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Cancer research has opened a new avenue of treatment options for neovascular eye conditions, including age-related macular degeneration and diabetic retinopathy. The common factor is the growth of abnormal new blood vessels. In the case of cancer, a solid tumor must have a blood supply in order to grow. The tumor tricks the circulatory system into providing it with new blood vessels, in a process called angiogenesis. In the wet form of macular degeneration, new blood vessels grow under the retina and leak blood, which interferes with retinal function. Researchers have identified a protein called vascular endothelial growth factor, VEGF, which is involved in the process of blood vessel growth. Drugs that block the function of VEGF are used to treat both cancer and neovascular eye conditions.
The first drug approved to treat wet macular degeneration was Macugen (pegaptanib). This is a VEGF receptor that binds to one form of VEGF. It has been successful in stabilizing vision, but not in producing improvements.
Lucentis (ranibizumab) is a monoclonal antibody fragment that targets VEGF, and is approved for wet age-related macular degeneration. According to Reference 2, this is the first treatment that can actually improve the patient's visual acuity.
Avastin (bevacizumab) is a complete monoclonal antibody that targets VEGF. It is not yet FDA approved for eye conditions, but it is currently being studied in 1,075 clinical trials, of which 103 are for macular degeneration and 127 for retinopathy. It is approved for breast cancer, colorectal cancer, lung cancer, glioblastoma, and kidney cancer.
Before the introduction of VEGF inhibitor drugs, the primary treatment for macular degeneration was photodynamic therapy, with the drug Visudyne (verteporfin) injected into a vein to direct the laser to the leaky blood vessels. This treatment helps stop the progression of the disease, but it is not a cure and may cause scarring. Multiple treatments may be required, as new blood vessels continue to grow.
Unfortunately, drug treatment for macular degeneration is not as simple as taking a pill. The drugs must be injected into the eye, in a procedure not much simpler than the laser surgery.
References:
Amy L. Sutton, ed, “Eye Care Sourcebook”, Omnigraphics, 2008.
Joussen AM et al, “The treatment of wet age-related macular degeneration”, Deutcsches Arzteblatt International 2009; 106(18): 312-7.
Macugen web site:
http://www.macugen.com/
Lucentis web site:
http://www.lucentis.com/
Avastin web site:
http://www.avastin.com/avastin/patient/index.m
American Macular Degeneration Foundation web site:
http://www.macular.org/news/aarpvegf.html
Bevacizumab (Avastin) clinical trials:
http://clinicaltrials.gov/ct2/results?term=bevacizumab
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.
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