Chronic fatigue syndrome (CFS), an unexplained fatigue not due to exertion and not relieved by rest, is recognized by the U.S. Centers for Disease Control and Prevention and treated through a variety of pharmaceutical and psychological means. Unfortunately, CFS has no validated biochemical markers and is diagnosed by assessing symptoms and eliminating other possible medical conditions.

The challenge for companies running clinical trials is thus to design studies with sufficiently rigorous entry criteria and end points to pass regulatory scrutiny. In the upcoming Phase III trials of its Ampligen nucleic acid-based antiviral agent in CFS, Hemispherx Biopharma Inc. (HEB, Philadelphia, Penn.) must use end points that do not directly measure disease state to demonstrate improvement since CFS is a subjectively diagnosed disorder with possibly multiple underlying causes.