Idenix Pharmaceuticals, Inc. And Novartis Corporation Release: New Data Shows Telbivudine Provided Significantly Greater Response Compared To Lamivudine In The Treatment Of Chinese Patients With Chronic Hepatitis B

SHANGHAI, China and CAMBRIDGE, Mass., March 27 /PRNewswire-FirstCall/ -- Idenix Pharmaceuticals, Inc. and Novartis today announced new data that demonstrate telbivudine, an investigational oral, once-daily nucleoside analogue, provided significantly greater antiviral and clinical efficacy in Chinese patients with chronic hepatitis B (CHB) after one-year of treatment when compared with a current standard of care, lamivudine. The one-year results from a phase III registration trial conducted in China were presented today at the biennial meeting of the International Liver Congress in Shanghai.

These data, together with one-year data from the international phase III GLOBE study, the largest registration trial ever conducted for a CHB treatment, were included in a recent regulatory submission to Chinese health authorities for marketing approval of telbivudine.

“The results from this study are very promising,” said Dr. Jinlin Hou, Director and Professor of Hepatology Unit and Department of Infectious Diseases at Nanfang Hospital, Southern Medical University, Guangzhou, China and a principal investigator in the study. “Telbivudine displayed increased efficacy compared to lamivudine on the key viral and clinical markers including significantly greater viral suppression, a higher percentage of patients with normalization of liver enzymes and a higher proportion of patients with HBeAg loss at one year. These data suggest that telbivudine, if approved in China, may become an important new treatment option for the millions of Chinese patients with this potentially life-threatening disease.”

“Chronic hepatitis B is a major public health threat worldwide and is a particularly serious problem in China, where nearly 1 out of 10 people are infected. We are pleased that telbivudine has now been submitted for regulatory approval in China and could provide a new treatment option for those patients,” said Jean-Pierre Sommadossi, chairman and chief executive officer of Idenix. “The positive results achieved in this trial are similar to the one-year results seen in the GLOBE study and demonstrated that telbivudine provided rapid and profound viral suppression in patients with chronic hepatitis B.”

About One-Year Results of Chinese Phase III Trial(1)

This trial is an ongoing, randomized, double-blind trial comparing 2 years of treatment with telbivudine or lamivudine in 332 Chinese adults with chronic hepatitis B. The majority of patients in this trial were HBeAg-positive (n=290) although HBeAg-negative patients also participated (n=42).

After one year of treatment, telbivudine displayed significantly greater antiviral and clinical efficacy compared with lamivudine. Telbivudine significantly reduced virus levels (HBV DNA) by 6.22 log10, or more than 1 million-fold, compared with 5.4 log10 for lamivudine (p<0.001). In addition, undetectable virus levels were achieved by significantly more telbivudine- treated patients compared with lamivudine-treated patients (70 and 43 percent, respectively; p<0.001). Therapeutic response (defined as a reduction of HBV DNA to below 5 log 10 copies/mL with HBeAg loss or ALT normalization) was achieved by a significantly higher percentage of telbivudine-treated patients compared with lamivudine-treated patients (87 and 64 percent, respectively; p<0.001).

Significantly more telbivudine-treated patients achieved normalization of liver enzymes (ALT) compared with lamivudine-treated patients (89 and 76 percent, respectively; p=0.003). In addition, HBeAg loss (in HBeAg positive patients only and an indicator of a potential durable response to treatment) occurred in a significantly higher percent of telbivudine-treated patients compared with lamivudine-treated patients (31 and 20 percent, respectively; p=0.047).

Seroconversion rates (in HBeAg positive patients only) were 25 percent for telbivudine and 18 percent for lamivudine. Resistance rates were 4.5 percent for telbivudine and 10.1 percent for lamivudine.

The overall safety profiles for telbivudine and lamivudine in this study closely resembled the recently-reported results from the GLOBE study. The rate of clinical adverse events was similar between the telbivudine and lamivudine treatment groups, with nasopharyngitis, (25 and 21 percent respectively) upper respiratory tract infection, (3.0 and 4.8 percent respectively) and fatigue, (3.6 percent for both treatment groups) occurring most commonly. As in the GLOBE study, serum ALT elevations were more common in lamivudine-treated patients compared to telbivudine and creatine kinase elevations, not requiring treatment modification, were more common with telbivudine compared to lamivudine.

