Pertuzumab for the treatment of patients with human epidermal growth factor receptor 2-positive breast cancer in Japan

Pertuzumab, a novel anti-human epidermal growth factor receptor 2 (HER2) agent, is effective for metastatic HER2-positive breast cancer when used in combination with taxane and trastuzumab. The aim of the present study was to describe the use of pertuzumab in Japan. A phase I clinical trial of pertuzumab for HER2-positive metastatic breast cancer was first conducted in the United States in 2001 (study ID no. TOC2297g) and for HER2-positive solid cancers in Japan in 2004 (study ID no. JO17076). However, Japanese patients were not enrolled in a global phase II trial for metastatic breast cancer (study ID no. BO17929) and no phase II trial of pertuzumab for Japanese patients has yet been conducted. A phase III trial on pertuzumab for metastatic breast cancer (CLEOPATRA study), which included 53 Japanese patients, revealed that pertuzumab significantly prolonged progression-free and overall survival. However, the superiority of the pertuzumab group was not verified in the subgroup analysis of Japanese patients, which was not a preplanned analysis. Therefore, a postmarketing clinical trial for Japanese patients with HER2-positive metastatic breast cancer (COMACHI study) was initiated in November, 2013, to investigate the clinical effectiveness of pertuzumab in Japanese patients. As of December, 2014, global trials on pertuzumab in the metastatic and adjuvant settings are currently ongoing. These trials included Japanese patients with HER2-positive breast cancer. Pertuzumab was approved in Japan in August, 2013 due to the positive findings of the CLEOPATRA study. Unlike the United States and Europe, the Japanes Pharmaceutical and Medical Devices Agency approved the administration of pertuzumab as second- or later-line treatment for HER2-positive metastatic breast cancer, as well as first-line treatment. Furthermore, pertuzumab may be used in combination with other chemotherapeutic agents, with the exception of docetaxel. The approval of the expanded use of pertuzumab is likely to accelerate the market penetration of pertuzumab in Japan more quickly compared with other countries.