Small molecules in anti-angiogenic therapy

Angiogenesis, or the formation of new blood vessels from pre-existing capillaries, is a sequence of events that occurs in many physiological and pathological conditions, including cancer. The identification of several pro-angiogenic factors and the recent description of endogenous inhibitors of angiogenesis, has made interference with vessel formation an attractive potential therapeutic option. Several compounds with anti-angiogenic or antivascular properties have been identified, and several of them have entered patient studies in cancer on the basis of promising preclinical results. However, this development of compounds that are not directly cytotoxic to cancer cells is problematic in terms of trial design and interpretation. This review discusses classes of molecules that interfere specifically with regulatory elements of the angiogenic process, and comments upon their stage of development and characteristics in clinical trials.