Clinical efficacy studies reported that the HER1 selective Erlotinib and Gefitinib, the HER1/HER2 selective Lapatanib and the pan-HER selective Canertinib have shown limited activity in the treatment of HER2 over-expressing breast cancer, despite evidence suggesting these cancers are highly dependent on HER2 function [37]. The gene discussed is EGFR; the disease is breast cancer.