Xermelo (telotristat ethyl)
An approved treatment for Neuroendocrine Tumors.
The same compound appears under different names depending on the context. Here is how to identify Telotristat ethyl wherever you encounter it, plus the key facts at a glance.
- Generic name
- Telotristat ethyl
- Brand name
- Xermelo
- Drug class
- Tryptophan hydroxylase inhibitor
- Manufacturer
- TerSera Therapeutics
- How it's taken
- 250 mg by mouth 3 times a day with food, added to the somatostatin injection a person already takes.
A pill taken 3 times a day with food for adults whose carcinoid syndrome diarrhea is not controlled by a somatostatin injection alone, used together with that injection. Approved February 28, 2017.
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Where Telotristat ethyl fits
An add-on for carcinoid syndrome diarrhea when lanreotide or octreotide is not enough on its own. It treats the diarrhea, not the tumor itself.
How Telotristat ethyl works
Many neuroendocrine tumors that have spread make large amounts of serotonin, which speeds up the gut and causes the diarrhea of carcinoid syndrome. Xermelo blocks tryptophan hydroxylase, the enzyme that makes serotonin, so less is produced. It is added to lanreotide or octreotide, not used instead of them.
Mechanism: Oral inhibitor of tryptophan hydroxylase, the enzyme neuroendocrine tumors use to make serotonin, which drives carcinoid syndrome diarrhea
Side effects and safety
- Constipation. Xermelo slows the bowel. Serious complications, including blockage and perforation, have been reported, mostly at higher than approved doses. It is stopped if constipation or severe or worsening belly pain develops.
- Bowel movements and belly pain, especially when starting
- Timing: short-acting octreotide is taken at least 30 minutes after Xermelo
Xermelo has no boxed warning. It can cause constipation, which has led to serious complications such as bowel blockage in some people, mostly at higher than approved doses, so it is stopped if constipation or worsening belly pain develops. People who have had an allergic reaction to telotristat must not take it. In its 12-week trial, nausea (13% against 11% on placebo), headache (11% against 4%) and a raised liver enzyme, GGT (9% against 0%), were the most common side effects, and depression was reported in 9% against 7%.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Telotristat ethyl
250 mg by mouth 3 times a day with food, added to the somatostatin injection a person already takes. When short-acting octreotide is also used, it is taken at least 30 minutes after Xermelo. A missed dose is skipped, not doubled.
Availability and cost
Only available as the brand-name product.
Help paying for Xermelo
Pick your insurance to see which help fits. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE; charity funds are the usual route there.
- Copay help
People with commercial insurance that covers Xermelo may pay as little as $0 per fill. TerSera pays up to an annual maximum that resets each calendar year but does not publish the dollar amount. You must be 18 or older. People on Medicare, Medicaid, VA, DoD or any other state or federal plan, and cash-paying patients, cannot use it.
For: private insurance · source - Free medicine program
Eligible patients who show financial need and do not have insurance coverage may get Xermelo at no cost through the Patient Assistance Program. Other terms apply.
For: no insurance · source - Insurance and case manager help
SupportSource checks your plan coverage, explains prior authorization and appeals, estimates your out-of-pocket costs and can refer eligible patients to independent assistance foundations. It also offers TerSera NurseSupport for patients prescribed Xermelo.
For: private insurance, Medicare, Medicaid, TRICARE, no insurance, underinsured · source
Good to know: The copay team's number is 1-855-680-4551. The patient assistance application includes a credit check to judge financial need.
Clinical trial results
In a 12-week placebo-controlled trial of 90 adults with carcinoid syndrome diarrhea who still had 4 to 12 bowel movements a day despite a stable somatostatin injection, daily bowel movements fell by an average of 1.4 on Xermelo against 0.6 on placebo, with the difference showing within 1 to 3 weeks.
Development history
Developed by Lexicon Pharmaceuticals and approved by the FDA on February 28, 2017 as the first pill for carcinoid syndrome diarrhea. It is now sold in the US by TerSera Therapeutics.
Explore Neuroendocrine Tumors trials
Other Neuroendocrine Tumors treatments
Lanreotide and octreotide injections are the base treatment for carcinoid syndrome, with short-acting octreotide used for breakthrough symptoms. Paltusotine, a once-daily pill, is in a Phase 3 trial for carcinoid syndrome (NCT07087054).
Common questions about Telotristat ethyl
▸What is Telotristat ethyl (Xermelo)?
A pill taken 3 times a day with food for adults whose carcinoid syndrome diarrhea is not controlled by a somatostatin injection alone, used together with that injection. Approved February 28, 2017.
▸How does Telotristat ethyl work?
Many neuroendocrine tumors that have spread make large amounts of serotonin, which speeds up the gut and causes the diarrhea of carcinoid syndrome. Xermelo blocks tryptophan hydroxylase, the enzyme that makes serotonin, so less is produced. It is added to lanreotide or octreotide, not used instead of them.
▸What are the side effects of Telotristat ethyl?
Xermelo has no boxed warning. It can cause constipation, which has led to serious complications such as bowel blockage in some people, mostly at higher than approved doses, so it is stopped if constipation or worsening belly pain develops. People who have had an allergic reaction to telotristat must not take it. In its 12-week trial, nausea (13% against 11% on placebo), headache (11% against 4%) and a raised liver enzyme, GGT (9% against 0%), were the most common side effects, and depression was reported in 9% against 7%.
▸How is Telotristat ethyl taken?
250 mg by mouth 3 times a day with food, added to the somatostatin injection a person already takes. When short-acting octreotide is also used, it is taken at least 30 minutes after Xermelo. A missed dose is skipped, not doubled.
▸Is Telotristat ethyl FDA approved?
Yes, Telotristat ethyl (Xermelo) is FDA approved (2017) for the treatment of Neuroendocrine Tumors.
▸Does Xermelo replace lanreotide or octreotide?
No. Xermelo is approved for use together with a somatostatin injection, for adults whose carcinoid syndrome diarrhea that injection alone does not control. It treats the diarrhea, not the tumor.
▸How fast does Xermelo work?
In its trial, the drop in daily bowel movements compared with placebo showed within 1 to 3 weeks and lasted through the 12 weeks.
Sources and references
Every factual claim on this page is drawn from the public sources listed below. Click any reference to open the original document.
- U.S. National Library of Medicine, DailyMed · 2026-08. XERMELO (telotristat ethyl) tablets: prescribing information. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a4ac9d62-887c-4c8f-b04d-a5f31cec7c86