Perjeta or Pertuzumab is a monoclonal antibody used to treat HER2-positive breast cancer. It is a highly specific targeting drug that works by preventing the HER2 receptor from interacting with other receptors. HER2-positive breast cancer is a type of breast cancer which is more aggressive than others and is found to occur in approximately 20-25% of all breast cancer cases.

Perjeta belongs to a class of drugs known as HER2 inhibitors, which are designed to block growth signals sent by the HER2 protein in cancer cells. Perjeta is an FDA approved drug that is used in combination with other drugs like Herceptin (Trastuzumab) and chemotherapy, as a first-line treatment for metastatic HER2-positive breast cancer.

The drug was first approved by the FDA in 2012 after a successful clinical trial demonstrated its effectiveness in treating HER2-positive breast cancer. This trial, known as the CLEOPATRA trial, showed that when Perjeta was used in combination with Herceptin and chemotherapy, it significantly improved progression-free survival (PFS) in patients with metastatic HER2-positive breast cancer.

Perjeta is administered intravenously once every three weeks. The drug is given in combination with Herceptin and chemotherapy and can be continued up to a year or more in certain patients who are responding well to treatment.

Even though Perjeta is a monoclonal antibody, it can potentially have side effects just like any other drug. Some of the common side effects of Perjeta include fatigue, nausea, diarrhea, and hair loss. However, these side effects are usually mild or moderate and can be managed with medication.

In conclusion, Perjeta is a highly specific drug used in the treatment of HER2-positive breast cancer. It has proven to be effective in clinical trials and has significantly improved the prognosis of patients with advanced HER2-positive breast cancer. Perjeta, however, needs to be administered under the supervision of healthcare professionals and patients must be counseled on the potential side effects of the drug.