Biogen Idec Inc. (BIIB) went public with a $356 million unsolicited offer Friday for drug developer Facet Biotech Corp. (FACT), after claiming that the smaller company shunned earlier attempts to reach a deal.

The $14.50-a-share offer for the Redwood City, Calif., company brings a 64% premium to Thursday's closing price. Shares were halted for news, last trading Friday at $8.79. Biogen shares rose 2.1% to $50.97.

Facet officials weren't immediately available to comment on the offer.

Notably, the offer by Biogen, a Cambridge, Mass., biotechnology company, is close to the amount of cash that Facet holds on its balance sheet, which may make it hesitate to agree such a deal.

"That is not going to get a deal done," said BMO Capital Markets analyst Jason Zhang, who has a $14 price target on the company, based mostly on its cash holdings.

"Our belief is that the price we are offering ascribes appropriate value," said Biogen spokeswoman Jennifer Neiman.

Aside from the cash holdings and clinical programs, Biogen factored Facet's obligations under a lease agreement and its recent collaboration with Trubion Pharmaceuticals Inc. (TRBN) that could pay out up to $176.5 million in milestone payments. In April, Facet disclosed that it had "significant lease and other obligations" in responding to activist shareholders who had pushed for the liquidation of the company, citing its large cash reserves.

Facet was spun off from PDL BioPharma Inc. (PDLI) in December in order to separate the company's biotech assets from its royalty-producing assets. PDL is essentially a shell company that produces revenue from its patent portfolio and license agreements.

After the spin-off, Facet had $405 million in cash in order to fund its operations for a number of years while it attempts to develop its pipeline. It has projected spending $110 million in 2009, and as of June 30 had $371.1 million.

That amounts to $15.12 a share in cash, based on its 24.5 million shares outstanding. Under the company's collaboration deal with Trubion Pharmaceuticals, Facet will pay $20 million upfront and make a $10 million investment in Trubion.

Zhang declined to estimate how much Biogen might have to pay to close the deal for Facet, but said he believes a tie-up makes sense because of the companies' previous relationship.

The two companies have worked together since 2005 on treatments for multiple sclerosis and solid tumors.

According to Biogen, it first expressed interest in Facet in mid-August, offering $15 a share and urging it to not undertake any material transactions.

Biogen contends that Facet rejected its offer and subsequently signed the deal with Trubion.

Biogen said it believes that the Trubion agreement "reduces the value of Facet, as apparently do Facet's investors," citing a 22% drop in its stock price since the deal. It also pointed to the deal in explaining its lowered $14.50-a-share offer.

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

(Jay Miller contributed to this story)