IDIX (MM)

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 a poster presentation featuring preclinical data for its uridine nucleotide prodrug candidate for the treatment of hepatitis C virus (HCV) infection at the 64th Annual Meeting of the American Association for the Study of Liver Diseases (AASLD), which will take place in Washington, DC, November 1-5, 2013. Full abstracts can now be viewed at the AASLD website at www.aasld.org.

The following abstract will be presented in a poster session during the AASLD Annual Meeting in the Poster Hall on Saturday, November 2, 2013, 2:00pm – 7:30pm Eastern Time:

• Abstract No. 485: "A Novel Uridine Nucleotide Prodrug, IDX20963, and Its Potential for Use in a Low-Dose Direct-Acting Antiviral Regimen for HCV."

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 170 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.

CONTACT: Idenix Pharmaceuticals Contact:
         Teri Dahlman, (617) 995-9807