A Study of CDX-011 (CR011-vcMMAE) in Patients With Advanced GPNMB-expressing Breast Cancer

CDX-011 consists of an antibody attached to a drug, monomethyl auristatin E (MMAE), that can kill cancer cells. The antibody delivers the drug to cancer cells by attaching to a protein called glycoprotein NMB (GPNMB) that is expressed on the cancer cell. The MMAE is then released inside of the cell, where it interferes with cell growth and may lead to cell death. This study will examine the effectiveness and safety of CDX-011 in patients with advanced breast cancer that makes the GPNMB protein. To better assess this, the effect of CDX-011 will be compared to treatment with currently available cancer chemotherapy. Eligible patients who enroll in the study will be randomly assigned by chance to receive treatment with CDX-011 or with a chemotherapy chosen by their study doctor from a list of currently available drugs ("Investigator's Choice" chemotherapy). For each three patients enrolled, two will receive CDX-011 and one will receive treatment with "Investigator's Choice". Patients initially assigned to "Investigator's Choice" chemotherapy may be offered treatment with CDX-011 if their cancer worsens during this initial treatment. All patients enrolled in the study will be closely monitored to determine if their cancer is responding to treatment, and for any side effects that may occur.