SyphilisPhase 2NCT05548426
Linezolid for Syphilis Pilot Study
A Phase 2 study testing Group B, Linezolid 10d and Group A, Penicillin in people with Syphilis, run by University of Southern California at 5 sites in United States.
Trial summary
The study aims to evaluate the efficacy of linezolid for the treatment of syphilis. Read more about this study
- Who is it for?
- Ages 16 years and older
- Conditions the study is for
- Syphilis
- What is being tested?
- Group B, Linezolid 10d and Group A, Penicillin
- Type of treatment
- Pill or oral medicine, Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 24 participants
- Where
- 5 sitesUnited States
- Study dates
- 28 Sep 2023to Aug 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 16 years and older
- All sexes
- No healthy volunteers
- Child, Adult, Older adult
Who may be able to join
None listed.
Who cannot join
- Pregnancy or a positive pregnancy test on the day of enrollment
- Patients showing signs and symptoms of neurosyphilis.
- Participants who receive certain psychotropic medications, e.g., MAO inhibitors, SNRIs, SSRIs
- Serofast RPR titer, defined as persistently positive RPR titer without more than 4-fold (2-titer level) change for 12 months or greater.
- Recent (within the past 7 days) or concomitant antimicrobial therapy with activity against syphilis, namely azithromycin, tetracycline, doxycycline, cefixime, ceftriaxone or other beta lactam antibiotics (e.g. amoxicillin)
- Individuals with HIV infection who report HIV treatment interruption for more than 4 weeks since their most recent viral load or CD4 test.
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- Individuals with known myelosuppressive conditions or receiving myelosuppressive medication
- Individuals weighing 150kg (330 lbs) or more.
- Individuals with known end renal stage disease, for example individuals in hemodialysis.
- Self-reported allergy to linezolid or penicillin.
- Unwilling or unable to attend follow-up visits.
Trial locations and contacts
5 sites in 1 country.
5 sites in 1 country
United States5 sites
Howard Brown Health
Chicago, Illinois, 60613
Wake Forest Baptist Health
Greensboro, North Carolina, 27405
Open Arms HealthCare Center
Jackson, Mississippi, 39216
University of Mississippi Medical Center
Jackson, Mississippi, 39216
Open Door Health
Providence, Rhode Island, 02907
About this study
Official title: Pilot Study of Linezolid for Early Syphilis Treatment
The study aims to evaluate the efficacy of linezolid for the treatment of syphilis.
Read the detailed description
This will be a randomized, open-label, non-comparative, pilot trial to evaluate the efficacy of linezolid 600mg orally, twice a day, for ten days, using a contemporaneous historical control group benzathine penicillin G (single dose of 2.4 million units) in participants with and without HIV infection.
In total, 24 participants will be enrolled across multiple clinical sites in the United States. Participants will participate in follow-ups to monitor clinical outcomes and serological response (RPR titer) at 1 month, 3 months, and 6 months. A 5 and 10-day phone call will ensure adherence to treatment and evaluate safety.
Study findings may identify an efficacious alternative syphilis treatment to penicillin that is effective for people living with HIV. Study findings may also help address the crisis of penicillin shortages, difficulty in administration, and offer options for those with penicillin allergy.
- Conditions
- Syphilis
- Being tested
- Group B, Linezolid 10d, Group A, Penicillin
- Keywords
- Linezolid, Treponema pallidum, Penicillin, Early Syphilis
- Medical subject headings
- Syphilis, Treponemal Infections
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Group B, Linezolid 10dDrug
Also called zyvox
Oral Linezolid 600mg, taken twice a day for 10 days
Group A, PenicillinDrug
Also called bicillin
Standard of care benzathine penicillin G, one intramuscular injection, 2.4MU
| Study group | Role | What they receive |
|---|---|---|
| Linezolid 10 Day | Experimental | Oral linezolid 600mg, taken twice a day for 10 days Receives: Drug: Group B, Linezolid 10d |
| Benzathine Penicillin G | Active comparator | Single intramuscular injection of 2.4 million units of benzathine penicillin G Receives: Drug: Group A, Penicillin |
What is being measured
The primary outcome is the main question the study is designed to answer.
