Big moves in biotech today as takeout attempts and trial results dominate the headlines. Let's jump right in a take a look at three biotechs posting big gains.

The top performer is easily Ardea Biosciences (Nasdaq: RDEA), up 52% on news of a buyout from AstraZeneca. The big British pharma makes sense as an acquirer, since AstraZeneca's pipeline is looking mighty barren after a couple of high-profile flops. The $1.26 billion offer is largely for gout drug Lesinurad, although Ardea also has stage 2 cancer assets currently licensed to Bayer. No one confuses Savient's (Nasdaq: SVNT) gout drug Krystexxa for a blockbuster, but that doesn't mean Lesinurad is doomed to poor sales as well. Savient unsurprisingly traded down 6% for the day, as it appears the company is running out of time to gain traction for its Krystexxa.

AstraZeneca says more (desperately needed) M&A is on the way and investors should hope that means more targeted deals like Ardea. Overpay on one or two late-stage assets, and it's not the end of the world. A big merger, on the other hand, could end disastrously.

Keryx Pharmaceuticals (Nasdaq: KERX) started hot and kept running to a nearly 30% gain on news that Zerenex aced a phase 3 study in the land of the rising sun. Keryx has a lot riding on its late-stage renal disease treatment after its former lead drug perifosine, shared with partner Aeterna Zentaris (Nasdaq: AEZS), met with failure in a phase 3 trial for colon cancer. Zerenex may not have the large market opportunity here, but perifosine is the company's best chance to turn a profit in the near future. It was shown in the Japanese trial to work better than RenaGel. That may be enough to get approved, but Zerenex will need to do better to hold off generic competition when Renagel goes off patent in 2014.

Finally we have Amylin (Nasdaq: AMLN), which hit a new 52-week high today, before closing up 14%. The company purportedly rejected Bristol-Myers Squibb's buyout offer at $22 a share, prompting activist investor Carl Icahn to sue the biotech. Amlyin may have correctly assessed its value, because shares now sit north of $26, as reports emerge that the company is entertaining multiple offers. The sudden enthusiasm comes after ending a sour relationship with Eli Lilly and, more importantly, getting approval for Bydureon, the once-weekly version of twice-a-day diabetes treatment Byetta. If Amylin can generate a bidding war, then the 90% run since Bydureon's approval is far from over.

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