Drug protects mice, monkeys from radiation damage

CHICAGO (Reuters) - An experimental drug helped protect mice and monkeys from the damaging effects of radiation, researchers said on Thursday, in a finding that may lead to less toxic cancer treatments or an emergency treatment for radiation exposure.

They said the drug protected animals' bone marrow and cells in the gut from being destroyed by radiation without interfering with radiation therapy's ability to fight cancer.

"These tissues fail because these cells choose to commit suicide. Our idea was to block these suicidal intentions," said Andrei Gudkov of the Roswell Park Cancer Institute in Buffalo, New York, whose study was published in the journal Science.

Gudkov, who also is chief scientific officer at Cleveland BioLabs Inc which is developing the drug, said radiation triggers cells to undergo a type of programmed cell death know as apoptosis, which helps rid the body of defective cells.

Tumors have figured out how to block this suicide mode. "Tumors simply throw it out by causing mutations," Gudkov said in a telephone interview.

He and colleagues decided to study this mechanism to find a way to protect cells from radiation damage. They developed a compound known as CBLB502 made from a salmonella protein that naturally makes cells resistant to cell suicide.

A single dose of the drug given to the animals shortly before receiving radiation therapy significantly reduced damage to sensitive bone marrow and gastrointestinal cells and prolonged their survival.

The drug also improved survival of mice when given an hour after the animals got a dose of radiation.

"We can temporarily and reversibly convert normal cells into something which is resistant to radiation -- but only for a couple of hours," Gudkov said.

That is key, he said, because otherwise the cells would develop into tumors. So far, Gudkov said the drug has proven to have few toxic side effects.

"We are basically developing this thing for two applications. One is for general protection from emergency situations -- dirty bombs or Chernobyl-type disasters," he said.

"For that we would want people to have a loaded syringe with this compound for intramuscular injection," he said.

The other is for use with radiation therapy in cancer patients to make the treatments more effective with fewer side effects.

Gudkov said the company is seeking U.S. regulatory approval to start testing the drug in healthy adults, which could begin as early as this summer.

Last week, the company won a $9 million contract from the U.S. Department of Defense to develop the treatment for radiation exposure.

(Editing by Cynthia Osterman)