HER2 is a transmembrane tyrosine kinase receptor in the EGFR (epidermal growth factor receptor) family. The role of HER2 has been most thoroughly studied in breast cancer, in which constitutively active HER2 is overexpressed in 18-22% of cases and is correlated with a poor prognosis. Hence, effective inhibition of the constitutive HER2 signaling in cancer cells has been a major goal in the design of therapies. Therapeutic targeting of HER2 with humanized antibodies such as trastuzumab (Herceptin TM, Genentech) South San Francisco, CA) has proven to be an effective approach for the treatment of breast cancer cells that over-express HER2. The encouraging results of trastuzumab in patients with metastatic and early breast cancer diseases have prompted the evaluation of new HER2 inhibitors for increasing the potential for combinatorial therapies. This review will focus on patents that target HER2 in anti-cancer treatment.