Bezlotoxumab: Targeted Toxin-B Neutralization Strategy to Reduce Recurrence of Clostridioides difficile Infection

Clostridioides difficile infection (CDI) remains a major healthcare-associated infection with substantial morbidity, mortality, and economic burden. Recurrence occurs in roughly 25% of patients after initial antibiotic treatment and increases with each subsequent episode. Notably, recurrence is driven not by persistent C. difficile infection but by ongoing toxin-mediated mucosal injury. This understanding highlights the need for preventive strategies that extend beyond traditional antimicrobial therapy. Bezlotoxumab (Bmab), a fully humanized monoclonal antibody (IgG1) approved by the FDA in 2016, was developed to neutralize toxin B (TcdB), the principal virulence factor responsible for colonic damage in CDI. Under normal circumstances, toxin B binds to Frizzled receptors (FZD1, FZD2, FZD7) and chondroitin sulfate proteoglycan 4 (CSPG4) on the basolateral surface of intestinal epithelial cells. Following internalization, the toxin inactivates Rho GTPases, disrupting the actin cytoskeleton, inducing cell rounding, triggering severe inflammation, and ultimately causing colon epithelial cell death. Bmab competitively binds to toxin B, thereby preventing its attachment to cellular receptors and blocking cellular entry. While standard antibiotics eradicate C. difficile, Bmab neutralizes circulating toxins, reducing epithelial injury and lowering the risk of recurrence. The Bmab scaffold confers a prolonged systemic half-life, enabling sustained toxin neutralization throughout the high-risk recurrence period. Because Bmab lacks antibacterial activity, it preserves the native gut microbiota and does not promote antimicrobial resistance. Clinical trials studies demonstrate a safety profile comparable to placebo, with generally mild adverse effects, including nausea, headache, and infusion-related reactions. In summary, Bmab represents a targeted, microbiota-sparing adjunctive therapy that addresses the toxin-driven pathophysiology of CDI recurrence. Complementing antibiotic treatment with durable toxin neutralization offers an effective strategy to reduce recurrent disease and improve patient outcomes.