Antibody drug conjugates (ADCs) are precision medicine agents uniquely designed for targeting tumor cells through the construction of a monoclonal antibody linked to a cytotoxic payload. They are approved for both solid tumors, including lung cancer and breast cancer, and hematologic malignancies, including lymphoma, multiple myeloma, and acute lymphoblastic leukemia. Examples are brentuximab vedotin—composed of a monoclonal antibody targeting the CD20 antigen and conjugated to microtubule disrupting agent monomethyl auristatin, which serves as the payload for Hodgkin’s lymphoma—and trastuzumab emtansine (T-DM1)—composed of the monoclonal antibody trastuzumab targeting HER2 conjugated to the microtubule inhibitor payload emtansine for breast cancer. Active investigation is ongoing to optimize antibody drug conjugates to achieve a more-precise targeting of the monoclonal antibody and greater cytotoxicity in the payload, to increase the bystander effect, and to reduce off-target toxicity.