What: Shares of the immune disorder specialist Receptos (NASDAQ: RCPT) climbed by 10.4% today after agreeing to a $7.2 billion buyout offer, or $232 per share, from Celgene Corp. (NASDAQ:CELG). This offer represents roughly a 12% premium compared to where Receptos' shares were trading yesterday. 

This deal significantly bolsters Celgene's Inflammation & Immunology business segment by giving the biotech giant access to Receptos' experimental relapsing multiple sclerosis drug, ozanimod, that's presently in late-stage development as a potential "best-in-class" treatment for this indication, and in earlier stage testing for ulcerative colitis and Crohn's disease. Celgene believes ozanimod could see peak sales in the neighborhood of $4 to $6 billion, if it's able to rack up approvals for all three indications. 

So what: Receptos has repeatedly been the subject of the buyout rumor mill over the last few months, and there's been a ton of chatter that pharmaceutical heavyweights like AstraZeneca, Gilead Sciences, and Teva Pharmaceutical Industries were keenly interested in acquiring this clinical-stage biopharma. The noteworthy part is that Receptos' management was reportedly holding out for an offer somewhere in the area of $350 a share, and several unconfirmed reports surfaced that they even rejected an offer from Gilead and Teva at $280 a share last June.

Now what: This steep discount -- relative to the numbers being floated on the Street last month -- certainly didn't go unnoticed by Receptos' shareholders. Immediately after this deal was announced, for instance, numerous law firms announced that they were investigating the terms of this buyout, given that multiple analysts estimated Receptos' current value at closer to $348 a share. 

Receptos thus looks like it just gave Celgene one heck of a sweetheart deal, especially in light of Celgene's own estimate of ozanimod's commercial potential. At the very least, this buyout stands in stark contrast, from a premium standpoint, to most of the other M&A activity taking place across the industry right now.

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