Shares of Synageva Biopharma Corp. (NASDAQ:GEVA) skyrocketed more than 115 percent Wednesday to an all-time high of $215.98, after Alexion Pharmaceuticals, Inc. (NASDAQ:ALXN) announced it will buy the biopharmaceutical company for $8.4 billion. The deal, in which Alexion will pay cash and stock, values Synageva at more than twice its current market value. 

Cheshire, Connecticut- based Alexion Pharmaceuticals, currently valued at $33 billion, will have eight medicines in clinical trials following the transaction, including Synageva's main product under development, Kanuma, a treatment for lysosomal acid lipase deficiency (LAL), a genetic disease that leads to the buildup of fatty material in the liver and blood vessels.

Shares of Alexion dropped 10 percent to $151.27 in afternoon trading. 

The deal marks the latest in the biotech space this year following a series of blockbuster deals. Teva Pharmaceutical Industries Inc. completed its purchase of Auspex Pharmaceuticals for $3.5 billion this week, and Ireland-based Shire announced plans in January to buy NPS Pharmaceuticals Inc. for $5.2 billion.

Following the announcement Wednesday, the Nasdaq Biotechnology index jumped more than 1 percent. The index, which includes companies such as Synageva, Alexion, Mylan NV and Shire, has gained nearly 12 percent so far this year.

The Lexington, Massachusetts-based Synageva, which has a market capitalization of $7 billion, is focused on the development of therapeutic products for patients with rare diseases. Synageva’s Kanuma is currently under “Priority Review” with the U.S. Food and Drug Administration (FDA) and has been granted “Breakthrough Therapy Designation” by the FDA for LAL deficiency presenting in infants. Regulatory decisions in the U.S. and Europe are expected in the second half of 2015.

Meanwhile, Alexion Pharmaceuticals develops therapeutic products for patients with severe and ultra-rare disorders, including its approved product Soliris (eculizumab), the first and only therapeutic approved for patients with two ultra-rare and severe disorders resulting from chronic uncontrolled activation of the complement component of the immune system. The two disorders include paroxysmal nocturnal hemoglobinuria (PNH), an ultra-rare and life-threatening blood disorder, and atypical hemolytic uremic syndrome (aHUS), an ultra-rare and life-threatening genetic disease.

“As Kanuma moves closer toward patients who suffer from LAL Deficiency, and the other pipeline programs continue to progress, I am confident that this transaction will help continue to improve the lives of patients with LAL Deficiency and other devastating, rare diseases for years to come,” Sanj K. Patel, president and chief executive officer of Synageva, said in a statement Wednesday. 

Under the terms of the deal, Alexion is offering $115 in cash and 0.6581 of its shares, or $225.92 per Synageva share. 

The deal is expected to close mid-2015.