Monoclonal antibodies are laboratory made proteins that are used for a specific kind of cancer called metastatic HER-2 positive breast cancer. Human epidermal growth factor receptor 2 protein (HER2) is a type of receptor found on normal cells and inside breast cancer cells. Women with HER2-positive breast cancer have too many HER2 receptors in their cancer cells. When HER2 receptors are activated by growth hormones they help the cancer cell grow and divide. Monoclonal antibodies bind to HER2 receptors on cancer cells, blocking growth hormones. This makes tumors shrink instead of growing and spreading to other areas of the body.
Herceptin (trastuzumab) and Perjeta (pertuzumab) are two widely used examples of this drug class. Both drugs are injected into a vein. Herceptin is used in combination with chemotherapy drugs for adjuvant breast cancer therapy. It can also be used after the completion of chemotherapy or in combination with paclitaxel for the treatment of metastatic breast cancer (cancer that has spread beyond its site of origin).
Perjeta is often given with Herceptin and docetaxel as first-line treatment for metastatic breast cancer. It may also be given with these drugs as neoadjuvant treatment, which refers to treatment given to shrink the tumor prior to surgical removal.
According to a combined analysis of 4 Herceptin studies with more than 10,000 women with early stage breast cancer, one year of Herceptin treatment increased the chance of being cancer free by 52% after 2 years of observation. In a clinical trial that included 417 women, 39.3% of the breast tumors showed a complete response compared to only 21.5% in patients not receiving Perjeta.
Side Effects and Drug Interactions
Side effects that commonly occur after the first treatment with Herceptin or Perjeta include fever and chills. Other possible side effects include nausea and vomiting, diarrhea, fatigue, headaches, rashes, and breathing problems. Monoclonal antibodies can affect the way the heart pumps blood, so patients taking these drugs require monitoring their heart function. It is also important that women of childbearing age should take contraception during treatment and for 7 months after treatment because these drugs can cause birth defects.
Herceptin should not be combined with drugs called anthracyclines (for example, doxorubicin) because this can lead to severe cardiovascular side effects. Furthermore, anthracyclines should be avoided for 7 months after the last dose of Herceptin.
Monoclonal antibodies are expensive. The manufacturers offer patient assistance programs to help with drug cost. The Average Wholesale Price (AWP) is $2930 for 440 mg of Herceptin and $4,890 per vial of Perjeta.