Afatinib is a small molecule covalently binding and inhibiting the EGFR, HER2 and HER4 receptor tyrosine kinases. In preclinical studies, afatinib not only inhibited the growth of models with common activating EGFR mutations, but was also active in lung cancer models harboring wild-type EGFR or the EGFR L858R/T790M double mutant. Clinical efficacy of afatinib has been extensively studied in the LUX-Lung study program. These trials showed promising efficacy in patients with EGFR-mutant NSCLC or enriched for clinical benefit from EGFR tyrosine kinase inhibitors gefitinib or erlotinib