Abstract

Carcinoid tumors are associated with serotonin (5-HT) secretion. High levels of serotonin are thought to contribute to the diarrhea and abdominal discomfort observed in patients with carcinoid syndrome. Telotristat etiprate (aka LX1606/LX1032) is an orallydelivered inhibitor of the rate-limiting enzyme in 5-HT synthesis, tryptophan hydroxylase (TPH). Telotristat etiprate has been shown in preclinical, as well as studies in healthy volunteers and carcinoid syndrome patients, to reduce peripheral 5-HT production. In humans this is evidenced by reductions in 24-hour urinary 5-hydroxyindoleacetic acid (5- HIAA) and blood 5-HT concentrations. Reducing the amount of 5-HT produced by metastatic carcinoid tumors may reduce many of the symptoms and sequelae commonly associated with carcinoid syndrome. Telotristat etiprate offers a potentially novel therapeutic approach to carcinoid syndrome palliation.