The US Food and Drug Administration on Tuesday approved Hemgenix, a new drug to treat hemophilia. Manufacturer CSL Behring set the price at $3.5 million per treatment, making it the most expensive drug in the world.

Hemgenix is a gene therapy to treat adults with hemophilia B, a genetic bleeding disorder in which people do not produce a protein needed to create blood clots. About 1 in 40,000 people have the disease, most of whom are men.

"Gene therapy for hemophilia has been on the horizon for more than two decades. Despite advancements in the treatment of hemophilia, the prevention and treatment of bleeding episodes can adversely impact individuals' quality of life," Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said in a statement. "Today's approval provides a new treatment option for patients with Hemophilia B and represents important progress in the development of innovative therapies for those experiencing a high burden of disease associated with this form of hemophilia."

The Institute for Clinical and Economic Review, an independent nonprofit research organization that analyzes the value of prescription drugs and other medical products, confirmed for CNN that Hemgenix is now the most expensive drug in the world.

In a recent cost-effectiveness analysis of the drug, weighing health benefits against offset costs, ICER suggested that a fair price for the drug to be between $2.93 million and $2.96 million.

FDA approved Hemgenix based on safety and effectiveness evaluated in two studies of about 60 adult men. The most common side effects included high liver enzymes, headaches, flu-like symptoms and mild infusion-related reactions.