U.S. FDA approves Novo Nordisk's drug for rare blood clotting disorder

(Reuters) - The U.S. Food and Drug Administration said on Monday it has approved Novo Nordisk's drug Tretten to prevent bleeding in patients with a rare blood clotting disorder. Patients with congenital Factor XIIIA-subunit deficiency do not make enough of the Factor XIII protein that is important for normal blood clotting, the FDA said. Factor XIII is composed of subunits A and B and Factor XIII deficiency is usually caused by a deficiency of the A subunit. Tretten was studied in 77 patients with the disorder and was effective in preventing bleeding in 90 percent of the patients when given monthly, the FDA said. Side effects included headache, pain in the extremities and at the injection site. Congenital Factor XIII affects an estimated one in 3 million people globally and is associated with life-threatening bleeding, impaired wound healing and miscarriage. The drug is expected to generate sales of $84 million by 2018, according to the average estimate of three analysts polled by Thomson Reuters. Novo Nordisk acquired the rights to Tretten from ZymoGenetics Inc in 2004. Novo agreed to pay a royalty on sales, although details of the royalty payment were not disclosed. ZymoGenetics was acquired by Bristol Myers Squibb Co in 2010. The product was approved last year in Europe and Canada. It is sold in Europe under the brand name NovoThirteen and contains the active substance catridecacog, which is structurally the same as the human Factor XIII A subunit. It is produced by genetically engineered yeast cells. (Reporting by Toni Clarke in Boston; Editing by Alden Bentley and Bill Trott)