Application of a trifunctional reactive linker for the construction of antibody–drug hybrid conjugates

A flexible, trifunctional poly(ethylene glycol)-succinamide-Lysine-Lysine-maleimide (PEG-SU-Lys-Lys-mal) linker was employed to simultaneously allow biotin tagging and cell-surface targeting through an integrin α4β1-binding peptidomimetic that was regiospecifically conjugated to an IgG1-derived Fc fragment with an engineered C-terminal selenocysteine residue. The resulting antibody derivative mediates Fc receptor binding by virtue of the Fc protein and selectively targets cancer cells expressing human integrin α4β1. The PEG-SU-Lys-Lys-mal linker may have general utility as an organic tether for the construction of antibody–drug conjugates.