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November 10, 2012

Idenix Pharmaceuticals Reports Clinical Data for HCV Drug Candidates - IDX719 and IDX184 - at the American Association for the Study of Liver Diseases (AASLD) Annual Meeting

CAMBRIDGE, Mass., Nov. 10, 2012 (GLOBE NEWSWIRE) -- Idenix Pharmaceuticals, Inc. (Nasdaq:IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases, today announced the presentation of safety and antiviral activity results for the Company's clinical-stage hepatitis C virus (HCV) drug candidates — IDX719, a next-generation pan-genotypic NS5A inhibitor, and IDX184, a nucleotide polymerase inhibitor. Idenix presented updated clinical findings from a three-day proof-of-concept study, which demonstrated that IDX719 was well-tolerated at daily doses up to 100 mg and showed potent antiviral activity across HCV genotypes 1-4, with mean maximal viral load reductions up to approximately 4.0 log10 IU/mL. The Company also presented updated cardiovascular safety and antiviral activity data from the phase IIb study of IDX184 in combination with pegylated interferon and ribavirin (PegIFN/RBV). The IDX719 and IDX184 clinical data are being reported in poster presentations during the 63rd Annual Meeting for the American Association for the Study of Liver Diseases (AASLD) in Boston.

IDX719 three-day proof-of-concept study

Study design

The three-day proof-of-concept study evaluated IDX719 in 64 treatment-naïve, genotype 1, 2, 3 or 4 HCV-infected patients. Genotype 1 patients were randomized to receive placebo, 25 mg QD (once-daily), 50 mg QD, 50 mg BID (twice-daily) or 100 mg QD for three days. Genotype 2, 3 or 4 patients were randomized to receive placebo, 50 mg BID or 100 mg QD for three days.

Study results

  • In genotype 1a patients (n=29), mean maximal viral load reductions ranged from 3.2 log10 IU/mL to 3.6 log10 IU/mL across treatment groups.
  • In genotype 1b patients (n=5), mean maximal viral load reductions were 3.0 log10 IU/mL in the 25 mg QD arm, and 4.3 log10 IU/mL in the 50 mg QD arm.
  • In genotype 2 patients (n=10), the mean maximal viral load reduction was 2.0 log10 IU/mL in both the 50 mg BID and 100 mg QD dose arms with a greater variability in responses among these patients (range: 0.3- 4.1 log10 IU/mL).  Four of the genotype 2 patients responded well to IDX719 treatment, and four patients had maximal reductions that were less than 1.0 log10 IU/mL. The decrease in viral load response in genotype 2 patients was associated with the pre-existence or emergence of the M31 polymorphism in the HCV NS5A gene.
  • In genotype 3 patients (n=10), mean maximal viral load reductions were 3.3 log10 IU/mL in the 50 mg BID arm and 3.4 log10 IU/mL in the 100 mg QD arm.
  • In genotype 4 patients (n=10), mean maximal viral load reductions were 3.9 log10 IU/mL in the 50 mg BID dose arm and 3.6 log10 IU/mL in the 100 mg QD dose arm.

No patients experienced a rebound ( > 1.0 log10 IU/mL increase over the lowest viral load) during the treatment period and maximum viral load reductions were typically achieved within 24-72 hours post dose. There were no safety-related discontinuations or serious adverse events. IDX719 was safe and well tolerated at daily doses up to 100 mg for three days. Idenix intends to initiate a phase II clinical trial evaluating IDX719 in combination therapy in 2013.

"To our knowledge, these are the most advanced clinical results validating the robust, pan-genotypic activity of an NS5A inhibitor in HCV," commented Douglas Mayers, M.D., Chief Medical Officer of Idenix. "We look forward to advancing this promising drug candidate into the next phase of clinical testing."

IDX184 phase IIb combination study

Study design

A randomized, double-blind phase IIb clinical trial is evaluating IDX184 in 67 treatment-naive genotype 1 HCV-infected patients. The study features two treatment arms, either 50 mg or 100 mg of IDX184 administered once-daily for 12 weeks, each arm in combination with PegIFN/RBV. Response-guided therapy is used to complete an additional 12 or 36 weeks of PegIFN/RBV treatment.

Study results

All patients had completed treatment with IDX184 when in August 2012, the U.S. Food and Drug Administration (FDA) placed IDX184 on partial clinical hold due to cardiac adverse events seen in a competitor's phase II clinical trial evaluating BMS-986094. The overall safety profile of IDX184 in combination with PegIFN/RBV remains consistent with the known safety profile of PegIFN/RBV alone. In light of the clinical hold, Idenix has evaluated multiple cardiac safety measurements, including electrocardiograms, echocardiograms and two cardiac biomarkers, ultrasensitive troponins and NT-proBNPs, from the ongoing IDX184 phase IIb study and has found no evidence of severe cardiac findings to date.

Similar numbers of patients achieved a complete early virologic response (cEVR; virus levels < 25 IU/mL at 12 weeks) in the 50 mg (26/34; 76%) and in the 100 mg (27/33; 82%) groups. Rates of rapid virologic response (RVR; virus levels < 25 IU/mL at 4 weeks) were also comparable between the 50 mg (18/34; 53%) and the 100 mg (18/33; 55%) groups. The difference in response rates from data previously reported is primarily due to an increased number of genotype 1b patients as well as IL28B CT/TT patients who were enrolled in the second patient cohort. No patient experienced virologic breakthrough during the 12-week IDX184/Peg-IFN/RBV treatment period. The majority of patients are in the ongoing PegIFN/RBV extension treatment phase, and complete sustained virologic response (SVR) results will be available in 2013.

"The IDX184 presentation at AASLD details much of the key clinical data we intend to submit to the FDA in our response package by the end of the year," said Ron Renaud, Idenix's President and Chief Executive Officer. "As always, patient safety is our top priority, and I am pleased with the thoroughness with which our R&D team and the trial investigators have gathered this information and that there have been no treatment-emergent cardiac or renal serious adverse events (SAEs) to date in the ongoing IDX184 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 hepatitis C infection. 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, 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," "plans," "anticipates," "intends," "will," and similar expressions are also intended to identify forward-looking statements, as are expressed or implied statements with respect to the Company's potential pipeline candidates, including any expressed or implied statements regarding the efficacy and safety of IDX184 and IDX719; and the likelihood and success of any future clinical trials involving IDX184 or IDX719. 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; management's expectations could be affected by unexpected regulatory actions or delays; uncertainties relating to, or unsuccessful results of, 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 in general; 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 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, 2011 and the quarterly report on Form 10-Q for the quarter ended September 30, 2012, each as filed with the Securities and Exchange Commission (SEC) and in any subsequent periodic or current report that the Company files with the SEC.

All forward-looking statements reflect the Company's estimates only as of the date of this release  (unless another date is indicated) and should not be relied upon as reflecting the Company's views, expectations or beliefs at any date subsequent to the date of this release. While Idenix may elect to update these forward-looking statements at some point in the future, it specifically disclaims any obligation to do so, even if the Company's estimates change.

CONTACT: Idenix Pharmaceuticals Contacts:

         Kelly Barry (617) 995-9033 (media)

         Teri Dahlman (617) 995-9807 (investors)
Source: Idenix Pharmaceuticals

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