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Telotristat ethyl.svg
Trade namesXermelo
Other namesTelotristat ethyl, LX1032, LX1606
  • [(S)-Ethyl 2-amino-3-(4-(2-amino-6-((R)-1-(4-chloro-2-(3-methyl-1H-pyrazol-1-yl)phenyl)-2,2,2-trifluoroethoxy)pyrimidin-4-yl)phenyl)propanoate]
Clinical data
Main usesDiarrhea due to carcinoid syndrome[1]
Side effectsAbdominal pain, liver problems, tiredness[2]
  • AU: B3
  • US: N (Not classified yet)
Routes of
By mouth (tablets)
Typical dose250 mg TID[1]
External links
US NLMTelotristat
License data
Legal status
Protein binding>99% (both telotristat ethyl and telotristat)
MetabolismHydrolysis via carboxylesterases
Elimination half-life0.6 hours (telotristat ethyl), 5 hours (telotristat)
ExcretionFeces (92.8%), urine (less than 0.4%)[3]
Chemical and physical data
Molar mass574.99 g·mol−1
3D model (JSmol)
  • CCOC(=O)C(CC1=CC=C(C=C1)C2=CC(=NC(=N2)N)OC(C3=C(C=C(C=C3)Cl)N4C=CC(=N4)C)C(F)(F)F)N
  • InChI=1S/C27H26ClF3N6O3/c1-3-39-25(38)20(32)12-16-4-6-17(7-5-16)21-14-23(35-26(33)34-21)40-24(27(29,30)31)19-9-8-18(28)13-22(19)37-11-10-15(2)36-37/h4-11,13-14,20,24H,3,12,32H2,1-2H3,(H2,33,34,35)/t20-,24+/m0/s1

Telotristat, sold under the brand name Xermelo, is a medication used to treat diarrhea due to carcinoid syndrome.[1] It is taken by mouth, three times per day.[1] It is used together with a somatostatin like agent.[1]

Common side effects include abdominal pain, liver problems, and tiredness.[2] Other side effects may include constipation.[1] Smaller doses may be required in those with liver problems.[2] Use during pregnancy is not recommended.[4] It works by blocking tryptophan hydroxylase, thereby decreasing the production of serotonin.[1][2]

Telotristat was approved for medical use in the United States and Europe in 2017.[1][2] In the United States it costs about 8,000 USD per month as of 2021.[5] This amount in the United Kingdom costs the NHS about £1,100.[4]

Medical uses

Telotristat is used in combination with somatostatin analog (SSA) therapy for the treatment of adults with diarrhea associated with carcinoid syndrome that SSA therapy alone has inadequately controlled.[6][7]


It is generally take three times per day at a dose of 250 mg.[1] Smaller doses may be required in those with liver problems.[2]

Side effects

Common adverse effects noted in clinical trials include nausea, headache, elevated liver enzymes, depression, accumulation of fluid causing swelling (peripheral edema), flatulence, decreased appetite, and fever. Constipation is also common, and may be serious or life-threatening (especially in overdose).[6]


Telotristat is an inhibitor of tryptophan hydroxylase,[8] which mediates the rate-limiting step in serotonin biosynthesis.[3] It is formulated as telotristat etiprate — a hippurate salt of telotristat ethyl.[3]

Action of telotristat on tryptophan hydroxylase


The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication.[9]

Society and culture


It is marketed by Lexicon Pharmaceuticals (as telotristat etiprate). 328 mg telotristat etiprate is equivalent to 250 mg telotristate ethyl.[3]

Telotristat etiprate


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 "Telotristat Monograph for Professionals". Retrieved 25 September 2021.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 "Xermelo EPAR". European Medicines Agency (EMA). Retrieved 17 April 2020.
  3. 3.0 3.1 3.2 3.3 3.4 "Xermelo- telotristat ethyl tablet". DailyMed. 30 October 2020. Retrieved 11 November 2020.
  4. 4.0 4.1 BNF (80 ed.). BMJ Group and the Pharmaceutical Press. September 2020 – March 2021. p. 938. ISBN 978-0-85711-369-6.CS1 maint: date format (link)
  5. "Xermelo Prices, Coupons & Patient Assistance Programs". Retrieved 25 September 2021.
  6. 6.0 6.1 "FDA Approves Xermelo for Carcinoid Syndrome Diarrhea" (Press release). U.S. Food and Drug Administration (FDA). February 28, 2017. Retrieved 1 March 2017.
  7. "Xermelo (telotristat ethyl) Tablets". U.S. Food and Drug Administration (FDA). 4 April 2017. Retrieved 17 April 2020.
  8. Kulke M, Hörsch D, Caplin M, Anthony L, Bergsland E, Oberg K, et al. (1 October 2016). "Integrated Placebo-Controlled Safety Analysis from Clinical Studies of Telotristat Ethyl for the Treatment of Carcinoid Syndrome". Annals of Oncology. 27 (6): 136–48. doi:10.1093/annonc/mdw369.07.
  9. New Drug Therapy Approvals 2017 (PDF). U.S. Food and Drug Administration (FDA) (Report). January 2018. Retrieved 16 September 2020.

External links

  • "Telotristat ethyl". Drug Information Portal. U.S. National Library of Medicine.
  • "Telotristat etiprate". Drug Information Portal. U.S. National Library of Medicine.
  • Kulke MH, O'Dorisio T, Phan A, Bergsland E, Law L, Banks P, et al. (October 2014). "Telotristat etiprate, a novel serotonin synthesis inhibitor, in patients with carcinoid syndrome and diarrhea not adequately controlled by octreotide". Endocrine-Related Cancer. 21 (5): 705–14. doi:10.1530/ERC-14-0173. PMC 4295770. PMID 25012985.