Vascular disrupting agents (VDAs) in anticancer therapy.

Vascular disrupting agents (VDAs) represent a novel class of drugs targeting the tumor's blood supply. Conceptually and operationally different from currently used antiangiogenic agents, VDAs have a high specificity for the established but abnormal tumor vasculature. Upon administration, rapid changes in the microtubule cytoskeleton of tumor endothelial cells are induced, resulting in a cascade of events ultimately leading to blood flow stasis and vascular collapse. Subsequently, the cells in the core of the tumor become necrotic and die. However, tumor repopulation occurs from a rim of viable tumor tissue on the edges of the tumor, stimulating the search for appropriate combination strategies designed to interfere with the regrowth from the viable rim. Such combinations include chemotherapy, radiation, and antiangiogenic drugs. In recent years, understanding of the molecular and cellular mechanisms taking place in response to VDA therapy has improved substantially. Multiple drug combinations have been designed and tested in preclinical models, some of which have shown encouraging results. Clinical benefits are currently under investigation in a number of ongoing clinical trials, including randomized phase III trials.