Facet Biotech Corp. (FACT) told shareholders not to tender their holdings for Biogen Idec Inc.'s (BIIB) $356 million takeover offer and disclosed that it has received inquiries from third parties.

Biogen launched the tender offer last week, but cash-rich Facet continues to argue that the $14.50-a-share offer doesn't put much value on its product pipeline and operations. Facet contends that Biogen is trying to cheaply acquire the full rights to daclizumab, a multiple-sclerosis treatment in development by the companies.

"We absolutely believe that the price put on the table was not an offer that appropriately values the assets and the long term prospects of the company," Facet Chief Executive Faheem Hasnain said in an interview.

Shares of Facet recently traded up 1.8% to $17.60; while Biogen dropped 1.5% to $49.75.

In a filing with the Securities and Exchange Commission Thursday, Facet said that it has received "inquiries from third parties that could lead to offers being made for all or a portion of the shares or the company's assets."

Facet declined to provide further information on those discussions, but noted that it may enter into confidentiality agreements with one or more parties in the process.

The company also stressed that it is not currently in talks with Biogen Idec about coming to a deal.

A Biogen spokeswoman said the company is reviewing Facet's filing and declined further comment.

Facet's stock has traded above the $14.50 bid since the offer became public last month, an indication that investors are expecting a deal to come at a higher price.

Facet has adopted a poison-pill plan to prevent a hostile takeover attempt, but Wall Street analysts project Biogen taking a friendlier approach and raising its offer closer to $20 a share in order to close the deal.

The shareholder-rights plan prevents any person or group from acquiring more than 15% of Facet's common stock without board approval.

"Given where are our shares are trading [Thursday].... I would be very surprised if there were many shareholders biting on that offer," Hasnain said.

Hasnain, who formerly served as head of Biogen's oncology and rheumatology business unit, said that Biogen's offer is "opportunistic" in relation to the companies' decision to start a phase 3 trial for daclizumab and its intimate knowledge of the program.

"Both companies know that daclizumab is a very interesting asset, so from that perspective this is not a surprise," Hasnain said.

He noted that Facet has no change of control agreements in commercial partnerships, so "any potential acquirer is free and clear to jump into our shoes."

Biogen and Facet have worked together since 2005 on treatments for multiple sclerosis and solid tumors, but Biogen went public with its interest in buying Facet last month after Facet rejected earlier takeover approaches.

In August, Biogen Chief Executive James Mullen called Hasnain and referred to its inital $15-a-share offer as a "starting point for negotiations," according to a SEC filing.

After the first rejection, Mullen asked Hasnain to propose a price for a deal, but Hasnain declined to do so.

Facet has refused to allow Biogen, or any other company, to perform due diligence unless a "bona fide" higher offer materializes.

In a twist, Facet said that Biogen board member Alex Denner, managing director of Icahn Partners LP who gained his board seat in a proxy fight earlier this year, called Hasnain earlier this month.

Denner wasn't immediately available for comment.

In the SEC filing, Facet states that Denner "repeatedly asked at what price Mr. Hasnain would accept Biogen Idec's offer to acquire the company."

Hasnain believes that Denner's call "just part of negotiations," but he responded that he wasn't in a position to name a price and that any offer would be considered by the Facet board.

Facet was spun off from PDL BioPharma Inc. (PDLI) in December in order to separate the company's biotechnology assets from its royalty-producing assets. After the spinoff, Facet had $405 million in cash to fund its operations for a number of years while it attempts to develop its pipeline.

-By Thomas Gryta, Dow Jones Newswires; 212-416-2169; thomas.gryta@dowjones.com