New research in mice suggests that metformin, a drug widely used to treat type 2 diabetes, may guard against lung cancer.

The drug’s prospects are not yet confirmed because researchers still need to test it in people. But, in mice, “this well-tolerated, FDA-approved diabetes drug was able to prevent tobacco carcinogen-induced lung tumors,” Dr. Phillip A. Dennis, senior investigator in the medical oncology branch of the U.S. National Cancer Institute, said in a news release from the American Association for Cancer Research.