Irritable Bowel Syndrome (IBS):  Lexicon's LX1031 drug candidate is under development as a potential treatment of IBS symptoms.  LX1031 acts by decreasing the production of serotonin locally in the gastrointestinal (GI) tract.  Serotonin is a molecule that stimulates GI motility and secretion and is associated with nausea, vomiting, and diarrhea. 

Tryptophan hydroxylase (TPH), found in enterochromaffin (EC) cells of the GI tract, is a key enzyme in the production of serotonin. 





















About the Disease
IBS is a common disorder characterized by abdominal pain, cramping, and changes in bowel function.  It is classified according to three categories:

• IBS-c: Constipation
• IBS-d: Diarrhea
• Mixed: Multiple symptoms

About the Market
According to the International Foundation for Functional Gastrointestinal Disorders, IBS is estimated to affect between 25-45 million Americans.  It is the most common diagnosis made by gastroenterologists, and is one of the disorders most frequently treated by primary care physicians. 

Most drugs targeting the serotonin pathway affect various serotonin receptor subtypes (e.g., 5-HT3 and 5-HT4 receptors). However, LX1031 inhibits TPH, the enzyme responsible for producing serotonin in the GI tract.



















Carcinoid Syndrome:  Lexicon’s LX1032 drug candidate is under development as a potential treatment for the symptoms of carcinoid syndrome.  LX1032 acts by decreasing production of serotonin peripheral to the central nervous system without affecting serotonin levels in the brain. In June 2008, Lexicon received Fast Track status from the FDA to develop LX1032.

Carcinoid syndrome is a combination of symptoms caused by the release of excessive serotonin and other substances into the blood stream from metastatic carcinoid tumors.














About the Disease
Carcinoid tumors are a type of neuroendocrine tumor that typically form in the gastrointestinal system.  Carcinoid syndrome is a combination of symptoms, including severe diarrhea, bronchial restriction, facial flushing and rapid heartbeat, caused by the release of excessive serotonin and other substances into the blood stream from metastatic carcinoid tumors.

About the Market
According to the American Cancer Society, approximately 12,000 patients are diagnosed with neuroendocrine tumors each year in the U.S., and the frequency of carcinoid tumor diagnoses has been increasing.  About 10% of people with carcinoid tumors will develop carcinoid syndrome.  Patients with this condition may live for many years experiencing these symptoms.