Endolysin selectively kills Gardnerella ex vivo in vaginal samples from women with bacterial vaginosis

Current treatments for bacterial vaginosis (BV) often result in recurrent disease. Gardnerella, a key player in BV pathogenesis, forms biofilms on vaginal epithelial cells. Recombinant endolysins have shown to specifically kill Gardnerella, but not commensal lactobacilli, in vitro. This study evaluated the pharmacodynamics of BNT331-endolysin (BNT331-EL) on vaginal samples from 49 women with BV (Nugent score ≥7, Amsel criteria, and clue cells). Whole genome sequencing confirmed BV-associated community state types IV-B and III, with Gardnerella dominating in 53% of samples and present in 86%. Ex vivo treatment with BNT331-EL reduced viable Gardnerella by ≥94% at 20-50 µg/mL over 19 h. L. iners was reduced by an average of 92% across samples, while L. crispatus proliferated where present in substantial amounts. Endolysin treatment effectively disrupted Gardnerella biofilms and reduced viable bacterial load in a time- and concentration-dependent manner. These results informed the definition of the treatment dose for a first-in-human trial with BNT331-EL.