The results of two large, randomized clinical trials published October 5, 2006, in the New England Journal of Medicine demonstrate that the drug ranibizumab is an effective treatment for neovascular macular degeneration, a complication of age-related macular degeneration that leads to the vast majority of legal blindness associated with the disorder.
In an accompanying editorial, Howard Hughes Medical Institute investigator Edwin M. Stone at the University of Iowa contends that now that these trials have shown the drug's "miraculous" effects on patients' eyesight, a crucial next step is to compare ranibizumab to a related drug, bevacizumab. Although it is not FDA-approved for use in the eye, bevacizumab also appears to be effective in treating neovascular macular degeneration. Importantly, a single dose of bevacizumab costs less than $150, compared to more than $2,000 per dose for ranibizumab.
Both ranibizumab and bevacizumab work by inhibiting a protein known as vascular endothelial growth factor (VEGF), which promotes blood vessel growth. Bevacizumab was originally designed to block blood vessel growth in tumors, halting cancer cells' growth by eliminating their oxygen supply. In 2004, bevacizumab, which is marketed by Genentech under the brand name Avastin, was approved by the FDA for the treatment of metastatic colon cancer.
In neovascular macular degeneration, new blood vessels grow underneath the retina, altering the eye's structure and function. Only about 10 percent of patients with macular degeneration develop neovascularization, but in those who do, the effects are often severe. While blocking blood vessel growth is exactly what doctors who treat neovascular macular degeneration would like to do, some scientists suspected bevacizumab might be too large a molecule to reach the part of the eye where it was needed. Ranibizumab is a smaller molecule, specifically designed to eliminate this problem.