Idenix begins underwritten registered public offering of common stock

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 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.

The shares will be issued pursuant to a shelf registration statement on Form S-3 previously filed with and declared effective by the Securities and Exchange Commission.  Idenix has also filed with the Securities and Exchange Commission a preliminary prospectus supplement with respect to the offering.

This announcement shall not constitute an offer to sell or the solicitation of an offer to buy any securities of Idenix, nor shall there be any offer or sale of securities in any state or jurisdiction in which an offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction. Copies of the preliminary prospectus supplement and accompanying prospectus may be obtained from J.P. Morgan Securities LLC via Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717 or by calling toll-free (866) 803-9204.