Americans live in fear of terrorists exploding a dirty bomb in their city, and those living near nuclear plants dread a terrorist incident or accident that exposes them to potentially deadly radiation. Currently, the prognosis for those exposed to large amounts of radiation is grim: Doctors can offer little help beyond easing their suffering.

"If you're exposed to a very, very high dose, it's rapid deterioration and immediate death," explained John S. Lazo, Ph.D., of the University of Virginia's Department of Pharmacology. "It's the lower doses that people — particularly governments — are concerned about. The type of exposure that might result from a dirty bomb or a nuclear accident. How do we alleviate the effects? What's the antidote? Right now, we just don't have anything."

Researchers at the University of Virginia School of Medicine are working on a solution and have identified compounds that could pave the way for the first radiation antidote. Some of them, including the drug rapamycin, have previously been shown to extend life in organisms such as worms and flies. UVA's research suggests that these compounds, or similar drugs, might counter the deadly effects of ionizing radiation.

Lazo and his colleague Elizabeth R. Sharlow, Ph.D., screened more than 3,400 existing drugs, vitamins, and other compounds to identify ones that might help cells withstand the effects of radiation exposure.

Their goal was to keep stem cells, the cells that produce the various cell types in the body, alive long enough to repair the damage caused by radiation.

"We wanted to find already approved drugs that would potentially keep stem cells, or progenitor cells, alive after radiation exposure," Sharlow said.

After they identified possibilities, they examined the substances' chemical structures and identified a cluster of promising compounds with similar structures, a lead in the search for an antidote.

Lazo says that it is unlikely any one drug or compound will work on its own. "A lot of us in this field think it will be a cocktail of things you take," he said. "And if you think you need cocktails, you need the individual ingredients. That's why we think this is pretty important — because it's providing new ingredients for that cocktail."