Partial 24-Week Data Demonstrate Valopicitabine (NM283) Combined with Pegylated Interferon Continues to Produce Greater Viral Su

CAMBRIDGE, Mass. and KOHALA COAST, HI, Dec. 14  /PRNewswire-FirstCall/ -- Idenix Pharmaceuticals, Inc. (NASDAQ:IDIX) announced partial 24-week data today from an ongoing phase IIb clinical trial evaluating valopicitabine combined with pegylated interferon in treatment-refractory patients with chronic hepatitis C.  These 24-week data demonstrate continued increased viral suppression in patients treated with the combination of valopicitabine plus pegylated interferon compared to patients retreated with ribavirin plus pegylated interferon.  All patients enrolled in this clinical trial are chronically infected with the genotype 1 strain of hepatitis C and have previously failed to respond to treatment with pegylated interferon plus ribavirin.  Dr. Christopher O'Brien, Professor of Clinical Medicine at the University of Miami and a principal investigator in the trial, presented these data at the Hep DART meeting in Hawaii.

This 48-week phase IIb clinical trial is evaluating three dosing regimens of valopicitabine, administered once-daily, in combination with pegylated interferon compared to retreatment with combination therapy of pegylated interferon plus ribavirin.  Valopicitabine combination dosing regimens include: valopicitabine 400 mg; valopicitabine ramping from 400 mg to 800 mg during Week 1 and continuing thereafter with 800 mg; and valopicitabine 800 mg.  In all three arms, valopicitabine is given in combination with pegylated interferon alfa-2a (Pegasys(R)) 180 µg with the initial dose of pegylated interferon administered on Day 8.

The partial 24-week data for 162 patients out of 178 patients in the intent to treat population demonstrated that the two higher-dose arms of valopicitabine plus pegylated interferon produced greater suppression of serum HCV RNA compared to the ribavirin plus pegylated interferon retreatment control arm. At Week 24, mean HCV RNA reductions in the two high-dose arms of valopicitabine plus pegylated interferon were 3.01 log10 and 3.32 log10, with 11 percent and 25 percent of patients achieving undetectable levels of virus. In comparison, patients in the pegylated interferon plus ribavirin retreatment control arm showed a mean HCV RNA reduction of 2.31 log10, with 19 percent of patients achieving undetectable levels of virus.

Patients in valopicitabine-containing arms also demonstrated a more consistent response than patients in the retreatment control arm.  At Week 24, the median HCV RNA reduction in the control arm was 1.21 log10, compared to median HCV RNA reductions of 3.01 log10 and 3.29 log10 in the two high-dose valopicitabine combination arms. Correspondingly, patients in the retreatment control arm had much higher residual viral levels at Week 24, with a median residual viral load (HCV RNA level) of 5.35 log10 copies/mL in the control arm, compared to residual HCV RNA levels of 3.81 log10 and 3.57 log10 copies/mL in the two high-dose valopicitabine combination arms.

"It is encouraging that we continue to see substantial viral reductions out to week 24 with the valopicitabine and pegylated interferon combination treatment arms in this refractory patient population," said Dr. O'Brien. "The consistency of response seen in the individual patient data in the valopicitabine combination arms compared to the control arm suggests that the differential in viral load reductions may continue to widen in favor of the valopicitabine combination arms as treatment progresses," he said.

In this phase IIb clinical trial, valopicitabine has demonstrated satisfactory safety and tolerance overall. To date, in this ongoing clinical trial, a low percentage of patients on valopicitabine have discontinued due to adverse events.  Four serious adverse events, diverse in nature, were considered attributable to combination treatment with valopicitabine plus pegylated interferon and all cases resolved after discontinuation of treatment.

The company anticipates presenting the complete 24-week data from this phase IIb clinical trial at scientific conferences in the spring of 2006.

