From the FDA website:
Dr. Stephen M. Hahn was sworn in as the 24th Commissioner of Food and Drugs on December 17, 2019. Dr. Hahn is a physician, scientist and health care leader with an extensive background in patient care, academic research and executive leadership.
Dr. Hahn is a dedicated clinician, having trained in both medical oncology and radiation oncology. In his previous leadership roles, he has always carefully balanced executive management with clinical time to continue to serve oncology patients, his true passion. He specializes in treating both lung cancer and sarcoma.