Trastuzumab (Herceptin®) and Ado‐Trastuzumab Emtansine (Kadcyla®): Treatments for HER2‐Positive Breast Cancer

Breast cancer is one of the commonest causes of death from a cancer in women. Human epidermal growth factor receptor 2 overexpression, found in 20–30% of breast cancer patients is associated with aggressive tumour behavior, and poorer prognosis. Trastuzumab (Herceptin), a biologically engineered, humanized immunoglobulin-1, anti-HER2 monoclonal antibody (mAb) developed by Genentech/ Roche, directed against the extracellular domain of HER2. It is the first commercially available mAb-based therapy for the treatment of breast cancer. Trastuzumab has been extensively trialed and now is used in the early and metastatic settings. Ado-trastuzumab emastasine (T-DM1, Genentech Roche) is a novel antibody–drug conjugate, whereby trastuzumab (T) is linked to mertansine (DM1). It is currently undergoing multicentered phase 3 trials exploring its full role within the treatment of Her2 overexpression breast cancer, with promising early results.