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Discovery Provides Ray of Hope in Fight Against Elderly Blindness
from Dr

Potential Gene Therapy May Stop Progress of Macular Degeneration and Diabetic Retinopathy

by Lee Hickling

Researchers at Northwestern University have made a discovery that could lead to development of a cutting-edge gene therapy capable of stopping the progress of two eye diseases which are the leading causes of blindness among older people in the United States.
Those conditions are incurable at present. Age-related macular degeneration can cause complete blindness in two years from its onset. Laser therapy has helped delay the loss of vision for some of its victims, and a new drug called Visudyne has been reported effective in doing the same thing in about two-thirds of cases.

Diabetic retinopathy and wet macular degeneration are both caused by the growth of new blood vessels in the back of the eye. Noel Bouck, Ph.D., and her research team have discovered that a protein that naturally occurs in the eye called pigment epithelium-derived factor -- PEDF for short -- can prevent that growth.

Bouck said when PEDF was administered to the eyes of laboratory mice that had been bred to be subject to an eye disease like human diabetes-related blindness, it stopped excessive new blood vessel formation in their retinas and in their maculas -- a crucial spot in the middle of the retina.

A Gaithersburg, Md., biotechnology company -- GenVec Inc. -- has obtained an exclusive license to develop ways of using PEDF to treat human eye diseases. Paul Fischer, chief executive officer of GenVec, said the studies required to file an Investigative New Drug application with the Food and Drug Administration are now under way. If the application is approved, that will be the first step in the long process necessary to win FDA approval of PEDF treatment for humans, which can take a minimum of three to five years.

Fischer said GenVec will use its proven technique of using adenovectors -- low doses of an altered common cold virus -- to deliver a sequence of genetic DNA material to the site of the problem. The DNA will then manufacture the PEDF protein, which will then stop the process called angiogenesis -- the manufacture of new blood vessels -- in that part of the eye.

He said the treatment, if successful, would not be able to reverse any damage already caused by overgrowth of blood vessels in the retina and macula, but it would prevent any further loss of vision.

Bouck said the discovery that PEDF can block abnormal blood vessel formation may have potential in the treatment of other disease conditions, including arthritis and cancer. Northwestern is currently talking to several other companies about other therapeutic uses of PEDF.

The overgrowth of blood vessels that causes diabetic retinopathy and wet macular degeneration begins with a decrease in the oxygen supply to the eye. That decreases the amount of PEDF present, and -- in the absence of the protein which inhibits the growth of new blood vessels -- the body makes more and more vessels until they block the passage of light to the light-sensitive retina.

The research that demonstrated PEDF's ability to stop the growth of new and unwanted blood vessels in the eye was done at the Robert H. Lurie Comprehensive Cancer Center of Northwestern University in Chicago. It grew out of a doctoral thesis project of a graduate student, David W. Dawson.

Bouck, a professor of microbiology and immunology, was the lead researcher. The results of the study will be published in an upcoming issue of the Proceedings of the National Academy of Sciences.
Date Published: 2/27/01

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Date last modified August 1, 2001