EGFR and lung cancer: Furthermore, 6b exhibited a great anti-proliferative effect against gefitinib-resistant H1975 lung cancer cells with mutant EGFR (L858R/T790M) expression (Figure 1B), gefitinib-resistant H1975 cells (IC50 = 3.65 μM) as compared with standard gefitinib (IC50 > 20 μM).