An ADC is engineered by linking cytotoxic cancer drug molecules to antibodies or antibody fragments. The antibody portion of the ADC can be designed to target specific proteins found primarily on tumor cells. The goal is to deliver the cytotoxic payload more directly to tumor cells and reduce the collateral damage to healthy tissue. Both parts of an ADC—the targeting region and the payload—can be altered to target different types of tumors with different cancer drugs.