Positive interim data from Idenix IDX184 12-week phase IIb trial on HCV

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 interim data from a 12-week phase IIb clinical trial of IDX184, the Company's lead product candidate for the treatment of hepatitis C virus (HCV) infection.  IDX184, a pan-genotypic oral nucleotide polymerase inhibitor, has demonstrated a high barrier to resistance in vitro and potent antiviral activity in both preclinical and clinical studies.

IDX184 Phase IIb Study DesignIn July 2011, the Company initiated enrollment of treatment-naive genotype 1 HCV-infected patients into a randomized, double-blind, parallel group phase IIb clinical trial of IDX184.  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 pegylated interferon and ribavirin (PegIFN/RBV). Study objectives include safety and tolerability, and antiviral activity endpoints.

IDX184 Phase IIb Interim Study ResultsThe first 31 patients have completed 28 days of treatment, and the interim data have shown that IDX184 was well-tolerated and that there were no serious adverse events associated with therapy. The side effect profile was consistent with that seen with PegIFN/RBV. The independent DSMB has reviewed the data for the first 31 patients and has recommended continuing enrollment of the study. The Company has submitted the interim data, along with the DSMB's recommendations, to the U.S. Food and Drug Administration (FDA) and is requesting the continuation of this study and removal of the partial clinical hold for IDX184.

RVR findings demonstrated that 73% of patients in the 100 mg IDX184 arm>

"These interim results are encouraging as they confirm the antiviral activity and safety of IDX184 in combination with pegylated interferon and ribavirin," Eric Lawitz, M.D., of Alamo Medical Research, Camden Medical Center, stated. "Nucleotide drugs such as IDX184 are becoming an important component in the rapidly evolving treatment regimens for HCV. Eventually, the goal for treatment will be to reduce or eliminate reliance on interferon and to shift to all oral combinations of direct-acting antiviral agents that can reduce potential side effects and decrease the amount of time on therapy."

Ron Renaud, President and Chief Executive Officer of Idenix, commented, "We are very pleased with the interim results for IDX184 and with the progress we made in 2011 across our programs. In 2012, we will build on this progress and believe we are well positioned to play a major role in treating HCV patients for the foreseeable future."