Lexicon's IBS Drug Completes Phase 1 Trials with Positive Results

Phase 2 Proof-of-Concept Clinical Trial in IBS Patients to be Initiated by Year End

THE WOODLANDS, Texas -- Lexicon Pharmaceuticals, Inc. (Nasdaq:LXRX), a biopharmaceutical company focused on discovering and developing breakthrough treatments for human disease, has successfully completed a Phase 1 multiple-dose escalation study in normal volunteers with LX1031, its oral drug candidate for irritable bowel syndrome (IBS). The company plans to progress the new drug candidate into Phase 2 studies in the fourth quarter. LX1031 is one of four programs in human clinical trials as part of Lexicon's 10TO10 program.

"LX1031 will be our second drug candidate to enter Phase 2 testing," said Arthur T. Sands, M.D., Ph.D., president and chief executive officer. "Our drug discovery strategy is continuing to produce a pipeline of drug candidates working through novel mechanisms that could ultimately enhance the lives of patients worldwide."

The recently completed trial was a randomized, double-blind, ascending multiple-dose study in which all dose levels were well tolerated over 14 days and no dose limiting toxicities were observed. LX1031 is designed to treat symptoms associated with IBS by decreasing the production of serotonin in the gastrointestinal tract. Serotonin is a key regulator of gastrointestinal sensation and motility. Importantly, the study showed that LX1031 decreased urinary 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of serotonin and biomarker for serotonin production, at all dose levels tested as compared to the placebo group.

These results are consistent with a significant reduction in gastrointestinal serotonin synthesis. Doses tested in this study were 250 mg, 500 mg, 750 mg, and 1,000 mg, each administered four times daily. Data from this study will be utilized to select a dosing regime for the Phase 2 proof-of-concept clinical trial.

"LX1031 has demonstrated an excellent safety and tolerability profile in Phase 1 clinical studies, consistent with our observations in preclinical studies," said Philip M. Brown, M.D., J.D., senior vice president of clinical development at Lexicon. "We are eager to assess LX1031 in patients suffering from IBS, who have limited treatment options."

Phase 2 Study

Based on the successful outcome of this Phase 1 study, Lexicon expects to initiate a Phase 2 proof-of-concept clinical trial in IBS patients in the fourth quarter of this year. The clinical trial is planned as a four-week, randomized, double-blind, placebo-controlled study designed to evaluate the safety, tolerability, and effects of LX1031 on symptoms associated with IBS.

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, cognitive disorders, diabetes and irritable bowel syndrome, all of which were discovered by the company's research team. For additional information about Lexicon and its programs, please visit the company's Web site.