Idenix does not believe that the patent application at issue in the interference is relevant to any of the compounds currently under development, including IDX719, its NS5A inhibitor which is expected to begin phase II studies in the first half of 2013, or its uridine nucleoside for which the Company expects to file an investigational new drug application in the first half of 2013.ABOUT IDENIX Idenix Pharmaceuticals, Inc., headquartered in Cambridge, Massachusetts, is a biopharmaceutical Company engaged in the discovery and development of drugs for the treatment of human viral diseases. Idenix's current focus is on the treatment of patients with hepatitis C infection. For further information about Idenix, please refer to www.idenix.com . CONFERENCE CALL AND WEBCAST INFORMATION Idenix will hold a conference call on Monday, March 25, 2013 at 8:00 a.m. ET. To access the call please dial (877) 640-9809 U.S./Canada or (914) 495-8528 International and enter passcode 28471980 or to listen to a live webcast go to "Events & Presentations" in the Idenix Investor Center at www.idenix.com . A replay of the call will also be available from 11:00 a.m. ET on March 25, 2013 until April 1, 2013, at 11:59 p.m. ET. To access the replay, please dial (855) 859-2056 U.S./Canada or (404) 537-3406 International and enter passcode 28471980. An archived webcast will also be available for one week after the call on the Idenix website. FORWARD-LOOKING STATEMENTS This press release contains "forward-looking statements" for purposes of the safe harbor provisions of The Private Securities Litigation Reform Act of 1995, including but not limited to the statements regarding the Company's future business and financial performance. For this purpose, any statements contained herein that are not statements of historical fact may be deemed forward-looking statements. Without limiting the foregoing, the words "expect," "will," "believe," and similar expressions are also intended to identify forward-looking statements, as are expressed or implied statements with respect to future actions taken by the Company, including any expressed or implied statements regarding future litigation or adverse proceedings. Actual results may differ materially from those indicated by such forward-looking statements as a result of risks and uncertainties, including but not limited to the following: the Company's ability to obtain, maintain and enforce patent and other intellectual property protection for its product candidates and its discoveries. Such forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause actual results to be materially different from any future results, performance or achievements expressed or implied by such statements. These and other risks which may impact management's expectations are described in greater detail under the heading "Risk Factors" in the Company's annual report on Form 10-K for the year ended December 31, 2012 as filed with the Securities and Exchange Commission (SEC) and in any subsequent periodic or current report that the Company files with the SEC.