UPDATED: Amylin shares rocket up on report of $3.5B buyout offer by Bristol-Myers

Shares of Amylin Pharmaceuticals ($AMLN) rocketed up 45% this morning, fueled by a report by Bloomberg that the Bydureon developer had turned a cold shoulder to a $22 per share buyout offer from Bristol-Myers Squibb ($BMY), putting the value on this new potential pearl at $3.5 billion.

Amylin has had an eventful schedule over the past year. First it sued its longtime partner Eli Lilly ($LLY) after Lilly forged a marketing pact with rival Boehringer, then it executed an expensive divorce from the pharma giant. Soon after, the FDA delivered on a long-awaited approval for Bydureon, the once-weekly successor to the Byetta franchise. Now Meg Tirrell and Jeffrey McCracken, quoting sources close to the deal, report that Amylin rejected Bristol-Myers offer to pay a 43% premium to buy the company--a deal that would register as the largest in a string of 19 BMS acquisitions over the past five years.

As Bloomberg notes, Amylin has been seeing its revenue from Byetta shrink as Novo's ($NVO) Victoza muscled into its market share. And it's been looking for a global partner who can step into Eli Lilly's shoes outside the U.S. But none of that persuaded Amylin to warm up to Bristol-Myers' offer. BMS hasn't been back in touch since it was rejected by Amylin.

Amylin struck a $1.6 billion deal to end its relationship with Lilly. That included a $250 million upfront and a $1.2 billion share of the Bydureon revenue. The FDA's approval came soon after the two companies split up.

News of the $3.5 billion bid quickly seized the attention of Wall Street analysts, who began to debate just what Amylin is worth. Its value has a lot to do with its prospects for Bydureon, of course, and as Adam Feuerstein at TheStreet notes, if the board is turning down a $22 offer, they must have a strong belief that they can go on to register blockbuster sales. But if Bristol can't prevail, adds Feuerstein, the likes of Takeda, GlaxosmithKline and AstraZeneca just might step in.

- here's the story from Bloomberg
- here's the report from TheStreet

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