Scientists have created a drug which they say could protect people from the effects of a nuclear attack.
The drug, currently called HE2100, has been developed by US company Hollis-Eden Pharmaceuticals.
There are fears terrorists could make a dirty bomb
Company bosses say it would protect most people outside the immediate ring of a nuclear attack.
Early tests suggest it can stem the loss of infection-fighting cells in the body and stop bleeding.
High levels of radiation destroy white blood cells which are essential for protecting the body against infection.
Death can also be caused by bleeding, as radiation also destroys the ability of blood clots to form.
Scientists at Hollis-Eden have tested the drug on animals. The drug cannot be tested in humans because it would be too dangerous to expose them to radiation.
But the animal tests have shown that the drug helps the body to produce white blood cells much more quickly.
Details of those tests were presented at the annual scientific meeting of the British Society for Haematology in Glasgow.
The company is now planning a larger trial. If the results are repeated the company will then apply to US regulatory authorities for permission to sell the drug.
Changes introduced last year enable the US Food and Drug Administration to licence drugs that have not been widely tested on humans.
The drug must be tested on primates like monkeys, gorillas and chimpanzees, and in a small number of people to establish that it is safe.
The US government has agreed to pay companies as much as $6 billion over the next few years as part of a programme to speed up the development of drugs that can combat bioterrorist attacks.
Bob Marsella, vice president of business development at Hollis Eden, said the drug would cost between $50 and $75 per course of treatment and that it can be stockpiled.
Professor Paul Wilkinson from the Centre for Terrorism Studies at St Andrews University, UK, told BBC News Online: "This is an interesting and potentially very useful innovation.
"It would not be a panacea. There would be people in the immediate area of a blast who would be exposed to such a high level of radiation that no medical intervention could save them.
"But there are people in the outer circle who may well benefit from this drug if it proves to be effective in further tests."
Professor Wilkinson said it would be crucial to be able to deliver the drug quickly to large numbers of people, as it was likely that a dirty bomb would be targeted at a densely populated area.