ABOUT IDX719IDX719 is an NS5A inhibitor with low picomolar, pan-genotypic antiviral activity in vitro. To date, IDX719 has been safe and well tolerated after single and multiple doses of up to 100 mg in healthy volunteers (n=36; up to 7 days duration) and HCV-infected patients (n=69; up to 3 days duration). There have been no treatment-emergent serious adverse events reported in the program. IDX719 has demonstrated potent pan-genotypic antiviral activity in HCV-infected patients with mean maximal viral load reductions up to approximately 4.0 log 10 IU/mL across HCV genotypes 1-4 in a proof-of-concept, three-day monotherapy study. ABOUT HEPATITIS C Hepatitis C virus is a common blood-borne pathogen infecting three to four million people worldwide annually. The World Health Organization (WHO) estimates that more than 170 million people worldwide are chronically infected with HCV, representing a nearly 5-fold greater prevalence than human immunodeficiency virus. 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 HCV. For further information about Idenix, please refer to www.idenix.com . 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. 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," "plans," "anticipates," "intends," "will," and similar expressions are also intended to identify forward-looking statements, as are any expressed or implied statements with respect to: the Company's plans to continue to developing nucleotide polymerase inhibitors for HCV; its clinical development plans for its uridine nucleotide analog drug candidate and IDX719; its plans to advance other preclinical nucleotides; and statements regarding the efficacy and safety of its clinical compounds. 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: there can be no guarantees that the Company will advance any clinical product candidate or other component of its potential pipeline to the clinic, to the regulatory process or to commercialization due to numerous risks inherent in pharmaceutical research and development; management's expectations could be affected by unexpected regulatory actions or delays; uncertainties relating to, or unsuccessful results of, preclinical and clinical trials, including additional data relating to the ongoing clinical trials evaluating its product candidates; the Company's ability to obtain additional funding required to conduct its research, development and commercialization activities; competition; and 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 important 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.