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Monoclonal antibodies are manmade and produced in a lab. While they act like antibodies that your body naturally produces, they are designed to target specific molecules on cancer cells. Bevacizumab (Avastin) is a monoclonal antibody that kills cancer cells by blocking a protein called VEGF, thereby cutting off the tumor’s ability to form a new blood supply. Avastin is used to treat colon and ovarian cancer. Trastuzumab (Herceptin) is a monoclonal antibody that works against the HER2 protein, which is found in large amounts on some types of breast cancer cells. When HER2 is activated, it helps cancers cells grow; trastuzumab binds to HER2 proteins and stops the cancer cells from multiplying. Herceptin is used to treat Her2-positive breast cancer.
Sometimes monoclonal antibodies are combined with additional cancer-fighting molecules, like radioactive particles or chemotherapy drugs. The monoclonal antibody delivers these added molecules to cancer cells. Like trastuzumab, ado-trastuzumab emtansine (Kadcyla, also called TDM-1) targets the HER2 protein. However, it has a chemotherapy drug called DM1 attached. It is also used to treat some breast cancer patients whose cancer cells have too much HER2.
Side effects for monoclonal antibody treatment can include rashes, low blood pressure and flu-like symptoms. Additional side effects may depend on which molecule the antibody targets. For example, although uncommon, bevacizumab can block blood supply to sections of the large intestine, leading to a rare but serious side effect known as bowel perforation.