Lapatinib (Tykerb), a dual tyrosine kinase inhibitor that interrupts the HER2/neu and epidermal growth factor receptor (EGFR) pathways, was approved for the use of breast cancer and other solid tumors, and was also shown to inhibit ABCB1- and ABCG2-mediated MDR in cancer cells [32]. The gene discussed is ABCG2; the disease is cancer.