Vitamin A Drug Could Stop Dry Macular Degeneration
We are often told that vitamin A is good for the eyes, and researchers have recently found this to be true when using a vitamin A-derived drug, fenretinide, to stop the advance of dry macular degeneration. They discovered that the most common form of this currently uncurable eye disease responds well to the drug.
Fenretinide shows promise in fighting dry macular degeneration
Macular degeneration (also known as age-related macular degeneration, or AMD), is an eye disease associated with aging that destroys a person’s sharp, central vision. It is a leading cause of vision loss in Americans age 60 and older. In most cases the loss of vision is gradual. Approximately 2 million adults in the United States have macular degeneration.
Age-related macular degeneration affects the macula, which is located in the center of the retina. The disease can occur in one of two forms—dry or wet—with dry comprising 85 to 90 percent of cases. Dry macular degeneration is characterized by drusen, a yellow substance that accumulates under the retina, and the breakdown of light-sensitive cells in the eye.
The promising news about fenretinide was presented at the Annual Meeting of the American Academy of Ophthalmology in Chicago on October 17 by Jason Slakter, MD, of New York University School of Medicine. He explained how fenretinide, which has been used to treat acne, psoriasis, rheumatoid arthritis, and certain cancers, reduced the chance that dry macular degeneration would progress to wet AMD in more than 50 percent of some patients.
In healthy eyes, the body removes waste products that result from the metabolism of nutrients in the inner layers of the eye. When the clean-up system malfunctions, debris known as lipofuscin, along with vitamin A metabolites, accumulate in the eye and cause damage to the retina. Fenretinide attaches itself to a retinal binding protein and thus reduces the chance that toxic build-up and lesion growth will occur.
One hundred seventy-eight patients with dry macular degeneration were enrolled in a phase 2, double-blind, placebo-controlled, 24-month study that was conducted at 30 sites around the United States. Sixty-eight patients received placebo, 52 received 100 mg daily of fenretinide, and 58 received 300 mg of fenretinide. A total of 246 patients completed the study. Individuals who showed the greatest decline in the amount of retinal binding protein also had the least risk of dry macular degeneration or progression to the wet form of the disease.
At 24 months, 22 percent of patients taking placebo had developed wet macular degeneration compared with 13.5 percent of patients who had taken 100 mg of fenretinide and 13.8 percent who had taken 300 mg. Dr. Slakter noted that the drug formulation was changed mid-way through the study, and that nearly all of the treatment benefit was seen in patients who took the original form of the 300-mg dose.
Dr. Slakter noted that “Evidence from our study and others points to fenretinide’s potential to treat and prevent diseases of the retina,” a major one of which is macular degeneration. This vitamin A-derived drug appears to protect healthy cells in the retina of people who have dry macular degeneration and inhibit progression into wet AMD. A phase 3 clinical trial is planned for 2011. Information on clinical trials can be seen on the government’s website.
American Academy of Ophthalmology
National Eye Institute