Bevacizumab has direct antivascular effects on human tumors

Bevacizumab, an antibody that blocks vascular endothelial growth factor (VEGF), seems to have direct and rapid antivascular effects on human tumors, according to a report published in the January 25th online issue of Nature Medicine.

Bevacizumab, which is being developed by Genentech Inc. under the trade name Avastin, is currently under review by the US Food and Drug Administration as a treatment for colorectal cancer (see Reuters Health report September 29, 2003). Despite its apparent efficacy in clinical trials, bevacizumab’s effects on the vascular biology of human tumors are unclear. In the new study, Dr. Christopher G. Willett, from Massachusetts General Hospital in Boston, and colleagues investigated the drug’s mechanisms of action in six patients with rectal cancer. The authors found that a single infusion of the drug decreased “tumor perfusion, vascular volume, microvascular density, interstitial fluid pressure, and the number of viable, circulating endothelial and progenitor cells.” In addition, such treatment increased the faction of blood vessels with pericyte coverage.”Collectively, these mechanisms may explain the unprecedented efficacy of bevacizumab in recent clinical trials, as well as the possible synergistic or additive interaction between antiangiogenic and cytotoxic therapies that has been observed in preclinical settings for more than a decade,” the researchers conclude.(Source: Nat Med 2004;January 25th online issue: Reuters Health: January 26, 2004: Oncolink)