LX1031

LX1031 is an investigational, oral, small-molecule inhibitor of tryptophan hydroxylase (TPH) developed by Lexicon Pharmaceuticals for the treatment of non-constipating irritable bowel syndrome (IBS), including diarrhea-predominant (IBS-D) and mixed (IBS-M) forms. Tryptophan hydroxylase is the rate-limiting enzyme in the synthesis of serotonin (5-hydroxytryptamine, 5-HT). LX1031 is designed to act locally within the gastrointestinal tract to reduce the synthesis of peripheral serotonin without affecting serotonin levels in the brain or central nervous system. By lowering excess peripheral serotonin, which is often elevated in IBS patients and contributes to abnormal gut motility and visceral hypersensitivity, LX1031 aims to improve stool consistency and alleviate abdominal pain. Clinical Phase 2 studies have demonstrated that the drug significantly reduces urinary 5-hydroxyindoleacetic acid (5-HIAA), a key biomarker of serotonin metabolism, correlating with clinical symptom relief.