Rabbits Milked for Human Protein; Drug Soon for Sale?

December 1, 2009

Dutch farmers are ready to start commercially milking rabbits, pending authorization from European authorities.

But that doesn't mean bunny cheese will soon be on store shelves—the genetically engineered rabbits would be milked to churn out a potentially lifesaving drug.

Developed by Netherlands-based biotech firm Pharming, the rabbits have been outfitted with a human gene that produces a protein called C1 inhibitor.

A drug made from the protein can be used to treat people with hereditary angioedema. People with this condition have naturally low levels of C1 inhibitor, which can result in episodes of severe swelling, similar to an allergic reaction.

Untreated, angioedema can cause painful cramps and potentially fatal suffocation.

Unlike drugs that can be made synthetically in the lab, therapeutic proteins need to be made by biological processes, making transgenic animals a popular option.

A rabbit, for instance, can produce an average of 120 milliliters of milk a day. In the modified rabbits, each liter contains 12 grams of human C1 inhibitor, according to Pharming spokesperson Marjolein van Helmond.

"Human C1 inhibitor can be obtained from donor blood, but our … product can be produced in unlimited quantities from a scaleable and stable production system, and there are no safety issues in terms of [blood] viruses," van Helmond said.

Rabbit Farming

Pharming has been milking rabbits experimentally for years, and recently developed a drug called Rhucin from the rabbit milk-derived C1 inhibitor protein.

In September Pharming submitted Rhucin for market approval by the European Medicines Agency, the European Union body that evaluates drug safety. An official verdict is due later next year. The drug has yet to be submitted for commercial approval in the United States.

If the drug is approved in Europe, Pharming would start milking a herd of about a thousand rabbits, company CEO Sijmen de Vries said in an email.

The rabbits are milked using mini pumping machines that attach to the female rabbits' teats. The method "can roughly be compared to cow milking, but of course on a smaller scale," de Vries said.

And like dairy cows, the rabbits stay relaxed and appear to suffer no discomfort during milking.

Researchers then extract the protein in the lab. Due to strict laws governing transgenic products, the rest of the rabbit milk has to be destroyed.

Easy Breeding

The Dutch bunnies wouldn't be the first animals milked in the name of human health.

A farm in Russia, for example, recently milked mice to produce the human breast milk protein lactoferrin, and the Russian researchers hope to scale up to milking the protein from goats.

But rabbits are particularly well suited to producing certain types of complex proteins that may lead to other new medicines, according to de Vries.

For instance, transgenic bunnies are also being investigated for potential treatments for stroke victims and organ-transplant patients.

"Breeding processes are relatively fast [compared to cattle and goats], and milk production sufficient," de Vries said.




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