Daily Doxycycline for Early Syphillis

NCT06683638 | Recruiting Phase 2 FDA Drug

• 1 other identifier: STUDY00021340
• Study Type: interventional
• Target: 15
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this clinical trial is to learn if doxycycline taken as 200mg daily for 14 days is effective to treat early stage syphilis. This is different from how doxycycline is typically used for syphilis because the full doxycycline dose will be taken at the same time of day, rather than split up into a twice daily regimen. Lab data support that taking the medication as a single daily dose should be effective as treatment, but it has not been studied clinically. The main question this study aims to answer is: Is doxycycline taken as a single daily dose of 200mg for 14 days an effective treatment for early syphilis based on a combined outcome of clinical improvement and blood test improvement? Participants will:

1. 1.Take doxycycline 200mg daily for 14 days
2. 2.Submit oral and rectal swabs that test for syphilis bacteria every other day for 2 weeks, returned by mail
3. 3.Complete 2 brief online surveys over the first 2 weeks
4. 4.Return to the clinic for an interview and blood draw every 3 months for a maximum of 3 study visits, including the first visit

Conditions

Syphilis

Keywords

syphilis; doxycycline

Outcome Measures

Primary Outcomes (1)

• Composite clinical and serological response

  Clinical response and serological response will be aggregated to arrive at one reported value, a binary outcome of "yes" (1) or "no" (0). Clinical response equates to resolution of clinical symptoms of syphilis the participants presented with, such as rash or chancre, without the development of new symptoms of syphilis. Resolution will be marked as "yes" or "no". Serological response equates to a fourfold decrease in RPR compared to the presenting RPR titer by 6 months. Resolution will be marked as "yes" or "no". Thus, to generate the composite response outcome, participants with outcomes of "yes" for both clinical response and serological response will qualify as a binary outcome of "yes" (1) . Participants who do not have outcomes of "yes" for both clinical response and serological response will qualify as a binary outcome of "no" (0).

  6 months

Study Arms (1)

Doxycycline 200mg daily for 14 days

EXPERIMENTAL

Participants diagnosed with early syphilis (primary, secondary, or early latent) with an RPR of 1:4 or greater will receive doxycycline 200mg daily to treat syphilis. Exclusions include pregnant persons, persons under 18 years of age, and persons on doxy PEP. During the two weeks of treatment, participants will perform oral and rectal swabs for syphilis, returned at the end of the 2 weeks by mail. Participants will submit brief online surveys twice over the two weeks of treatment. Repeat blood tests for syphilis, reactive plasma reagin (RPR), will be done at follow-up visits at 3 and 6 months to monitor serological response. Participants with response at the 3-month visit will not need to come to a 6-month visit.

Drug: Doxycycline 200mg daily for 14 days

Interventions

Doxycycline 200mg daily for 14 days DRUG

Doxycycline will be taken as a single dose of 200mg daily, rather than the current CDC-recommended 100mg twice daily regimen for early syphilis. The duration will still be 14 days of therapy.

Doxycycline 200mg daily for 14 days

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Clinical diagnosis of syphilis (primary or secondary) or laboratory-confirmed early latent syphilis. Specifically: This will include persons meeting any one of the following criteria:
• Clinical diagnosis of primary syphilis (based on the presence of a chancre) and either a positive qualitative RPR in the absence of a prior positive RPR on their most recent serological test for syphilis or a positive darkfield microscope exam of material taken from a chancre, OR
• Clinical diagnosis of secondary syphilis with a positive qualitative RPR in the absence of a prior positive RPR on their most recent serological test for syphilis, OR
• A laboratory-confirmed diagnosis of early latent syphilis within one month (i.e. \<31 days prior).

You may not qualify if:

• age under 18
• persons with evidence of neurosyphilis (including ocular and otic syphilis) or tertiary syphilis
• persons who are unable to give informed consent
• persons deemed by the study investigators to be unable to complete study follow-up visits
• persons with an allergy to doxycycline
• pregnant persons
• persons with HIV who report that they are off antiretroviral medication or that they are not virologically suppressed
• persons with other known forms of immunosuppression (e.g., persons taking systemic immunosuppressant drugs, persons with primary immunodeficiencies)
• persons taking medications that would interact with doxycycline
• persons whose initial RPR is lower than 1:4
• persons currently prescribed doxy PEP
• breastfeeding persons
• Persons whose initial laboratory serological tests do not confirm the diagnosis of syphilis with an RPR of 1:4 or higher will be informed that they do not meet study criteria and advised to discontinue doxycycline 200mg once daily. Their subsequent treatment will be based on the judgement of non-research, clinical staff in the clinic and reflect shared decision making between clinical providers and their patient.

Sponsors & Collaborators

• University of Washington: lead

Study Sites (1)

Public Health Sexual Health Clinic

Seattle, Washington, 98104, United States

RECRUITING

MeSH Terms

Conditions

Syphilis

Interventions

Doxycycline

Condition Hierarchy (Ancestors)

Treponemal Infections; Spirochaetales Infections; Gram-Negative Bacterial Infections; Bacterial Infections; Bacterial Infections and Mycoses; Infections; Sexually Transmitted Diseases, Bacterial; Sexually Transmitted Diseases; Communicable Diseases; Genital Diseases; Urogenital Diseases

Intervention Hierarchy (Ancestors)

Tetracyclines; Naphthacenes; Polycyclic Aromatic Hydrocarbons; Hydrocarbons, Aromatic; Hydrocarbons, Cyclic; Hydrocarbons; Organic Chemicals; Polycyclic Compounds

Study Officials

• Travis Hunt, MD

  University of Washington

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Travis Hunt, MD

CONTACT

206-685-4456; thunt91@uw.edu

Matthew Golden, MD, MPH

CONTACT

206-744-6829; golden@uw.edu

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Clinician Researcher, Division of Allergy and Infectious Diseases

Model Details: This study will enroll one prospective arm of 15 persons. To contextualize the finding, the investigators will separately determine point-estimates of 6-month treatment response to standard of care regimens in the sexual health program using de-identified retrospective cohorts of 60 persons each.

Study Record Dates

• First Submitted: November 8, 2024
• First Posted: November 12, 2024
• Study Start: March 3, 2025
• Primary Completion (Estimated): June 26, 2026
• Study Completion (Estimated): June 26, 2026
• Last Updated: June 25, 2025

Record last verified: 2025-06

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)