Clinical aspects of natural anti-angiogenic drugs.

Natural products represent a rich resource for drug delivery and are currently being exploited to target tumour angiogenesis. A vast array of products of natural origin have been shown to have anti-angiogenic potential in preclinical models, including purified endogenous inhibitors, and exogenous compounds derived from varied species of plant, animal and micro-organism. Over a dozen of these agents have now entered clinical trial. This review discusses evidence for the efficacy of this drug class and key issues in the translation of pre-clinical results into the development of efficacious drugs for clinical use.