Trastuzumab deruxtecan (Enhertu) continuously shows its superior efficacy as a treatment of breast cancer
February 23, 2022
Trastuzumab deruxtecan (Enhertu) is an antibody-drug-conjugate (ADC), meaning that a chemotherapy drug, deruxtecan (topoisomerase I inhibitor) is attached to a monoclonal antibody targeting HER-2 protein. Because some breast cancer cells have high numbers of HER2, the antibody binds to cancer cells more readily than to normal and healthy cells. Once it binds to cancer cells, it releases deruxtecan into cancer cells, leading to cell death.
Trastuzumab deruxtecan (Enhertu) is currently approved for the patients with metastatic HER2-positive breast cancer as well as HER2-postive gastric cancer (please see our previous posts on 7/13/2020 and 9/24/2021). In order to determine the positivity of HER2 in breast cancer, pathologists determine numbers of HER2 protein in a biopsied tumor tissue using techniques called “immunohistochemistry (IHC)” and “in situ hybridization (ISH)”. Currently, the metastatic breast cancer patients with HER2-numeric score 3 from immunohistochemistry (IHC) or higher and/or HER2-numeric score 1 from in situ hybridization (ISH) are approved for Trastuzumab deruxtecan (Enhertu).
More than 50% of breast cancer patients have tumors with HER2 - IHC score of 1 or 2 in combination with a negative ISH score, and thus are not eligible for Trastuzumab deruxtecan (Enhertu) or other HER2-targeted therapies. According to the latest results from the phase 3 clinical trial, DESTINY-Breast04 (NCT03734029), Trastuzumab deruxtecan (Enhertu) shows significant efficacy in metastatic breast cancer patients with low levels of HER2. When the patients with low levels of HER2 were treated with Trastuzumab deruxtecan (Enhertu), they survived longer and showed much delayed cancer progression compared to those treated with standard of care chemotherapy. The detailed results of this trial are going to be presented in coming medical meetings. Looking forward to hearing of the complete results!