ATryn is the brand name of the anticoagulant antithrombin made from the milk of goats that have been genetically modified to produce human antithrombin, a plasma protein with anticoagulant properties. It is a product of Massachusetts-based U.S. company GTC Biotherapeutics. ATryn is the first medicine produced using genetically engineered animals. Genetically modified goat can produce the same amount of antithrombin in a year as 90,000 blood donations. Goats were chosen rather than cattles because they reproduce more rapidly than cattle and produce more protein than rabbits or mice. On February 6, 2009, ATryn was approved by the U.S. Food and Drug Administration (FDA) for treatment of patients with hereditary antithrombin deficiency who are undergoing surgical or childbirth procedures.