Comparison of AMD Treatments Trials (CATT) Q&A

What is the CATT?

The Comparison of AMD Treatments Trials (CATT) was a National Eye Institute (NEI)-funded clinical study aimed at identifying the best-possible drug and treatment regimen for the wet form of age-related macular degeneration (AMD). The CATT showed that Lucentis and Avastin, two similar drugs used to treat wet AMD, are equally effective.

What is AMD?

AMD is the most common cause of legal blindness among older Americans. AMD distorts central vision, which is necessary for daily tasks such as reading and driving. Severe AMD can cause severe loss of central vision resulting in legal blindness.

What are the retina and macula?

The retina is the layer of light-sensing tissue that lines the back of the eye. When stimulated, cells of the retina signal the brain. The macula is the central portion of the retina that allows us to see fine visual detail.

What is AMD?

AMD exists in forms: dry and wet.

Dry AMD, an early stage of the disease, occurs when fatty deposits accumulate in the macula. These deposits, known as drusen, can distort central vision. Letters may appear distorted or straight lines may seem warped or curved. In geographic atrophy, an advanced stage of dry AMD, large areas of the retina die.

Wet AMD occurs when abnormal blood vessels grow behind the macula. The new blood vessels are fragile and tend to leak fluid, which raises the macula from its normal place at the back of the eye, distorting vision.

Both geographic atrophy and wet AMD can lead to profound loss of central vision and legal blindness.

What is Avastin?

Avastin® is the brand name of the drug bevacizumab, which is used "off-label" to treat wet AMD. Avastin is made by Genentech, Inc., and was approved in 2004 by the U.S. Food and Drug Administration (FDA) to treat colon cancer. Avastin inhibits a protein called vascular endothelial growth factor (VEGF). People with wet AMD express high levels of VEGF, which has been shown to promote blood vessel growth.

What is Lucentis?

Lucentis® is the brand name of the drug ranibizumab. Like Avastin, Lucentis is made by Genentech and also inhibits VEGF activity. Genentech specifically developed Lucentis to treat wet AMD. In 2005, Genentech showed in clinical trials that monthly Lucentis eye injections improved vision in participants with wet AMD. Shortly after Lucentis trial results were announced, but before Lucentis became available, ophthalmologists began successfully treating AMD patients off-label with the similar Avastin.

Why did the NEI compare the two drugs?

The NEI conducted the CATT to determine the best treatment for wet AMD. When the CATT was launched in 2008, the majority of AMD patients were being treated with Avastin. However, it was unknown how the two drugs compared.

Who participated in the CATT?

More than 1,100 people, average age 79 years, with wet AMD participated in the CATT. All participants had untreated, active wet AMD and visual acuity between 20/25 and 20/320. The CATT comprised 43 clinical centers across the U.S.

How often did CATT participants receive injections?

The CATT assigned participants to one of four treatment groups: 1) monthly Lucentis injections, 2) monthly Avastin injections, 3) as-needed Lucentis injections, or 4) as-needed Avastin injections.

The CATT compared monthly and as-needed treatment regimens for two reasons: 1) Genentech-sponsored Lucentis trials tested only monthly dosing, and 2) ophthalmologists, prior to the CATT, were typically injecting Avastin as-needed, based on evaluation of the macula. Ophthalmologists had adopted the Avastin as-needed regimen based on anecdotal reports in the scientific literature; not evidenced-based clinical trials. As-needed Avastin injections were typically given less frequently than once a month.

What did the CATT measure?

The CATT compared visual acuity-measured by eye chart readings- before and after one year of treatment. The CATT also measured the incidence of side effects, such as eye infection, stroke, or heart attack.

What were the CATT results?

When injected either monthly or as-needed, the two drugs yielded virtually identical improvement in vision.

Which is safer, Avastin or Lucentis?

The occurrences of side effects were similar for both drugs. Although participants in the Avastin group had slightly more serious side effects, notably hospitalizations, the number of CATT participants was not large enough to determine whether the increase was due to the study drug or random chance. Side effects were distributed across many different conditions, most of which were not associated with Avastin in cancer clinical trials where the drug was administered at 500 times the dose used for AMD.

Are monthly injections better than as-needed injections?

The CATT concluded that injecting Lucentis or Avastin only when signs of disease were present was just as effective as regular monthly injections. In the CATT, participants given as-needed injections were given, on average, 4 to 5 fewer injections per year. However, people with wet AMD should have their eyes checked for disease activity at least once a month.

Which drug is best for me?

It is best to talk with your doctor to determine which drug is best for you.

Are Avastin and Lucentis effective treatment for dry AMD or geographic atrophy?

No.

What is the NEI?

The NEI is part of the National Institutes of Health and is the Federal government's lead agency for vision research that leads to sight-saving treatments and plays a key role in reducing visual impairment and blindness. The NEI also provides health information about visual disorders.

Resources about AMD

For more information about AMD, visit www.nei.nih.gov/health/maculardegen.
For more information about the CATT, visit www.nei.nih.gov/catt.

Posted: September 29, 2011