EGFR and non-small cell lung carcinoma: In 2004, Erlotinib (TarcevaTM, CP‐358774) was approved by the FDA as the first‐line treatment of metastatic NSCLC with mutated EGFR, such as Ex19Del and L858R substitution.[141] The mutation of the gatekeeper residue Thr790 leads to resistance against the first‐generation of EGFR TKIs, as it causes a steric hindrance with the aromatic ring of these drugs.[142]