Merck enters into definitive agreement with Idenix

Merck (NYSE:MRK), known as MSD outside the United States and Canada, and Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), today announced that the companies have entered into a definitive agreement under which Merck will acquire Idenix for $24.50 per share in cash. The transaction, which values the purchase of Idenix at approximately $3.85 billion, has been approved by the boards of directors of both companies.

"Idenix has established a promising portfolio of hepatitis C candidates based on its expertise in nucleoside/nucleotide chemistry and prodrug technologies," said Dr. Roger Perlmutter, president, Merck Research Laboratories. "Idenix's investigational hepatitis C candidates complement our promising therapies in development and will help advance our work to develop a highly effective, once-daily, all oral, ribavirin-free, pan-genotypic regimen that has a duration of treatment as short as possible for millions of patients in need around the world."

Idenix is a biopharmaceutical company engaged in the discovery and development of medicines for the treatment of human viral diseases, whose primary focus is on the development of next-generation oral antiviral therapeutics to treat hepatitis C virus (HCV) infection. The company currently has three HCV drug candidates in clinical development: two nucleotide prodrugs (IDX21437 and IDX21459) and a NS5A inhibitor (samatasvir). These novel candidates are being evaluated for their potential inclusion in the development of all oral, pan-genotypic fixed-dose combination regimens.

"Merck has established a strong legacy of leadership and innovation in treating hepatitis C," said Ron Renaud, Idenix's President and Chief Executive Officer. "This agreement creates shareholder value by positioning Idenix's strong portfolio of candidates for future success with a leading healthcare company with the experience and commitment to develop fixed-dosed combinations with the potential to impact the global burden of hepatitis C."

Merck's research and development portfolio includes several HCV medicines in development, the leading of which is a combination of MK-5172, an investigational HCV NS3/4A protease inhibitor and MK-8742, an investigational HCV NS5A replication complex inhibitor. The combination of these two investigational candidates has received Breakthrough Therapy designation from the U.S. Food and Drug Administration for the treatment of HCV. In April 2014, Merck announced initiation of Phase 3 clinical trials for MK-5172/MK-8742 to evaluate the combination with and without ribavirin in various genotypes and across a broad range of patient populations with chronic HCV. Study information can be found at www.clinicaltrials.gov.

Under the terms of the agreement, Merck, through a subsidiary, will initiate a tender offer to acquire all outstanding shares of Idenix Pharmaceuticals, Inc. The closing of the tender offer will be subject to certain conditions, including the tender of shares representing at least a majority of the total number of Idenix's outstanding shares (assuming the exercise of all options), the expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act and other customary conditions. Upon the completion of the tender offer, Merck will acquire all remaining shares through a second-step merger. The companies expect the transaction to close in the third quarter of 2014.

Credit Suisse acted as financial advisor to Merck in this transaction and Hughes Hubbard & Reed LLP as its legal advisor. Centerview Partners acted as financial advisor to Idenix and Sullivan & Cromwell as its legal advisor.

Important Information about the Tender Offer

The tender offer for the outstanding shares of Idenix has not yet commenced. This press release is for informational purposes only and is neither an offer to purchase nor a solicitation of an offer to sell shares, nor is it a substitute for the tender offer materials that Merck and its subsidiary will file with the Securities and Exchange Commission (SEC). At the time the planned tender offer is commenced, a tender offer statement on Schedule TO will be filed by Merck with the SEC and Idenix will file a solicitation/recommendation statement on Schedule 14D-9, with respect to the tender offer. The tender offer materials (including an offer to purchase, a related letter of transmittal and other tender offer documents) and the solicitation/recommendation statement will contain important information that holders of Idenix common stock shares are urged to read carefully when they become available, as each may be amended or supplemented from time to time, and because they will contain important information that holders of shares of Idenix common stock should consider before making any decision regarding tendering their shares. The tender offer materials will be made available to Idenix's stockholders at no expense to them. In addition, all of those materials (and other tender offer documents filed with the SEC) will be made available at no charge on the SEC's website at www.sec.gov. Additional copies of the tender offer materials may be obtained at no charge by contacting Merck at One Merck Drive, Whitehouse Station, NJ, 08889 or by phoning (908) 423-1000. In addition, Merck and Idenix file annual, quarterly and current reports and other information with the SEC. You many read and copy any reports or other information filed by Merck or Idenix at the SEC public reference room at 100 F Street, N.E., Washington, D.C., 20549. For further information on the SEC public reference room, please call 1-800-SEC-0330. Merck's and Idenix's filings with the SEC are also available to the public from commercial document-retrieval services and at the SEC's website at www.sec.gov.