A Phase 3 interventional study of Amoxicillin and Penicillin G, Benzathine in Syphilis Acquired, sponsored by Hospital de Niños R. Gutierrez de Buenos Aires. Recruiting at 1 site in Argentina. Open to participants aged Up to 18 Years. Per ClinicalTrials.gov, last updated 2026-10-27.
Sponsored by Hospital de Niños R. Gutierrez de Buenos Aires · Phase 3, Interventional, and Treatment
The goal of this clinical trial is to learn if oral amoxicillin has comparable therapeutic response than penicillin G benzathine for the treatment of acquired pediatric syphilis. It will also learn about the adverse events and biomarkers of therapeutic response associated with oral amoxicillin. The main questions it aims to answer are:
Participants will:
A randomized, phase III, multicenter, prospective, open-label, non-inferiority clinical trial in pediatric outpatients with a diagnosis of acquired syphilis has been designed in order to compare oral amoxicillin against penicillin G benzathine for the treatment of pediatric syphilis. The primary hypothesis of this study is that oral amoxicillin is non-inferior to the standard treatment of intramuscular procaine benzathine penicillin (PGB) for the treatment of syphilis.
The primary objective of this study is to evaluate the noninferiority of oral amoxicillin compared to intramuscular PGB in treating primary, secondary, or early latent acquired syphilis in a pediatric population. The secondary outcome is to study adverse events and molecular biomarkers of therapeutic response by real-time PCR (qPCR) in both treatment arms.
Diagnostic Criteria:
Diagnosis is based on the presence of lesions compatible with syphilis, accompanied by positive results on both non-treponemal tests (VDRL/RPR) and treponemal tests (rapid strip, ELISA, or chemiluminescence).
Secondary Syphilis: Manifested by cutaneous or mucosal lesions, which may include:
Demographic, epidemiological, and clinical data, including information on concomitant medications, will be collected at baseline. A physical examination and comprehensive clinical evaluation will be conducted for all subjects following standard clinical practices.
Diagnostic studies will be performed in accordance with national and international standards for the diagnosis of primary and secondary syphilis. These include:
A venous blood sample of 2 ml will be collected at diagnosis and subsequently at 2, 4, 6, 12 (endpoint), and 24 months post-treatment to evaluate the serological curve and perform molecular biology analyses
Control laboratory tests will be conducted prior to treatment and at the end of treatment (14 days post-initiation) and will include:
Given the well-documented safety profiles of both amoxicillin and procaine benzathine penicillin (PGB), it is anticipated that no significant adverse events will occur in the treated population. Nonetheless, all participants will undergo a clinical evaluation one week after the initiation of treatment to assess any medication-related adverse events and to ensure treatment compliance.
Following this initial evaluation, participants will be contacted via telephone every two weeks until week 8 to monitor additional safety outcomes, clinical responses, and the use of concomitant medications.
Additional visits will be scheduled as needed during follow-up for patients who exhibit clinical nonresponse (persistence or worsening of lesions) within 8 weeks after the initiation of treatment, or for those who experience clinical recurrence at any point during follow-up. During these visits, epidemiological and clinical information will be gathered, and a comprehensive physical examination will be conducted. Blood samples will be collected for serological testing, and swabs will be taken from any existing lesions for further analysis.
qPCR Assays: DNA extraction will be performed using commercial columns (Qiagen, USA). Detection of Treponema pallidum pallidum (TPA) DNA will be accomplished with primers that amplify sequences from the target genes tpp47 and polA. The detection will use TaqMan probes labeled with the FAM fluorophore (Invitrogen, USA) on the CFX96 system (Bio-Rad). The human RNase P gene will serve as an internal control for the assay, while heat-killed TPA samples provided by the Centers for Disease Control and Prevention (CDC, USA) will be used as standards.
Treatment:
A medication intake and administration record form will be provided to document the dose received and any adverse events reported by the participants. This form is designed to support adherence to the treatment regimen and serve as a "memory aid" to ensure compliance with therapy.
