Protein Blocker Curbs Blindness
An experimental drug that blocks abnormal blood vessel growth in the eye is an effective treatment for the leading cause of age-related blindness, according to new research.
Macugen -- a drug being developed by Pfizer Inc. and Eyetech Pharmaceuticals Inc., both based in New York -- was 27% more effective than a placebo at limiting vision loss in patients with the “wet” form of macular degeneration in a late-stage trial, said Dr. Carmen Puliafito, director of Bascom Palmer Eye Institute in Miami and the study’s lead investigator.
The research was presented Saturday in Anaheim at the American Academy of Ophthalmology’s annual convention.
In macular degeneration, the central and most important area of the retina -- the macula -- deteriorates.
The more common “dry” form results in gradual vision loss. In the more serious, wet form of the disease, vision loss occurs quickly as blood vessels leak and form a mound. The mound later contracts, leaving a scar that blocks vision. This form of macular degeneration afflicts an estimated 1.2 million Americans and the incidence is expected to rise as baby boomers age.
Macugen is designed to block a protein called vascular endothelial growth factor (VEGF) deemed largely responsible for the overgrowth of blood vessels in the eye.
“VEGF is probably the most important biologic mediator of blood vessel growth. Now we have antagonists that can block that action,” Puliafito said.
The drug, given every six weeks by injection directly to the eye, stabilized or improved vision in 33% of patients. The placebo by comparison stabilized or improved vision in 23% according to the 54-week late-stage trial of 1,168 patients.
Puliafito said that 70% of Macugen patients achieved the trial’s goal of limiting vision loss to no more than three lines on an eye chart versus 55% of the placebo group.
“The trial took all comers. The results imply that we are going to have a treatment for most patients with wet AMD [age-related macular degeneration],” he said.
Only one other drug has been approved to treat the disease, Visudyne, developed by Canadian firm QLT Inc. and Swiss drug maker Novartis, but it is only effective in about 30% of patients.
Side effects of Macugen included a small number of eye infections, he said. But concerns that curbing VEGF could aggravate heart disease appear to be unfounded -- the death rate for both the drug and placebo groups was 2%, the investigator said.
Biotech company Genentech Inc., based in South San Francisco, is developing an antibody-based inhibitor of VEGF, called Lucentis. It is also being tested in late-stage human trials.
Pfizer and Eyetech, which is in the process of going public, are also studying Macugen as a treatment for diabetic macular edema, another leading cause of blindness.
