Afatinib (BIBW 2992) is an orally active, potent and irreversible dual specificity inhibitor of ErbB family (EGFR and HER2), with IC50 values of 0.5 nM, 0.4 nM, 10 nM and 14 nM for EGFRwt, EGFRL858R, EGFRL858R/T790M and HER2, respectively. Afatinib can be used for the research of esophageal squamous cell carcinoma (ESCC), non-small cell lung cancer (NSCLC) and gastric cancer.