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Friday, 19 April, 2002, 23:11 GMT 00:11 UK
'Destroyer' drug unveiled
The new drugs are in the early stages of development
The new drugs are in the early stages of development
A new breed of "destroyer" drug which only targets diseased and cancerous cells has been unveiled by researchers.

The drugs are at a very early stage of development, but open up a whole new area for scientists to investigate.

The body's antibodies and T-cells spot different types of abnormal proteins, called antigens - but they do not recognise the same ones.

Twenty years ago, scientists discovered a kind of drugs called monoclonal antibodies, which can seek out and destroy diseased cells.


The hope that they can be used as 'magic bullets' to target drugs to tumours is probably over-optimistic

Dr Doreen Cantrell, Cancer Research UK
It is only recently that they have been developed into effective treatments for diseases such as breast cancer, leukaemia and arthritis. Ten such drugs are now on sale.

But they can only target the antigens on a cancer cell's surface - 10 to 15% of the total number.

The new class of drugs, called monoclonal T-cell receptors or mTCRs, can also seek out antigens inside cancer cells, thereby allowing them to attack all diseased cells.

Independent

T-cells in the body use the receptors to check protein fragments called peptides which appear on the surface of all cells.

They are the remains of proteins from within the cell.

T-cells can tell if the protein the peptides come from should be there. If it should not, the cell is destroyed.

British company Avidex, which is based in Abingdon, Oxfordshire, and Sunol Molecular, based in Florida, USA are developing the drugs.

They key to their research has been the ability to create artificial T-cell receptors that exist independently from the T cells themselves.

The genes that manufacture the receptor were extracted from human T-cells, then put into E. coli bacteria.

The bacteria then produced identical copies of the receptor protein.

There was no difference between them and those on T-cells.

The researchers suggest the drugs could be used to attack particular cancer cells by screening patients' T-cells to find ones already targeted by diseased cells so they can identify the right receptor to clone.

Another approach is to alter receptor genes until mTCRs that attach to particular target cells are produced.

Both companies have already discovered mTCRs that attach to cancer cells.

Useful tool

Animal tests have been begun by Avidex.

But Dr Bent Jakobsen, chief scientific officer for Avidex told BBC News Online it could be around two years before the drugs could be tested on people.

He added: "This opens up a whole new area of research.

"The drugs are from the same class as monoclonal antibodies. The thing that's better is that they can hit targets that are broader.

"The limitations of monoclonal antibodies is that they can only hit certain antigens."

He added: "The most obvious thing that could be targeted is cancer, but mTCRs could also have applications in treating viral infections."

Dr Doreen Cantrell, head of lymphocyte activation at Cancer Research UK said: "The TCR reagents described are a triumph of technology and will undoubtedly provide very useful research tools for scientists.

"The hope that they can be used as 'magic bullets' to target drugs to tumours is probably over-optimistic. "

She said using antibodies as 'magic bullets' had been clinically difficult, and the mTCRs were difficult to make and had all the same problems as monoclonal antibodies.

She added: "The hopes for monoclonal TCRs may be high but usefulness of these reagents is hypothetical- within the realms of possibility but not within the realms of feasibility at least in the foreseeable future."

The research is featured in New Scientist.

See also:

28 Mar 02 | Health
Cancer drug given go-ahead
23 Apr 02 | Health
HIV 'singled out for destruction'
22 Nov 01 | Health
Genetic trickery 'cons' cancer
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