SGN-LIV1A (ladiratuzumab vedotin) is an antibody-drug conjugate (ADC) that we are developing for the treatment of breast cancer. Most metastatic breast cancers express LIV-1, which also has been detected in a number of other cancers, including melanoma, prostate, ovarian, uterine, and cervical cancers. Ladiratuzumab vedotin consists of a LIV-1-targeted monoclonal antibody linked to a potent microtubule-disrupting agent, monomethyl auristatin E (MMAE) by a protease-cleavable linker. This novel ADC agent is designed to bind to LIV-1 on cancer cells and release the cell-killing agent into target cells upon internalization. Ladiratuzumab vedotin may also cause antitumor activity through other mechanisms, including activation of an immune response.