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Angiogenesis Inhibitors for Macular Degeneration

Angiogenesis is the formation or growth of new blood vessels. In the most severe form of age-related macular degeneration (known as "wet" ARMD) abnormal angiogenesis occurs under the retina resulting in irreversible loss of vision. The loss of vision is due to scarring of the retina secondary to the bleeding from the new blood vessels. Only 10% of patients with age-related macular degeneration will grow abnormal blood vessels under their retinas and thus progress from the "dry" form to the "wet" form of ARMD.

Current treatments for "wet" ARMD utilize laser based therapy to destroy offending blood vessels. However, this treatment is not optimal since the laser can permanently scar the overlying retina and the offending blood vessels often re-grow. Recently, new trials have begun to investigate if angiogenesis inhibitors can effectively inhibit the growth of new vessels in age-related macular degeneration. 

These drugs known scientifically as anti-angiogenesis factors inhibit new blood vessel formation or angiogenesis. New blood vessel growth is a normal response in some situations like wound healing, but when these new blood vessels grow under the macula they cause dry macular degeneration to become "wet." It is the wet form of macular degeneration that causes the most severe visual loss from macular degeneration.

After years of extensive research many of the body chemicals that cause these blood vessels to form have been identified and blocking chemicals have been developed. The cascade of reactions that cause angiogenesis is complex but one of the intermediate substances is called vascular endothelial growth factor known by its acronym VEGF. Two drugs have been developed that block the activity of VEGF and are known as anti-VEGF compounds. One of the drugs was developed by Genentech using the monoclonal antibody technique. The other developed by Eyetech is know as an aptamer, which is an artificial compound that also binds to VEGF and inhibits its action. These two drugs are given by injecting them directly into the eye.

There is another compound being developed by Alcon Pharmaceuticals that is derived from the steroid molecule but has no traditional steroid activity. This drug called Anecortave Acetate inhibits not only VEGF but other chemicals in the angiogenesis process. This drug is injected behind the eye and has prolonged activity.