Pharma Products Made in Transgenic Animals
The first therapeutic protein produced in the milk of transgenic animals to be approved for marketing was antithrombin, an anticoagulant protein that can be administered prophylactically to treat patients with a congenital deficiency. In the United States, a company called GTC Biotherapeutics (Framingham, MA) markets recombinant antithrombin purified from the milk of transgenic goats under the trade name ATryn.17 The European Medicines Agency approved this drug for clinical use in August 2006, and the U.S. Food and Drug Administration did so in February 2009.
Recombinant proteins designed for industrial use have also been produced in transgenic farm animals. For example, dragline silk made by orb spiders is the strongest known material by weight. After scientists isolated the genes coding for spider silk, they attempted without success to produce this material in bacteria and mammalian cell culture. In 2001, however, scientists at Nexia Biotechnologies in Canada inserted genes coding for spider silk proteins into goat embryos. When the transgenic goats matured, the spider genes were expressed in the mammary glands of females, which began to secrete tiny strands of spider silk in their milk. The strands were purified and spun into a fine thread, which can be further processed into a light, tough, flexible material suitable for use in military uniforms, medical sutures, and tennis racket strings.19