While some argue whether genetic engineering of animals is ethical, the FDA has approved the first drug made from a just such an animal.

The drug, ATryn, is made from milk from goats that have had their DNA altered to produce more of a substance called antithrombin, which serves as a blood thinner. The company GTC Biotherapeutics said regulators approved the drug to treat patients with a rare hereditary disorder that puts them at high risk of deadly blood clots, according to The Associated Press.

Scientists put a snippet of DNA for the human antithrombin protein into goat embryos, AP explained. The embryos are inserted into the wombs of surrogate goat mothers who produce baby goats that in turn make the medicinal milk.

Other genetic engineering efforts aim to produce human organs, perhaps in pigs, for transplant.

The FDA issued guidelines last month to govern genetic engineering of animals. "Developers of these animals must demonstrate that the construct and any new products expressed from the inserted construct are safe for the health of the GE animal and, if they are food animals, for food consumption," the guidelines state.

“Genetic engineering is a cutting edge technology that holds substantial promise for improving the health and well being of people as well as animals," said Randall Lutter, deputy commissioner for policy at the FDA.