Brequinar-d 3 (DUP785-d 3 ) is deuterium labeled Brequinar. Brequinar (DUP785) is a potent inhibitor of dihydroorotate dehydrogenase (DHODH) with an IC 50 of 5.2 nM for human DHODH. Brequinar has potent activities against a broad spectrum of viruses. Brequinar also has an anti- SARS2 activity.