The U.S. Food and Drug Administration (FDA) on March 16, 2007, approved the orphan drug eculizumab (Soliris) for the treatment of paroxysmal nocturnal hemoglobinuria (PNH), a rare blood disorder that affects approximately one in a million people. It is the first drug to be approved for this disorder.

“This product is important in that it offers a treatment other than blood transfusion that may help this small population of patients who are often very ill,” said Steven Gatson, MD, MPH, director of the Center for Drug Evaluation and Research at FDA. “This approval is one of multiple examples of how the orphan products program can benefit the public health with urgently needed products that would otherwise not be commercially available.”

Soliris was designated an “orphan” drug in 2003. This designation is for products being developed to treat diseases or conditions affecting fewer than 200,000 Americans. The manufacturer who obtains marketing approval for a designated orphan product is given seven years of marketing exclusivity.

PNH is characterized by abnormal development of red blood cells. When the abnormal cells are present in the bloodstream, naturally-occurring proteins that are components of the body’s immune system attack them and break them down. This causes anemia and may result in pain, fatigue, debilitating weakness, the need for frequent blood transfusions, and blood clots. In severe cases, the disease may lead to life-threatening heart attacks and strokes.

Soliris doesn’t cure PNH but it works to halt the destruction of red blood cells. It is a new molecular entity that contains an ingredient not previously marketed in the United States. The drug was developed by Alexion Pharmaceuticals, Inc., of Cheshire, Ct.

Because the drug acts by blocking certain actions within the body’s natural immune system, it carries a potential risk of increasing susceptibility to certain serious infections, particularly meningococcal infections. A special risk management plan has been developed for patients taking the drug to address this risk.