KADCYLA® (Ado-Trastuzumab Emtansine, T-DM1) is an antibody-drug conjugate (ADC) comprised of the antibody HERCEPTIN® (Trastuzumab) and a chemotherapy agent Emtansine, linked together. Upon binding to the HER2 receptor, KADCYLA® not only inhibits the HER2 signaling pathways but also delivers Emtansine, a microtubule inhibitor, directly inside the tumor cells and destroys them. In the TH3RESA trial, treatment with KADCYLA® significantly improved Progression Free Survival compared to physicians choice, for those patients who had previously received HERCEPTIN® and TYKERB® (Lapatinib) and this therefore makes KADCYLA® the treatment of choice, for this patient population.