EGFR and squamous cell carcinoma: One of the most potent compounds in the EGFR-TK inhibitor series is the quinazoline derivative PD153035 [12, 13], which exhibits well-defined selectivity and tremendously high affinity for EGFR-TK (Ki: 5 pM) coupled with remarkable cytotoxicity against several types of tumors in vitro such as the A431 epidermoid carcinoma cell line (IC50: 29 pM).