US Stock Futures: HOT STOCKS TO WATCH

Among the companies whose shares are expected to actively trade in Thursday's session are Exar Corp. (EXAR), Alexion Pharmaceuticals Inc. (ALXN) and China Sky One Medical Inc. (CSKI).

Exar cut its revenue and non-GAAP gross margin guidance for its fiscal third quarter due to weaker economic conditions in Asia and Europe and continued inventory corrections. Shares dropped 3.3% to $6.45 in recent after-hours trading.

Alexion Pharmaceuticals Inc. (ALXN) agreed to acquire privately held Enobia Pharma Corp. in a deal valued at up to $1.08 billion, expanding Alexion's presence in the treatment of ultra-rare and life-threatening diseases. Shares fell 1.7% to $69.75 recently in late trading.

China Sky One Medical said Chief Financial Officer Hongyu Pan has left the company for personal reasons, and a search for his replacement has begun. Shares slid 2.9% to $1.10 in recent after-hours trading.

 
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Chesapeake Midstream Partners LP (CHKM) agreed to buy midstream assets in the Marcellus Shale ultimately owned by Chesapeake Energy Corp. (CHK) for $865 million.

StellarOne Corp. (STEL) said it repaid a remaining $22.5 million for preferred shares it issued to the government under the U.S. Treasury's Troubled Asset Relief Program during the financial crisis in late 2008.

-Edited by Ian Thomson and Corrie Driebusch; write to [e-mail] and [e-mail]