What Are Monoclonal Antibodies?
Monoclonal antibodies, sometimes called "MAbs," are a new weapon in the fight against cancer. They have been designed to kill cancer cells while leaving normal cells relatively unharmed. In many cases, this has resulted in better treatment outcomes with fewer side effects.
The human immune system normally produces proteins called antibodies in response to specific antigens. Antigens are protein markers found on the surface of all cells. When foreign invaders such as germs, viruses and bacteria enter the body, antibodies recognize them, attach to their antigens and mark them for destruction.
Monoclonal antibodies are artificial antibodies, created in a lab, that attach to a specific antigen protein on the surface of cancer cells. For example, some monoclonal antibodies used to treat lymphoma are specifically designed to target the CD20 protein found on B cell lymphocytes, a cell type that is most often involved in lymphoma.
How Do Monoclonal Antibodies Work?
There are two types of monoclonal antibodies:
- Naked or Unconjugated monoclonal antibodies
- Conjugated monoclonal antibodies
Naked or Unconjugated monoclonal antibodies do not have any drugs or radiation attached to them. Typically, they attach to antigens on the cancer cell, acting as a signal for the body's immune system to destroy them. An example of this type of monoclonal antibody is Rituximab (Rituxan), used to treat lymphoma. This drug attaches to a protein called CD20, which is only found on B cells. Rituximab also lowers the number of healthy B cells in your body, but they are quickly replenished.
Conjugated monoclonal antibodies act as a carrier to deliver drugs, toxins, or radioactive isotopes directly to the cancer cell. An example of a conjugated monoclonal antibody is Ibritumomab Tiuxetan (Zevalin). This drug carries a cancer- killing radioactive particle directly to the cancerous blood cells of non-Hodgkin lymphoma.
How Are Monoclonal Antibodies Given?
Monoclonal antibodies are given intravenously (through a vein), often in the hospital or clinic. You may be given other drugs beforehand to decrease the likelihood of side effects. When used as a treatment for leukemia or lymphoma, monoclonal antibodies are usually given in combination with chemotherapy. The type of cancer you have and the drug you are receiving will determine how often the therapy will be administered.
Side Effects of Monoclonal Antibody Therapy
Since monoclonal antibody drugs are specifically designed to attack cancer cells while minimizing harm to healthy cells, the side effects are typically mild compared to those of chemotherapy or radiation. They are usually similar to allergic- type reactions. Potential side effects may include:
- Fevers, chills, flu-like symptoms
- Muscle weakness or pain
- Headaches
- Nausea, vomiting, and diarrhea
- Allergic reactions such as rashes or hives
- Low blood cell counts, especially those MAbs that are conjugated with radiation
- Heart problems, low blood pressure
Most side effects of monoclonal antibodies are temporary and usually only last as long as the actual infusion of the drug and for a few hours afterward. In addition, the likelihood of having a reaction decreases with each treatment received as the patient adjusts to the therapy.
Monoclonal Antibodies FDA Approved For Blood Cancers
| Drug Name | Type of Cancer |
|---|---|
| Alemtuzumab (Campath®) | Chronic Lymphocytic Leukemia |
| Gemtuzumab (Mylotarg®) | Acute Myelogenous Leukemia |
| Ibritumomab Tiuxetan (Zevalin®) | Non- Hodgkin Lymphoma |
| Rituximab (Rituxan®) | Non- Hodgkin Lymphoma |
| Tositumomab (Bexxar®) | Non- Hodgkin Lymphoma |
| Ofatumumab (Arzerra®) | Chronic Lymphocytic Leukemia |
