One of the biggest concerns at the Nov. 30 meeting of the FDA’s Antimicrobial Drugs Advisory Committee is that, if Merck & Co. Inc.-Ridgeback Biotherapeutics Inc.’s antiviral drug, molnupiravir, is authorized for use in treating mild to moderate COVID-19 in patients at high risk of progressing to severe disease, it might be used too broadly, given its potential risks.