cyclophosphamide + pertuzumab + trastuzumab

This is a combination regimen consisting of three drugs—cyclophosphamide, pertuzumab, and trastuzumab—used primarily in the treatment of HER2-positive breast cancer. Cyclophosphamide is an alkylating agent that interferes with DNA replication and cell division, leading to cell death. Pertuzumab and trastuzumab are monoclonal antibodies targeting the human epidermal growth factor receptor 2 (HER2). Trastuzumab binds to subdomain IV of HER2, inhibiting downstream signaling and mediating antibody-dependent cellular cytotoxicity (ADCC), while pertuzumab binds to subdomain II, preventing dimerization with other ErbB receptors. The dual blockade provided by pertuzumab and trastuzumab enhances anti-tumor activity compared to either agent alone when combined with chemotherapy such as cyclophosphamide. This regimen is used in both neoadjuvant (pre-surgery) and adjuvant (post-surgery) settings for early-stage or metastatic HER2-positive breast cancer[1][3][5].