Shares of the biopharmaceutical company Tercica Inc. soared 99.55 percent on Thursday after it agreed to be purchased by the French firm Ipsen SA for $9 a share or $663 million.

The deal was double the price of Tercica closing price on Wednesday. Today shares soared to its highest since December 2005.

Tercica, a U.S. company, manufactures two important drugs, Increlex and Somatuline Depot, which are treatments for hormone disorders.