Cancer-targeting Antibody-Drug Conjugates: Site-specific Conjugation of Doxorubicin to Anti-EGFR 528 Fab' through a Polyethylene Glycol Linker

Antibody-drug conjugates have been prepared to examine the effect that attaching small-molecule drugs to an antibody fragment has on antibody activity. The anticancer drug doxorubicin was covalently attached through a polyethylene glycol linker to a cancer-targeting, anti-epidermal growth factor receptor antibody fragment (Fab'). The reactivity of maleimide was compared with a substituted maleimide derivative (citraconimide) in conjugation reactions with cysteine residues on a Fab'. Introduction of polyethylene glycol increased aqueous solubility of the cytotoxic drug, which led to an improvement in overall yield of the conjugation reaction with the antibody fragment. Antibody-drug conjugates prepared retained activity of the parent antibody, as determined by antigen binding experiments measured by surface plasmon resonance.