In a clinical study of 31 patients with trastuzumab-resistant HER2-positive breast cancer who had previously progressed on trastuzumab therapy, the combination of tanespimycin (450 mg/m2) and trastuzumab demonstrated significant anticancer activity, with an ORR of 22%, clinical benefit rate (CBR) of 59%, median PFS of 6 months, and median overall survival (OS) of 17 months [101]. This evidence concerns the gene ERBB2 and breast cancer.