Are monoclonal antibodies a type of targeted therapy?
Yes. The National Cancer Institute says many monoclonal antibodies are used to treat cancer and that they are a type of targeted cancer therapy, meaning they are designed to interact with specific targets.
They are one of the two halves of targeted therapy. NCI's targeted therapy page says most targeted therapies are either small-molecule drugs or monoclonal antibodies. Small-molecule drugs are small enough to enter cells easily, so they reach targets inside a cell. Monoclonal antibodies are proteins made in a lab. They are designed to attach to specific targets on cancer cells.
Why some are also called immunotherapy
Antibodies made by the body recognize germs and mark them for destruction. Lab-made ones recognize a target the same way. What happens next depends on the design. Some designs recruit the immune system.
NCI gives two worked examples.
Rituximab binds to a protein called CD20 on B cells and some cancer cells. That causes the immune system to kill them. B cells are a type of white blood cell.
Blinatumomab binds two things at once: CD19, found on the surface of leukemia cells, and CD3, found on T cells. That pulls the T cell close enough to respond to the leukemia cell and kill it.
NCI also describes antibodies that work without the immune system. They stop cancer cells growing, make them self-destruct, or carry toxins to them.
So one antibody can sit under both labels. The words describe what a drug does, not which shelf it belongs on.
No target, no drug
Because these drugs work by attaching to something specific, that something has to be there.
NCI is clear about the exception and the rule. For a few cancers, such as chronic myelogenous leukemia, most people will have the target. Most of the time the tumor has to be tested first. That is called biomarker testing. It may require a biopsy, which carries risks that depend on the tumor's size and place.
Targets can also stop working. NCI says cancer cells can become resistant in two ways. The target itself changes, so the drug can no longer interact with it. Or the cells find new ways to grow that do not need the target. That is why these drugs are often combined with each other, or with chemotherapy and radiation.
What the side effects look like
NCI corrects an early assumption directly. Scientists once thought targeted therapy would be less toxic than chemotherapy; they learned it can cause serious side effects too.
The most common are diarrhea and liver problems. Others include clotting and wound healing problems, high blood pressure, fatigue, mouth sores, nail changes, loss of hair color, and rash or dry skin. Most go away after treatment ends.
Monoclonal antibodies add their own, since they are infused. Needle-site reactions include pain, swelling, soreness, redness, itchiness, and rash. Flu-like symptoms include chills, fatigue, fever, muscle aches, nausea, vomiting, and diarrhea.
Less often they cause mouth and skin sores that lead to serious infections, high blood pressure, heart failure, heart attacks, and inflamed lung disease. Allergic reactions range from mild to severe. NCI notes that in rare cases one is severe enough to cause death.
Two syndromes have names worth knowing. In capillary leak syndrome, fluid and proteins escape tiny blood vessels into nearby tissue, dropping blood pressure to dangerous levels. In cytokine release syndrome, immune signaling substances rise suddenly. It is often mild, and can cause fever, nausea, headache, rash, fast heartbeat, low blood pressure, and trouble breathing.
What to do during an infusion
Report symptoms as they happen. Fever, chills, flushing, rash, itching, dizziness, or trouble breathing during a dose should go to the nurse in the room at once. The drip can still be slowed or stopped.
Before treatment starts, ask whether biomarker testing has been done and what target was found. Our guide to monoclonal antibodies explained covers how they are made, and how targeted therapy works covers the wider class.
NCI's monoclonal antibodies page was posted on September 24, 2019, and its targeted therapy page was updated on May 31, 2022.
Sources
Want the full picture? Read our complete explanation: Monoclonal Antibodies Explained
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