Thursday, February 15, 2007
Wired reports: [edited]
With its tranquil ponds and rolling fields, the GTC Biotherapeutics farm in Charlton, Massachusetts, looks like a typical pastoral retreat. But its 1,400 goats don't produce butter or cheese. Instead, the animals are sophisticated drug incubators, with millions of dollars of potential profit accumulating in their udders each day.
GTC Biotherapeutics is perfecting the art of "pharming" - genetically modifying animals to churn out drugs for disorders like haemophilia and cancer. The first government-approved drug from transgenic animals, GTC's anti-clotting agent ATryn, was approved in Europe late last year, vindicating biotech's years-long quest to move animal husbandry in entirely new directions.
The technique offers a way to produce large quantities of drugs that are otherwise difficult to develop. It involves genetic modification of an animal embryo's genetic makeup, or genome. Just after fertilization, "pharmers" insert into the embryo a human gene that codes for a particular protein - usually one that's produced naturally in humans, but that's lacking in people who have certain diseases.
They attach that DNA code with a gene that codes for a sugar found in mammalian milk, insuring that the therapeutic protein will be expressed only in the animals' milk or eggs.
GTC's ATryn contains the human protein antithrombin, which helps prevent blood clots that could lead to a stroke or heart attack. About one in every 5,000 people has a genetic deficiency of this protein. The drug is also administered during surgery because excessive bleeding can lower blood levels of the protein, leading to clots.
Antithrombin is typically extracted from human blood plasma donations, but it's present only in very small quantities. That makes soliciting donors and extracting proteins from the plasma expensive and labour-intensive.
But now that GTC's goat herd has reached critical mass, the protein can be harvested in massive quantities. "Each of our goats can produce a kilogram of antithrombin each year," Cox says. "It takes 50,000 people to donate that same amount."
Catherine Willett, a science policy advisor for People for the Ethical Treatment of Animals, stressed the welfare issues.
"Genetic engineering is responsible for a skyrocketing increase in the numbers of animals being used in laboratory experiments," she said. "(and) is likely to have drastic long term ill-effects in the animals themselves."
But Origen scientist Marie Cecile Van de Lavoir said the potential human health benefits justify tinkering with nature's plan.
"If a transgenic animal produces a great cancer therapy," she says, "I won't hear anyone saying, 'You shouldn't do that.'"