Doxycycline for Syphilis Prevention

Overseen By Troy Grennan, MD

Age: 18+

Sex: Male

Trial Phase: Phase 4

Sponsor: British Columbia Centre for Disease Control

Must be taking: Doxycycline

Must not be taking: Barbiturates, Phenytoin, Carbamazepine, Isotretinoin

Disqualifiers: Allergy to doxycycline, Myasthenia gravis, others

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

Approved in 5 Jurisdictions This treatment is already approved in other countries

Compensation: Varies

Number of Visits: Unknown

Duration: 48 weeks

52 Participants Needed

Trial Summary

What is the purpose of this trial?

Syphilis is a sexually transmitted infection (STI) disproportionately affecting gay, bisexual and other men who have sex with men (gbMSM), with the potential for significant sequelae - particularly in those who are Human Immunodeficiency Virus (HIV)-positive. Rising rates of this STI have prompted a search for novel prevention solutions. A recent pilot study of daily doxycycline prophylaxis demonstrated promise as a novel STI prevention tool. This innovative approach to STI prevention has solid clinical precedent, both from the HIV pre-exposure prophylaxis (PrEP) literature, as well as doxycycline's use as prophylaxis for other infections. The overarching goal of this project is to determine whether the daily use of doxycycline is an efficacious and acceptable intervention for syphilis prevention in high-risk, HIV-positive gbMSM.

Research Team

Troy Grennan, MD

Principal Investigator

BC Centre for Disease Control

Eligibility Criteria

The trial is for HIV-positive gay, bisexual, and other men who have sex with men (gbMSM) over 18 years old. Participants must have had condomless anal sex in the past 6 months and a recent syphilis diagnosis. They can't join if they're allergic to doxycycline or tetracyclines, have myasthenia gravis, use isotretinoin or certain other medications.

Inclusion Criteria

Able to provide informed consent

I identify as a man who has sex with men.

I have had unprotected anal sex with a man in the past 6 months.

Exclusion Criteria

I am not taking medications like barbiturates, phenytoin, or carbamazepine.

I am capable of becoming pregnant.

I am currently taking isotretinoin.

Timeline

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Treatment

Participants receive daily doxycycline or placebo for syphilis prevention

48 weeks

Regular visits for monitoring adherence and drug levels

Follow-up

Participants are monitored for safety and effectiveness after treatment

4 weeks

Treatment Details

Interventions

• Doxycycline
• Placebo

Trial Overview This study tests whether taking daily doxycycline can prevent syphilis in high-risk gbMSM compared to a placebo. It builds on previous research suggesting that this antibiotic could be an effective preventive measure against sexually transmitted infections.

Participant Groups

Group I: Doxycycline arm Experimental Treatment 1 Intervention

Participants in this intervention group will receive doxycycline 100mg orally daily, which is available as a 100mg capsule. This single daily dose was chosen to maximize adherence, given the common use of once-daily Human Immunodeficiency Virus (HIV) pre-exposure prophylaxis (PrEP), as well as its efficacy as once-daily prophylaxis against malaria and its utility as dosing as infrequent as once weekly for another spirochete infection, leptospirosis.

Group II: Placebo arm Placebo Group 1 Intervention

Participants in this control group will receive a placebo capsule identical in appearance, taste, and size to the capsule provided to the intervention group.

Doxycycline is already approved in United States, European Union, Canada, Japan for the following indications:

Approved in United States as Doxycycline for:

• Acne
• Bacterial infections
• Chlamydia
• Gonorrhea
• Lyme disease
• Malaria
• Pneumonia
• Rosacea
• Urinary tract infections

Approved in European Union as Doxycycline for:

• Acne
• Bacterial infections
• Chlamydia
• Gonorrhea
• Lyme disease
• Malaria
• Pneumonia
• Rosacea
• Urinary tract infections

Approved in Canada as Doxycycline for:

• Acne
• Bacterial infections
• Chlamydia
• Gonorrhea
• Lyme disease
• Malaria
• Pneumonia
• Rosacea
• Urinary tract infections

Approved in Japan as Doxycycline for:

• Acne
• Bacterial infections
• Chlamydia
• Gonorrhea
• Lyme disease
• Malaria
• Pneumonia
• Rosacea
• Urinary tract infections

Who Is Running the Clinical Trial?

British Columbia Centre for Disease Control

Lead Sponsor

Trials

11

Recruited

2,600+