New Treatment in Clinical Trials Angiogenesis, the growth of blood vessels from pre-existing blood vessels, occurs throughout ones' lifetime. As an adult, it is generally limited to the natural process of wound healing and menstruation. It may also be triggered, however, by certain pathological conditions, such as cancer. The continuing growth of solid tumors and metastasis requires nourishment from new blood vessels. Angiogenesis is induced by tumors as a life-line for oxygen and nutrients and also provides exits for cancer cells to spread to other parts of the body. First proposed in 1972 by Dr. Judah Folkman of Harvard University, anti-angiogenesis focuses on cutting of a tumor’s blood supply. Recent research has focused on whether or not the inhibition of angiogenesis can limit tumor growth, extend the period of disease-free remission in patients who respond to front-line therapy, and reduce the potential for metastases. There are four approaches to anti-angiogenesis. Some seek to block factors that stimulate the formation of blood vessels. Others use inhibitors that occur naturally in the body. Another approach blocks molecules that allow newly forming blood vessels to invade surrounding tissue. Still others seek to incapacitate newly dividing cells. More than 300 angiogenesis inhibitors have been discovered to date and at least 4,000 cancer patients have been enrolled in clinical trials. Over 140 companies are involved in drug development programs and there are currently over 40 anti-angiogenic drugs in clinical trials at over 200 medical centers. Endostatin, Angiostatin, Marimastat, and Prinomastat are among those that have received the most attention. Interleukin-12, TNP-40 and thalidomide are in kidney cancer clinical trials. Researchers do not believe that the inhibitors will replace standard treatments such as chemotherapy, but that they may improve its effectiveness to a point where smaller amounts of such toxic drugs will be necessary. “Tumor cells have a high rate of mutation,” Dr. Folkman has cautioned. “Eventually, the mutations result in new varieties of cells with resistance to drugs used in chemotherapy. We hope that angiogenesis inhibitors can take over when chemotherapy has to stop.” Because inhibitors occur naturally, the body does not mount an immune resistance to them. As a result, patients can take them for extended periods, or perhaps even indefinitely. For more information on anti-angiogenesis and current clinical trials visit the National Cancer Institute: http://cancertrials.nci.nih.gov or call 1-800-4-CANCER.
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