“…28), activated esters (28a), anhydrides (117a), and activated lactams (118a). 266,[317][318][319] The NHS ester is the most widely used reagent for lysine conjugation in antibodies. 266,[320][321][322] The ease of synthetic manoeuvrability allows the installation of chemically orthogonal handles like alkyne, azide, aldehydes, and hydrazones to place a desired tag in the subsequent step.…”