Facet Biotech shareholders rejected Biogen Idec's bid to acquire the company for $493 million or $17.50 per share, while leaving the door open to a higher bid from Biogen or other potential suitors. For it’s part, after threatening to launch a proxy fight to unseat Facet’s board, but soon after a midnight December 16 deadline it set came and went, Biogen said it would allow its “best-and-final” offer to expire.

Facet had adopted a poison pill provision, forbidding any shareholder from holding more than 15 percent of the company's shares. But on December 16, Facet's board moved to amend that rule and strengthen its power to block offers it found unsuitable. The amendment allows its two largest shareholders to increase their stakes in the company to as much as 20 percent, so long as they vote the additional shares as the board recommends or proportionally with shareholders.

The company said it will “continue to pursue appropriate opportunities” and says it has told its financial advisor, Centerview Partners, to solicit additional offers. Meanwhile, Facet CEO Faheem Hasnain says the company will “continue to offer Biogen Idec the opportunity to engage in due diligence discussions to determine whether (it) would make a materially increased offer.”

Facet’s latest rejection follows a series of offers from Biogen, which is developing a drug for treating multiple sclerosis, Daclizumab, and a treatment for solid tumors, Volociximab, jointly with Redwood City, California-based Facet.

Daclizumab, now in mid-stage trials, could soon offer a big payday for Facet. As soon as the first patient is enrolled in a late-stage trial of the drug, Biogen will owe Facet a $30 million milestone payment.

Hasnain says he and Facet's board are pleased that the company's stockholders rejected Biogen's offer, which he called “inadequate” and not reflective of the company's true value or prospects.