Phase II Study With the Trifunctional Antibody Ertumaxomab to Treat Metastatic Breast Cancer After Progression on Trastuzumab Therapy

This study has the purpose to demonstrate clinical efficacy of the investigational new drug ertumaxomab in patients with human epidermal growth factor receptor-2 (HER-2/neu) overexpressing (3+ or 2+ with a positive Fluorescence In Situ Hybridization (FISH) test result) metastatic breast cancer progressing after trastuzumab treatment. Ertumaxomab is a trifunctional bispecific antibody targeting Her-2/neu on tumor cells and CD3 on T cells. Trifunctional antibodies represent a new concept for targeted anticancer therapy. This new antibody class has the capability to redirect T cells and accessory immune effector cells (e.g. macrophages, dendritic cells \[DCs\] and natural killer \[NK\] cells) to the tumor site. According to preclinical data, trifunctional antibodies activate these immune cells, which can trigger a complex anti-tumor immune response.