Biogen Idec, which has put itself up for sale, may get bids of around $25-30 billion from several of the world's top drugmakers keen to expand in the hot area of biotech medicine.
Pfizer, Sanofi-Aventis and Johnson & Johnson could all use the U.S. company to gain scale in protein and antibody drug manufacturing, sales and research, bankers and industry analysts said on Monday.
Roche Holding, however, may be less interested - despite its collaboration with Biogen on cancer drug MabThera/Rituxan - since it already has a major presence in biotech medicine production.
GlaxoSmithKline, another player with a potential appetite, is also probably not in the running, as it focuses on other priorities, some industry experts said.
Roche's Swiss rival Novartis , meanwhile, has a competing presence in multiple sclerosis which could rule it out from buying Biogen.
Officials at all the firms declined to comment.
"A number of big companies have said recently they don't think they are big enough in biotech yet, so I would think there will be quite a lot of interest," said Paul Diggle of Nomura Code Securities.
Acquiring Biogen will not be cheap, however.
The unexpectedly rich price of $15.6 billion paid for U.S. biotech firm MedImmune by AstraZeneca earlier this year - equivalent to 11-times annual sales - showed big pharma's appetite for biotech assets.
That same high valuation would value Biogen at about $34 billion.
In practice, analysts believe threats to Biogen's core multiple sclerosis franchise from new products and the risk of biogeneric competition to its established MS drug Avonex in the years ahead mean a lowlier rating is justified.
New MS Drug Tysabri a Wild Card
On the plus side, new MS drug Tysabri is now seen by some analysts as a potential multibillion-dollar-year seller. Biogen collaborates on the drug with Elan .
"The key variable in the take-out price is the outlook for Tysabri," said Geoffrey Porges, an analyst at Sanford Bernstein, who estimates Biogen will fetch between $85 to $100 a share.
Investors are clearly anticipating a keen tussle, with Biogen shares rising 19 percent in Nasdaq trade on Monday to $82.50, valuing the business at around $23 billion.
The prize offered Biogen is a bridgehead into the biological medicines market, where growth is faster and margins higher than in traditional pharmaceuticals.
"A lot of people want biological capacity. Those who have it already probably won't be bidders, so I guess you can probably count out Roche and AstraZeneca," said Ben Yeoh, an industry analyst at Dresdner Kleinwort.
France's Sanofi-Aventis , the world's third-largest drugmaker, said last month it was looking for acquisitions in biotechnology - particularly in manufacturing.
Pfizer , the global number one in pharmaceuticals, has also trumpeted its determination to be a leader in biotech.
"Sanofi is looking for more biological products and Pfizer is doing the same," said Tim Race of brokerage ING.
Biogen's announcement late on Friday comes four years after Biogen was acquired by Idec Pharmaceutical for $6.7 billion.
The company said it hired Goldman Sachs and Merrill Lynch to help find a buyer and that it has already received "expressions of interest."
One interested party is billionaire investor Carl Icahn, who recently took control of ImClone Systems and has increased his stake in Biogen to about 4 percent.