Human epidermal growth factor receptor 2 (HER2) is an important driver of malignant growth and progression in many cancer types and is activated through dimerization with itself or other HER family members. Targeting of HER2 therefore represents a potentially effective strategy for the treatment of certain cancers. Pertuzumab is a humanized antibody designed as an inhibitor of HER2 heterodimerization and is the first example of a new class of targeted therapeutics referred to as HER dimerization inhibitors. Pertuzumab has shown broad-spectrum antitumor activity both in preclinical models and in several phase II clinical studies. The antibody is currently undergoing further clinical evaluation in combination with trastuzumab in breast cancer, and with selected cytotoxic agents in ovarian and lung cancer.