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.