Telotristat ethyl (LX1606) is a orally-delivered inhibitor of tryptophan hydroxylase that reduces serotonin production.

Telotristat ethyl, at a dosage of 200 mg/kg administered orally once daily, has been shown to protect against inflammatory bowel disease (IBD) in mice, as evidenced by histopathology evaluations[1] and by alleviating the severity of colitis induced by trinitrobenzene sulfonic acid (TNBS)[2]. At various dosages (15, 50, 150, 300 mg/kg), Telotristat ethyl effectively reduces serotonin (5-HT) levels in the jejunum, though it does not affect serotonin levels in the brain or impact the enteric neuronal serotonin nor constitutive gastrointestinal motility at a 200 mg/kg dosage. Additionally, it prevents the TNBS-induced increase in blood neutrophil counts, highlighting its significant protective role in a mouse model of IBD, without altering serotonin content within the brain, even at differing concentrations (15, 50, 150, 300 mg/kg, administered orally once daily).