Drug Puts Brakes on Vision Loss
Macugen slows progress of age-related macular degeneration
WEDNESDAY, Dec. 29, 2004 (HealthDayNews) -- Until now, no drug has been effective at stopping the progress of age-related macular degeneration (AMD), a disease that strikes up to 1 million Americans and causes them to lose all or some of their vision.
But researchers reporting in the Dec. 30 issue of the New England Journal of Medicine say a newly approved drug, Macugen (pegaptanib), may offer people with the worst form of AMD new hope.
In two separate studies, "the group that received the drug did much better in every kind of endpoint that we looked at," said Dr. Evangelos Gragoudas, director of retina services at the Massachusetts Eye and Ear Infirmary and a professor of ophthalmology at Harvard Medical School.
AMD is caused by the abnormal growth of blood vessels within the eye. "They can bleed, they can exude fluid, and eventually they form a scar and destroy the central vision," explained Gragoudas, the study's lead author.
For years, scientists have searched for the underlying cause of this abnormal vessel growth, and experts now believe it is linked to a naturally occurring compound called vascular endothelial growth factor (VEGF).
Macugen, one of the family of anti-angiogenesis drugs, effectively slows the growth of new blood vessels by blocking VEGF activity within the eye. "It prevents the growth of new vessels, and it also prevents the exudation -- the leakage of fluid -- which is very common in abnormal vessels," Gragoudas said. "Sometimes, even if the vessels themselves don't completely disappear or regress, the fact that the fluid is absorbed can have a good effect on the patient."
On Dec. 20, the U.S. Food and Drug Administration approved Macugen for use in patients with the most serious form of AMD, called "wet" AMD.
In two major clinical trials involving more than 1,200 AMD patients from 117 eye clinics worldwide, Gragoudas' team of researchers compared the effectiveness of various doses of Macugen to a placebo. The drug was administered via regular injections into the eye.
The researchers report a reduced risk for vision loss in a majority of patients receiving Macugen compared to those on placebo. This slowing of vision impairment began as early as six weeks into therapy, and continuing through to study's end at 54 weeks.
One simple way the researchers measured vision loss is by counting the number of letters on a standard eye chart that become illegible to patients over the course of the study. While a loss of 15 letters would be considered moderate vision loss, a loss of 50 letters or more (six lines) would be considered severe.
Among patients receiving 0.3 milligrams of Macugen, "70 percent lost fewer than 50 letters, compared with just 55 percent among the controls [receiving placebo]," Gragoudas said.
Macugen is "a significant new therapy that inhibits the growth of new blood vessels and reduces leakage in a disease that relentlessly causes gradual loss of functioning vision in the elderly population," said Dr. Stanley Chang, chairman of ophthalmology at Columbia University.
But Chang also pointed out that "there is more research that needs to be done because, despite treatment, approximately 40 percent of study eyes continued [on] to legal blindness by one year."
In a journal commentary, Dr. Frederick Ferris III of the National Eye Institute noted that Macugen's success rate in reducing vision loss did not exceed that of photodynamic laser therapy, the only other treatment currently approved for use.
But Gragoudas countered that the laser technique "is only allowed in a small number of patients, because a lot of [AMD] subtypes can't be treated with photodynamic therapy." And he added that, because Macugen is a drug and not a surgical intervention, its success in slowing vision loss "starts early on and continues through the whole treatment."
"The bottom line is that this is the first anti-angiogenic treatment that has been used for the eye," he said, "and it certainly decreases the rate of visual loss."
To learn more about AMD, head to the National Eye Institute.