Idenix Pharmaceuticals Provides Update on IDX184 and IDX19368 Development Programs

Idenix Pharmaceuticals Provides Update on IDX184 and IDX19368 Development

Management to Host a Conference Call and Webcast Today at 4:30 pm ET

CAMBRIDGE, Mass., Feb. 4, 2013 (GLOBE NEWSWIRE) -- 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 the Company has elected not to continue its clinical development
program for IDX184, a nucleotide polymerase inhibitor in phase IIb testing for
the treatment of hepatitis C virus (HCV) infection, or to continue its
development of IDX19368, an HCV nucleotide polymerase inhibitor for which the
Company had previously filed an IND but had not initiated patient dosing. In
August 2012, the U.S. Food and Drug Administration (FDA) placed IDX184 on
partial clinical hold and IDX19368 on clinical hold due to cardiac adverse
events seen in a competitor's phase II clinical trial of BMS-986094. All three
drug candidates are 2′-methyl guanosine nucleotide prodrugs. In December,
Idenix completed the submission of requested cardiac safety data for IDX184 to
the FDA. Idenix has found no evidence of severe cardiac findings to date. In
February, the FDA communicated that the IDX184 and IDX19368 programs would
remain on clinical hold, and, as a result, the Company has determined it will
not continue the development of these programs.

"Although we are choosing not to continue our IDX184 and IDX19368 programs, we
intend to maintain our strong presence in developing nucleotide polymerase
inhibitors for HCV based on our broad discovery platform," said Ron Renaud,
Idenix's President and Chief Executive Officer. "We are completing
IND-enabling studies for a uridine nucleotide analog, which is in a sub-class
of nucleotide polymerase inhibitors distinct from IDX184, IDX19368 and
BMS-986094. We anticipate filing an IND for this next-generation compound
during the first half of 2013, and we also plan to continue to advance other
preclinical nucleotide prodrugs in earlier-stage development."

Mr. Renaud continued, "Further, we are pleased with the progress of IDX719,
our potent, pan-genotypic NS5A inhibitor for HCV. In January 2013, we entered
into a non-exclusive collaboration with Janssen Pharmaceuticals, Inc. for the
development of all-oral direct-acting antiviral (DAA) HCV combination
therapies incorporating IDX719. Following an initial drug-drug interaction
study to begin in the first quarter of 2013 and pending approval from
regulatory authorities, we expect to begin the first phase II study under this
program of a two-DAA regimen, including IDX719."


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


Idenix will hold a conference call today at 4:30 p.m. ET. To access the call
please dial (877) 640-9809 U.S./Canada or (914) 495-8528 International and
enter passcode 97346472 or to listen to a live webcast go to "Events &
Presentations" in the Idenix Investor Center at A replay of
the call will also be available from February 4, 2013, at 7:30 p.m. ET until
February 10, 2013, at 11:59 p.m. ET.To access the replay, please dial (855)
859-2056 U.S./Canada or (404) 537-3406 International and enter passcode
97346472. An archived webcast will also be available for two weeks after the
call on the Idenix website.


This press release contains "forward-looking statements" for purposes of the
safe harbor provisions of The Private Securities Litigation Reform Act of
1995. 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 any expressed or implied statements with
respect to: the Company's plans to continue to developing nucleotide
polymerase inhibitors for HCV; its clinical development plans for its uridine
nucleotide analog drug candidate and IDX719; its plans to advance other
preclinical nucleotides; and statements regarding the efficacy and safety of
its clinical compounds. 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 following: there can be no
guarantees that the Company will advance any clinical product candidate or
other component of its potential pipeline to the clinic, to the regulatory
process or to commercialization due to numerous risks inherent in
pharmaceutical research and development; management's expectations could be
affected by unexpected regulatory actions or delays; uncertainties relating
to, or unsuccessful results of, preclinical and clinical trials, including
additional data relating to the ongoing clinical trials evaluating its product
candidates; the Company's ability to obtain additional funding required to
conduct its research, development and commercialization activities;
competition; and 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 important 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, 2011 and the quarterly report on Form 10-Q for the
quarter ended September 30, 2012, 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.

CONTACT: Idenix Pharmaceuticals Contacts:
         Teri Dahlman (617) 995-9807
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