About 50,000 people in the U.S. are diagnosed annually with head, neck, nasal and oral cancers. Most are treated with radiation, and of those, 70-80 percent develop a painful and debilitating side effect called severe oral mucositis (SOM). While some drugs are available to treat SOM once it develops, none can prevent it. But today, researchers are reporting on a new drug, called GC4419, that appears to do just that. Although still in clinical trials, it has already been designated by the U.S. Food and Drug Administration as a “breakthrough therapy.”