Vascular targeting agents.

The role of the vascular network of a tumor has been the focus of much recent research. Angiogenesis, or the growth of new tumor blood vessels, was initially the main target in the development of novel antitumor agents. More recently, new therapeutic strategies have been designed to destroy established tumor blood vessels. These vascular targeting agents (VTAs) exert their action by producing a rapid shutdown of tumor blood flow, resulting in ischemia and tumor cell necrosis. VTAs can be broadly divided into biologic agents and small molecules. In contrast to the biologic agents, drug-based vascular targeting molecules have developed much further, with many clinical trials ongoing. Evidence suggests that VTAs may be useful as single agents but can be more effective when used in combination with other therapeutic regimens.