Seattle Genetics, Inc. (NASDAQ:SGEN) today announced the initiation of a phase 1 clinical trial evaluating SGN-LIV1A for patients with LIV-1-positive metastatic breast cancer. SGN-LIV1A utilizes Seattle Genetics’ industry-leading antibody-drug conjugate (ADC) technology. The trial is designed to assess the safety and antitumor activity of SGN-LIV1A, an ADC targeted to LIV-1 (SLC39A6), a protein which is expressed in most subtypes of metastatic breast cancer. “ADCs represent a novel treatment approach that have demonstrated activity in both hematologic and solid tumors. SGN-LIV1A is one of four ADCs that we are advancing into the clinic during 2013, demonstrating our significant investment in this approach for the treatment of cancer,” said Jonathan Drachman, M.D., Chief Medical Officer and Executive Vice President, Research and Development, at Seattle Genetics. “The target expression in breast cancer, preclinical antitumor activity, and need for novel therapeutic options for advanced breast cancer patients all support the clinical evaluation of SGN-LIV1A.” ADCs are designed to harness the targeting ability of antibodies to deliver cell-killing agents directly to cancer cells. This approach is intended to spare non-targeted cells and thus reduce many of the toxic effects of traditional chemotherapy while enhancing antitumor activity. The study is a phase 1, open-label, dose-escalation clinical trial to evaluate the safety and antitumor activity of SGN-LIV1A in patients with LIV-1-positive metastatic breast cancer. The trial is enrolling patients with triple negative disease who have previously been treated with at least two prior cytotoxic regimens in the metastatic setting, or patients with ER-positive and/or PR-positive and HER2-negative disease who have previously been treated with at least two prior cytotoxic regimens in the metastatic setting, and at least three prior hormonal therapies. The primary endpoint of the trial is safety, with key secondary endpoints of objective response, duration of response and progression-free survival (PFS). The study is expected to enroll up to 70 patients at multiple centers in the United States.