Targeted therapy in breast cancer: what's new?

Breast cancer is the most commonly diagnosed malignancy and one of the major causes of death among women. Breast cancer is also one of the most investigated diseases but whose biological features are still not well understood, several effective treating strategies having been explored in dealing with different types of advanced breast cancer, such as endocrine therapy and molecular targeted therapy. Trastuzumab is the first approved targeted anti-cancer agent to show an attractive response rate and outcomes in treating HER-2 positive metastatic breast cancer patients. However, primary or acquired trastuzumab resistance usually occurs some time into the use of trastuzumab and leads to treatment resistance or tumour progression. The promising results with trastuzumab targeted therapy encouraged further investigations in this area exploring several novel targeted agents aiming to overcome the resistance drawback of trastuzumab. In this review we discuss the major newly developed targeted agents in breast cancer treatment, including the novel anti-HER-2 monoclonal antibody pertuzumab or ertumaxomab, small molecular tyrosine inhibitor lapatinib, selective PARP1 inhibitor olaparib, mTOR inhibitor rapamycin analogues, and sheddase inhibitors. Many of these novel targeted drugs or molecules showed additional or complementary effects to trastuzumab therapy that need further and wider investigation.