Osimertinib was developed to treat the “gatekeeper” EGFR mutation, which replaces a threonine at codon 790 with a methionine (T790M) that is acquired in approximately 50% of cases of non-small cell lung cancer (NSCLC) during treatment with first-generation TKIs [22,23]. This evidence concerns the gene EGFR and non-small cell lung carcinoma.