Pertuzumab is a monoclonal antibody used primarily in the treatment of HER2-positive breast cancer. It works by binding to the extracellular domain of the HER2 receptor, inhibiting dimerization with other HER family receptors, particularly HER3, which suppresses downstream signaling pathways that drive tumor cell proliferation and survival. It is commonly used in combination with trastuzumab and chemotherapy agents such as docetaxel for first-line treatment of metastatic HER2-positive breast cancer. Pertuzumab is also approved for neoadjuvant use in early-stage HER2-positive breast cancer to shrink tumors before surgery, and as adjuvant therapy to reduce the risk of recurrence. Due to its mechanism of targeting a specific receptor overexpressed in certain cancers, pertuzumab improves progression-free and overall survival in patients with HER2-positive disease, making it a key component of targeted cancer therapy regimens.