Margetuximab and trastuzumab deruxtecan: New generation of anti-HER2 immunotherapeutic agents for breast cancer

Advances in the development of anti-HER2 monoclonal antibodies (mAbs) represent one of the most significant milestones in the treatment of HER2+ breast cancer patients. However, HER2+ metastatic breast cancer (MBC) patients display resistance towards first-generation anti-HER2 mAbs or antibody-drug conjugate (ADC) treatment. In recent years, new generation of anti-HER2 mAb and ADC including margetuximab and trastuzumab deruxtecan (T-DXd), respectively, have been approved for the treatment of previously treated HER2+ MBC patients. The successes of margetuximab and T-DXd have renewed the interest in the research and development of anti-HER2 immunotherapies for both HER2+ and HER2-low breast cancer patients. In this review, we focus on these two immunotherapeutics in terms of their mechanisms of action, preclinical findings and clinical trials leading to their approval, as well as the mechanisms of resistance to conventional anti-HER2 immunotherapies (i.e. trastuzumab, pertuzumab and T-DM1). In the future, combination of either margetuximab or T-DXd with small molecule inhibitors such as tyrosine kinase inhibitors that elicit anticancer immunogenicity may further enhance the efficacy of margetuximab or T-DXd in the treatment of HER2+ MBC patients.