Perjeta (pertuzumab) is a targeted therapy used in the treatment of breast cancer. It is specifically designed to interfere with the HER2 protein, which is overexpressed in some types of breast cancer cells. By blocking the ability of the HER2 protein to receive growth signals, Perjeta helps to slow or stop the growth of the cancer cells. It is often used in combination with other medications, such as trastuzumab and chemotherapy, to treat patients with HER2-positive metastatic breast cancer, or as a part of a regimen for early-stage breast cancer to reduce the risk of the cancer returning. Perjeta is administered through an intravenous infusion and its use is associated with specific side effects, which healthcare providers monitor closely.