Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are 
the evidence-based first-line treatment for advanced non-small-cell lung cancer 
that harbors sensitizing EGFR mutations (EGFRm(+)) such as exon 19 deletions and 
L858R substitutions in exon 21. However, acquired resistance to EGFR TKIs is 
mostly driven by a second-site EGFR T790M mutation, which negates their 
inhibitory activity. Osimertinib (AZD9291, Tagrisso™), an oral, third-generation 
EGFR TKI, has been designed to target the EGFR T790M mutation, while sparing 
wild-type EGFR. In this up-to-date review, focus is not only on the structure, 
mechanisms, and pharmacokinetics of osimertinib but also on summarizing clinical 
trials and making recommendations of osimertinib for patients with 
non-small-cell lung cancer.