Synthetic Antibody-Rhamnose Cluster Conjugates Show Potent Complement-Dependent Cell Killing by Recruiting Natural Antibodies

Monoclonal antibodies (mAbs) are one of the most rapidly growing drug classes used for the treatment of cancer, infectious and autoimmune diseases. Complement-dependent cytotoxicity (CDC) is one of the effector functions for antibodies to deplete target cells. We report here an efficient chemoenzymatic synthesis of structurally well-defined conjugates of a monoclonal antibody with a rhamnose- and an alpha Gal trisaccharide-cluster to recruit natural anti-rhamnose and anti-alpha Gal antibodies, respectively, to enhance the CDC-dependent targeted cell killing. The synthesis was achieved by using a modular antibody Fc-glycan remodeling method that includes site-specific chemoenzymatic Fc-glycan functionalization and subsequent click conjugation of synthetic rhamnose- and alpha Gal trisaccharide-cluster to provide the respective homogeneous antibody conjugates. Cell-based assays indicated that the antibody-rhamnose cluster conjugates could mediate potent CDC activity for targeted cancer cell killing and showed much more potent efficacy than the antibody-alpha Gal trisaccharide cluster conjugates for CDC effects.

Automated summary

Monoclonal antibodies are rapidly growing in use for cancer, infectious, and autoimmune disease treatment. A chemoenzymatic synthesis method was developed to create structurally well-defined conjugates of antibodies with rhamnose and alpha Gal trisaccharide clusters, enhancing targeted cell killing through CDC. These antibody-rhamnose cluster conjugates showed potent CDC activity for cancer cell killing compared to the antibody-alpha Gal trisaccharide cluster conjugates.