What are monoclonal antibodies?
Monoclonal antibodies are molecules that are produced by researchers in a lab that target and attack specific antigens, such as those on cancer cells.
Under normal circumstances, the immune system produces a significant amount of antibodies that attack foreign substances within the body, such as germs, infections and diseases. Antibodies attach themselves to the foreign antigen and engage other immune system mechanisms to target and attack the foreign cells.
Types of monoclonal antibodies
Certain monoclonal antibodies have been proven to be more effective against specific cancer types than others. Their function is to make cancer cells more visible to the immune system, block growth signals, stop new blood vessels from forming, and deliver chemotherapy and radiation to cancer cells.
The most common type of monoclonal antibodies used to treat cancer are naked monoclonal antibodies. They work on their own; there is no radioactive substance or other drug involved. In most cases, naked monoclonal antibodies attach to cancer cell antigens. However, they also attach to noncancerous cell antigens and/or free-floating proteins.
Examples of naked monoclonal antibodies include alemtuzumab (Campath, Genzyme) for the treatment of chronic lymphocytic leukemia, and trastuzumab (Herceptin, Genentech) for the treatment of stomach and breast cancers that contain the HER-2 protein.
Conjugated monoclonal antibodies — also known as labeled, loaded or tagged antibodies — are radioactive particles that are combined with a chemotherapy drug. These monoclonal antibodies deliver the therapy directly to cells that need it the most and decreases damage to normal cells within the body.
Examples of conjugated monoclonal antibodies include ibritumomab tiuxetan (Zevalin, Spectrum), which is used to treat certain types of non-Hodgkin’s lymphoma, and ado-trastuzumab emtansine (Kadcyla, Genentech), for the treatment of HER-2–positive breast cancer.
Other monoclonal antibodies are bispecific. This type consists of two antibodies that are able to attach to different proteins at the same time, which brings the cancer cells and immune cells together and causes the immune system to attack cancer cells. An example of a bispecific monoclonal antibody is blinatumomab (Blincyto, Amgen), used to treat certain types of acute lymphocytic leukemia.
The occurrence of adverse events associated with monoclonal antibodies are dependent upon the mechanism to which they attach. Naked monoclonal antibodies are associated with few adverse events. In some cases, conjugated antibodies are more dominant when compared with naked monoclonal antibodies, yet conjugated monoclonal antibodies are associated with more adverse events depending upon what they are attached to.
Some of the most common adverse events associated with monoclonal antibodies include chills, diarrhea, fever, headache, low blood pressure, nausea, rashes, vomiting and weakness. Other less common but more serious adverse events include reactions to infusions, significantly low blood counts, heart and skin issues and bleeding.
Looking ahead, monoclonal antibodies have been significantly transformed during the past few decades, and new research and development for monoclonal antibodies is ongoing. An average of 30 monocolonal antibodies are currently available for use across the U.S. and Europe, with more in the pipeline.
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