Lexicon Initiates Phase 2 Clinical Trial of LX1032 in Patients With Carcinoid Syndrome

Lexicon Initiates Phase 2 Clinical Trial of LX1032 in Patients With Carcinoid
Syndrome
- Drug Candidate Designed to Reduce Peripheral Serotonin Production

THE WOODLANDS, Texas, July 7 /PRNewswire-FirstCall/ -- 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 LX1032, the
company's oral drug candidate for managing gastrointestinal symptoms
associated with carcinoid syndrome. LX1032 is designed to reduce serotonin
production in patients with metastatic carcinoid tumors. Elevated levels of
serotonin contribute to the gastrointestinal and possibly other symptoms
experienced by these patients.

In addition to LX1032, Lexicon has three other drug candidates progressing
through various stages of clinical development, including LX1031 for irritable
bowel syndrome, LX2931 for rheumatoid arthritis, and LX4211 for diabetes. For
more information about Lexicon's clinical development programs, please visit
www.lexpharma.com.

"This is an important study, designed to evaluate LX1032's effect on the
gastrointestinal symptoms experienced by patients with carcinoid syndrome who
have become refractory to current treatment options," said Philip M. Brown,
M.D., J.D., senior vice president of clinical development at Lexicon. "We
are encouraged by the clinical results obtained to date in which LX1032
demonstrated potent reductions in serotonin production in healthy volunteers."

The Phase 2 clinical trial is designed as a four-week, randomized,
double-blind, placebo-controlled study to evaluate the safety and tolerability
of LX1032 and its effects on symptoms associated with carcinoid syndrome. The
study will include up to 28 patients with carcinoid syndrome who are
symptomatic despite treatment with currently available therapy. Up to four
dose levels may be evaluated in a serial ascending fashion. Once an optimal
or maximal dose is identified, additional patients will be added to confirm
clinical observations.

"The clinical trial will be conducted at multiple cancer centers in the United
States," said Brian P. Zambrowicz, Ph.D., executive vice president and chief
scientific officer at Lexicon. "The clinical trial sites will include The
University of Texas M.D. Anderson Cancer Center in Houston, Texas; the H. Lee
Moffitt Cancer Center & Research Institute in Tampa, Florida; and Hematology
Oncology Services of Little Rock, Arkansas."

LX1032 is being developed in a product development collaboration with Symphony
Capital Partners, L.P. and its co-investors.

About LX1032
LX1032 was discovered and developed at Lexicon to reduce serotonin production
by inhibiting tryptophan hydroxylase (TPH), a key enzyme in the synthesis of
serotonin. Excessive levels of serotonin have been implicated in symptoms
associated with carcinoid syndrome. Serotonin's breakdown product, 5-HIAA, is
a biomarker used in the diagnosis of the condition. In preclinical studies,
LX1032 reduced peripheral serotonin and urinary 5-HIAA levels in several
different species without affecting serotonin levels in the brain. In Phase 1
clinical studies, LX1032 reduced serotonin levels and urinary 5-HIAA in
healthy volunteers consistent with preclinical results. LX1032 is being
developed for the treatment of gastrointestinal symptoms associated with
carcinoid syndrome in patients who no longer respond to the standard of care
under Fast Track designation from the U.S. Food and Drug Administration.

About Carcinoid Syndrome
Carcinoid syndrome is a chronic condition caused by metastatic neuroendocrine
tumors that usually originate from the gastrointestinal tract. These tumors
secrete large amounts of serotonin, which can cause a variety of symptoms
including severe diarrhea and abdominal discomfort. Patients with carcinoid
syndrome currently have limited therapeutic options, and the standard of care
includes chronic therapy with somatostatin analogues, which are delivered by
injection. With current therapy, the gastrointestinal symptoms return over
time in the vast majority of patients, hence the need for new agents.

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. The company has used its proprietary gene
knockout technology to identify more than 100 promising drug targets. Lexicon
has focused drug discovery efforts on 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.

Safe Harbor Statement
This press release contains "forward-looking statements," including statements
relating to Lexicon's clinical development of LX1032 and the potential
therapeutic and commercial potential of LX1032. 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
LX1032 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, 2008, 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.

SOURCE Lexicon Pharmaceuticals, Inc.

Jason Ray, Manager, Corporate Communications and Investor Relations of Lexicon
Pharmaceuticals, Inc., +1-281-863-3225, jray@lexpharma.com