Retinal vein occlusion (RVO) is a common and serious cause of vision loss that affects an estimated 684,000 people each year in the United States. The loss of vision occurs when blood flow through a retinal vein becomes blocked, such as by a blood clot. The blockage causes swelling under the retina, called macular edema, and hemorrhages in the retina itself. Sudden blurring or vision loss in all or part of one eye is common with RVO. Branch RVO occurs when one of the branches of the main vein of the eye becomes blocked, while in central RVO the blockage occurs in the main vein of the eye, located at the optic nerve.

A significant advancement for the treatment of RVO has now been achieved. A phase 3 clinical trial showed that treatment with the angiogenesis inhibitor ranibizumab (Lucentis®) can improve vision in patients with macular edema due to branch RVO. Ranibizumab, which is already approved as an antiangiogenic treatment for age-related macular degeneration (AMD), is a monoclonal antibody targeting the protein VEGF (vascular endothelial growth factor), a primary mediator of angiogenesis in eye diseases and other conditions, including cancer. In people with RVO and AMD, VEGF causes blood vessels in the eye to leak and proliferate abnormally, causing hemorrhages that gradually destroy vision. Anti-VEGF therapies, such as ranibizumab, inhibit the growth of these vessels, and can halt or even reverse vision loss in patients.

The phase 3 study, named BRAVO, was a multi-center, randomized, controlled study enrolling 397 patients at 93 sites across the United States. BRAVO evaluated the safety and efficacy of 6 monthly injections of ranibizumab compared to monthly sham (control) injections. Patients treated with the two doses of ranibizumab studied (0.3 mg or 0.5 mg) showed a statistically significant improvement in best-corrected visual acuity — the best vision a person can achieve with an eyeglass or contact lens prescription — at 6 months compared to control treatments. The safety of ranibizumab was acceptable, with no new adverse events related to ranibizumab observed.

“Retinal vein occlusion is a difficult to treat eye disorder related to angiogenesis,” said Dr. William W. Li, President and Medical Director of the Angiogenesis Foundation. “The BRAVO results in RVO are another milestone for antiangiogenic therapy.”

The full results will be presented at the Retina Congress, which will take place from September 30 to October 4, 2009, in New York City.  Another phase 3 trial of ranibizumab for central RVO, named CRUISE, is expected to be completed later this year.