Idenix Pharmaceuticals Initiates Phase II Clinical Trial of IDX184 in Combination With Pegylated Interferon and Ribavirin for the Treatment of Hepatitis C Virus (HCV)

CAMBRIDGE, Mass., Nov. 3 /PRNewswire-FirstCall/ -- Idenix Pharmaceuticals, Inc. (Nasdaq: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases, announced today that it has initiated a Phase II clinical trial evaluating IDX184, a liver-targeted nucleotide prodrug candidate for the treatment of HCV, in combination with pegylated interferon and ribavirin, in treatment-naive hepatitis C genotype 1-infected patients. Antiviral activity, safety and tolerability of the triple combination will be assessed at 14 days. Patients will continue on treatment with pegylated interferon and ribavirin for 14 days and Rapid Viral Response (RVR), the proportion of patients with undetectable virus at week 4, will be determined at Day 28.

"IDX184 was well tolerated and exhibited favorable antiviral activity in the initial 3-day, proof-of-concept study," said Douglas Mayers, M.D., chief medical officer of Idenix. "We look forward to evaluating IDX184 over a longer treatment period and as a component of combination therapy. This trial will also help us determine the optimal doses for broader clinical development."

The clinical trial is a Phase II, randomized, double-blind, placebo-controlled, sequential dose-escalation study evaluating the safety, tolerability, pharmacokinetics and antiviral activity of IDX184 in combination with pegylated interferon and ribavirin in treatment-naïve HCV genotype 1-infected patients. Patients will receive a daily dose of IDX184 or placebo plus pegylated interferon and ribavirin for 14 days and then continue on pegylated interferon and ribavirin for an additional 14 days. Antiviral activity will be assessed at the 14-day and 28-day timepoints. All patients in the study will have the option to continue pegylated interferon and ribavirin for up to 48 weeks. Four doses of IDX184 ranging from 50 to 200 mg per day will be evaluated. Each cohort of the study will evaluate twenty patients randomized 16 to IDX184 and 4 to placebo. This study is being conducted at multiple centers in the United States and Argentina.

About IDX184
IDX184 is a novel, liver-targeted nucleotide prodrug of 2'-methyl guanosine, which includes Idenix's proprietary liver-targeting technology. This technology enables the delivery of nucleoside monophosphate to the liver, leading to the formation of high levels of nucleoside triphosphate, thus potentially maximizing drug efficacy and limiting systemic side effects.

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 infections caused by the hepatitis C virus. For further information about Idenix, please refer to 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 "expect," "plans," "anticipates," "will," "expects," "goal" or similar expressions, or by express or implied statements with respect to the company's clinical development programs or commercialization activities in hepatitis C, or any potential pipeline candidates, including any expressed or implied statements regarding the efficacy and safety of IDX184, the likelihood and success of any future clinical trials involving IDX184 or successful development of novel combinations of direct-acting antivirals for the treatment of hepatitis C. 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 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. In particular, 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; changes in the company's business plan or objectives; 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 its product candidates and its discoveries. These and other risks which may impact management's expectations 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, 2008 and the Quarterly Report on Form 10-Q for the quarter ended September 30, 2009, as filed with the Securities and Exchange Commission (SEC) and other filings that the company makes with the SEC.

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.

    Idenix Pharmaceuticals Contact:
    Teri Dahlman (617) 995-9905