Early study results indicate that a potential new age-related macular degeneration (AMD) therapy may improve vision within one week of injection, researchers announced at the Macula Society meeting of international retinal specialists.
Avastin, the drug used in initial studies, works by inhibiting growth of abnormal blood vessels in the back inner part of the eye (retina), a condition that occurs in the "wet" form of AMD. Researchers at the University of Miami’s Bascom Palmer Eye Institute said Avastin substantially reduced blood vessel leakage contributing to vision loss. A larger study is needed to determine if benefits of Avastin as a macular degeneration therapy outweigh risks, said Philip J. Rosenfeld, MD, PhD, associate professor of ophthalmology at the Institute.
Both Avastin and Macugen (the first ophthalmic anti-VEGF drug approved by the FDA in December 2004) target a specific type of protein thought to cause abnormal blood vessel growth. Avastin currently has FDA approval for treatment of metastasis colorectal cancer, but not for macular degeneration. The use of Avastin for macular degeneration is "off label." It is not manufactured to the quality standards for an ophthalmic drug and no ocular safety testing has been done.
The FDA has issued a caution that Avastin, when used to treat cancer patients, has been shown to increase risk of stroke and heart attack. Patients who are receiving blood thinning agents, including aspirin, must be precluded from using Avastin. Any patient with any history of abnormal blood chemistry and urinalysis must be excluded from using this drug, the researchers cautioned.
"A potential advantage of Avastin over other therapies for wet AMD is that vision improvement can occur within one week of treatment," said Dr. Rosenfeld, the principal investigator of the Bascom Palmer clinical trial. "In addition to the improved vision, Avastin causes a reduction in leakage from the abnormal blood vessels, and we observed a restoration of normal macular anatomy." Avastin, also known as bevacizumab, is manufactured by Genentech, Inc.
Patients with neovascular or the wet form of macular degeneration are thought to have elevated levels of vascular endothelial growth factor (VEGF) in their affected eyes. VEGF is a protein that causes abnormal blood vessels to grow, leak, bleed and damage the macula resulting in vision loss. New anti-VEGF drugs work by blocking this protein and the formation of abnormal blood vessels that grow in the eye.
"We have been injecting anti-VEGF drugs for the past three years with very encouraging results. Genentech recently released the results from two studies investigating Lucentis for the treatment of wet AMD. In those press releases, it was announced that Lucentis therapy in large multi-center trials improved vision at one year in patients with wet AMD. One of the differences between Lucentis and Avastin is that Lucentis is designed for injection into the eye and Avastin is designed for systemic infusion," said Dr. Rosenfeld.
Dr. Rosenfeld went on to emphasize that Avastin therapy isn’t a cure and it’s not the right treatment for everyone with wet AMD. Avastin is only for patients in the early stages of the disease and should be used within 6 months to 12 months from the time of onset, said Dr. Rosenfeld. Some people would rather have an injection in the eye than worry about the risks of a systemic drug. What this offers us is a new potential option for patients with wet AMD. It also provides us with additional evidence that VEGF is the major factor for blood vessel growth and vision loss in wet AMD.
"We don’t know how many treatments will be needed," Rosenfeld said. "In this study patients were treated two or three times over a twelve week period. As most patients commonly get wet AMD in both eyes, an added advantage of this therapy is that both eyes can be treated with a single infusion into the arm. [Avastin is now delivered as an intraocular injection.] A larger clinical trial is needed to determine if the benefits of Avastin outweigh the risks."
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- Bascom Palmer Eye Institute, Miami FL, March 2005