Three broad types of drug repurposing have been described: off‐label use for the same molecular aberration in a different indication (such as the repurposing of trastuzumab from human epidermal growth factor receptor 2 (HER2) amplified breast cancer to HER2 amplified gastric cancer); off‐target activity (such as the use of imatinib to target KIT mutations in gastrointestinal stromal tumours); and combination approaches based on in vitro assays.8 This evidence concerns the gene ERBB2 and breast carcinoma.