Achillion Pharmaceuticals' stock rockets after Alexion Pharmaceuticals $930 million buyout deal

Shares of Achillion Pharmaceuticals Inc. rocketed 82% in premarket trading Wednesday, after the biopharmaceutical company agreed to be acquired by Alexion Pharmaceuticals Inc. in a cash deal valued at $930 million. Alexion's stock slipped 0.1% ahead of the open. Under terms of the deal, Alexion will pay $6.30 for each Achillion share outstanding, which is 73% above Tuesday's closing price of $3.65 and implies a market-capitalization of $880.05 million. The deal also includes potential for an additional payment for Achillion shares in the form of contingent value rights (CVRs) to be paid if certain clinical and regulatory milestones are achieved. The CVRs include $1 a share for U.S. Food and Drug Administration approval of danicopan and $1 a share for ACH-5228 phase 3 initiation. Danicopan, Achillion's lead drug candidate, has received breakthrough therapy designation for treatment, in combination with a C5 monoclonal antibody, for patients with a rare blood disorder paroxysmal nocturnal hemoglobinuria (PNH). Over the past three months, Achillion's stock has rallied 47.8% and Alexion shares have dropped 14.7%, while the iShares Nasdaq Biotechnology ETF has slipped 2.9% and the S&P 500 has eased 0.3%.

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