Seattle Genetics, Inc. announced enrollment of the first patient in a multicenter phase 1 clinical trial of SGN-CD352A for patients with relapsed or refractory multiple myeloma (MM). SGN-CD352A is an investigational CD352-targeted antibody-drug conjugate (ADC) utilizing Seattle Genetics’ proprietary ADC technology, an engineered cysteine antibody (EC-mAb) stably linked to a highly potent cytotoxic agent called a pyrrolobenzodiazepine (PBD) dimer. CD352 is broadly expressed on B-cell cancers including multiple myeloma, chronic lymphocytic leukemia and non-Hodgkin lymphoma, while exhibiting low expression on normal white blood cells. The trial is designed to assess the safety and antitumor activity of SGN-CD352A. This study represents Seattle Genetics’ first clinical-stage ADC program in development for MM, demonstrating the breadth of potential therapeutic applications for its ADC technology platform. The phase 1, open-label multicenter clinical study is designed to evaluate the safety and preliminary antitumor activity of SGN-CD352A as a single agent in adults with relapsed or refractory MM. The trial will be conducted in two parts, with a dose escalation part to identify the maximum tolerated dose of SGN-CD352A followed by an expansion part to further define safety and antitumor activity. SGN-CD352A will be administered every four weeks, and the study will enroll approximately 75 relapsed or refractory patients at multiple centers in the United States. Preclinical SGN-CD352A data presented at the 2016 American Association of Cancer Research (AACR) Annual Meeting demonstrated that SGN-CD352A specifically binds to target cells and induces potent antitumor activity in both MM and non-Hodgkin lymphoma disease models. In addition to being a potential new monotherapy for MM, the tolerability profile from preclinical results suggests that SGN-CD352A may be combined with current standard of care treatments for MM. ADCs are designed to selectively deliver cell-killing agents to tumor cells, and thus may reduce many of the toxic effects of traditional chemotherapy while enhancing antitumor activity.