EGFR and neoplasm: Erlotinib is a potent and selective EGFR TKIs that blocks tumor cell division in EGFR-overexpressing human tumor cells, produces cell cycle arrest, and initiates programmed cell death which will inhibit the binding of ATP to the EGFR intracellular tyrosine kinase domain, thereby inhibiting receptor intracellular phosphorylation and blocking downstream signal transduction.