MedImmune (MEDI:Nasdaq) slipped after the Gaithersburg, Md.-based biotechnology company said it intends to sell $1 billion in convertible senior notes to qualified institutional buyers. The company said it plans to offer $500 million in convertible senior notes due 2011 and $500 million in convertible senior notes due 2013. The notes will be convertible, in certain circumstances, into a combination of cash and MedImmune common stock. MedImmune said it expects to use about $500 million of the proceeds to fund the repurchase of the 1% convertible senior notes on July 15. Also, the company expects to use up to $150 million of the net proceeds to buy shares of its common stock in privately negotiated transactions concurrently with the offering of the notes. Shares dropped $1.05, or 3.59%, to $28.18.

NPS Pharmaceuticals (NPSP:Nasdaq) gained on news that billionaire investor George Soros had increased his stake in the Salt Lake City-based company, according to a filing with the Securities and Exchange Commission, to 7.1% from 6.8%. Soros controls nearly 3.3 million shares of the company through Quantum Partners, which is an affiliate of Soros Fund Management. Shares gained 15 cents, or 3.13%, to $4.95.