Idenix Pharmaceuticals Announces Declaration of a Patent Interference by the USPTO

CAMBRIDGE, Mass., March 6, 2012 /PRNewswire/ -- 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 the United States Patent and Trademark Office (USPTO) declared a patent interference between Idenix's U.S. Patent Application no. 12/131,868 and Pharmasset Inc.'s (acquired by Gilead Sciences) U.S. Patent no. 7,429,572, both related to certain nucleoside compounds useful in treating patients with hepatitis C virus (HCV) infection.

"We are confident in our robust intellectual property position. While the claims in this interference are not related to our nucleotide inhibitor, IDX184, or any other candidate in our pipeline, we believe it is important to deepen the strength of our existing patent portfolio," said Ron Renaud, Idenix's President and Chief Executive Officer.

A patent interference is an administrative proceeding conducted by the USPTO in order to determine which party is entitled to a patent when two or more parties claim patent rights to the same technology. Under current U.S. law, a patent is awarded to the first party to invent a particular technology, subject to certain limitations. The applicant who filed the earlier patent application is referred to as the senior party in the patent interference and the applicant with the later filing date is referred to as the junior party. The junior party bears the burden of proof to demonstrate that it invented the technology in question before the senior party.

In this case, the USPTO has initially determined that Idenix is the senior party and that Pharmasset Inc. (acquired by Gilead Sciences) is the junior party.

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.

FORWARD-LOOKING STATEMENTS

This press release contains "forward-looking statements" for purposes of the safe harbor provisions of The Private Securities Litigation Reform Act of 1995, including but not limited to the statements regarding the Company's position in its interference proceedings with Gilead Sciences.   For this purpose, any statements contained herein that are not statements of historical fact may be deemed forward-looking statements. Without limiting the foregoing, the words "expect," "plans," "anticipates," "intends," "will," and similar expressions are also intended to identify forward-looking statements, as are expressed or implied statements with respect to the Company's intellectual property rights and potential pipeline candidates. Actual results may differ materially from those indicated by such forward-looking statements as a result of risks and uncertainties, including but not limited to the Company's ability to obtain, maintain and enforce patent and other intellectual property protection for its product candidates and its discoveries. Such forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause actual results to be materially different from any future results, performance or achievements expressed or implied by such statements. These and other risks which may impact management's expectations are described in greater detail under the heading "Risk Factors" in the Company's annual report on Form 10-K for the year ended December 31, 2010, and the quarterly report on Form 10-Q for the quarter ended September 30, 2011, each as filed with the Securities and Exchange Commission (SEC) and in any subsequent periodic or current report that the Company files with the SEC.

All forward-looking statements reflect the Company's estimates only as of the date of this release  (unless another date is indicated) and should not be relied upon as reflecting the Company's views, expectations or beliefs at any date subsequent to the date of this release. While Idenix may elect to update these forward-looking statements at some point in the future, it specifically disclaims any obligation to do so, even if the Company's estimates change.

Idenix Pharmaceuticals Contacts:
Kelly Barry (617) 995-9033 (media)
Teri Dahlman (617) 995-9807 (investors)

SOURCE Idenix Pharmaceuticals, Inc.