A drug qualifies as an orphan if the disease it treats affects fewer than 200,000 people in the United States. There are about 6,000 such diseases recognized today, affecting an estimated 25 million Americans. Some are obscure, like Pompe disease. Better-known ones are Tourette's syndrome and ALS (Lou Gehrig's disease).

The Orphan Drug Act provides incentives for commercial development of treatments. It allows for extended exclusive marketing rights to give drug and device makers the chance to recoup some of their research and development expenses. Genzyme, the Massachusetts company that will manufacture the Pompe disease drug Myozyme, has exclusive marketing rights for the next seven years.

The Office of Orphan Products Development, which administers the act, awards about $14 million a year in grants to support clinical trials of orphan drugs. Duke University Medical Center and UNC Hospitals have been frequent recipients.

Dr. Marlene Haffner, the office's director, said the results of the federal government's investment speak for themselves.

Since 1983, when the law took effect, 288 drugs and biological products have been brought to market, she said. In the decade before 1983, just 10 treatments for orphan diseases were introduced commercially.

The National Institutes of Health recently established a new clinical research network that will expand work in 10 rare disease categories and create a centralized information system to share study results internationally. The project is supported with a five-year, $71 million award from NIH.

Duke and UNC have both been selected as research sites in the new Rare Diseases Clinical Research Network.