Anti-angiogenesis drugs don't attack cancer cells directly. Instead, they target the blood vessels the cancer cells need to survive and grow. By doing this, they may help prevent new tumors from growing. They may also make large tumors shrink if their blood supply is cut off.

Scientists have found a number of different pathways that cancer cells can use to cause blood vessel growth. Each step in these pathways is a possible target for cancer treatment. Different drugs may work at different steps in these pathways.

For example, one of the most important proteins in new blood vessel growth is vascular endothelial growth factor (VEGF). This protein is not made in large amounts by normal cells, but some cancer cells make it and release it into the area around them. VEGF then attaches to a protein (called the VEGF receptor, or VEGFR) on the surface of nearby endothelial cells. This signals the cells' control centers, to start growing and forming new blood vessels.

Many of the anti-angiogenesis drugs used today attack the VEGF pathway. Bevacizumab (Avastin^®) was the first drug targeted at new blood vessels to be approved for use against cancer. It is a monoclonal antibody -- a man-made version of an immune system protein -- that binds to VEGF and keeps it from reaching the VEGF receptor. Other drugs, like sunitinib (Sutent^®) and sorafenib (Nexavar^®), are small molecules that attach to the VEGF receptor itself, keeping it from being turned on and making new blood vessels.

Drugs that target other blood vessel pathways are now being tested.

Some drugs already used to treat cancer have been found to affect blood vessel growth, too. But it's not clear how they work. For example, doctors have found that some chemotherapy drugs, if given around the clock in low doses, may prevent tumor growth without causing the serious side effects that higher doses would. Some research suggests the drugs may work because they stop the growth of endothelial cells.

Some other drugs used to treat cancer, such as thalidomide (Thalomid^®) and lenalidomide (Revlimid^®), are also known to affect blood vessel growth. But they work against cancer in other ways, too.

Last Medical Review: 03/10/2009
Last Revised: 03/10/2009

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