The cytotoxicity assay indicated that the IC50 values of olmutinib for ABCB1-, ABCG2-, and ABCC1-overexpressing cancer cells (KB-C2, NCI-H460/MX20 and KB-CV60) were 11.42, 12.19, and 17.14 μM. The gene discussed is ABCG2; the disease is cancer.