The sudden resignation of Scott Gottlieb, the commissioner of the Food and Drug Administration, leaves a giant hole atop an agency that oversees a quarter of the U.S. economy. Which, of course, leads to an equally big question: Who will replace him? Top contenders include Amy Abernethy, formerly the chief medical officer at health data firm Flatiron Health, who became Gottlieb’s principal deputy commissioner early this year. Another contender is Ned Sharpless, director of the National Cancer Institute since October 2017, who would bring a deep knowledge of biotech to an FDA stint. And another is Brett Giroir, the current HHS assistant secretary for health, with experience in government, academia, and industry.