The leading cause of blindness in the elderly is a progressive eye disease called macular degeneration, which in its most serious, or “wet,” form is caused by abnormal blood vessel growth and subsequent blood leakage in the eye. Current treatments use lasers or light-activated drugs to clot these vessels but are generally ineffective; fewer than 3 percent of patients show improved vision following treatment. But in an emerging area of biotechnology, a small New York City company believes it sees a better approach. The key is a biomolecule that stops blood vessels from growing. Injected into the eye, a short piece of artificial RNA, called an aptamer, sticks to proteins that cause abnormal blood vessel growth and inactivates them.

The treatment, which is being developed by Eyetech Pharmaceuticals, showed promise in early clinical trials that ended last year; 80 percent of patients showed stable or improved vision and 26 percent showed significant improvement three months after a single treatment. The drug, called Macugen, “is highly promising,” says Nobel laureate David Baltimore, president of Caltech, who counts the treatment among potential new biotech breakthroughs. “It would be a wonderful validation of this unlikely but very powerful technology.”

Indeed, aptamers could work against other diseases, too. Regado Biosciences, in Durham, NC, is developing aptamer drugs that treat cardiovascular disease by attacking proteins that cause blood clots. Other companies are in the early stages of searching out aptamers that treat inflammatory disease and infection in a similar, protein-attacking fashion, part of a growing trend toward RNA-based medicine (see “Prescription RNA,” TR December 2002/January 2003).

But even if those other applications don’t pan out, big bets are being placed on aptamers as a cure for the most serious form of macular degeneration. Last December, Pfizer inked a $745 million licensing deal with Eyetech, which has launched an advanced clinical trial that could eventually lead to approval from the U.S. Food and Drug Administration. To be sure, aptamers are still in their infancy. But it’s a technology that may prove visionary.