(IDIX) to Present at Two Upcoming Healthcare Conferences

CAMBRIDGE, Mass., Nov. 25, 2013  — Idenix Pharmaceuticals, Inc. (Nasdaq:IDIX), announced today that Idenix management will participate in a fireside chat discussion at the 2013 Deutsche Bank BioFEST on Monday, December 2, 2013, at 10:45 a.m. ET at the Four Seasons Hotel in Boston, MA. Management will also present a corporate overview at the Oppenheimer 24th Annual Healthcare Conference on Tuesday, December 10, 2013, at 4:30 p.m. ET at the Crowne Plaza Hotel in New York, NY.

The live and archived webcasts of the company presentations can be accessed under “Events and Presentations” in the Idenix Investor Center at www.idenix.com. Please log in approximately 5-10 minutes before each event to ensure a timely connection. The archived replay will be available on the Idenix website for two weeks following the conferences.

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