SyphilisPhase 2NCT06683638
Daily Doxycycline for Early Syphillis
A Phase 2 study testing Doxycycline 200mg daily for 14 days in people with Syphilis, run by University of Washington at 1 site in United States.
Trial 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… Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Syphilis
- What is being tested?
- Doxycycline 200mg daily for 14 days
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 15 participants
- Where
- 1 siteUnited States
- Study dates
- 3 Mar 2025to 26 Jun 2026
- Phase
- Phase 2
- 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
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- 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).
Who cannot join
- 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
Show all 13Show fewer
- 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.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
Public Health Sexual Health Clinic
Seattle, Washington, 98104
Jakar Delacruz, 206-744-3590, fkajonny@uw.edu
Travis Hunt, MD, 206.685.4456, thunt91@uw.edu
About this study
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?
Read more
Participants will:
- Take doxycycline 200mg daily for 14 days
- Submit oral and rectal swabs that test for syphilis bacteria every other day for 2 weeks, returned by mail
- Complete 2 brief online surveys over the first 2 weeks
- Return to the clinic for an interview and blood draw every 3 months for a maximum of 3 study visits, including the first visit
The investigators will compare the percentage of participants in the study who have response to treatment by 6 months to that of persons who have received standard (CDC-recommended) regimens. To do this, the investigators will calculate response percentage estimates following a shot of long-acting penicillin or 14 days of doxycycline 100mg twice daily from 60-person samples from the sexual health program's records.
Read the detailed description
This is an open-label prospective cohort of 15 participants diagnosed with early syphilis treated with doxycycline 200mg daily for 14 days. The outcome of interest is clinical improvement and fourfold decline in RPR by 6 months. This study will include rectal and oropharyngeal sampling with syphilis transcription-mediated amplification (TMA), every other day for the 14-day course, returned by mail. The investigators will obtain 6-month point estimates for cure following single-dose intramuscular benzathine penicillin G or 14 days of doxycycline 100mg twice daily in retrospective cohorts of 60 persons. The investigators will use binomial exact calculation with an alpha of 0.05, two-tailed, to create a point estimates of percent cure. The investigators will report TMA positivity descriptively.
- Conditions
- Syphilis
- Being tested
- Doxycycline 200mg daily for 14 days
- Keywords
- syphilis, doxycycline
- Medical subject headings
- Syphilis
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Doxycycline 200mg daily for 14 daysDrug
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.
| Study group | Role | What they receive |
|---|---|---|
| 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. Receives: Drug: Doxycycline 200mg daily for 14 days |
What is being measured
The primary outcome is the main question the study is designed to answer.
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).
Measured: 6 months
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted12 Nov 2024
- Study start3 Mar 2025
- Primary completion26 Jun 2026 (estimated)
- Study completion26 Jun 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for SyphilisStudies of the same condition, open and under way.
- More trials run by University of WashingtonThe 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 2
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Model description
- 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.
- Masking
- None (open label)
- Enrolment
- 15 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Washington
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Travis J Hunt, University of Washington
- Investigators
- Travis Hunt, MD, Principal investigator, University of Washington
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06683638
- Sponsor's protocol ID
- STUDY00021340
- Status last verified
- Jun 2025
- First submitted
- 8 Nov 2024
- Last updated
- 25 Jun 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 25 Jun 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Daily Doxycycline for Early Syphillis
- ClinicalTrials.gov ID
- NCT06683638
- Acronym / sponsor ID
- STUDY00021340
- Conditions
- Syphilis
- Keywords
- syphilis, doxycycline
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 15 participants (estimated)
- Lead sponsor
- University of WashingtonUniversity, hospital or other
- Study start
- 3 Mar 2025 (actual)
- Primary completion
- 26 Jun 2026 (estimated)
- Study completion
- 26 Jun 2026 (estimated)
- First posted
- 12 Nov 2024 (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.
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:
- Take doxycycline 200mg daily for 14 days
- Submit oral and rectal swabs that test for syphilis bacteria every other day for 2 weeks, returned by mail
- Complete 2 brief online surveys over the first 2 weeks
- Return to the clinic for an interview and blood draw every 3 months for a maximum of 3 study visits, including the first visit
The investigators will compare the percentage of participants in the study who have response to treatment by 6 months to that of persons who have received standard (CDC-recommended) regimens. To do this, the investigators will calculate response percentage estimates following a shot of long-acting penicillin or 14 days of doxycycline 100mg twice daily from 60-person samples from the sexual health program's records.
Detailed description
This is an open-label prospective cohort of 15 participants diagnosed with early syphilis treated with doxycycline 200mg daily for 14 days. The outcome of interest is clinical improvement and fourfold decline in RPR by 6 months. This study will include rectal and oropharyngeal sampling with syphilis transcription-mediated amplification (TMA), every other day for the 14-day course, returned by mail. The investigators will obtain 6-month point estimates for cure following single-dose intramuscular benzathine penicillin G or 14 days of doxycycline 100mg twice daily in retrospective cohorts of 60 persons. The investigators will use binomial exact calculation with an alpha of 0.05, two-tailed, to create a point estimates of percent cure. The investigators will report TMA positivity descriptively.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- 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.
| Arm | Type | Receives |
|---|---|---|
| Doxycycline 200mg daily for 14 days | Experimental | Drug: Doxycycline 200mg daily for 14 daysParticipants 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. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (4 listed)
- 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).
Key exclusion criteria (13 listed)
- 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
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 200mg daily for 14 daysDoxycycline 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. | Drug | Doxycycline 200mg daily for 14 days |
Primary outcome
Composite clinical and serological response
Time frame: 6 months
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).
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 25 Jun 2025.
- Individual participant dataSharing planned: No
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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.
Travis Hunt, MD principal investigator
University of Washington
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing Doxycycline 200mg daily for 14 days in people with Syphilis, run by University of Washington at 1 site 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 4 inclusion and 13 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 25 Jun 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site 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 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
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 Travis Hunt, MD (206-685-4456, thunt91@uw.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Composite clinical and serological response (time frame: 6 months). 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 25 Jun 2025.