Shares of Idenix Pharmaceuticals are up more than 230% after announcing Merck will buy the company for $US3.85 billion.
The deal values Idenix $US24.50 per share; shares of Idenix closed at $US7.23 on Friday.
Idenix is engaged in the development of hepatitis C drugs, and according to the merger announcement, Idenix has three hepatitis C drugs in clinical development.
Gilead Sciences, which has seen shares gain more than 120% since the beginning of 2013, received FDA approval for its hepatitis C drug Sovaldi in December. Shares of Gilead are down about 1.5% in pre-market trading.
Merck and Idenix expect the deal to close in the third quarter. In pre-market trading Merck is down 0.7%.
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