**Abstract**

Antibody drug conjugates (ADCs) continue to change the treatment paradigm of breast cancer and recent regulatory approvals of next generation ADCs are shifting how breast cancer is classified and treated. ADCs combine precision targeting with traditional cytotoxic treatment allowing for the delivery of highly potent chemotherapeutic agents to malignant cells. This chapter will cover ADCs used for the treatment of breast cancer including pharmacology, novel mechanism of action, pharmacokinetic and pharmacodynamic properties, clinical outcomes and role in breast cancer therapy, key toxicities and monitoring.

**Keywords:** breast cancer, antibody drug conjugates, ADC, bystander effect, HER2 low, ado-trastuzumab emtansine, fam-trastuzumab deruxtecan, sacituzumab govitecan
