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LEXICON INITIATES TRIALS OF DRUG FOR IRRITABLE BOWEL SYNDROME

January 26, 2007

Lexicon Genetics has initiated Phase I clinical trials of LX1031, its oral drug candidate for irritable bowel syndrome (IBS) and other gastrointestinal disorders.

The trial is a randomized, double-blind, ascending-single-dose study that will evaluate LX1031's safety, tolerability and pharmacokinetics in approximately 40 normal healthy volunteers. This trial is expected to be followed by a randomized, double-blind, ascending-multiple-dose study of similar size. Lexicon expects results from both of these trials in 2007.

LX1031 is an orally dosed drug candidate for irritable bowel syndrome and other gastrointestinal disorders. The drug's target was internally identified as a key control point for the regulation of peripheral serotonin levels. LX1031 is designed to act locally in the gastrointestinal tract by reducing the serotonin available for receptor activation, without affecting serotonin levels in the brain or its central nervous system functions. In preclinical studies, LX1031 showed a dose-dependent reduction of serotonin levels in the gastrointestinal tract of multiple species. In human clinical trials, Lexicon intends to use serotonin as a biomarker by which to evaluate the activity of LX1031.

The target of LX1031 is an enzyme that is found predominantly in the gastrointestinal tract. Lexicon discovered that mice lacking this enzyme have virtually no peripheral serotonin but normal levels of brain serotonin.