The sheep, bred by the same Edinburgh-based team of researchers that produced Dolly, the world's first animal cloned from an adult cell, were grown from embryos into which fragments of human DNA had been inserted. This caused them to produce a protein, normally obtained from human blood, in their milk.
It is the first time that the Medicines Control Agency has given the go-ahead for a clinical trial involving a transgenic product. The drug, transgenic alpha-antitrypsin (TgAAT), will initially be given to 12 male patients at Papworth Hospital in Cambridge in order to assess its safety and tolerability. It will be compared with a placebo.
A further study at a later stage will examine the effects of the drug when administered to 60 cystic fibrosis patients over four weeks. This will be followed by a six-month trial involving 160 patients at up to 20 centres.
The drug is produced by PPL Therapeutics in the Roslin Institute, Edinburgh,
The biotechnology company was set up to exploit the genetic engineering and cloning techniques developed at the Roslin Institute, where the pioneering sheep clone Dolly was born. However, the Dolly team was not involved in developing the transgenic cystic fibrosis drug.
Phase one trials of the drug, which involved healthy volunteers, were successfully completed last month.
Dr Ron James, the managing director of PPL, said: "We believe it is the first time that the UK authorities have examined a transgenically derived product, and it is a significant milestone for PPL."
The trial will be led by Dr Diana Bilton, consultant chest physician and head of the cystic fibrosis service at Papworth Hospital.
She said: "This could potentially be very exciting news for cystic fibrosis sufferers. It does not offer a cure, but it may prove to offer better control of lung disease."
Cystic fibrosis is the commonest serious genetic disease in Caucasian children, and it affects about one person in 2,000.
The disease causes the mucus-secreting glands to go into overdrive, resulting in repeated attacks of bronchitis and affecting the pancreas. Sufferers rarely live beyond the age of 30. A spokesman for the Cystic Fibrosis Trust said: "We are very excited indeed. It's an indication of what this type of research can achieve.
"The greatest problem for people with cystic fibrosis now is the tremendous damage done over a number of years to the lungs.
"This treatment reduces the inflammation which leads to further infection and eventually the lungs failing. It could be a very, very significant treatment."Reuse content