Site-selective antibody conjugation is widely recognized as a key strategy for the optimum construction of antibody-drug conjugates (ADCs). Achieving such bioconjugation directly onto native antibodies would represent the ideal solution, as it would afford greatly improved homogeneity whilst avoiding the need for genetic engineering, and even allow the repurposing of existing antibodies "off-the shelf." Here we describe a protocol for the use of next-generation maleimides (NGMs) for the selective modification of the four interchain disulfide bonds present in a typical IgG1 antibody format. These reagents retain the efficiency of classical maleimides whilst serving to rebridge each reduced disulfide bond, affording one attachment per disulfide. The approach is simple, uses readily available reagents, and generates robustly stable conjugates which are ideal for in vitro or in vivo applications. In addition to use in the construction of ADCs these reagents can also be used to develop antibody conjugates for imaging, bispecifics, and broadly for use across biology and medicine.
Keywords: Antibody–drug conjugates (ADCs); Disulfide bridging; Next-generation maleimides (NGMs); Site-selective antibody conjugation.