On Feb. 6, 2009, the U.S. Food and Drug Administration (FDA) approved the first genetically engineered animal for production of a recombinant form of human antithrombin.

ATryn, a recombinant form of human antithrombin developed by rEVO Biologics, formerly GTC Biotherapeutics, was approved by the FDA for the prevention of peri-operative and peri-partum thromboembolic events in hereditary antithrombin deficient patients. Atryn is made from the milk of goats that have been genetically modified to produce human antithrombin.