Monoclonal Antibody Therapy

Diagram: antibody and antigens

Monoclonal Antibody (mAB) Therapy is a type of immunotherapy. It employs specific antibodies to target cancer cells for removal from the body. This type of therapy relies on the body's own immune system to fight the cancer, rather than attacking the cells with damaging chemotherapy and radiation.

To understand how this therapy works, you must understand what antigens and antibodies are. Antigens are cell markers that are produced in every type of cell – the cells of your body, bacteria, and viruses. These markers are different in every cell type, so your body can tell them apart. Antibodies are designed to bind to antigens, like fitting two puzzle pieces together. Monoclonal antibodies are large groups of antibodies that only bind to one antigen.

In monoclonal antibody therapy, doctors inject patients with antibodies that bind to the antigens on cancer cells. In this way, they are "tagging" the bad cells. When cells are tagged with these antibodies, they are marked for removal by immune cells. Thus, the body removes its own tumors. It is for this reason that mABs are classified as immunotherapy.

Immunotherapy typically does not have the symptoms of chemotherapy and radiation because the body's immune system will not attack healthy cells. Chemotherapy and radiation, on the other hand, attack any type of fast growing cell, even if it's not a tumor. For this reason, immunotherapy is a highly researched and evolving branch of cancer treatment.

It is important to remember that an antibody designed to mark a certain type of cell – a B-cell, let's say – will not work on a T-cell cancer. The antibodies will only bind to one type of antigen, and antigens are cell specific.

In some cases, immunotherapy by itself is not enough. So scientists have found a way to mix the mABs with radiation. By attaching a radionuclide (radioactive molecule) to the antibody, small amounts of radiation can be applied directly to tumors. Since the antibodies will automatically bind the cancer cells, the radiation is delivered to tumors and the damage to healthy cells is minimized. This type of therapy is particularly effective on lymphomas because they are highly sensitive to radiation.

Immunotherapy can be combined with chemotherapy for advanced cancers.

The following are FDA approved mABs. For more information on monoclonal antibodies and a more complete list of FDA-approved drugs, see this article from the Mayo Clinic.

Rituxan (generic name rituximab)

A non-radioactive monoclonal antibody

Zevalin

A radioactive mAB with an yttrium-90 radiolabel

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