We found that in the TMES, using concentrations that correspond to human therapeutic plasma levels, gefitinib was effective against the NSCLC cell line H1650 that carries the EGFR mutant exon 19 del(E746-A750), and that the NSCLC line carrying the T790M EGFR mutation, H1975, was insensitive to gefitinib. This evidence concerns the gene EGFR and non-small cell lung carcinoma.