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Investigational peptide (development stalled)Human trialsNot FDA approved

Larazotide

Larazotide acetate

Last reviewed October 27, 2026 · 17 sources · Written for general readers · Compare with another compound →

The bottom line

Larazotide is a small swallowed peptide designed to keep the gut lining's seals closed. In several trials with hundreds of people with celiac disease it did not measurably tighten the gut, symptom benefits showed up only at the lowest dose, and the phase 3 trial was stopped in 2022 for lack of effect. It is not approved anywhere, and a long COVID trial that ended in 2026 has no published results.

Where the evidence stands

What it is

Larazotide is a short peptide made of 8 amino acids. The drug form tested in trials is larazotide acetate.[1][2] It was developed as a pill that works locally inside the gut rather than being absorbed into the blood.[2]

It was designed for celiac disease, an immune reaction to gluten that damages the small intestine. The idea was to help people who still have symptoms even though they follow a strict gluten free diet.[2]

Sellers often promote it for leaky gut, the idea that a too porous gut lining causes many health problems. Celiac trials measured gut leakiness directly, so that claim can be checked against data.[3]

Name
Larazotide (Larazotide acetate)
Other names
AT-1001, AT1001, larazotide acetate
Type
Investigational peptide (development stalled)
Sequence
GGVLVQPG
CAS number
258818-34-7

What it does in the body

Larazotide is a lab made peptide of 8 amino acids, not a molecule the body makes.[1] It is designed to act on tight junctions, the seals that hold gut lining cells together, and researchers describe it as blocking zonulin, a body signal that loosens those seals.[4][5] It was built as a pill meant to work inside the gut rather than in the blood.[2]

This is the biology, area by area. A change measured in the body, like a higher blood level, does not always mean a person feels a benefit. The claims check below covers that.

Gut lining

Measured in people

In lab cell layers it stopped gluten pieces and inflammatory signals from opening tight junctions.[6] In pig gut tissue injured by lost blood flow, only the middle of three strengths tested helped the lining recover its seal.[7] But in people with celiac disease, sugar drink tests of gut leakiness did not differ from placebo in trials of 86 and 184 people, or in a pooled analysis of 626 patients.[8][9][3]

Immune response to gluten

Measured in people

In 184 people with celiac disease who ate gluten daily for six weeks, celiac antibody levels rose about 4 to 8 times from baseline with larazotide versus about 19 times with placebo.[9] In mice bred to react to gluten, it reduced the buildup of immune cells in the gut lining.[6]

Gut symptoms

Measured in people

In 342 adults with ongoing celiac symptoms on a gluten free diet, only the lowest of three strengths reduced days with gut symptoms, by 26 percent versus placebo.[2] The phase 3 trial was stopped in 2022 because it was not showing a benefit.[10]

Blood and immune recovery after COVID-19

Measured in people

In children with MIS-C, a severe inflammatory illness after COVID-19, virus spike protein in the blood became undetectable in all four children treated in a first case series, and it cleared faster than in 22 children given standard care.[4] A 12 child placebo controlled trial also found faster clearance and recovery.[11]

Joints

Seen in animals

In mice prone to autoimmune arthritis, a leaky gut came before joint disease, and larazotide reduced the onset of arthritis.[5] No human arthritis study exists.

How it works

The gut lining is a single layer of cells held together by seals called tight junctions.

  • Larazotide is meant to stop these seals from opening, which would keep gluten fragments from reaching the tissue underneath and triggering inflammation.[2]
  • In lab cell layers, it blocked the opening of tight junctions caused by gluten pieces, by inflammatory signals, and by a related peptide taken from a cholera bacteria toxin.[6]
  • In people, gut leakiness is usually measured with a sugar drink test, comparing how much of two sugars, lactulose and mannitol, ends up in the urine.[8]

The mechanism is supported by lab and mouse work, but trials in people did not show a measurable tightening of the gut.

What the research shows

We keep animal and human evidence apart. A result in animals is a reason to study something in people, not proof that it works in people.

Animal and lab studies

Protected the gut lining in mice and pig tissue

  • In mice bred to react to gluten like people with celiac disease, larazotide reduced the buildup of immune cells in the gut after gluten exposure and kept the tight junction structure normal.[6]
  • In human gut cell layers grown in the lab, it reduced the passage of a gluten fragment across the cells.[6]
  • In mice prone to autoimmune arthritis, rising zonulin and a leaky gut came before joint disease, and larazotide reduced the onset of arthritis.[5]
  • In pig gut tissue injured by lost blood flow, larazotide helped the lining regain its electrical seal at the middle strength tested but not at lower or higher strengths.[7]

Limit: Mouse models of celiac disease only partly copy the human disease.

