Updated from 12:14 p.m. EDTImClone ( IMCL) investors have indicated -- via a 40% stock rally -- that they expect more than the $60 Bristol-Myers Squibb ( BMY) offered for their shares Thursday. The all-cash bid from Bristol-Myers, a 17% shareholder in ImClone, represents a 29% premium over ImClone's closing price Wednesday. It's important to remember, however, that activist investor Carl Icahn, who serves as chairman of ImClone's board, has a history of fighting for a premium price with his investments. Icahn reportedly snubbed offers for ImClone in the $50/share range in the summer of 2006, amid rumors that he would take no less than $70 a share. That was prior to ImClone's promising Erbitux data in non-small cell lung cancer, and now ImClone has five midstage prospects in its pipeline. Icahn -- who had been a shareholder and board member at MedImmune -- helped jimmy the sale of that biotech company to AstraZeneca ( AZN) for more than $15 billion, and a per-share price that represented a 53% premium to the closing price of MedImmune's shares the day prior. Bristol's bid for ImClone also represents a 39% premium to ImClone's 30-day average price. "My first reaction was that it would be about 10% higher, or a 50% premium from their 30-day average," said Carol Werther, biotech analyst for Summer Street research who recently upgraded ImClone stock to buy. The 50% premium would be roughly $67 a share. But it's difficult to peg value of ImClone's midstage pipeline, she says. The low price being the $60 bid, Werther says, the high price might be $75. Narrowing that down a bit more, Stanford Group Co. analyst Han Li says a potential acquisition price might be $65 to $70 a share based on recent biotech M&A premiums.