Idenix Pharmaceuticals Announces Proposed Public Offering of Common Stock

Idenix Pharmaceuticals, Inc.

today announced that it has commenced an underwritten registered public offering of shares of its common stock. All of these shares are being sold by Idenix. J.P. Morgan Securities LLC is acting as sole book-running manager and underwriter for the offering. Idenix intends to grant the underwriter a 30-day option to purchase up to an additional 15 percent of the amount sold to cover over-allotments, if any. The offering is subject to market conditions, and there can be no assurance as to whether or when the offering may be completed, or as to the final size or terms of the offering.