Thursday's Winners & Losers: Tercica

Yahoo!(YHOO Quote) fell 69 cents, or 2.6%, to $26.16 following a letter from Chairman Roy Bostock to activist investor Carl Icahn, disputing the latter's claims that Yahoo! has put in place a "poison pill" to dissuade Microsoft(MSFT Quote) from bidding for the company.

Shares of Tercica (TRCA Quote) surged on news Ipsen, a French specialty drug company that owns 25% of the biopharmaceutical company, will buy all of the Tercica shares that it doesn't already own for $9 a share in cash. The deal values Tercica at $663 million. The price is a 104% premium to Tercica's closing price on Thursday.

Ipsen and its affiliates currently own roughly 25.3% of the company and agreed to immediately exercise its outstanding Tercica warrant and convert outstanding convertible notes, after which it will own around 42.7% of Tercica's outstanding stock.

Tercica shares jumped $4.39, or 99.6%, to $8.80.

Level 3 Communications(LVLT Quote) added 43 cents, or 11%, to $4.33 after the company said it has sold its advertising distribution business, Vyvx, to DG FastChannel for $129 million in cash.

Also Thursday, Credit Suisse analyst Michael Aberman downgraded Regeneron (REGN Quote) to neutral from outperform and lowered its price target to $24 from $30. Aberman wrote in a note to investors that after attending the annual meeting of the American Society of Clinical Oncology this year, his team came away with a more cautious view on Regeneron's aflibercept based on its potential to result in more toxicity than Genentech's (DNA Quote) Avastin. Regeneron's shares were down $3.79, or 19.9%, at $15.29. Genentech shares were up 58 cents, or 0.8%, at $73.05.