Monoclonal antibody drugs for cancer: How they work
Monoclonal antibody drugs are cancer treatments that enlist natural immune system functions to fight cancer. These drugs may be used in combination with other cancer treatments.
If you and your doctor are considering using a monoclonal antibody drug as part of your cancer treatment, find out what to expect from this therapy. Together you and your doctor can decide whether a monoclonal antibody treatment may be right for you.
How does the immune system fight cancer?
The immune system is composed of a complex team of players that detect and destroy disease-causing agents, such as bacteria and viruses. Similarly, this system may eliminate damaged or abnormal cells, such as cancer cells.
One factor in the immune system is the work of antibodies. An antibody attaches itself to a specific molecule (antigen) on the surface of a problematic cell. When an antibody binds to the antigen, it serves as a flag to attract disease-fighting molecules or as a trigger that promotes cell destruction by other immune system processes.
Cancer cells may outpace the immune system, avoid detection, or block immune system activity.
What is a monoclonal antibody?
Monoclonal antibodies are laboratory-produced molecules engineered to serve as substitute antibodies that can restore, enhance or mimic the immune system's attack on cancer cells. They are designed to bind to antigens that are generally more numerous on the surface of cancer cells than healthy cells.
How do monoclonal antibody drugs work?
Monoclonal antibodies are designed to function in different ways. A particular drug may actually function by more than one means. The role of the drug in helping the immune system may include the following:
- Flagging cancer cells. Some immune system cells depend on antibodies to locate the target of an attack. Cancer cells that are coated in monoclonal antibodies may be more easily detected and targeted for destruction.
- Triggering cell-membrane destruction. Some monoclonal antibodies can trigger an immune system response that can destroy the outer wall (membrane) of a cancer cell.
- Blocking cell growth. Some monoclonal antibodies block the connection between a cancer cell and proteins that promote cell growth — an activity that is necessary for tumor growth and survival.
- Preventing blood vessel growth. In order for a cancerous tumor to grow and survive, it needs a blood supply. Some monoclonal antibody drugs block protein-cell interactions necessary for the development of new blood vessels.
- Blocking immune system inhibitors. Certain proteins that bind to immune system cells are regulators that prevent overactivity of the system. Monoclonal antibodies that bind to these immune system cells give the cancer-fighting cells an opportunity to work with less inhibition.
- Directly attacking cancer cells. Certain monoclonal antibodies may attack the cell more directly, even though they were designed for another purpose. When some of these antibodies attach to a cell, a series of events inside the cell may cause it to self-destruct.
- Delivering radiation treatment. Because of a monoclonal antibody's ability to connect with a cancer cell, the antibody can be engineered as a delivery vehicle for other treatments. When a monoclonal antibody is attached to a small radioactive particle, it transports the radiation treatment directly to cancer cells and may minimize the effect of radiation on healthy cells. This variation of standard radiation therapy for cancer is called radioimmunotherapy.
- Delivering chemotherapy. Similarly, some monoclonal antibodies are attached to a chemotherapeutic drug in order to deliver the treatment directly to the cancer cells while avoiding healthy cells.
- Binding cancer and immune cells. Some drugs combine two monoclonal antibodies, one that attaches to a cancer cell and one that attaches to a specific immune system cell. This connection may promote immune system attacks on the cancer cells.
What cancers may be treated with monoclonal antibody drugs?
Monoclonal antibody treatments have been developed for some but not all cancers, and certain types of cancer cells are more vulnerable than others to monoclonal antibody interventions. Nonetheless, treatments have been approved for a number of cancers, including the following:
- Brain cancer
- Breast cancer
- Chronic lymphocytic leukemia
- Colorectal cancer
- Head and neck cancers
- Hodgkin's lymphoma
- Lung cancer
- Non-Hodgkin's lymphoma
- Prostate cancer
- Stomach cancer
How are monoclonal antibody drugs used in cancer treatment?
Monoclonal antibodies are administered through a vein (intravenously). How often you undergo monoclonal antibody treatment depends on your cancer and the drug you're receiving. Some monoclonal antibody drugs may be used in combination with other treatments, such as chemotherapy or hormone therapy.
Some monoclonal antibody drugs are a part of standard treatment plans. Others are still experimental and used when other treatments have not been successful.
What types of side effects do monoclonal antibody drugs cause?
In general, monoclonal antibody treatment carries fewer side effects than do traditional chemotherapy treatments.
However, monoclonal antibody treatment for cancer may cause side effects, some of which, though rare, can be very serious. Talk to your doctor about what side effects are associated with the particular drug you're receiving.
Common side effects
In general, the more common side effects caused by monoclonal antibody drugs include:
- Allergic reactions, such as hives or itching
- Flu-like signs and symptoms, including chills, fatigue, fever, and muscle aches and pains
- Nausea, vomiting
- Skin rashes
- Low blood pressure
Serious side effects
Serious, but rare, side effects of monoclonal antibody therapy may include:
- Infusion reactions. Severe allergy-like reactions can occur and, in very few cases, lead to death. You may receive medicine to block an allergic reaction before you begin monoclonal antibody treatment. Infusion reactions usually occur while treatment is being administered or soon after, so your health care team will watch you closely for a reaction.
- Low blood cell counts. Monoclonal antibodies that deliver radioactive particles or chemotherapy drugs may be associated with low blood cell counts that can be severe and persistent.
- Heart problems. Certain monoclonal antibodies increase the risk of high blood pressure, congestive heart failure and heart attacks.
- Lung problems. Some monoclonal antibodies are associated with a higher risk of inflammatory lung disease.
- Skin problems. Sores and rashes on your skin can lead to serious infections in some cases. Serious sores can also occur on the tissue that lines your cheeks and gums (mucosa).
- Bleeding. Monoclonal antibody drugs designed to stop cancer from forming new blood vessels have an increased risk of severe internal bleeding.
What should you consider when deciding on monoclonal antibody drug treatment?
Discuss your cancer treatment options with your doctor. Together you can weigh the benefits and risks of each treatment and decide whether a monoclonal antibody treatment is right for you.
Questions to ask your doctor include:
- Has my tumor been tested to see if a monoclonal antibody treatment might be of benefit? Simple tests on tumor samples can often tell if the currently available monoclonal antibody treatments might help your specific cancer.
- Has the monoclonal antibody drug shown a clear benefit? Ask your doctor about evidence of the treatment's effect in studies. Did it slow cancer growth? Did it result in reduced tumor sizes? Is this a first line of treatment or a treatment we try when others don't work?
- What are the likely side effects of monoclonal antibody treatment? With your doctor, you can determine whether the potential side effects of treatment are worth the likely benefit.
- How much will monoclonal antibody treatment cost? Monoclonal antibody drugs can cost thousands of dollars for each treatment. Ask your care team to help you determine if the treatment is covered by your insurance.
- Is monoclonal antibody treatment available in a clinical trial? Clinical trials, which are studies of new treatments and new ways to use existing treatments, may be available to you. In a clinical trial, the cost of the monoclonal antibody drug may be paid for as a part of the study. Also, you may be able to try new monoclonal antibody drugs. Talk to your doctor about what clinical trials may be open to you.