(P398) Preliminary Results from a Clinical Trial Comparing the Efficacy of Cefixime Versus Penicillin G for the Treatment of Early Syphilis

Background: Syphilis has reemerged as a global health concern globally. The treatment recommendation for syphilis at all stages is injectable benzathine penicillin G. Cefixime is proposed as an alternative to penicillin as it is a widely available, oral, low cost and safe in pregnancy. A previous pilot study showed that cefixime was likely efficacious for the treatment of early syphilis. The goal of this study is to evaluate the effectiveness of cefixime compared to benzathine penicillin G.

Methods: We are conducting a randomized, multisite, open-label, non-inferiority clinical trial to evaluate the effectiveness of cefixime (400mg, orally, twice a day, for 10 days) compared to benzathine penicillin G (2.4 million units, intramuscularly), in patients with and without human immunodeficiency virus (HIV) infection. The trial seeks to enroll 400 participants from 10 clinical sites in the United States and Peru. Patients return at 3, 6, and 9 months for clinical evaluation and rapid plasma reagin (RPR) testing. The primary outcome is serological response by 3- or 6- months post-treatment, defined as 4-fold or greater RPR titer decrease from baseline.

Results: As of January 5^th, 2023, 56 participants have been enrolled. Of those, the majority are HIV infected (85.7%) and men who have sex with men (85.7%). Currently, 34 participants have returned for 3-month evaluation, and 28 participants have returned for 6-month evaluation. To date, 93.3% (14/15) of cefixime participants and 92.3% (12/13) of penicillin participants achieved a 4-fold or greater RPR titer decrease by 3 or 6-months after treatment.

Conclusion: Efficacy appears similar between both treatment arms. Enrollment and data collection is ongoing. The anticipated study completion date is June 2025.