Inclusion criteria include: subjects of both sexes with primary, secondary or early latent syphilis. Exclusion criteria are: a) known allergy to any of the investigational drugs and/or excipients, in particular known hypersensitivity to penicillin, cephalosporin or other beta-lactam agents, b) clinical neurosyphilis, c) pregnant or lactating women, d) antibiotic treatment potentially active against T. pallidum (i.e., beta-lactams, cephalosporins, macrolides, tetracyclines) within the last week, e) concomitant symptomatic sexually transmitted disease (gonorrhea, chlamydia, lymphogranuloma venereum, Mycoplasma genitalium) or other infectious disease requiring antibiotic treatment potentially active against T. pallidum, f) having received treatment for syphilis.
The interventions planned to be performed on patients are as follows: clinical examination, blood count, hepatogram, renal function, urinalysis, serological studies (non-treponemal and treponemal test) for syphilis, qPCR for tpp47 gene of blood and/or lesions. And the laboratory parameters for the analysis are: kinetics of antibodies by RPR and Chemiluminescence. Paired (pre and posttreatment) qPCR results. Adverse events register per treatment arm.
Hospital de Niños R. Gutierrez de Buenos Aires is the lead sponsor of 15 studies on the registry; 3 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
1. Known allergy or to any of the drugs or their , particularly to penicillin, cephalosporins, or other beta-lactam agents.
2. Diagnosis of clinical neurosyphilis. 3. Pregnant or lactating women. 4. Recent antibiotic treatment (within the past week) with drugs potentially active against Treponema pallidum, such as beta-lactams, cephalosporins, macrolides, or tetracyclines.
5. Acute or chronic renal failure with a declining . 6. Concomitant symptomatic sexually transmitted diseases (e.g., gonorrhea, chlamydia, lymphogranuloma venereum, Mycoplasma genitalium) or other infectious diseases requiring antibiotic treatment that could affect T. pallidum.
7. Previous treatment for diagnosed syphilis. 8. Conditions that prevent oral administration of medication. 9. Other acute or chronic ailments or congenital disorders that, in the investigator's judgment, contraindicate participation in the trial or may interfere with the assessment of the efficacy, safety, or pharmacokinetics of the investigational product.
10. Anticipated noncompliance with the protocol, treatment, or clinical trial testing and follow-up, as judged by the investigator.
11. Cases involving prosecuted sexual abuse.
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Excipients
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Amoxicillin: Administered orally at a dosage of 40-50 mg/kg/day, divided into three doses. The treatment duration is 14 days for early syphilis and 21 days for late syphilis or syphilis of unknown duration. The maximum dose is 500 mg every 8 hours.
Drug: Amoxicillin
Intramuscular Penicillin G Benzathine: Administered as a single dose of 50,000 IU/kg for early syphilis, and as three consecutive weekly doses for late syphilis or syphilis of unknown duration. The maximum dose is 2,400,000 IU per dose.
Drug: Penicillin G, Benzathine
Participants randomized to the intervention group will receive oral amoxicillin at a dose of 40-50 mg/kg/day (maximum 1500 mg/day), administered in three doses daily for 14 days for early syphilis and 21 days for late syphilis or syphilis of unknown duration.
Drug page: Penicillin G
Participants randomized to the control group will receive intramuscular procaine benzathine penicillin (PGB) at a dose of 50,000 IU/kg (maximum 2,400,000 IU/day), administered as a single dose for early syphilis and as three consecutive weekly doses for late syphilis or syphilis of unknown duration.
Therapeutic Response Criteria
•Serologic Response: An adequate serologic response is defined as a fourfold (2 dilutions) decrease in rapid plasma reagin (RPR) titer or seroconversion to a negative result during follow-up (6-12 months post-treatment).
Time frame: 2 weeks to 12 months
Adverse Events
Assessment of adverse events related to treatment with amoxicillin compared to those related to standard treatment with PGB within 8 weeks of treatment initiation.
Time frame: 8 weeks
Treatment Tolerance
Evaluation of treatment tolerance for amoxicillin versus PGB within 8 weeks of the start of the assigned treatment. The percentage of patients who do not complete treatment due to adverse events will be measured.
Time frame: 8 weeks
Antibiotic Response
Evaluation of antibiotic response through the detection of negative Treponema pallidum (TPA) DNA by qPCR in paired samples (blood and swabs) collected before and after treatment during the scheduled visits
Time frame: 2 weeks to 12 months
Plan to share: Undecided
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From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drug tested here: Amoxicillin
Treponemal Infections
Hospital de Niños R. Gutierrez de Buenos Aires