Arrowhead Pharmaceuticals Inc., of Pasadena, Calif., said data from a phase Ia/Ib study of ARC-AAT, an earlier generation of the company's RNAI candidate for the treatment of liver disease associated with alpha-1 antitrypsin (AAT) deficiency, can achieve "deep durable and dose-dependent reductions" of AAT, with the highest dose studied in healthy volunteers achieving near full suppression of the liver production of the AAT protein.