(Adds details on drug) WASHINGTON, Jan 16 (Reuters) - Australian company CSL Ltd <CSL.AX> won U.S. approval on Friday to sell an intravenous treatment for a bleeding disorder seen in patients with a rare genetic defect. The Food and Drug Administration cleared the product, Riastap, for people with congenital fibrinogen deficiency. The disorder limits the blood's ability to clot and puts patients at risk of life-threatening bleeding without treatment, the FDA said. Between 150 to 300 people in the United States have the condition, the agency said. Riastap is made from human plasma by the company's CSL Behring unit and is already sold in Europe. The product's U.S. approval was supported by a study that showed an increase in clot firmness for 14 of 15 patients, the FDA said. Further study of the drug's benefit will be required after it reaches the market. Fever and headache were the most common reactions reported, the FDA said. (Reporting by Lisa Richwine, editing by Leslie Gevirtz)
