Targeted cancer therapies are treatments that target specific characteristics of cancer cells, such as a protein that allows cancer cells to grow in a rapid or abnormal way. Some targeted therapies work like the antibodies made naturally by the immune system. These types of targeted therapies can help the immune system recognize the cancer.
One way the immune system defends the body against foreign invaders is by making large numbers of antibodies. An antibody is a protein that sticks to an antigen. Antigens are proteins and other substances on the surface of and inside foreign cells that the body doesn’t recognize. Antigens trigger the immune system to attack them and the cells they are in or on, whether viruses, bacteria, or something else. Antibodies circulate throughout your body until they find and attach to the antigen. Once attached, antibodies can recruit other immune system cells to destroy the cells containing the antigen.
Researchers have designed antibodies that specifically target a certain antigen, such as one found on specific cancer cells. These are known as monoclonal antibodies.
Some monoclonal antibodies recognize specific proteins on the surface of cancer cells, called target proteins, and then bind to those target proteins. When the monoclonal antibody binds to the target protein, it blocks the target protein’s function and kills the cancer cell. Monoclonal antibodies that work like this and are approved by the U.S. Food and Drug Administration (FDA) to treat breast cancer are:
- Herceptin (chemical name: trastuzumab), which kills HER2-positive breast cancer cells by binding to the HER2 receptor and blocking cancer cells’ ability to receive growth signals
- Perjeta (chemical name: pertuzumab), which, like Herceptin, kills HER2-positive breast cancer cells by binding to the HER2 receptor and blocking cancer cells’ ability to receive growth signals
- Kadcyla (chemical name: T-DM1 or ado-trastuzumab emtansine) is a combination of Herceptin and the chemotherapy medicine emtansine; Kadcyla delivers emtansine to HER2-positive cancer cells in a targeted way by attaching emtansine to Herceptin, which binds to the HER2 receptors in the cancer cells and delivers the emtansine directly to the tumor
Visit the links above to learn more about how Herceptin, Perjeta, and Kadcyla work, as well as their side effects.
When Herceptin, Perjeta, Kadcyla, and other monoclonal antibodies bind to cancer cells, they can act as a marker so the immune system can now recognize the cancer cells and kill them. Rituxan (chemical name: rituximab) is another similar antibody used to treat non-Hodgkin lymphoma, chronic lymphocytic leukemia, and autoimmune diseases such as rheumatoid arthritis and Wegener’s granulomatosis (an autoimmune disorder that causes inflammation in blood vessels). Rituxan binds to the CD20 protein on healthy and diseased B cells, a type of white blood cell. When Rituxan binds to the B cells, it attracts immune cells to destroy both the cancerous B cells and the normal B cells.
Still other monoclonal antibodies bind to specific immune cells, such as T cells, to boost the ability of those cells to kill cancer cells. All of the immune checkpoint inhibitors that have been approved by the FDA are monoclonal antibodies. These immune checkpoint inhibitors bind to proteins on T cells and other immune cells.
Besides Herceptin, Perjeta, and Kadcyla, no other immune targeted therapies have been approved to treat breast cancer.