Previous work revealed that removal of the native glycan at Asn297 of the CH2 domain of an IgG1 mAb such as trastuzumab exposes two proximal tyrosine residues (Y296 and Y300) that can be used for strain-promoted oxidation-controlled cycloalkyne-quinone (SPOCQ) reaction (Scheme 2A). Here, we tailor this approach for conjugation to azide-functionalized payloads, i.e., DpTs