The idea of arming antibodies with other molecular moieties such as toxins or chemotherapeutics dates back to the 1980s, when such antibodies were first being developed for clinical use. Today, so called ”naked” antibodies are being harnessed to fight cancer cells in many different forms – several of which have become blockbuster therapies. Theoretically, if coupled to cytotoxic substances, antibodies could become even more powerful while eliciting fewer side – effects. Despite these hypothetical advantages and the outlay of huge R&D efforts, particularly in oncology, few antibody drug conjugates (ADCs) exist in today’s market. In 2000, gemtuzumab ozogamicin (Mylotarg™) – intended to treat acute myeloid leukemia – became the first ADC to make it to the clinic. It was voluntarily withdrawn from the market in 2012 after post – marketing surveillance data showed it did not improve the chances of survival, but heightened the risk of fatal toxicity.