Location of common clinically relevant mutations in EGFR Location of common clinically relevant mutations in EGFR. Depicted is a representation of the EGFR protein with the relative sizes of each exon in the kinase domain noted. Location of common clinically relevant mutations in EGFR. Depicted is a representation of the EGFR protein with the relative sizes of each exon in the kinase domain noted. The activating point mutations G719S and L858R as well as exon 19 deletion mutations are associated with sensitivity to EGFR TKIs. Insertion mutations in exon 20 are associated with primary resistance and the T790M point mutation with secondary resistance to gefitinib and erlotinib. Peter S. Hammerman et al. Clin Cancer Res 2009;15:7502-7509 ©2009 by American Association for Cancer Research