About Chronic Hepatitis B

Chronic hepatitis B is the tenth leading cause of death worldwide(2) with approximately 350 million people chronically infected (lifelong infection).(3) Additionally, chronic hepatitis B is responsible for up to 80 percent of the world’s primary liver cancer(4), and annually an estimated 1.2 million individuals die from hepatitis B-related chronic liver disease.(2) Mainland China has the largest population affected by the hepatitis B virus of any nation with 120 million infected (nearly one out of every ten people in China) and 30 million chronic sufferers.(5)

Idenix/Novartis Collaboration

Idenix is developing its hepatitis B clinical product candidates, telbivudine and valtorcitabine, in collaboration with Novartis Pharma AG under a development and commercialization arrangement established in May 2003. The collaboration arrangement further provides that Novartis Pharma AG and Idenix will co-promote telbivudine and valtorcitabine and other product candidates that Novartis Pharma AG has licensed, if successfully developed and approved for marketing, in the United States, France, Germany, Italy, Spain and the UK. Novartis Pharma AG holds the exclusive license to commercialize telbivudine and valtorcitabine in the rest of the world. The collaboration also provides Novartis Pharma AG with an exclusive option to license and collaborate with Idenix in the development and commercialization of other product candidates in Idenix’s portfolio, including valopicitabine (NM283), a direct antiviral for the treatment of chronic hepatitis C.

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.

About Novartis

Novartis Pharmaceuticals Corporation researches, develops, manufactures and markets leading innovative prescription drugs used to treat a number of diseases and conditions, including central nervous system disorders, organ transplantation, cardiovascular diseases, dermatological diseases, respiratory disorders, cancer and arthritis. The company’s mission is to improve people’s lives by pioneering novel healthcare solutions.

Located in East Hanover, New Jersey, Novartis Pharmaceuticals Corporation is an affiliate of Novartis AG -- a world leader in offering medicines to protect health, treat disease and improve well-being. Our goal is to discover, develop and successfully market innovative products to treat patients, ease suffering and enhance the quality of life. Novartis is the only company with leadership positions in both patented and generic pharmaceuticals. We are strengthening our medicine-based portfolio, which is focused on strategic growth platforms in innovation-driven pharmaceuticals, high-quality and low-cost generics and leading self-medication OTC brands. In 2005, the Group’s businesses achieved net sales of USD 32.2 billion and net income of USD 6.1 billion. Approximately USD 4.8 billion was invested in R&D. Headquartered in Basel, Switzerland, Novartis Group companies employ approximately 91,000 people and operate in over 140 countries around the world. For more information, please visit http://www.novartis.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 “very promising,” “may become,” “could,” “will,” “if” or similar expressions or by express or implied discussions regarding regulatory submissions, potential market approval and clinical trial development of telbivudine. 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. There can be no guarantees that telbivudine will be approved for sale in any market or that if approved, revenues from the sale of such product will reach any specific level. In particular, management’s expectations could be affected by the acceptance for filing and approval, if any, of the regulatory filings seeking authorization to market telbivudine; results of clinical trials, including additional data relating to the ongoing phase III and IIIb clinical trial evaluating telbivudine; the decision by Novartis regarding the possible exercise of the option it holds to license valopicitabine; the ability to advance valopicitabine into phase III clinical trials, 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 telbivudine, valopicitabine, its other product candidates and its discoveries. These and other risks which may impact management’s expectations regarding telbivudine and Idenix’s other product candidates are described in greater detail under the caption “Risk Factors” in the company’s annual report on Form 10-K for the year ended December 31, 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.

References: 1. Hou JL, Yin YK, Xu DZ, et. al. A phase III comparative trial of telbivudine and lamivudine for treatment of chronic hepatitis B in Chinese patients: first-year results. Abstract presented at International Liver Congress March 27, 2006 2. Lavanchy D. J Viral Hepat. 2004 Mar 11 (2): 97-107 3. WHO Hepatitis B Fact Sheet #204 4. World Health Organization. Expanded programme on immunization hepatitis B vaccine -- making global progress 5. Lai CL, Ratziu V, Yuen M, Poynard T. Viral hepatitis B. Lancet. 2003; 362: 2089 Idenix Pharmaceuticals’ Contacts: Media: Teri Dahlman 617-995-9905 Investors: Amy Sullivan 617-995-9838

Idenix Pharmaceuticals, Inc.

CONTACT: Media: Teri Dahlman, +1-617-995-9905, or Investors: Amy Sullivan,+1-617-995-9838, both of Idenix Pharmaceuticals, Inc.

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