Monoclonal antibody drugs for cancer: How they work

Monoclonal antibody drugs are treatments that enlist your body's germ-fighting immune system against diseases, including cancer.

If your health care provider recommends a monoclonal antibody drug as part of your cancer treatment, find out what to expect from this therapy. Learn enough about monoclonal antibody drugs so that you feel comfortable asking questions and making decisions about your treatment. Work with your health care provider to decide whether a monoclonal antibody treatment may be right for you.

How does the immune system fight cancer?

The immune system is made up of a complex team of players that detect and destroy disease-causing agents, such as bacteria and viruses. Similarly, this system may eliminate damaged cells, such as cancer cells.

One way the immune system finds and destroys invaders is with antibodies. An antibody attaches itself to a specific molecule (antigen) on the surface of the target cell, such as a cancer cell. When an antibody binds to the cell, 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 are often able to avoid detection by the immune system. The cancer cells might mask themselves so they can hide or the cancer cells might release signals that block the immune system cells from working correctly.

What is a monoclonal antibody?

Monoclonal antibodies are laboratory-produced molecules engineered to serve as substitute antibodies that can restore, enhance, modify or mimic the immune system's attack on cells that aren't wanted, such as cancer 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. Examples include:

• 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 cancer 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. Your body keeps your immune system from being overactive by making proteins that control the activity of the immune system cells. Monoclonal antibodies can interfere with that process so that your immune system cells are allowed to work without controls against cancer cells.
• Directly attacking cancer cells. Certain monoclonal antibodies may attack the cell more directly. 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 combined with a small radioactive particle, it transports the radiation treatment directly to cancer cells and may minimize the effect of radiation on healthy cells.
• Delivering chemotherapy. Similarly, some monoclonal antibodies are combined with a chemotherapy 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.

How are monoclonal antibody drugs used in cancer treatment?

Many monoclonal antibodies have been approved for treating many different types of cancer. Clinical trials are studying new drugs and new uses for existing monoclonal antibodies.

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?

Monoclonal antibody treatment for cancer can cause side effects, some of which, though rare, can be very serious. Talk to your health care provider about what side effects are associated with the particular drug you're receiving. Balance the potential side effects with the expected benefits to determine whether this is the right treatment for you.

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
• Diarrhea
• 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, very rarely, 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. You might need to stay at the treatment facility for a few hours for monitoring.
• 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. Some monoclonal antibody drugs carry a risk of internal bleeding.

What should you consider when deciding on monoclonal antibody drug treatment?

Discuss your cancer treatment options with your health care provider. 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 health care team include:

• Have my cancer cells been tested to see if a monoclonal antibody treatment might be of benefit? Tests of your cancer cells can often tell if monoclonal antibody treatments might help your specific cancer.
• Has the monoclonal antibody drug shown a clear benefit? Ask about evidence of the treatment's effect in studies. Did it slow cancer growth? Did it shrink the cancer? 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 provider, you can determine whether the potential side effects of treatment are worth the likely benefit.
• Do the potential benefits outweigh the risks? Consider asking what might happen if you choose not to have monoclonal antibody treatment.
• How much will monoclonal antibody treatment cost? Monoclonal antibody treatments can be very expensive.
• 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. A clinical trial may give you a chance to try new monoclonal antibody drugs. Ask whether any clinical trials may be open to you.