Trastuzumab emtansine (T-DM1) was the first and one of the most successful antibody-drug conjugates (ADCs) approved for treating refractory HER2-positive breast cancer. Despite its initial clinical efficacy, resistance is unfortunately common, necessitating approaches to improve response. Here, we found that in sensitive cells T-DM1 induced spindle assembly checkpoint (SAC)-dependent immunogenic cell death (ICD), an immune-priming form of cell death. The payload of T-DM1 mediated ICD by …