CAMBRIDGE, MA, USA I June 20, 2013 I Idenix Pharmaceuticals, Inc. (IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases, today announced the Company has received verbal communication from the U.S. Food and Drug Administration (FDA) requesting additional preclinical safety information for IDX20963, Idenix‘s lead uridine nucleotide prodrug candidate. Initiation of clinical trials for IDX20963 is on hold and the Company must provide a satisfactory response to the FDA before clinical trials can begin in the United States. As a result, the Company anticipates a delay in the initiation of the clinical program for IDX20963 while it responds to the FDA’s comments. Idenix recently submitted an Investigational New Drug (IND) application for IDX20963 to the FDA, including preclinical data demonstrating potent, pan-genotypic activity.

ABOUT HEPATITIS C

Hepatitis C virus (HCV) 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 HCV infection. For further information about Idenix, please refer to www.idenix.com.

SOURCE: Idenix Pharmaceuticals