Fig. 3.6.

Structure of ado-trastuzumab emtansine formed by covalently coupling trastuzumab to the cytotoxic microtubule inhibitor, mertansine, or DM1 (shown in red), via the bifunctional cross-linker SMCC (succinimidyl trans-4-(maleimidylmethyl)cyclohexane-1-carboxylate) that contains a reactive succinimide ester and a reactive maleimide that links to thioethers (shown in blue). The succinimide reacts with a trastuzumab lysine; the maleimide group covalently links to the free sulfhydryl group of DM1. The mertansine structure of the resultant complex together with the linkage group is designated the emtansine component. Ado-trastuzumab emtansine contains an average of 3.5 DM1 molecules for every molecule of trastuzumab