Antibody-drug conjugates in breast cancer: the chemotherapy of the future?

Purpose of review Antibody-drug conjugates (ADCs) represent an interesting new class of anticancer agents, capable of exploiting the specificity of monoclonal antibodies toward cellular-antigens for a targeted release of potent cytotoxic drugs, with a potential increased activity and reduced toxicity compared with traditional chemotherapies. The aim of this article is to review the efficacy and safety of ADCs in breast cancer. Recent findings Following the approval of T-DM1 both in early and advanced human epidermal growth factor receptor 2 (HER2)-positive breast cancer, novel anti-HER2 ADCs have been investigated. Some of these compounds, such as the recently FDA-approved trastuzumab deruxtecan, have shown relevant activity in T-DM1-pretreated patients, possibly thanks to the so-called bystander effect, namely the ability to exert cytotoxic activity also against antigen-negative cells. Such feature allows to overcome the HER2 intratumoral heterogeneity in breast cancer and could explain in the preliminary activity demonstrated also in HER2-low breast cancers. However, several ADCs targeting other cancer-associated antigens than HER2 are under development, representing a promising strategy for the treatment of triple-negative tumors, exemplified by the encouraging results of sacituzumab govitecan. ADCs are innovative and effective therapeutic drugs in breast cancer. Research efforts are ongoing to identify novel targets and combination with other treatment modalities, particularly with immunotherapy, to further improve patients' outcomes.