EDINBURGH, Jan 14: Scientists have created the world’s first breed of designer chickens, genetically modified to lay eggs capable of producing drugs that fight cancer and other life-threatening diseases.

According to a report in Sunday Times, researchers at the Roslin Institute near Edinburgh, which created Dolly the cloned sheep, have bred a 500-strong flock of the birds.

The breakthrough offers the prospect of mass-producing drugs that currently cost the NHS thousands of pounds a year per patient, at a fraction of the price.

The ISA Browns, a common breed of egg-laying hen, have each had human genes added to their DNA to enable them to produce complex medicinal proteins. These human proteins are secreted into the whites of the birds’ eggs, from which they can be easily extracted to produce drugs.

The Roslin scientists have achieved a world first in creating birds that “breed true”, meaning the added human genes are passed on from generation to generation. This opens the way for the creation of industrial-scale flocks and offers a potentially unlimited cheap source of medicinal proteins.

One of the chicken lines produces human interferon of a kind closely resembling a drug widely used to treat multiple sclerosis. Such drugs have a potential worldwide market worth hundreds of millions. Another line could be useful in treating skin cancer, by producing miR24, an antibody that could also potentially treat arthritis, which afflicts 7m people in Britain.

The institute is understood to have created at least two other lines of genetically modified chicken, whose eggs could produce drugs with the potential to fight cancer.

The research is a triumph for Dr Helen Sang, the leader of the Roslin team who, since 1997, has sought to make the technique work without new genes being lost as they are transmitted down the generations. Ian Wilmut, the Edinburgh University professor who created Dolly at Roslin, was an adviser on the project.

“This is potentially a very powerful new way to produce specialised drugs,” said Dr Karen Jervis of Viragen Scotland, a biotech company that is working closely with Roslin. “We have bred five generations of chickens so far and they all keep producing high concentrations of pharmaceuticals.”

Other researchers have already produced transgenic chickens — with artificially altered DNA — but the ability to make desirable proteins has generally vanished in a generation or two.

At present, therapeutic proteins are mainly made in bio-reactors, vats of bacteria or other cells that have been genetically modified. However, extracting the relevant proteins is expensive and difficult.

In Roslin’s research — to be published in the Proceedings of the National Academy of Sciences tomorrow — the scientists will describe how they extracted embryonic cockerels from hens, before the eggs had formed.

The embryos, just small clusters of cells, were then each injected into surrogate eggs and “infected” with a virus genetically modified to contain human genes. These genes contained the blueprint for the human proteins that the researchers were trying to produce.