The U.S. Food and Drug Administration granted orphan drug designation to Arrowhead Pharmaceuticals Inc.'s investigational medicine ARO-AAT to treat a rare genetic liver disease associated with alpha-1 antitrypsin deficiency.

Alpha-1 antitrypsin deficiency, A1AD or AATD, is a genetic disorder that may result in lung disease or liver disease.

Pasadena, Calif.-based Arrowhead filed a clinical trial application in December 2017, requesting regulatory permission to begin first-in-human studies of the drug.