Healthcare Industry News:  Novartis Pharma AG 

Biopharmaceuticals

 News Release - January 9, 2006

Idenix Pharmaceuticals Reports Positive 4-Week Data From A Phase IIb Clinical Trial Evaluating Valopicitabine (NM283) Combined with Pegylated Interferon in Treatment-Naive Hepatitis C Patients

SAN FRANCISCO, Jan. 9 (HSMN NewsFeed) -- Idenix Pharmaceuticals, Inc. (Nasdaq: IDIX ) announced partial 4-week data today from an ongoing phase IIb clinical trial demonstrating that treatment with valopicitabine combined with pegylated interferon resulted in rapid and marked reduction in virus levels in treatment-na´ve genotype 1 hepatitis C patients. The mean reduction in virus levels was greater than or equal to 4 log10, or 99.99 percent, after 4 weeks of treatment among patients in the two dose groups that began on Day 1 with 800 mg doses of valopicitabine. This trial is almost fully enrolled, with a target enrollment of 175 patients at more than 20 medical centers in the U.S. These partial data will be presented at the 24th Annual JP Morgan Healthcare Conference on Wednesday, January 11 at 2:00 p.m. (PST).

"We are quite encouraged by the virologic responses demonstrated to date with these four-week data and believe that valopicitabine combined with pegylated interferon has the potential to substantially improve treatment efficacy compared to current therapy for chronic hepatitis C patients," said Jean-Pierre Sommadossi, Ph.D., chairman and chief executive officer of Idenix. "We look forward to presenting additional data from this phase IIb clinical trial in the spring and initiating a phase III clinical trial in this patient population in the second half of 2006."

This ongoing 48-week phase IIb clinical trial in treatment-na´ve patients includes the following five randomized treatment arms, all involving dosing regimens of valopicitabine, administered once-daily, in combination with pegylated interferon alfa-2a (Pegasys«) 180 Ág per week: (A) pegylated interferon beginning on Day 8 plus valopicitabine ramping from 400 mg to 800 mg beginning at Day 29; (B) valopicitabine 200 mg beginning on Day 1 plus pegylated interferon beginning on Day 8; ę valopicitabine ramping from 400 mg to 800 mg beginning on Day 1 plus pegylated interferon beginning on Day 8; (D) valopicitabine 800 mg beginning on Day 1 plus pegylated interferon beginning on Day 8; and (E) valopicitabine 800 mg plus pegylated interferon, both beginning on Day 1.

The partial 4-week data demonstrated that the four treatment arms that included valopicitabine in combination with pegylated interferon during the first four weeks (arms B-E) all produced proportionally greater suppression of serum HCV RNA as compared to the arm that included pegylated interferon alone for the first four weeks (arm A). At Week 4, mean HCV RNA reductions were 4.00 log10, 4.17 log10, 3.50 log10 and 3.09 log10, respectively, for arm E (15 patients), arm D (14 patients), arm C (18 patients) and arm B (17 patients). In comparison, patients in the arm receiving pegylated interferon alone for the first 4 weeks (arm A, 19 patients) achieved a mean HCV RNA reduction of 2.00 log10 . The mean HCV RNA reduction for the two 800 mg dose valopicitabine arms (arms D and E) was significantly greater than that of the pegylated interferon alone arm (arm A) (p<0.01). The addition of 800 mg of valopicitabine to pegylated interferon (arm D) led to viral clearance (PCR- negativity) in 50 percent of patients, compared to 11 percent in arm A, at Week 4.

Rapid virologic response (RVR), or a greater than or equal to 2 log10 reduction in viral load by Week 4, was achieved in 93 percent of patients in the two 800 mg dose valopicitabine arms (arms D and E), indicative of a degree of virologic response which, in treatment na´ve patients, is thought to correlate with potentially sustained viral clearance post treatment.

Preliminary data from the first 4 weeks of treatment indicate valopicitabine continues to demonstrate adequate tolerability when administered in combination with pegylated interferon. Of the 150 patients enrolled in the trial to date, ten patients discontinued treatment by week four; nine discontinuations were due to adverse events (including 1 SAE of severe dehydration), and one for logistical reasons.

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. Data from the phase I clinical trial sponsored by Idenix demonstrated 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 phase II 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 these 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.(1)

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, "target," "will be," "quite encouraged," "believe," "potential", "look forward," "expected," 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.

(1)Davis G. et al., Liver Transplantation 2003; Vol 9, No 4:331-338 Pegasys« is a registered trademark of Hoffmann-La Roche, Inc.

Idenix Pharmaceuticals' Contact:
Teri Dahlman office: 617-995-9905 or cell: 617-817-8655
(please call cell number from 1/9/06 - 1/12/06)


Source: Idenix Pharmaceuticals

Issuer of this News Release is solely responsible for its content.
Please address inquiries directly to the issuing company.



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