Antibody drug conjugates (ADCs) are attracting a tremendous amount of attention from both academia and industry because they have the potential to revolutionize cancer treatment. Monoclonal antibodies allow the selective delivery of cytotoxic agents to tumor cells leaving healthy surrounding tissue unharmed thereby potentially mitigating some of the damaging side-effects of cancer chemotherapy. This concept is not only the realization of Paul Ehrlich’s magic bullets but may one day be personalized for each individual patient.