Monoclonal antibodies are immune system proteins that are created in the lab. Antibodies are produced naturally by your body and help the immune system recognize germs that cause disease, such as bacteria and viruses, and mark them for destruction. Like your body’s own antibodies, monoclonal antibodies recognize specific targets.

Many monoclonal antibodies are used to treat cancer. They are a type of targeted cancer therapy, which means they are designed to interact with specific targets. Learn more about targeted therapy.

Some monoclonal antibodies are also immunotherapy because they help turn the immune system against cancer. For example, some monoclonal antibodies mark cancer cells so that the immune system will better recognize and destroy them. An example is rituximab, which binds to a protein called CD20 on B cells and some types of cancer cells, causing the immune system to kill them. B cells are a type of white blood cell.

Other monoclonal antibodies bring T cells close to cancer cells, helping the immune cells kill the cancer cells. An example is blinatumomab (Blincyto®), which binds to both CD19, a protein found on the surface of leukemia cells, and CD3, a protein on the surface of T cells. This process helps the T cells get close enough to the leukemia cells to respond to and kill them.

Many monoclonal antibodies have been approved to treat a wide variety of cancers.

To learn about specific treatments for your cancer, see the PDQ® adult cancer treatment summaries and childhood cancer treatment summaries.

Monoclonal antibodies can cause side effects, which can differ from person to person. The ones you may have and how they make you feel will depend on many factors, such as how healthy you are before treatment, your type of cancer, how advanced it is, the type of monoclonal antibody you are receiving, and the dose.

Doctors and nurses cannot know for sure when or if side effects will occur or how serious they will be. So, it is important to know which signs to look for and what to do if you start to have problems.

Like most types of immunotherapy, monoclonal antibodies can cause skin reactions at the needle site and flu-like symptoms.

Needle site reactions include:

• pain
• swelling
• soreness
• redness
• itchiness
• rash

Learn more about skin changes caused by cancer treatment.

Flu-like symptoms include:

• chills
• fatigue
• fever
• muscle aches and pains
• nausea
• vomiting
• diarrhea

Learn more about flu-like symptoms caused by cancer treatment.

Monoclonal antibodies can also cause:

• mouth and skin sores that can lead to serious infections
• high blood pressure
• congestive heart failure
• heart attacks
• inflammatory lung disease

Monoclonal antibodies can cause mild to severe allergic reactions while you are receiving the drug. In rare cases, the reaction is severe enough to cause death.

Some monoclonal antibodies can also cause capillary leak syndrome. This syndrome causes fluid and proteins to leak out of tiny blood vessels and flow into surrounding tissues, resulting in dangerously low blood pressure. Capillary leak syndrome may lead to multiple organ failure and shock.

Cytokine release syndrome can sometimes occur with monoclonal antibodies, but it is often mild. Cytokines are immune substances that have many different functions in the body, and a sudden increase in their levels can cause:

• fever
• nausea
• headache
• rash
• rapid heartbeat
• low blood pressure
• trouble breathing

How Monoclonal Antibodies Treat Cancer