ImClone Systems Inc. (NASDAQ: IMCL) had good results today, with shares closing up 6.7% at $67.94. The biotechnology company rejected Bristol-Myers Squibb (NYSE: BMY)'s offer to buy the remaining 83% of the company at $60 a share, saying it is considering a buyout offer worth $70 per share from an unidentified large pharmaceutical company. It seems that chairman Icahn has been busy.

To be sure, I was one of the skeptics when the billionaire investor last rejected BMY's offer, as was my colleague Doug McIntyre. But if this new offer is for real, then I must admit I underestimated him. Apparently, he "has been in talks with the chief executive of the pharmaceutical company that made the new offer, which would be worth about $6.1 billion." ImClone said it has not decided if the offer is adequate -- talk about playing hard ball all the way.

Bristol-Myers is ImClone's partner in selling its only product, the colon and head-and-neck cancer drug Erbitux. Analysts believe this would force BMY to offer $70 as well. A partnership between BMY and ImClone makes sense strategically. But I guess it all depends on who is the other pharmaceutical company BMY is competing with. Many pharma companies are losing sales to generic companies as their drugs go off patent, and without having much in the pipeline, but enough cash on their hands, any of them could be an interested buyer.

Some specific names mentioned by analysts include Sanofi-Aventis (NYSE: SNY), GlaxoSmithKline PLC (NYSE: GSK) and possibly AstraZeneca PLC (NYSE: AZN). Germany's Merck KGaA, which already sells Erbitux in some countries outside North America, is another likely candidate, as is Pfizer Inc. (NYSE: PFE), which has been trying to expand its portfolio of oncology drugs.

It's interesting that negotiations with the other company have been kept so tight, except for the price of course. BMY wins either way -- even if it can't get ImClone -- as it still holds 17% of BMY shares. Icahn, of course, would be a big winner too. Other options ImClone has been entertaining was spinning off the Erbitux division into a separate firm. The parent company would focus on developing drugs in its pipeline.