The FDA recently issued this draft guidance to assist industry in drug development to combat rare diseases.
10% of people will get a rare disease. That sounds strange because a rare disease is, well, rare. It is defined (by the Orphan Drug Act of 1983) as a disorder or condition that affects fewer than 200,000 people in the U.S., and most rare diseases affect far fewer people. The reason so many people get rare diseases is that there are a lot of rare diseases — 7,000 in total.
The challenges to develop drugs to treat rare diseases are great. As the FDA explains, the problems are not just financial. Because relatively few people suffer from rare diseases, medical understanding of the diseases lag and there tend to be few definitive study results that demonstrate potential treatments are safe and effective.