The current disclosure provides binding polypeptides (e.g., antibodies), and effector moiety conjugates thereof (e.g., antibody-drug conjugates or ADCs), comprising a site-specifically engineered drug-glycan linkage within native or engineered glycans of the binding polypetpide. The current disclosure also provides nucleic acids encoding the antigen-binding polypeptides, recombinant expression vectors and host cells for making such antigen-binding polypeptides. Methods of using the antigen-binding polypeptides disclosed herein to treat disease are also provided.