Lexicon Initiates Phase 2 Clinical Trial of LX1031 in Patients With Irritable Bowel...

Lexicon Initiates Phase 2 Clinical Trial of LX1031 in Patients With Irritable
Bowel Syndrome

THE WOODLANDS, Texas, Jan. 12, 2009 (GLOBE NEWSWIRE) -- Lexicon Pharmaceuticals,
Inc. (Nasdaq:LXRX), a biopharmaceutical company focused on discovering and
developing breakthrough treatments for human disease, announced today that it
has initiated a Phase 2 clinical trial of LX1031, the company's oral drug
candidate for irritable bowel syndrome (IBS). Lexicon has three additional drug
candidates progressing through various stages of clinical development, including
LX1032 for carcinoid syndrome, LX2931 for rheumatoid arthritis, and LX4211 for
diabetes.

"Patients with IBS have limited treatment options and are in need of safer, more
effective therapies," said Philip M. Brown, M.D., J.D., senior vice president of
clinical development at Lexicon. "LX1031 is intended to treat symptoms
associated with IBS, including diarrhea and abdominal discomfort, by operating
through an important new mechanism to reduce serotonin levels locally in the
gastrointestinal tract."

The Phase 2 clinical trial, which began at the end of December 2008, is designed
as a four-week, randomized, double-blind, placebo-controlled study to evaluate
the safety and tolerability of LX1031 and its effects on symptoms associated
with IBS. The study will include 150 patients with either diarrhea-predominant
IBS or mixed IBS. Two dose levels will be evaluated: a 250 mg dose and a 1,000
mg dose, each administered four times daily. The endpoints will include
assessments of the effects of LX1031 on specific symptoms associated with IBS,
as well as a global assessment of adequate relief.

About LX1031

LX1031 is an oral drug candidate for IBS and other gastrointestinal (GI)
disorders. LX1031 was developed by Lexicon's research team, which also
identified its target as a key control point for the regulation of peripheral
serotonin levels. LX1031 is designed to treat symptoms associated with IBS by
decreasing the production of serotonin in the GI tract without affecting
serotonin levels in the brain. In Phase 1 clinical trials, all dose levels were
well tolerated, with no dose-limiting toxicities observed, and LX1031 was shown
to reduce levels of 5-HIAA, a biomarker of serotonin production.

LX1031 is being developed in a product development collaboration with Symphony
Capital Partners, L.P. and its co-investors.

About Irritable Bowel Syndrome

Irritable bowel syndrome is a disorder most commonly characterized by cramping,
abdominal pain, bloating, constipation or diarrhea. Symptoms of IBS are believed
to be mediated through serotonin, which has been shown to play an important role
in modulating motility and signaling feelings of GI discomfort to the brain.

About Lexicon

Lexicon is a biopharmaceutical company focused on discovering and developing
breakthrough treatments for human disease. Lexicon currently has five drug
candidates in development for autoimmune disease, carcinoid syndrome, diabetes,
glaucoma and irritable bowel syndrome, all of which were discovered by the
company's research team. Lexicon's goal is to advance 10 drug candidates into
human clinical trials by the end of 2010, the strategic objective of its 10TO10
program. The company has used its proprietary gene knockout technology to
identify more than 100 promising drug targets. Lexicon has applied small
molecule chemistry and antibody technology to these biologically-validated
targets to create its extensive pipeline of clinical and preclinical programs.
For additional information about Lexicon and its programs, please visit
www.lexpharma.com.

The Lexicon Pharmaceuticals, Inc. logo is available at
http://www.globenewswire.com/newsroom/prs/?pkgid=4799

Safe Harbor Statement

This press release contains "forward-looking statements," including statements
relating to Lexicon's clinical development of LX1031 and the potential
therapeutic and commercial potential of LX1031. This press release also contains
forward-looking statements relating to Lexicon's growth and future operating
results, discovery and development of products, strategic alliances and
intellectual property, as well as other matters that are not historical facts or
information. All forward-looking statements are based on management's current
assumptions and expectations and involve risks, uncertainties and other
important factors, specifically including those relating to Lexicon's ability to
successfully conduct clinical development of LX1031 and preclinical and clinical
development of its other potential drug candidates, advance additional
candidates into preclinical and clinical development, obtain necessary
regulatory approvals, achieve its operational objectives, obtain patent
protection for its discoveries and establish strategic alliances, as well as
additional factors relating to manufacturing, intellectual property rights, and
the therapeutic or commercial value of its drug candidates, that may cause
Lexicon's actual results to be materially different from any future results
expressed or implied by such forward-looking statements. Information identifying
such important factors is contained under "Factors Affecting Forward-Looking
Statements" and "Risk Factors" in Lexicon's annual report on Form 10-K for the
year ended December 31, 2007, as filed with the Securities and Exchange
Commission. Lexicon undertakes no obligation to update or revise any such
forward-looking statements, whether as a result of new information, future
events or otherwise.

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CONTACT: Lexicon Pharmaceuticals, Inc.
Bobbie Faulkner, Manager, Investor and Public Relations
281/863-3503
bfaulkner@lexpharma.com