The incidence of age-related macular degeneration (AMD), a condition normally affecting individuals over the age of 55, is expected to double by the year 2020 as more Americans age. For the first time, new drugs and approaches to treatment are offering patients hope where there once was little or none.
The National Eye Institute (NEI) estimates that more than 15 million adults in the United States have some type of AMD, which is the leading cause of blindness in older persons. It's a diagnosis that can be devastating for patients, taking both a physical and emotional toll. Over time, patients experience loss of their central vision because of a progressive deterioration of the macula, the part of the retina responsible for straight-ahead vision.
Of the two types of AMD, "dry" (nonneovascular) AMD is the more common, occurring in 90% of cases; it leads to only mild to moderate changes in vision. However, the "wet" (neovascular) form of AMD is more severe and more likely to lead to blindness. Patients may have both types at once, in one or both eyes, and about 10% of dry-AMD sufferers will eventually progress to wet AMD.
In focus "Macugen is a revolutionary, breakthrough treatment for neovascular AMD as it targets the pathological processes underlying the disease," said Donald J. D'Amico, M.D., professor of ophthalmology at Harvard Medical School. The drug is the first in a new class of ophthalmic drugs to specifically target vascular endothelial growth factor (VEGF), a protein that plays a critical role in angiogenesis.
"Pegaptanib binds to one of the major ocular forms of pathological VEGF," said Richard G. Fiscella, R.Ph., M.P.H., clinical professor, department of pharmacy practice at the University of Illinois at Chicago (UIC). "The drug was demonstrated to be effective in suppressing neovascularization and slowed the progression of AMD in two phase II/III clinical trials," he added. Specifically, the results showed 70% of pegaptanib-treated patients lost fewer than three lines of vision on the eye chart, compared with 55% receiving control treatment. Study results were published in the Dec. 30 New England Journal of Medicine.
According to the manufacturer, the drug is approved for use in all subtypes of neovascular AMD and is administered as a 0.3-mg intravitreal injection once every six weeks. Adequate anesthesia and a broad-spectrum microbicide should be given prior to the injection. Eyetech announced the list price for pegaptanib as $995 per injection; it will be available from three specialty pharmaceutical companies: McKesson Specialty, Priority Healthcare, and Besse Medical.
Another anti-VEGF agent in development is ranibizumab (Lucentis, Genentech), a humanized antibody fragment designed to bind and inhibit the action of VEGF. According to the company, ranibizumab will bind to all five isoforms of VEGF; thus it has the potential to completely inhibit the protein.