Response to Treatment
Percentage of linezolid participants with a 4-fold decrease or greater in the serum RPR titer by 180 days after treatment
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 posted21 Sep 2022
- Study start28 Sep 2023
- Primary completionAug 2026 (estimated)
- Study completionAug 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.
- 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
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Enrolment
- 24 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Southern California
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Jeffrey D Klausner, University of Southern California
- Investigators
- Jeffrey D Klausner, MD MPH, Principal investigator, University of Southern California
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05548426
- Sponsor's protocol ID
- APP-22-04165
- Status last verified
- Mar 2026
- First submitted
- 16 Sep 2022
- Last updated
- 12 Mar 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No: No IPD will be shared with other researchers
Study at a glance
From the registry record, last updated by the sponsor on 12 Mar 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Pilot Study of Linezolid for Early Syphilis Treatment
- ClinicalTrials.gov ID
- NCT05548426
- Acronym / sponsor ID
- APP-22-04165
- Conditions
- Syphilis
- Keywords
- Linezolid, Treponema pallidum, Penicillin, Early Syphilis
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 24 participants (estimated)
- Lead sponsor
- University of Southern CaliforniaUniversity, hospital or other
- Study start
- 28 Sep 2023 (actual)
- Primary completion
- Aug 2026 (estimated)
- Study completion
- Aug 2026 (estimated)
- First posted
- 21 Sep 2022 (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 study aims to evaluate the efficacy of linezolid for the treatment of syphilis.
Detailed description
This will be a randomized, open-label, non-comparative, pilot trial to evaluate the efficacy of linezolid 600mg orally, twice a day, for ten days, using a contemporaneous historical control group benzathine penicillin G (single dose of 2.4 million units) in participants with and without HIV infection.
In total, 24 participants will be enrolled across multiple clinical sites in the United States. Participants will participate in follow-ups to monitor clinical outcomes and serological response (RPR titer) at 1 month, 3 months, and 6 months. A 5 and 10-day phone call will ensure adherence to treatment and evaluate safety.
Study findings may identify an efficacious alternative syphilis treatment to penicillin that is effective for people living with HIV. Study findings may also help address the crisis of penicillin shortages, difficulty in administration, and offer options for those with penicillin allergy.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Linezolid 10 Day | Experimental | Drug: Group B, Linezolid 10dOral linezolid 600mg, taken twice a day for 10 days |
| Benzathine Penicillin G | Active comparator | Drug: Group A, PenicillinSingle intramuscular injection of 2.4 million units of benzathine penicillin G |
Who may qualify
- Ages
- 16 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child, Adult, Older adult
Key inclusion criteria (0 listed)
Key exclusion criteria (11 listed)
- Pregnancy or a positive pregnancy test on the day of enrollment
- Patients showing signs and symptoms of neurosyphilis.
- Participants who receive certain psychotropic medications, e.g., MAO inhibitors, SNRIs, SSRIs
- Serofast RPR titer, defined as persistently positive RPR titer without more than 4-fold (2-titer level) change for 12 months or greater.
- Recent (within the past 7 days) or concomitant antimicrobial therapy with activity against syphilis, namely azithromycin, tetracycline, doxycycline, cefixime, ceftriaxone or other beta lactam antibiotics (e.g. amoxicillin)
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 |
|---|---|---|
| Group B, Linezolid 10dAlso: zyvoxOral Linezolid 600mg, taken twice a day for 10 days | Drug | Linezolid 10 Day |
| Group A, PenicillinAlso: bicillinStandard of care benzathine penicillin G, one intramuscular injection, 2.4MU | Drug | Benzathine Penicillin G |
Primary outcome
Response to Treatment
Time frame: 6 months
Percentage of linezolid participants with a 4-fold decrease or greater in the serum RPR titer by 180 days after treatment
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 12 Mar 2026.
- Individual participant dataSharing planned: No. No IPD will be shared with other researchers
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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. This study is not recruiting at the moment.
Jeffrey D Klausner, MD MPH principal investigator
University of Southern California
5 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing Group B, Linezolid 10d and Group A, Penicillin in people with Syphilis, run by University of Southern California at 5 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 0 inclusion and 11 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: under way, not looking for participants, as of the sponsor's last update on 12 Mar 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 5 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 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?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Response to Treatment (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 12 Mar 2026.