a1 U.S. Food and Drug Administration
Orphan drug products generally are used in treating or preventing rare diseases. The small number of patients available for study may create special problems in the evaluation of these products. This paper examines some of the special problems that are associated with the design and implementation of studies to evaluate the safety and efficacy of orphan drugs. The U.S. Food and Drug Administration (FDA) has not established special criteria for evaluating orphan drugs per se, but the FDA has been flexible in evaluating drug products that present special problems, especially when these products are for treatment of serious of life-threatening illnesses. The FDA and other U.S. governmental agencies also have taken steps to promote the development and availability of drugs for rare diseases, including making these products available to patients who are in need, even before the drugs have full FDA marketing approval.