# Telotristat ethyl

Source: https://onco.cc/drugs/telotristat-ethyl/  
OnCo record `telotristat-ethyl` (Treatment). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Telotristat ethyl (Xermelo) is a tablet that cuts the serotonin that neuroendocrine tumours pour out, easing the constant diarrhoea of carcinoid syndrome when somatostatin analogue injections are not enough.

## Summary

Telotristat ethyl was approved by the FDA in February 2017 and authorised in the EU in September 2017 for carcinoid syndrome diarrhoea in combination with somatostatin analogue therapy in adults inadequately controlled by that therapy, on the TELESTAR phase 3 trial (135 patients) in which the 250 mg three-times-daily dose reduced daily bowel movements more than placebo, a statistically significant difference, and lowered urinary 5-HIAA. It is the first oral drug for carcinoid syndrome and the first tryptophan hydroxylase inhibitor approved for any indication. Nausea, headache, raised liver enzymes, depression and constipation are the main adverse effects. Marketed by TerSera in the US and SERB in Europe.

## Fields

- Kind: Treatment
- Status: approved
- Last checked: 2026-09-10
- Also known as: LX1032; Telotristat etiprate
- Tags: ema-list; supportive
- Brand: Xermelo
- Modality: Oral tryptophan hydroxylase inhibitor
- Mechanism: Prodrug of telotristat, which inhibits tryptophan hydroxylase, the rate-limiting enzyme of peripheral serotonin synthesis in neuroendocrine tumour cells, lowering urinary 5-HIAA and bowel frequency without crossing into the brain.
- Approvals: US 2017: Carcinoid syndrome diarrhoea with somatostatin analogue therapy in adults inadequately controlled by SSA alone; EU 2017: Same (Xermelo)

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Telotristat_ethyl
- EPAR (EMA): https://www.ema.europa.eu/en/medicines/human/EPAR/xermelo
- US label (DailyMed): https://dailymed.nlm.nih.gov/dailymed/search.cfm?labeltype=all&query=telotristat

## Connected records

- drugs: [Somatostatin analogues (octreotide, lanreotide)](https://onco.cc/drugs/octreotide-lanreotide/)
- cancers: [Neuroendocrine tumours](https://onco.cc/cancers/neuroendocrine/), [Small intestinal neuroendocrine tumours](https://onco.cc/cancers/small-intestinal-net/)
- companies: [SERB Pharmaceuticals](https://onco.cc/companies/serb-pharmaceuticals/), [TerSera Therapeutics](https://onco.cc/companies/tersera-therapeutics/)
- trials: [A Safety and Efficacy Study of XERMELO® + First-line Chemotherapy in Patients With Advanced Biliary Tract Cancer](https://onco.cc/trials/nct03790111/), [Telotristat With Lutathera in Neuroendocrine Tumors](https://onco.cc/trials/nct04543955/)
- targets: [Tryptophan hydroxylase 1](https://onco.cc/targets/tph1/)

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