Conservation of AZD5148 Binding Epitope Across Global Clostridioides difficile Strains

Overview

AZD5148, a human monoclonal antibody targeting the glucosyltransferase domain of Clostridioides difficile toxin B, demonstrates a highly conserved binding epitope across 9134 global C. difficile genomes. This epitope conservation surpasses that of bezlotoxumab, and AZD5148 exhibits broad in vitro neutralization against multiple recent ribotypes.

Background

Clostridioides difficile infection (CDI) is a significant cause of morbidity and mortality, with toxin B (TcdB) being a key virulence factor. Recurrence rates of CDI are high, and effective prevention strategies are needed. Monoclonal antibodies targeting TcdB, such as bezlotoxumab, have been used clinically but have limitations. AZD5148 is a novel human monoclonal antibody that neutralizes TcdB by binding to its glucosyltransferase domain, potentially offering a new therapeutic option.

Data Highlights

Key Findings

• The AZD5148 binding epitope on TcdB is highly conserved globally with a 99.58% average conservation frequency across diverse C. difficile strains collected from 2015 to 2023.
• AZD5148’s epitope conservation is significantly higher than that of bezlotoxumab, which shows 82.47% conservation at its binding site.
• Phylogenetic and sequence typing analyses confirmed low genomic diversity at the AZD5148 binding site across multiple sequence types and ribotypes.
• In vitro assays demonstrated broad neutralization of cytotoxicity by AZD5148 against eight recently circulating C. difficile ribotypes.
• The AZD5148 epitope is located on the glucosyltransferase domain of TcdB, a critical functional region for toxin activity and cellular intoxication.

Clinical Implications

The high conservation of the AZD5148 binding epitope suggests that this monoclonal antibody could provide broad and effective neutralization against diverse C. difficile strains worldwide. AZD5148 may represent a promising therapeutic candidate for preventing CDI recurrence with a potentially favorable safety profile and microbiome-sparing properties. Its broad activity across multiple ribotypes supports its utility in varied clinical settings.

Conclusion

AZD5148 targets a highly conserved epitope on C. difficile toxin B, maintaining broad neutralization capacity across global strains. This supports its potential as a robust therapeutic agent for CDI prevention and recurrence reduction.

References

1. Kroh et al 2023 -- Structural basis of AZD5148 binding to TcdB glucosyltransferase domain
2. EnteroBase C. difficile Genome Repository 2024
3. Bezlotoxumab Clinical Data 2016
4. IHMA Clinical Isolates Collection 2019-2022