254Goats Engineered To Provide Meds In Milk
- Jan 7, 2009Drug from genetically engineered goats a first
WASHINGTON You've heard of making cheese from goats' milk, but
prescription drugs? In what would be a scientific first, an
anti-clotting drug made from the milk of genetically engineered goats
moved closer to government approval Wednesday after experts at the
Food and Drug Administration reported that the medication works and
its safety is acceptable.
Called ATryn, the drug is intended to help people with a rare
hereditary disorder that makes them vulnerable to life-threatening
Its approval would be a major step toward new kinds of medications
made not from chemicals, but from living organisms genetically
manipulated by scientists. Similar drugs could be available in the
next few years for a range of human ailments, including hemophilia.
ATryn was developed by a Massachusetts biotechnology company, GTC
Biotherapeutics, by altering the genes of goats so they would produce
milk rich in antithrombin, a protein that in humans acts as a natural
About 1 in 5,000 people don't produce enough of the protein, putting
them at risk of developing blood clots in their veins. Such clots can
be extremely painful. If they break loose and travel through the
bloodstream to the lungs or the brain, the consequences can be
catastrophic. Pregnant women with the disorder are at high risk of
miscarriage or stillbirth, because of blood clots in the placenta.
In their everyday lives, patients with antithrombin deficiency are
managed with conventional blood thinners. That would not change. ATryn
is for use only when patients are undergoing surgery or having a baby,
times when the risk of dangerous clots is particularly high. Those
patients would receive the drug by intravenous infusion for a limited
time before and after their procedures.
Karen Janes of Santa Fe, N.M., whose teenage daughter Mary Karen died
of a brain clot linked to the disorder, said the issue is whether the
drug works, not how it is made.
"I think this goat thing is just wonderful," said Janes. "I do want
this drug to go through all the rigors of testing by the FDA. But if
it can work, and it can save other families from what we went through,
I think that's marvelous." Her daughter died in 1998.
Scientific advisers to the FDA will weigh the risks and benefits of
ATryn at a meeting Friday, and make a recommendation on approval. The
FDA will make the final decision.
"It's the first time we've held an advisory committee meeting on any
product from a genetically engineered animal," said FDA spokeswoman
Siobhan DeLancey. If the drug is approved, the FDA may require
follow-up monitoring to make sure that patients' immune systems don't
start making antibodies in reaction to the medication.
"I think this is an important tipping point," said Geoffrey Cox,
chairman of GTC, the drug maker. "The real dramatic thing that is
happening here is that we've been able to reduce some very clever
science to the practical level of producing a drug that's safe and
efficacious. Those things aren't trivial."
To make the drug, scientists at GTC put DNA for the human antithrombin
protein into single cell embryos of goats. Goat embryos with the gene
were then inserted into the wombs of surrogate mothers who gave birth
to baby goats carrying the new trait.
The first of these goats were called the "founders." Their offspring
also carry the gene. The females produce high levels of antithrombin
in their milk, from which the protein is collected and purified.
GTC's production comes from a herd of about 200 goats on a farm in
central Massachusetts, milked twice a day. They look no different from
any other goats.
Up to now, antithrombin has been produced from blood products
collected from human donors. Making the protein from goats may be
better for humans, said Dr. Stephan Moll, a hematologist at the
University of North Carolina, Chapel Hill, who consults for the
company. It would ensure a steady supply and reduce concerns about
"It's a new mechanism by which drugs could be produced in pretty large
volume in the future," said Moll, who is also a top medical adviser to
the National Alliance for Thrombosis and Thrombofilia, a group that
represents patients with the blood disorder.
ATryn has already been approved in Europe.