Scientists claim their GM chickens will be able to lay life-saving eggs

American scientists have developed a method of breeding genetically-modified chickens able to produce insulin and other life-saving drugs in their eggs.

American scientists have developed a method of breeding genetically-modified chickens able to produce insulin and other life-saving drugs in their eggs.

The work could open the way for large-scale production of revolutionary new drugs based on human proteins, which might now be manufactured inside the whites of chickens' eggs.

Scientists have long believed they can produce human proteins in milk from cows or other animals, but a US company listed on the London Stock Exchange will say today that it can produce commercial quantities of the proteins in chicken eggs.

Because the birds breed earlier and more often than large mammals, the company, Tran-XenoGen, believes it will revolutionise drug research and production.

Once fertilised, each hen can generate a brood of 120 chickens in six months, since gestation time is just 21 days. TranXenoGen says it will also be easier and more hygienic to extract the proteins from inside an egg than from milk.

The gene for a particular protein, for example insulin, is engineered in the laboratory and transferred into a fertilised egg to produce what is called a chimeric chicken. The chimeric chicken is then bred to produce offspring, some of which will be transgenic and contain the insulin gene. The eggs from the transgenic chickens will be screened for the insulin gene and the chicken producing the highest quantity of insulin will be selected for commercial production.

Insulin is in increasing demand as the number of cases of diabetes in the Western world balloons. An estimated 17million people have diabetes in the US alone.

Global demand for the drug is estimated to be £2bn and growing at 5 per cent a year.

The chickens are also likely to be able to produce human antibodies, which form the basis of a new class of drug to tackle diseases ranging from cancer to arthritis.

The average chicken lays around 300 eggs a year, each rich in protein. At the moment, a chronic shortage of human proteins is holding back disease research and raising doubts as to whether any drugs that result from the research could ever be made in large enough quantities.

Transgenesis, the insertion of genes from one animal into another, could break the bottleneck, said Edward Husband, biotechnology expert at Numis Securities, a City investment bank. "The production of proteins for therapeutic use is no small issue. Current contract manufacturing facilities are booked out for at least the next five years."

TranXenoGen is chaired by Kim Tan, who has founded a string of British biotechnology companies. It aims to be producing antibodies for biotech drugs by 2004, and commercial quantities of insulin by 2005.