Lexicon Receives Fast Track Status for Carcinoid Syndrome Drug

LX1032 Multi-Dose Trial to be Initiated in June

THE WOODLANDS, Texas -- Lexicon Pharmaceuticals, Inc. (Nasdaq:LXRX) has received Fast Track status from the U.S. Food and Drug Administration (FDA) for development of LX1032, an orally-delivered small molecule drug candidate for managing gastrointestinal symptoms associated with carcinoid syndrome.

"Fast Track status can accelerate the development and expedite the review of LX1032," said Arthur T. Sands, M.D., Ph.D., president and chief executive officer at Lexicon. "The FDA recognizes the serious unmet medical need of patients with carcinoid syndrome who no longer respond to standard care and the potential benefits that LX1032 could have for those suffering from this disease."

Having completed a single-dose Phase 1a clinical trial, Lexicon will initiate a multi-dose Phase 1b clinical trial of LX1032 in June 2008.

The Phase 1b trial is a randomized, double-blind, ascending multiple-dose study designed to evaluate the safety and tolerability of LX1032 in approximately 40 healthy volunteers. Lexicon expects data from the Phase 1b clinical trial before the end of the year. Results from this study will be used to support the exploration of potentially therapeutic doses in patients with carcinoid syndrome in accordance with its Fast Track status.

"Lexicon's drug development strategy includes targeting indications for Fast Track status to advance potential medical breakthroughs to market," said Philip M. Brown, M.D., J.D., senior vice president of clinical development at Lexicon. "Gaining Fast Track status for LX1032 is an important step forward for our development plan. We believe that LX1032 may be an important new therapy to treat patients with carcinoid syndrome who have no other treatment options."

Lexicon recently completed an initial Phase 1a clinical trial of LX1032, a double-blind, randomized, placebo-controlled, ascending single-dose study in healthy volunteers. The study was designed to evaluate the safety, tolerability, and pharmacokinetics of LX1032 and provided the basis for advancing to the multiple dose study. Lexicon is currently awaiting the analysis of final results from this trial.

Clinical development of LX1032 is being funded through a product development collaboration with Symphony Capital Partners, L.P. and its co-investors.

About Fast Track

FDA's Fast Track program facilitates the development of potential new drugs and expedites the review of new drugs intended to serve unmet medical needs in serious or life-threatening conditions. Fast Track status also provides formal mechanisms for sponsors to communicate with the FDA on product development issues, including clinical trial design.

Fast Track benefits include eligibility for an early review process that may significantly shorten FDA approval times by allowing for the possibility of a "rolling submission" for marketing authorization.

Carcinoid syndrome is the first therapeutic indication for which Lexicon has obtained Fast Track status.

About the Target
The target for LX1032 was identified through the Genome5000(tm) program, Lexicon's initiative to identify the function of 5,000 druggable genes in the human genome. LX1032 was discovered and developed at Lexicon as a potent inhibitor of tryptophan hydroxylase (TPH), a rate-limiting enzyme in the synthesis of serotonin. Excessive levels of serotonin have been implicated in symptoms associated with carcinoid syndrome. Its breakdown product, 5HIAA, is a biomarker used in the diagnosis of the condition. In preclinical studies, LX1032 was able to reduce peripheral serotonin and urinary 5HIAA in several different species without affecting serotonin levels in the brain.

About the Disease
Carcinoid syndrome is a chronic condition that is the result of metastatic neuroendocrine tumors that usually originate from enterochromaffin cells in the gastrointestinal tract. These tumors secrete large amounts of serotonin, which can cause a variety of symptoms including severe diarrhea and abdominal discomfort. According to the American Cancer Society, about 11,000 to 12,000 neuroendocrine tumors and neuroendocrine cancers are diagnosed each year in the United States. 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. Lexicon's Fast Track designation was granted specifically to LX1032 for the treatment of gastrointestinal symptoms associated with carcinoid syndrome in patients who no longer respond to the standard of care.

About Lexicon
Lexicon is a biopharmaceutical company focused on discovering and developing breakthrough treatments for human disease. Through its proprietary gene knockout technology, the company has systematically discovered the physiological and behavioral functions of nearly 5,000 genes. To advance the development and commercialization of its programs, Lexicon is working both independently and through collaborators including Bristol-Myers Squibb Co., Genentech, Inc. and N.V. Organon. For additional information about Lexicon and its programs, please visit the company's Web site.