Portland, Ore.

An experimental drug is showing promise in treating patients afflicted with age-related macular degeneration (AMD), the leading cause of blindness among the elderly. Researchers at Oregon Health & Science University's Casey Eye Institute have been conducting a clinical trial to test the effectiveness of the drug.

Macugen is an anti-angiogenic drug, a class of drugs being studied for their ability to block the growth of new blood vessels in the body. Macugen works by blocking a protein called vascular endothelial growth factor, or VEGF, which is involved in new blood vessel growth in the eye. This is the first treatment for AMD to target this source of the disease.

Macugen is designed to treat "wet" AMD. The less common though more severe form of the disease, it results in more rapid vision loss than the "dry" form and is responsible for blindness in a disproportionate number of cases. Wet AMD occurs when an abnormal growth of blood vessels behind the retina leak and bleed, forming scar tissue that damages central vision. An estimated 1.2 million American's suffer from this form of the disease, and that number is expected to grow as the population ages.

"The finding is significant in that this is the first anti-angiogenic drug shown in large clinical trials to demonstrate a beneficial effect for the broad spectrum of patients with the wet form of AMD" said Michael Klein, M.D., director of the Macular Degeneration Center at OHSU's Casey Eye Institute. "The treatment appears to result primarily in a limitation of further vision loss from wet AMD rather than an improvement in vision," Klein cautioned. "The drug will not be available for general use for quite some time, pending FDA approval, and its greatest potential value may be using it in combination with other therapies for AMD."

In the just-completed phase III trial, Macugen was injected directly into the eye every six weeks for a year. After a year of treatment, 70 percent of patients achieved the study's goal of limiting vision loss to no more than three lines on an eye chart, compared with 55 percent of patients in the control group that did not receive the drug. This represents a 27 percent increase in the number of patients who experienced a limitation of vision loss by receiving Macugen. OHSU's Casey Eye Institute was one of three centers to initiate clinical testing of the drug five years ago and was one of 115 centers around the world participating in the randomized clinical trial that enrolled 1,168 patients. The results were presented at a recent meeting of the American Academy of Ophthalmology in Anaheim, Calif.