At present, there are ongoing clinical trials including the following: “A Phase III Randomized Trial of Metformin vs Placebo in Early Stage Breast Cancer (NCT01101438)”, “A Study of Liposomal Doxorubicin + Docetaxel + Trastuzumab + Metformin in Operable and Locally Advanced HER2 Positive Breast Cancer (NCT02488564)”, “Neoadjuvant Toremifene With Melatonin or Metformin in Locally Advanced Breast Cancer”, and “Metformin Plus Neoadjuvant Chemotherapy in Breast Cancer”. Here, ERBB2 is linked to breast cancer.