Engineering affinity-matured variants of an anti-polysialic acid monoclonal antibody with superior...

Monoclonal antibodies (mAbs) that specifically recognize cell surface glycans associated with cancer and infectious disease hold tremendous value for basic research and clinical applications. However, high-quality anti-glycan mAbs with sufficiently high affinity and specificity remain scarce, highlighting the need for strategies that enable optimization of antigen-binding properties. To this end, we engineered the affinity of a polysialic acid (polySia)-specific antibody called mAb735, which possesses only modest affinity. Using a combination of rational design and directed evolution, we isolated several affinity-matured IgG variants with ∼5- to 7-fold stronger affinity for polySia relative to mAb735. The higher affinity IgG variants opsonized polySia-positive cancer cells more avidly and triggered greater antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). Collectively, these results demonstrate the effective application of molecular evolution techniques to an important anti-glycan antibody, providing insights into its carbohydrate recognition and uncovering variants with greater therapeutic promise due to their enhanced affinity and potency.