EGFR and neoplasm: In order to target tumor cells via a surface molecule such as EGFR, the anti-tumor fusion toxin must: (1) recognize and bind with high affinity; (2) exhibit high selectivity for EGFR-overexpressing tumor cells to minimize unwanted side-effects against normal tissues eventually expressing low levels of target antigen; and (3) have a catalytically active cytotoxic domain effectively inducing apoptosis at low concentrations [173].