A recombinant fusion protein composed of the diphtheria toxin with the receptor-binding domain replaced by human epidermal growth factor (EGF). When administered, EGF binds to the endothelial cell growth factor receptor, EGFR, which is upregulated in many solid tumors. After binding to the EGF receptor, the agent is internalized by the cell, where the diphtheria toxin moiety exerts its cytotoxic effect, inhibiting protein synthesis through ADP-ribosylation of elongation factor 2.