Clarithromycin is a potent inhibitor of tumor-induced angiogenesis.

We investigated the inhibitory effect of clarithromycin, a 14-membered ring macrolide antibiotic, on tumor-induced angiogenesis in vivo using a mouse dorsal air sac model. The inhibitory effect of clarithromycin was dose-dependent, and 100 mg/kg of clarithromycin administered intraperitoneally twice a day reduced the area of dense capillary network to about 30% that of the control. However, in concentrations up to 50 microM clarithromycin had no effect on lung cancer cells and human vascular endothelial cell growth, endothelial cell migration, or lung cancer cell production of the angiogenesis-inducing factors interleukin-8 and vascular endothelial growth factor. Clarithromycin in concentrations greater than 10 microM inhibited endothelial cell tube formation on Matrigel in a dose-dependent manner. These data suggest clarithromycin is a potent inhibitor of tumor-induced angiogenesis that exerts its effect by inhibiting endothelial cell tube formation, and may be a possible candidate for therapeutic application.