The diabetes drug metformin helped prevent tumors in mice that were exposed to a cancer-causing agent found in tobacco, said researchers at the AACR annual meeting. Compared with untreated mice, those that received the drug had a 53 percent reduction in lung tumor burden after exposure to the carcinogen, which is called nicotine-derived nitrosamine. The animals were treated with an oral form of metformin for 13 weeks at drug levels that would be achievable in humans, the researchers said.

“Metformin is a very interesting drug for cancer prevention,” said lead researcher Dr. Phillip A. Dennis of NCI’s Center for Cancer Research, who presented the results. “We prevented over half of the lung tumors that would have occurred from exposure to the main carcinogen in tobacco, and that’s a real and important reduction.” Dr. Dennis’ group is planning a clinical trial to test the FDA-approved drug in people at highest risk of developing lung cancer, he said.