

5. nejm.org nejm.org/doi/full/10.1056/NEJMoa2211934

Postexposure Doxycycline to Prevent Bacterial Sexually ... The combined incidence of gonorrhea, chlamydia, and syphilis was lower by two thirds with doxycycline postexposure prophylaxis than with standard care.

6. cdc.gov cdc.gov/sti/hcp/doxy-pep/index.html

Doxy PEP for Bacterial STI Prevention Doxy PEP has proven to reduce the risk of getting some bacterial STIs for gay, bisexual, and other men who have sex with men and transgender women at increased ...

7. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC8360665/

Doxycycline for Sexually Transmitted Infection Prevention The goal of the ongoing studies is to provide sufficient data to inform guidelines and if doxycycline prophylaxis is shown to be safe and effective for STI ...