A drug widely used to treat asthma and allergies may also help fight aggressive cancers, reports a new Northwestern Medicine study that uncovered how tumors hijack common white blood cells to evade immunotherapy.

The findings in mice as well as human cells and tumor samples point to a practical, new way to improve treatment for tough tumors, such as triple-negative breast cancer, where immunotherapy often fails. The study was published in Nature Cancer.

At the center of the discovery is a molecule called CysLTR1, which is best known for its role in asthma and inflammation. Drugs that block it, such as montelukast (also called Singulair), have been prescribed for decades to treat asthma.