Human studies

Several placebo controlled trials, with a failed phase 3

  • Gluten challenge, 2012: 86 people with diet controlled celiac disease took larazotide pills or placebo for 14 days, most while eating gluten daily. The sugar test of gut leakiness was too variable to show an effect. Some lower doses seemed to limit symptom worsening, the highest did not. Headache and urinary tract infection were the most common side effects, and none were serious.[8]
  • Gluten challenge, 2013: 184 people ate gluten daily for six weeks with larazotide or placebo. Gut leakiness did not differ. The lowest dose limited symptoms, and celiac antibody levels rose less with larazotide. Side effect rates were similar to placebo.[9]
  • Phase 2b, 2015: 342 adults with ongoing symptoms despite a gluten free diet took larazotide or placebo for 12 weeks. Only the lowest of three dose levels helped, with 26 percent fewer days with gut symptoms. Side effects were about the same as placebo, mostly gut complaints, and none serious were linked to the drug.[2]
  • Review, 2022: four randomized trials with 626 patients found no effect on gut leakiness, symptom benefit only during gluten challenge, less gluten related diarrhea, and other side effects similar to placebo.[3]
  • Phase 3, CeDLara: the larger trial enrolled about 300 adults. In June 2022 the company stopped it after an interim look showed far too many extra patients would be needed to show a benefit.[14][10]
  • MIS-C case series (2022): four children aged 3 to 17 took larazotide by mouth for 21 days with steroids or immune globulin. None had side effects, spike protein in the blood became undetectable in all four, and gut symptoms resolved faster than in 22 earlier children given usual care alone.[4]
  • MIS-C, 2025: 12 children with a severe inflammatory illness after COVID-19 got larazotide or placebo for three weeks alongside usual care. Treated children recovered faster on several measures and had no drug related side effects over 24 weeks.[11]
  • Long COVID: a placebo controlled trial in 107 children and adults finished in June 2026. We found no published results yet.[13]

Limit: The only clear positive results came from the lowest dose in phase 2 and a tiny children's trial, and the large phase 3 trial did not confirm a benefit.

Claims check

The most common claims about this compound, and what studies actually found. Verdicts rate the evidence, not whether you should use it.

Fixes leaky gut

No benefit in trials so far

In a 14 day trial of 86 people with celiac disease and a 6 week trial of 184 people, the sugar drink test of gut leakiness did not differ between larazotide and placebo.[8][9] A 2022 review pooling four trials with 626 patients found no difference in gut leakiness, with or without gluten.[3]

Eases celiac disease symptoms

Mixed results

In a 12 week trial of 342 adults with ongoing symptoms on a gluten free diet, only the lowest of three dose levels helped, with 26 percent fewer days with gut symptoms than placebo.[2] The larger phase 3 trial was stopped in 2022 because it was not showing a benefit.[10] Pooled trials found symptom benefit only during gluten challenges, not on a gluten free diet.[3]

Protects against gluten exposure

Mixed results

In 184 people with celiac disease who ate gluten daily for six weeks, the lowest dose limited symptom worsening, and the rise in celiac antibody levels was smaller with larazotide (about 4 to 8 times baseline) than with placebo (19 times).[9] In an 86 person gluten challenge, only some lower doses limited symptoms.[8] It was only ever tested alongside a gluten free diet, never as a replacement for one.[2]

Speeds recovery from MIS-C after COVID-19

Mixed results

In a first case series, four children aged 3 to 17 with MIS-C took larazotide by mouth for 21 days with usual care. All tolerated it, spike protein in the blood became undetectable, and gut symptoms cleared faster than in 22 children treated earlier with usual care alone.[4] In a placebo controlled trial of 12 children, those given larazotide had faster relief of gut symptoms, faster clearance of virus protein and faster return to normal activities, with no drug related side effects.[11] The trial stopped early as cases became rare, so the evidence is far too small to be sure.[12]

Treats long COVID

Not tested

A placebo controlled trial in 107 children and adults with long COVID finished in June 2026, but we found no published results, so there is no evidence either way yet.[13]

Helps autoimmune disease or arthritis

Only in animals

In mice prone to autoimmune arthritis, larazotide tightened the gut barrier and reduced the onset of arthritis.[5] No human trial has tested larazotide for arthritis or any autoimmune disease other than celiac disease.

Known risks and side effects

  • Likely does not work for its main use. The phase 3 celiac trial was stopped because it was not showing a meaningful benefit over placebo.[10]
  • Side effects reported in trials. Side effects were about as common as with placebo. Headache, urinary tract infection and gut complaints were the most often reported, and none serious were linked to the drug.[8][2]
  • Not a substitute for a gluten free diet. Larazotide was only ever tested as an add on for people already on a strict gluten free diet.[2]
  • Long term safety unknown. Trials lasted about three months at most, so there is no long term safety record.[2]
  • Unregulated online products. Larazotide is not approved and is not on FDA's compounding lists, so any product sold online has no FDA check on content, purity or sterility.[15] WADA's S0 category bans drugs with no current government approval for human use, which covers larazotide, and the 2027 list keeps that rule.[16][17]

