Congenital Syphilis Treatment Trial (CONSISTENT) in Neonates

The Investigator hypothesize that the treatment efficacy will be similar in both study arms. Secondary outcomes and endpoints will characterize safety by comparing adverse events (AEs), tolerability, and adherence to therapy in each arm. This is a Phase 4, open-label, multicenter trial designed to evaluate the efficacy of a single injected dose of intramuscular (IM) BPG (Arm 1) compared to oral amoxicillin administered twice daily (BID) for 10 days (Arm 2). The study will involve infants aged ≤ 30 days old with suspected untreated syphilis. The trial will be conducted at 12 sites across the U.S., enrolling approximately 374 participants. Upon randomization, participants will undergo baseline study sample collection (blood, oropharyngeal, and nasal mucosal swabs for PCR testing) and then receive either treatment with oral amoxicillin or IM BPG, both with directly observed therapy. The participant enrolled in the optional pharmacokinetic (PK) sub-study will have additional blood samples collected for PK analysis within the first 24-48 hours after treatment. Participants will be discharged from the hospital following routine procedures, with the oral amoxicillin dosing continued at home (BID) by the caregiver.

Inclusion Criteria: 1. Confirmed staged maternal syphilis in pregnancy with rapid plasma reagin (RPR) + and T. pallidum hemagglutination antibody (TPHA) or other evidence of active syphilis (i.e. ulcerative anogenital lesion with positive darkfield microscopy or PCR+ for T. pallidum) 2. Inadequate therapy (non-BPG regimen, incomplete regimen for stage, \1000 copies/mL at or within 4 weeks of delivery) or HIV-exposed infants who require three drug antiretroviral post exposure prophylaxis. 3. Unable to ensure infant follow up through six months of age