About Valopicitabine

Valopicitabine, which is administered orally once a day, is intended to block HCV replication by specifically inhibiting the HCV RNA polymerase, the enzyme that makes new copies of HCV viral chromosome inside infected cells. Initial phase I clinical trials sponsored by Idenix showed that valopicitabine is active in patients infected with the genotype 1 strain of HCV, the strain that infects the majority of patients in North America, Europe, and Japan. The ongoing clinical trials are designed to evaluate the combination of valopicitabine and pegylated interferon in hepatitis C genotype 1 patients who previously failed to respond to antiviral treatment, as well as in genotype 1 patients who have not been treated previously. Preliminary results from phase II clinical trials to date have demonstrated that the antiviral effect of valopicitabine is enhanced when this agent is used in combination with pegylated interferon.

About Hepatitis C

Hepatitis C is an infectious liver disease caused by the hepatitis C virus. The World Health Organization estimates that 170 million individuals worldwide carry chronic HCV infection, with 3 to 4 million new infections occurring globally each year. It is the most common chronic blood-borne infection in the United States with 2.7 million chronically infected. Chronic HCV infection causes inflammation of the liver, which may cause progressive liver damage that can lead to cirrhosis (liver scarring), hepatocellular carcinoma (liver cancer), liver failure, and death. Patients infected with HCV genotype 1 are difficult to treat, with half or fewer such patients achieving sustained responses to current standard treatment regimens involving a combination of pegylated interferon plus ribavirin. These "non-responders" or treatment-refractory patients comprise a growing patient population, who have no proven alternative treatments available and who are at risk for progressive HCV-associated liver disease. As the prevalence of severe liver disease attributable to chronic hepatitis C rises, deaths due to complications from hepatitis C infection, currently 8,000 to 10,000 per year in the United States, are expected to increase dramatically over the next 15 to 20 years.

About Idenix

Idenix Pharmaceuticals, Inc. is a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral and other infectious diseases. Idenix's current focus is on the treatment of infections caused by hepatitis B virus, hepatitis C virus and human immunodeficiency virus (HIV).  Idenix's headquarters are located in Cambridge, Massachusetts and it has drug discovery and development operations in Montpellier, France and drug discovery operations in Cagliari, Italy.  For further information about Idenix, please refer to http://www.idenix.com/.

Forward-looking Statements

This press release contains "forward-looking statements" within the meaning of The Private Securities Litigation Reform Act of 1995. Such forward- looking statements can be identified by the use of forward-looking terminology such as, "it is encouraging," "suggests," "anticipates," "may," or similar expressions or by express or implied discussions regarding the potential therapeutic benefits and successful development of valopicitabine, or regarding any potential future revenues from valopicitabine. Such forward- looking statements are subject to numerous factors, risks and uncertainties that may cause actual events or results to differ materially from the company's current expectations. There can be no guarantee that valopicitabine will be successfully developed or approved for sale in any market, or that it will reach any particular level of revenue. In particular, management's expectations regarding valopicitabine could be affected by risks and uncertainties relating to the results of clinical trials and other studies with respect to valopicitabine, including further analysis of existing clinical data, additional data from the ongoing phase IIb clinical trials and data from any subsequent phase III clinical trials; the timing, acceptance and approval, if any, of regulatory filings submitted to the FDA or other regulatory bodies around the world, the company's dependence on its collaboration with Novartis Pharma AG; the company's ability to obtain additional funding required to conduct its research, development and commercialization activities; the ability of the company to attract and retain qualified personnel; competition in general; and the company's ability to obtain, maintain and enforce patent and other intellectual property protection for valopicitabine. These and other risks which may impact management's expectations regarding valopicitabine are described in greater detail under the caption "Factors That May Affect Future Results" in the company's quarterly report on Form 10-Q for the quarter ended September 30, 2005 and filed with the Securities and Exchange Commission and other filings that the company makes with the Securities and Exchange Commission.

All forward-looking statements reflect the company's expectations only as of the date of this release 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. Idenix anticipates that subsequent events and developments may cause these views, expectations and beliefs to change. However, while Idenix may elect to update these forward-looking statements at some point in the future, it specifically disclaims any obligation to do so.

  Pegasys(R) is a registered trademark of Hoffmann-La Roche, Inc.

   Idenix Pharmaceuticals' Contact:
   Teri Dahlman: 617-995-9905


DATASOURCE: Idenix Pharmaceuticals, Inc.



CONTACT:  Teri Dahlman of Idenix Pharmaceuticals, Inc., [phone] 



Web site:  http://www.idenix.com/

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