Regulatory status

Today: Larazotide is not approved in the United States or elsewhere. Its phase 3 celiac trial was terminated in 2022, and a phase 2 long COVID trial was completed in June 2026.[14][13] It is not on FDA's compounding lists.[15] It is not named on WADA's 2027 list, but the list's S0 rule bans drugs with no current approval for human use, which covers larazotide.[17]

  1. The phase 2b trial of 342 patients was published, showing a benefit only at the lowest dose.[2]
  2. The phase 3 CeDLara trial began.[14]
  3. The sponsor stopped the phase 3 trial after an interim analysis showed it was unlikely to succeed.[10]
  4. A small trial in children with MIS-C ended early because of falling case numbers.[12]
  5. Results of the 12 child MIS-C trial were published, reporting faster recovery.[11]
  6. A phase 2 trial of larazotide for long COVID in children and adults was completed with 107 participants.[13]

Sources

  1. U.S. Food and Drug Administration and NCATS. Global Substance Registration System: larazotide (UNII ZN3R5560ZV), codes and sequence. FDA GSRS
  2. Leffler DA, Kelly CP, Green PHR, et al. Larazotide Acetate for Persistent Symptoms of Celiac Disease Despite a Gluten-Free Diet: A Randomized Controlled Trial. Gastroenterology. 2015;148(7):1311-1319.e6. PMID 25683116
  3. Hoilat GJ, Altowairqi AK, Ayas MF, et al. Larazotide acetate for treatment of celiac disease: A systematic review and meta-analysis of randomized controlled trials. Clin Res Hepatol Gastroenterol. 2022;46(1):101782. PMID 34339872
  4. Yonker LM, Swank Z, Gilboa T, et al. Zonulin Antagonist, Larazotide (AT1001), As an Adjuvant Treatment for Multisystem Inflammatory Syndrome in Children: A Case Series. Crit Care Explor. 2022;10(2):e0641. PMID 35211683
  5. Tajik N, Frech M, Schulz O, et al. Targeting zonulin and intestinal epithelial barrier function to prevent onset of arthritis. Nat Commun. 2020;11(1):1995. PMID 32332732
  6. Gopalakrishnan S, Durai M, Kitchens K, et al. Larazotide acetate regulates epithelial tight junctions in vitro and in vivo. Peptides. 2012;35(1):86-94. DOI 10.1016/j.peptides.2012.02.015
  7. Slifer ZM, Hernandez L, Pridgen TA, et al. Larazotide acetate induces recovery of ischemia-injured porcine jejunum via repair of tight junctions. PLoS One. 2021;16(4):e0250165. PMID 33886649
  8. Leffler DA, Kelly CP, Abdallah HZ, et al. A randomized, double-blind study of larazotide acetate to prevent the activation of celiac disease during gluten challenge. Am J Gastroenterol. 2012;107(10):1554-1562. PMID 22825365
  9. Kelly CP, Green PHR, Murray JA, et al. Larazotide acetate in patients with coeliac disease undergoing a gluten challenge: a randomised placebo-controlled study. Aliment Pharmacol Ther. 2013;37(2):252-262. PMID 23163616
  10. Chudleigh H. Disappointing Results End 9 Meters' Phase III Trial for Celiac Treatment. BioSpace. June 21, 2022. News report
  11. Yonker LM, Kane AS, Swank Z, et al. Viral spike antigen clearance and augmented recovery in children with post-COVID multisystem inflammatory syndrome treated with larazotide. Sci Transl Med. 2025;17(809):eadu4284. PMID 40737433
  12. Massachusetts General Hospital. Phase 2a study of AT1001 (larazotide acetate) for COVID-19-related MIS-C in children. ClinicalTrials.gov NCT05022303. NCT05022303
  13. Massachusetts General Hospital. Phase 2a Randomized, Double-Blind, Placebo-Controlled, Multi-Center Study to Evaluate the Safety and Efficacy of Larazotide (AT1001) for the Treatment of Long COVID in Children and Adults. ClinicalTrials.gov NCT05747534. NCT05747534
  14. 9 Meters Biopharma. A Phase 3, Randomized, Double-Blind, Placebo Controlled Study to Evaluate the Efficacy and Safety of Larazotide Acetate for the Relief of Persistent Symptoms in Patients With Celiac Disease on a GFD. ClinicalTrials.gov NCT03569007. NCT03569007
  15. U.S. Food and Drug Administration. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the FD&C Act (category lists). Updated May 14, 2026. FDA 503A category lists
  16. World Anti-Doping Agency. World Anti-Doping Code International Standard: Prohibited List 2026. Effective 1 January 2026. WADA 2026 List, S0
  17. World Anti-Doping Agency. International Standard: The 2027 Prohibited List. Comes into effect 1 January 2027. WADA 2027 List, S0
Medical disclaimer

This page is educational information only. It is not medical advice and does not replace care from a licensed medical provider. Do not use this page to decide whether to take any substance. Talk to a licensed medical provider first.

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