Antibody-drug conjugates (ADCs) are becoming an increasingly important sub-class of antibody-related therapeutics. Two ADCs, brentuximab vedotin (Adcetris) and ado-trastuzumab emtansine (Kadcyla), were recently approved for marketing both by the US Food and Drug Administration (FDA) and the European Medicine Agency (EMA). Brentuximab vedotin is marketed as therapy for hematological malignancies (Hodgkin lymphoma, systemic anaplastic large cell lymphoma), while ado-trastuzumab emtansine is marketed for treatment of a solid tumor (breast cancer). The approvals of these two ADCs followed the mitigated success of gemtuzumab ozogamicin (Mylotarg), which was withdrawn from the US market in 2010, ten years after approval by the FDA.