Targeted therapies in breast cancer: established drugs and recent developments

In the past few years many encouraging advancements have been made in understanding the molecular mechanisms underlying carcinogenesis and tumor progression. These improvements have led to the identification of promising new targets for cancer therapy. There has been much success with the HER2 targeting antibody trastuzumab (Herceptin) in the treatment of early stage and metastatic breast cancer. Consequently, several antibodies inhibiting cellular signaling of VEGF and EGFR were tested with respect to their efficacy in breast cancer. In phase II and III clinical trials the humanized anti-VEGF antibody bevacizumab (Avastin) alone or in combination with capecitabine exhibited responses in patients with metastatic breast cancer. Recent developments focus on small molecules interfering with different signal transduction pathways in tumor cells. Numerous inhibitors of EGF and VEGF receptor tyrosine kinases and farnesyl transferases are in early stages of clinical development for breast cancer. Another promising approach is the targeting of endothelins and their two G-protein coupled receptors (ET(A)R und ET(B)R). In this article, we will shortly outline well established targeted treatments and discuss the current development of novel agents to be utilized for molecular targeted breast cancer therapy. Due to the heterogeneity of disease and varying response to conventional systemic therapies, these new perceptions may lead to substantial patient benefit and provide a promising basis for future clinical application.