For the first time in a quarter of a century, researchers have identified a new treatment for diabetic macular edema, a potentially blinding disorder that affects about 1 million Americans, researchers said Tuesday.
The treatment uses a drug called ranibizumab, which when administered in combination with laser phototherapy is twice as effective at reversing vision loss as laser therapy alone. Laser therapy to prevent leakage of blood vessels in the retina has been the gold standard since it was introduced in 1985. The findings were reported online in the journal Ophthalmology.
"This will have a major impact on how ophthalmologists will treat macular edema in people with diabetes," said Dr. Neil M. Bressler of the Wilmer Eye Institute at Johns Hopkins University, who led the study. The drug, sold under the brand name Lucentis, is already approved for treatment of macular degeneration, and physicians can use it off-label to treat macular edema, he said.
Macular edema is a form of diabetic retinopathy, which is the most common cause of vision loss in working-age Americans. It is marked by leakage of small blood vessels in the retina, the light-sensitive portion of the eye.
When fluid accumulates in the center of the retina — the macula — the condition is called macular edema. Increased pressure damages the cells, impairing vision. Because the macula is the most important part of the retina for reading, driving and recognizing faces, macular edema can be severely disabling.
Ranibizumab, manufactured by the biotech company Genentech, is what's known as a monoclonal antibody — a protein created to bind to a molecule in a specific way. Injected into the eye, it slows leakage by blocking the receptor for a hormone called vascular endothelial growth factor, or VEGF.
Bressler's team studied 691 diabetics at 52 clinical centers. Some had both eyes treated, for a total of 854 eyes. Patients were divided into four groups — receiving either ranibizumab plus prompt laser treatment, the drug plus delayed laser treatment, laser treatment plus an injected steroid called triamcinolone, or laser treatment plus a sham injection.
After a year of follow-up, nearly 50% of those receiving Lucentis had a visual improvement of two lines on a vision chart, meaning they could read letters that were at least a third smaller than they could read before the study. It didn't matter whether laser treatment was prompt or deferred.
About 28% of those receiving laser treatment alone or in combination with triamcinolone had a similar improvement. But though there were very few complications related to Lucentis — primarily infections associated with the injection — about 30% of those receiving triamcinolone developed high intraocular pressure requiring treatment, and 60% developed cataracts requiring surgery.
The trial was funded by the National Eye Institute, but Genentech donated the expensive drug and contributed $9 million to the cost of the trial.
After earlier small studies suggested that such treatment could benefit macular edema patients, some ophthalmologists have been using Genentech's anti-cancer drug Avastin, which also blocks VEGF receptors, to treat the condition macular edema because it is much cheaper. It costs less than $100 per dose, compared with about $2,000 for Lucentis, and the eye institute has been criticized for testing Lucentis rather than the cheaper drug.
Dr. Frederick L. Ferris III, the institute's clinical director, acknowledged at a news conference that Genentech's financial contributions to the trial had swayed the decision-making process.