Could a pill replace the syphilis shot? new trial tests oral antibiotic
NCT ID NCT05069974
First seen Jul 07, 2026 · Last updated Jul 30, 2026 · Updated 5 times
Summary
This trial compares an oral antibiotic called linezolid to the standard penicillin injection for treating early syphilis. Linezolid can reach the brain, which may help prevent neurosyphilis. About 224 adults with primary, secondary, or early latent syphilis will be randomly assigned to receive either linezolid pills for 5–10 days or a single penicillin shot. The study tracks whether sores heal and blood tests show the infection is cleared.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- Linezolid
- What this could lead to
- If it works, this could offer an oral alternative to painful penicillin injections for syphilis, especially for patients with penicillin allergies.
- What could go wrong
- This is a Phase 3 trial, but linezolid is not yet proven for syphilis in humans. It may be less effective than penicillin or cause side effects like nerve damage or bone marrow suppression.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
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Phase 3
Large-scale testing in a bigger group. Usually the last step before a treatment can be approved.
- Participants
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165 people
The number who actually took part.
- Started
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Oct 2021
- Finished
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Apr 2026
- Lead sponsor
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Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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18 to 99 years
- Sex
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Anyone
- Healthy volunteers
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Not accepted
This study is not open to healthy volunteers. The entry requirements below say who it is open to.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
Inclusion Criteria: 1. Age 18 years or older at baseline visit. 2. Primary, secondary or early latent syphilis diagnosis based on SEIMC/IUSTI Guidelines\* 1. Primary syphilis is defined as typical ulcer (chancre) and one of the following: detection of T.p. by Polymerase chain reaction (PCR), positive darkfield examination (DFE) or positive serological test (RPR≥1:4) for syphilis. 2. Secondary syphilis is defined based on typical clinical symptoms with positive treponemal and non-treponemal tests (RPR≥1:4). 3. Early latent syphilis is defined as positive serological treponemal and non-treponemal tests (RPR≥1:4) with no clinical evidence of infection, with a previous negative syphilis serology,or a four-fold increase in RPR titer of a non-treponemal test within the past 12 months.Serological tests for syphilis performed within 10 days prior to study inclusion visit willbe acceptable for enrollment. 3. Signature of written informed consent. 4. Ability to comply with the requirements of the study protocol. 5. If women of childbearing potential, use of a highly effective method of contraception (abstinence,hormonal contraception, intra-uterine device \[IUD\], or anatomical sterility in self or partner)committed during 1 week after last IMP administration. 6. If men, use of condom during heterosexual intercourse and use of a highly effective method ofcontraception (abstinence, hormonal contraception, intra-uterine device \[IUD\], or anatomical sterilityin self or partner) in female partner committed during 1 week after last IMP administration. * For inclusion purposes, positive point of care tests (POCT) will be accepted in selected patients without previous syphilis history and negative serological tests for syphilis during the last 12 months (Syphilis rapid diagnostic test \[RDT\] or Chembio DPP syphilis screen \& confirm assay \[DPP\]), or with a previous history of syphilis and negative non-treponemal tests during the last 12 months (DPP). Further confirmation by the methods described in a), b) or c) will be necessary. Participants whose diagnosis is not confirmed will be excluded from the efficacy analyses. Exclusion Criteria: 1. Known allergy to any of the IMPs and/or excipients, particularly known hypersensitivity to penicillin, cephalosporins or other beta-lactam agents and/or allergy to soya or peanut. 2. Lactose or galactose intolerance or glucose-galactose malabsorbtion. 3. Diagnosis criteria of symptomatic neurosyphilis. 4. Pregnant or breastfeeding women. 5. Current treatment with any drugs likely to interact with the study medication (see Appendix 6). 6. Have taken any antibiotics with potential activity against syphilis (e.g. beta lactams, cephalosporines, macrolides, tetracyclines) within 1 week prior to randomization. 7. Uncontrolled hypertension, pheochromocytoma, thyrotoxicosis, carcinoid syndrome, bipolar disorder, incapacitating psycho-affective disturbance, acute confusional state. 8. Renal function impairment requiring hemodialysis. 9. Symptomatic concomitant STI (i.e., gonococcus, chlamydia, lymphogranuloma venereum, Mycoplasma genitalium) or other infection disease requiring antibiotic treatment potentially active against syphilis. 10. Having received treatment for the early syphilis recently diagnosed (In the previous 6 months)
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
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56 Dean Street
London, United Kingdom
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Barcelona Checkpoint
Barcelona, Barcelona, 08015, Spain
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CAP Drassanes-Hospital Universitari Vall d'Hebron
Barcelona, Barcelona, 08001, Spain
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Hospital 12 de Octubre
Madrid, Madrid, Spain
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Hospital Clínic de Barcelona
Barcelona, Barcelona, 08036, Spain
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Hospital Germans Trias Pujol
Barcelona, Barcelona, 08916, Spain
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Leeds Sexual Health
Leeds, United Kingdom
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Mortimer Market Centre
London, United Kingdom
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North Manchester General Hospital and Central Manchester Foundation Trust
Manchester, United Kingdom
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Saint Mary's Hospital
London, United Kingdom
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Trafalgar Clinic and Waldron Centre Lewisham
Lewisham, United Kingdom