Irritable Bowel Syndrome-Diarrhea Type (IBS-d)IBS is the most common functional gastrointestinal disorder. IBS patients may be sub-classified into those having mainly diarrhea, mainly constipation and those alternating between the two patterns. IBS-d is considered a disorder of altered gut motility, particularly with regard to exaggerated contractions in the lower colon. The total cost to society attributable to IBS is estimated to be $30 billion, including $10 billion in direct costs from physician visits and prescription pharmaceuticals. IBS-d patients account for approximately one-third of the entire IBS market and are typically diagnosed by frequent bowel movements (more than 3 per day), loose stools and urgency.Tranzyme is developing a motilin receptor antagonist, TZP-201, for the treatment of IBS-d in order to reduce lower gut motility. Motilin is also a gut hormone and it mediates interdigestive and postprandial gut motility. High circulating motilin levels are observed in IBS-d patients and motilin-induced intestinal hypermotility appears to be an important contributor to the diarrhea symptoms in IBS-d. As with ghrelin, Tranzyme is focused on the motilin receptor as an ideal target for a mechanism-based treatment for IBS-d.