Antibody-drug conjugates in breast cancer: current evidence and future directions

Antibody-drug conjugates (ADCs) are a rapidly evolving class of antitumor drugs and have already revolutionized the treatment strategy of many hematologic and solid cancers. So far, trastuzumab emtansine (T-DM1), trastuzumab deruxtecan (T-DXd), sacituzumab govitecan (SG) and datopotamab deruxtecan (Dato-DXd) are the four ADCs that have been approved by US food and drug administration (FDA) in treatment of breast cancer, and SKB264 has been approved by Chinese national medical products administration (NMPA). Many ADCs for treatment of breast cancer are currently being tested in late-phase clinical trials, with several encouraging results achieved recently. However, major issues arise during the use of ADCs, including emergence of acquired resistance, occurrence of treated-related toxicities, and identification of biomarkers of response and resistance. ADCs are being increasingly tested in combination with other agents, and novel next-generation ADC development is progressing rapidly. A better understanding of the design and development of ADCs will promote ADC development for cancer treatment. In this review, we aim to provide a broad overview of the design and the recent advances of ADCs in breast cancer. We also propose several notable future directions of ADCs in treatment of breast cancer.