When it rejected both of Bristol-Myers Squibb’s bids of $60, then $62 per share, ImClone said it had been approached by “a large pharmaceutical company” offering $70 per share, or $6.1 billion, subject to due diligence. Some wondered whether this was a bluff. Now, it seems the mystery suitor may be closer to owning the New York-based biotech company. On Monday, Carl C. Icahn, ImClone’s chairman, released a statement saying the unnamed company had completed due diligence and that negotiations were underway. Icahn said the bidder would not be named until negotiations were completed.

Rumors abound in today’s news that Eli Lilly is the mystery bidder. A Wall Street Journal story cites unidentified sources close to the deal, but for the moment neither ImClone nor Lilly has confirmed or commented on the speculation.

On Tuesday, Merck KGaA jumped in the ImClone-takeover mix and said it might be interested in the company, according a Reuters report. Karl-Ludwig Kley, Merck KGaA’s chief executive officer, told a group of business journalists that his company is not ImClone’s mystery bidder, and would not seek to purchase ImClone on its own, but that Merck is open to a possible partnership with another company. Merck owns the development and marketing rights outside the US for ImClone’s cancer drug “Erbitux.” Kley said, “Anyone who wants to take Erbitux further would be well advised to talk to us.”

Stay tuned for more on the mystery bidder, the negotiations, and who will ultimately own ImClone.