'Destroyer' drug unveiled

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.

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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.

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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.