Pertuzumab and its accelerated approval: Evolving treatment paradigms and new challenges in the management of HER2-positive breast cancer

The addition of trastuzumab, a monoclonal antibody to human epidermal growth factor receptor 2 (HER2), to standard chemotherapy in patients with HER2-positive breast cancer has resulted in major improvements in breast cancer outcomes, including improved survival, in both the adjuvant and metastatic settings. However, some patients experience disease relapse despite adjuvant trastuzumab-containing therapy, and resistance to trastuzumab develops in the majority of patients in the metastatic setting. An understanding of the molecular mechanisms underlying trastuzumab resistance has aided the development of novel HER2-targeted therapies. In June 2012, the HER2 dimerization inhibitor pertuzumab was approved by the US Food and Drug Administration (FDA) for use with chemotherapy and trastuzumab in the first-line treatment of metastatic HER2-positive breast cancer. In September 2013, accelerated approval was granted for use of pertuzumab in the neoadjuvant setting, representing a landmark decision by the FDA. This article discusses the development of pertuzumab to date, with a particular focus on the accelerated approval decision. We highlight the need to identify reliable biomarkers of sensitivity and resistance to HER2-targeted therapy, which would make possible the individualization of treatment for patients with HER2-positive breast cancer.