Last Friday, the U.S. Food and Drug Administration approved the first drug made by animals carrying a human gene. The drug, a protein called antithrombin that prevents fatal blood clots, is excreted by goats into their milk, and then purified. Though patients have been taking drugs made by animals for many years now, including insulin (and more notoriously, heparin), these goats are the first herd of animals genetically engineered to serve as drug factories. The animals were bred by the company GTC Biotherapeutics and are maintained on a farm in Massachusetts.

The New York Times reports that the approval will open the way for other such drugs:

The F.D.A.’s move “really takes away one of the biggest issues that have always been on the table, which is how do regulatory agencies view this kind of technology,” said Samir Singh, president of the American operations of Pharming, another company using such technology.

Two years ago I wrote about transgenic chickens that produce high levels of protein drugs in their eggs. At that time, researchers speculated that poultry would be easier to “pharm” than mammals. However, both chicken-pharming companies I mentioned in the 2007 story appear to have gone under. In August the SEC revoked Viragen’s stock, and Avigenics’ website has disappeared.

The Times reports that animal-rights groups are worried; the story quotes assurances from the company that none of the goats’ milk or flesh will make it into the food supply. Making drugs in giant vats of microbes called bioreactors doesn’t raise quite as many issues for animal-rights and bioethics groups as does pharming, but it has some limitations. The reactors are expensive to maintain, and bacteria can’t make every protein drug, because they simply can’t perform the extensive protein-processing of which animal cells are capable.