 ZD6474 is an investigational drug that has not yet received approval from the FDA. ZD6474 is designed to limit VEGF. Vascular endothelial growth factor VEGF is considered to play a key role in the development of pleural effusion. Pleural effusion is an abnormal collection of pleural fluid in the pleural lining surrounding the lungs. The pleural lining is the thin covering that protects and cushions the lungs. It is made up of two layers of tissue that are separated by a small amount of fluid. 