A drug used to help prevent recurring breast cancer appears to hold promise as a treatment for deadly fungal infections, new research has found.

University of Rochester Medical Center researchers found that tamoxifen kills yeast in mice with Candida infections, which can be fatal to people with compromised immune systems, including people with cancer or HIV and those taking immunosuppressants for chronic conditions.

At extremely high levels, tamoxifen slashed yeast levels by 150-fold, causing most fungus cells to break up and die while halting surviving cells from progressing into a disease-causing state, their study found.

“It’s still early, but if tamoxifen, or molecules like it, turns out to be an effective treatment against serious fungal infections, it’ll be a welcome addition to our arsenal,” Dr. Damian Krysan, an assistant professor of pediatrics at the university and an author of the study, said in a university news release.

The results are published in the August issue of Antimicrobial Agents and Chemotherapy.

Available antifungal medications pose some issues for people who need them the most, according to background information in the news release. The only new class of antifungals approved for use in the past two decades is generally effective, but they can only be taken intravenously, which poses logistic and other problems for some patients. And the most common oral antifungal medication only slows fungus cell growth, making it difficult for immune-compromised patients to completely shake their infections.

“We don’t have vaccines against fungal infections, and the few drugs we do have aren’t always effective,” Krysan said. “We’ve got a lot more work to do to figure out whether tamoxifen could be used in high doses or whether it could be used in combination with other treatments, but we’re excited about the possibility of giving doctors another way to help these critically ill patients.”