May 9, 2011

Comparing Treatments for Age-Related Eye Disease

Photo of children with the center severely blurred A scene as it might be viewed by a person with age-related macular degeneration.

The first year of a 2-year clinical trial has shown that a colon cancer drug used off-label to treat age-related macular degeneration (AMD) is as effective as another medication that’s FDA-approved to treat the disease.

AMD is the leading cause of blindness and vision loss in older Americans. It affects the macula, a region at the back of the eye that gives you detailed central vision. AMD comes in 2 forms: wet and dry. In the “wet” form, abnormal blood vessels grow and leak fluid and blood under the macula. When the macula is damaged, patients can lose the ability to drive, read and recognize faces.

Avastin and Lucentis are 2 drugs made by Genentech that limit blood vessel growth. Avastin was approved by the FDA in 2004 for treating colon cancer. Genentech later developed Lucentis, derived from a protein similar to Avastin, for injection in the eye to block blood vessel growth in AMD. In 2005, Genentech-sponsored clinical trials established Lucentis as highly effective for the treatment of wet AMD. The FDA approved the treatment in 2006.

During the year between the announcement of the Lucentis trial results and its release, ophthalmologists began injecting AMD patients with low doses of Avastin. While Avastin isn’t licensed for treating AMD, it is similar to Lucentis and was already available. Many noticed improvements with Avastin, but a formal clinical trial comparing the 2 drugs hadn’t been done.

The Comparison of AMD Treatments Trials (CATT) was launched by NIH’s National Eye Institute (NEI) to compare the effectiveness of Avastin and Lucentis. The study tested monthly dosing, which Genentech’s Lucentis trials had used, or dosing as needed (called pro re nata, or PRN), as doctors had used for Avastin treatment of AMD. The results from the first year of data were published online in the New England Journal of Medicine on April 28, 2011.

The researchers found no difference between Avastin and Lucentis in the ability of patients to read letters on an eye chart. Both drugs improved sharpness of vision. A monthly schedule with either drug yielded greater visual gains than PRN, but the PRN schedule still gave patients substantially improved vision. Lucentis led to a greater reduction in fluid under the retina, requiring slightly fewer PRN injections.

“In addition to the primary finding of equivalence between Lucentis and Avastin for visual acuity, CATT also demonstrates that PRN dosing is a viable treatment option for either of these drugs,” says CATT study chair Dr. Daniel F. Martin, chairman of the Cole Eye Institute at the Cleveland Clinic. “Substantial visual acuity gains may be accomplished with a lower treatment burden.”

The researchers saw serious adverse events in 24% of the patients receiving Avastin and 19% of those receiving Lucentis. However, they couldn’t definitely link these adverse events to the treatments. These events varied broadly and were in a population with a median age over 80. The researchers will collect more information on the long-term effects of the drugs during the trial’s second year.

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