Antibody drug conjugates (ADCs) represent a relatively new therapeutic modality, mainly focused towards the treatment of cancer. ADCs are monoclonal antibodies with covalently bound cytotoxic drugs. In general terms the ADC is designed to bind to antigens that are overly expressed on cancer cells, but minimally expressed on healthy cells. The targeted delivery and use of highly potent cytotoxic carries the hope of killing the cancer cells with minimal systemic toxicities. The concept of ADCs was first validated in the clinic with gemtuzumab ozogamicin, a conjugate of an anti-CD33 antibody and the cytotoxic agent calicheamicin, and was approved for bone cancer by the FDA in 2000. The product was recently withdrawn from the market after raised safety concerns and its failure to demonstrate benefit to patients. In 2011, Brentuximab vedotin (Adcetris™) was approved for Hodgkin’s disease and anaplastic large cell lymphoma. Later that year, ado-trastuzumab emtansine (Kadcyla™) was approved for metastatic HER2 positive breast cancer [1,2].