Skin cancer breakthrough in an egg
Published: July 24, 2005
Chicken eggs containing a drug that can target and treat skin cancer have been produced by Scottish scientists.
Researchers at the Roslin Institute near Edinburgh, where Dolly the Sheep was cloned, used genetically modified hens to lay the drug-laced eggs.
By “hijacking” the biological processes of the hens they were able to concentrate high levels of the drug inside the egg whites.
The drug comes in the form of an antibody in the egg white. It specifically targets the malignant melanoma cells that cause skin cancer.
The breakthrough has raised hopes that large quantities of the cancer drug can be harvested for patients from chicken eggs.
It is the first time drugs have been successfully produced in large quantities inside animal food products. Previous attempts to grow drugs inside sheep milk have proven to be ineffective.
Researchers at the Roslin Institute are now trying to breed a second generation of hens capable of laying drug-laced eggs in a bid to produce larger flocks that can be used as “factories” for making the drug.
Standard laboratory methods used to produce the drug, called Anti-R24(h), are expensive and time consuming. But using genetically modified chickens, researchers were able to produce large quantities of the drug cheaply and quickly.
“We are hijacking one of the protein genes and replacing it with our drug protein instead,” said Dr Helen Sang, of the Roslin Institute. “With a modified cockerel it should be possible to produce a whole flock of transgenic hens. Each hen lays one egg a day, so it means we could produce a lot of the drug from that.”
The Avian Transgenic Manufacturing project is a joint venture between the Roslin Institute, US-based drug company Viragen and the biotechnology firm Oxford BioMedica.
They are aiming to have the first chicken egg-produced drugs available for use by cancer patients within five years after initial clinical trials of the antibody drug have already proven to be successful.
It works by hunting out and detecting molecules on the outside of the cancer cells and helping the body’s immune system destroy them.
Sang claims while patients could take the drug by eating one of the “designer” eggs, it is unlikely the drug regulation authorities would allow it to go on the market unpurified. “It is a nice idea, but eggs contain a lot of other things. All drugs have to meet stringent criteria and have to be a certain purity, and it would be difficult to prove the drug is pure in an uncracked egg.”
Genetics experts last night hailed the method as a major breakthrough. Professor Richard Wilson, of Glasgow University, said: “Being able to produce viable drugs inside chicken eggs is a big step and being able to obtain a drug by cracking an egg is very attractive.”
Previous attempts to produce drugs in animal products have failed to live up to the same expectations. A spin off company from the Roslin Institute, PPL Therapeutics, aimed to produce drugs in sheep milk, but the firm went bust within a few years. Other firms have also tried to use milk from goats and cows to produce drugs but none have proved commercially viable.
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