LONDON (Reuters) — The deadly poison cyanide may have a role as a powerful cancer killer, British scientists said on Wednesday.

Researchers at London's Imperial College told a science meeting that they had harnessed a cyanide-generating system used by plants as a defense against insects and believed the mechanism could be developed to produce anti-cancer drugs.

Plants like the hydrangea and African potato contain an enzyme called linamarase that is capable of generating cyanide when they are damaged by animals or insects.

The scientists believe they can attach that enzyme to a cancer-seeking antibody capable of recognizing a protein found only in certain cancers. The method — known as AGENT (Antibody Guided Enzyme Nitrile Therapy) — would produce an agent that could potentially kill cancer cells and leave healthy tissue unharmed.

Dr Mahendra Deonarain of Imperial College's Department of Biochemistry told the British Association's Festival of Science meeting in London that the work was still at an early stage but was promising.

"We have demonstrated that this system is able to specifically kill tumour cells by cyanide intoxication," he said. "The next step is to identify the best molecule to proceed before we go on to animal studies."

Despite the deadly nature of cyanide, the amount generated by the technique is only sufficient to kill the specific cancer cell targeted by the combined enzyme-antibody molecule.

A natural enzyme produced in the human liver should detoxify any cyanide that leaks away from the tumour.

The record of success for new drugs entering clinical trials is only about one in 10 but the potential prize is large. Top-selling cancer drugs typically generate annual sales of $500 million to $1 billion.

Antisoma Plc, the biotechnology firm funding the work, said it had not decided whether to take the idea into development.

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But investors bet that the company might have found the basis for a blockbuster cancer drug and sent its stock price up 20 percent to 170 pence, its highest level in four months.

Chief Executive Glyn Edwards said the first animal studies on the project were 12-18 months away and clinical trials on humans would not start for two to three years — assuming the research got that far.

"How much value this adds to the company at this stage I would not like to say. But I think it has drawn investor attention to Antisoma which has underperformed the (biotechnology) sector recently," he told Reuters.

The research has been submitted for publication in the British Medical Journal.

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