Idenix Pharmaceuticals Announces Initiation Of Enrollment In A Phase II All-Oral Combination Study Of Samatasvir (IDX719), Simeprevir, And TMC647055 For The Treatment Of Hepatitis C Virus (HCV) Infection

CAMBRIDGE, Mass., Dec. 2, 2013 (GLOBE NEWSWIRE) -- 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 the initiation of patient enrollment in the phase II HELIX-2 clinical trial evaluating an all-oral, direct-acting antiviral (DAA) HCV combination regimen of samatasvir, Idenix's once-daily pan-genotypic NS5A inhibitor, simeprevir, a once-daily NS3/4A protease inhibitor jointly developed by Janssen R&D Ireland and Medivir AB, and TMC647055, a once-daily NS5B non-nucleoside polymerase inhibitor boosted with low-dose ritonavir developed by Janssen.

The HELIX-2 trial is a 12-week, randomized, open-label study evaluating the efficacy, safety and tolerability of samatasvir, simeprevir, and TMC647055. The trial will evaluate genotype 1 HCV-infected patients who are either treatment-naïve or who have relapsed after prior treatment with interferon and ribavirin. Patients will receive 50 mg samatasvir, 75 mg of simeprevir and 450 mg of TMC647055/ritonavir (30 mg), each once daily for 12 weeks, with or without ribavirin.

The HELIX-2 trial is the second study in HCV-infected patients to commence under a non-exclusive collaboration agreement signed with Janssen in January 2013. The HELIX-1 trial of samatasvir in combination with simeprevir was initiated in May 2013 and is ongoing.

"We are pleased with the continuing progress of our clinical program for samatasvir, which will provide additional important information on the use of this promising compound as part of all-oral HCV combination regimens," said Doug Mayers, M.D., Idenix's Chief Medical Officer. "With the advancement of the samatasvir program as well as that of our novel nucleotide prodrug inhibitor, IDX21437, we anticipate initiating the evaluation of our own HCV combination regimen in 2014."

ABOUT THE IDENIX/JANSSEN COLLABORATION

In January 2013, Idenix entered into a non-exclusive collaboration with Janssen Pharmaceuticals for the clinical development of all-oral direct-acting antiviral (DAA) HCV combination therapies.  The collaboration is evaluating combinations including samatasvir, simeprevir, and TMC647055.  The HELIX-1 and HELIX-2 clinical trials are being conducted by Idenix.  Both Idenix and Janssen retain all rights to their respective compounds under the agreement.

ABOUT SAMATASVIR (IDX719)

Samatasvir is an NS5A inhibitor with low picomolar, pan-genotypic antiviral activity in vitro. To date, samatasvir has been safe and well-tolerated after single and multiple doses of up to 150 mg in healthy volunteers up to 14 days duration, and in HCV-infected patients up to 12 weeks duration. There have been no treatment-emergent serious adverse events reported in the program. Samatasvir has demonstrated potent pan-genotypic antiviral activity in HCV-infected patients with mean maximal viral load reductions up to approximately 4.0 log 10 IU/mL across HCV genotypes 1-4 in a proof-of-concept, three-day monotherapy study.

ABOUT SIMEPREVIR

Simeprevir is an NS3/4A protease inhibitor jointly developed by Janssen R&D Ireland and Medivir AB for the treatment of chronic hepatitis C infection in combination with other antivirals in HCV genotype 1- and 4-infected subjects with compensated liver disease, including cirrhosis.

Simeprevir was approved for the treatment of genotype 1 hepatitis C in September 2013 in Japan, in November 2013 in Canada and in November 2013 in the United States. A Marketing Authorisation Application was submitted to the European Medicines Agency (EMA) in April 2013 by Janssen-Cilag International NV seeking approval of simeprevir for the treatment of genotype 1 or genotype 4 chronic hepatitis C. To date, more than 3,700 patients have been treated with simeprevir in clinical trials. For further details please visit http://www.medivir.com.

ABOUT TMC647055

TMC647055 is a potent non-nucleoside hepatitis C polymerase inhibitor with broad genotypic coverage. TMC647055 is in phase II clinical development and is developed by Janssen R&D Ireland to treat chronic hepatitis C virus infections. TMC647055 is being investigated in combination with other DAA agents in all oral interferon-free regimens. There have been no treatment-emergent serious adverse events reported in the program.

ABOUT HEPATITIS C

Hepatitis C virus is a common blood-borne pathogen infecting three to four million people worldwide annually. The World Health Organization (WHO) estimates that more than 150 million people worldwide are chronically infected with HCV, representing a nearly 5-fold greater prevalence than human immunodeficiency virus.

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 patients with hepatitis C infection.  For further information about Idenix, please refer to www.idenix.com.

FORWARD-LOOKING STATEMENTS

This press release contains "forward-looking statements" for purposes of the safe harbor provisions of The Private Securities Litigation Reform Act of 1995, including but not limited to the statements regarding the Company's future business and financial performance. For this purpose, any statements contained herein that are not statements of historical fact may be deemed forward-looking statements. Without limiting the foregoing, the words "expect," "plans," "anticipates," "intends," "will," and similar expressions are also intended to identify forward-looking statements, as are expressed or implied statements with respect to the Company's potential pipeline candidates, including any expressed or implied statements regarding the efficacy and safety of samatasvir or any other drug candidate; the successful development of novel combinations of direct-acting antivirals for the treatment of HCV; the likelihood and success of any future clinical trials involving samatasvir, IDX21437 or our other drug candidates; and expectations with respect to funding of operations and future cash balances. Actual results may differ materially from those indicated by such forward-looking statements as a result of risks and uncertainties, including but not limited to the following: 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; 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; the Company's expectations regarding the benefits of the restructuring of its collaboration with Novartis; 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. 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. These and other risks which may impact management's expectations are described in greater detail under the heading "Risk Factors" in the Company's annual report on Form 10-K for the year ended December 31, 2012 and the quarterly report on Form 10-Q for the quarter ended September 30, 2013, each as filed with the Securities and Exchange Commission (SEC) and in any subsequent periodic or current report that the Company files with the SEC.

All forward-looking statements reflect the Company's estimates only as of the date of this release  (unless another date is indicated) 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. While Idenix may elect to update these forward-looking statements at some point in the future, it specifically disclaims any obligation to do so, even if the Company's estimates change.

CONTACT: Idenix Pharmaceuticals Contact:         Teri Dahlman, Dahlman.Teresa@idenix.com

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