TKT and neoplasm: Erlotinib is capable of inhibiting the TK activity of EGFR in selective and reversible manners via direct competition with adenosine triphosphate for binding to the TK domain of EGFR.[16] Erlotinib can exert anti‐tumor effects against advanced head and neck cancer, pancreatic carcinoma, ovarian cancer, hepatocellular carcinoma, NSCLC, and squamous cell carcinoma of the vulva.[44, 45, 46, 47, 48, 49, 50] However, the therapeutic effects of erlotinib against GC are restricted and unsatisfactory.