Telotristat etiprate, a novel inhibitor of serotonin synthesis for the treatment of carcinoid syndrome

Excessive serotonin secretion is the hallmark of carcinoid syndrome. It leads to diarrhea, cramping, abdominal pain, wheezing and flushing. It is also associated with serious cardiac valve disease and lower life expectancy. Efforts to control serotonin production in carcinoid syndrome are currently limited to the use of somatostatin analogues and antitumor therapies such as surgery, radiation, or embolization. A significant proportion of patients still suffer from excess serotonin production and its debilitating symptoms. This review addresses the development of telotristat etiprate, a novel serotonin synthesis inhibitor currently being investigated in carcinoid syndrome. Early clinical studies support the conduct of TELESTAR, a Phase III pivotal trial that may determine whether telotristat etiprate will become the first approved serotonin synthesis inhibitor.