Arrowhead Pharmaceuticals Inc. (NASDAQ:ARWR) gained $5.29 (38%) to $19.39 Thursday after reporting initial data showing that monthly doses of its third-generation RNAi therapy ARO-HBV reduced circulating HBV surface antigen (HBsAg) in a broad population of patients with chronic HBV infection. The biotech added $465 million in market cap on the data.