By blocking the development of new blood vessels, researchers are hoping to cut off the tumor's supply of oxygen and nutrients, and therefore its continued growth and spread to other parts of the body. About 20 angiogenesis inhibitors are currently being tested in human trials. Some are in or entering phase III testing. In phase III trials, hundreds of people around the country are involved in studies to determine how effective the drug is. In normal tissue, new blood vessels are formed during tissue growth and repair, during the normal female reproductive cycle, and during the development of the fetus during pregnancy.
Blood vessels supply tissues with oxygen and nutrients necessary for survival and growth.
Endothelial cells, the cells that form the walls of blood vessels, are the source of new blood vessels and have a remarkable ability to divide and migrate. The creation of new blood vessels occurs by a series of sequential steps. Eventually, strings of new endothelial cells organize into hollow tubes, creating new networks of blood vessels that make tissue growth and repair possible. Most of the time endothelial cells lie dormant. But when needed, short bursts of blood vessel growth occur in localized parts of tissues.