Larazotide: the celiac peptide that almost made it

What larazotide was meant to do

Celiac disease is an immune reaction to gluten that damages the small intestine; the only established treatment is a strict lifelong gluten-free diet, and many people still have symptoms on it. Larazotide acetate is a synthetic peptide of eight amino acids, taken by mouth, designed to act on the tight junctions that seal the gaps between intestinal cells ¹. A 2021 review describes it as thought to act as a zonulin antagonist, reducing zonulin-driven increases in permeability and rearranging tight-junction proteins, with later work linking it to inhibition of myosin light chain kinase (review) ². One of that review's authors disclosed being a major shareholder in a company that merged into larazotide's last developer ².

The idea was attractive: if gluten fragments slip through a 'leaky' barrier and trigger the immune response, closing the barrier might blunt the reaction to accidental gluten exposure.

The early trials: symptoms yes, permeability no

A 2007 proof-of-concept study looked promising: after gluten, intestinal permeability rose 70% on placebo and not at all on larazotide, with fewer gastrointestinal symptoms (human study) ³. The larger trials did not reproduce the permeability effect. In a 2012 gluten-challenge trial, the permeability measure was too variable to show an effect, though some lower doses limited worsening of symptoms (randomised trial) ⁴. In a 2013 trial with 2.7 g of gluten a day, the permeability ratio did not differ from placebo; the 1 mg dose limited symptoms, and all doses blunted the rise in an antibody linked to celiac activity (randomised trial) ⁵.

A 2022 meta-analysis of four randomised trials with 626 patients confirmed the pattern: the lactulose-to-mannitol permeability ratio did not differ from placebo, whether or not patients were exposed to gluten; during gluten challenge, larazotide improved symptom scores and reduced gluten-related diarrhoea, but on a gluten-free diet it did not (meta-analysis) ⁶.

The permeability test and why it is hard to move

The trials measured gut leakiness with the lactulose-to-mannitol test: a person drinks two sugars, one large and one small, and the ratio that appears in the urine reflects how much the gut lets through. It is simple and non-invasive, but noisy. The 2012 trial reported that the measure was too variable to show an effect at all ⁴, and across four trials it never separated from placebo ⁶. That leaves two possibilities, neither comfortable for the drug: either larazotide did not change permeability in people, or the test was too crude to see it. Either way, the trials ended up resting on symptom scores, which are more open to placebo effects and to day-to-day variation in what people eat.

How the phase 2b trial was designed

The 2015 trial used a design meant to reduce noise: a four-week placebo run-in before treatment, 12 weeks of treatment, and a four-week placebo run-out afterwards, with the primary endpoint the average on-treatment score on a celiac gastrointestinal symptom scale ⁷. It also reported exploratory gains at 0.5 mg, including more improved symptom days ⁷. Careful designs like this are exactly why the single-dose result was taken seriously, and also why phase 3 tested lower doses again rather than the higher ones that had failed.

The phase 2b puzzle: only the lowest dose worked

The trial that justified phase 3 enrolled 342 adults who had been on a gluten-free diet for at least a year but still had symptoms. They took 0.5, 1 or 2 mg three times a day or placebo for 12 weeks. Only 0.5 mg met the primary endpoint, with fewer symptoms than placebo and 26% fewer symptomatic days; the 1 mg and 2 mg doses were no different from placebo (randomised trial) ⁷.

A drug that works at the lowest dose but not at higher ones can have a real explanation, but it is also the pattern chance produces when several doses and endpoints are tested at once. It was a warning sign that a larger trial would have to settle.

Phase 3: stopped at the interim analysis

Larazotide's phase 3 trial, CeDLara, enrolled adults with celiac disease who still had symptoms on a gluten-free diet. On June 21, 2022, its sponsor announced that a pre-specified interim analysis, run by an independent statistician on roughly the first half of the target enrolment after the 12-week double-blind period, had found that the number of additional patients needed to show a significant difference from placebo was too large to support continuing the trial ⁸. ClinicalTrials.gov lists the trial as terminated by the sponsor ¹.

The company said it would look for any subgroup or symptom that might have responded, and that completion of those analyses and discussion with FDA would determine further plans ⁸. As of October 3, 2026, larazotide is not approved anywhere, and Drugs@FDA holds no application ¹.

The zonulin question

Larazotide's story is tied to zonulin, a protein proposed as a key regulator of gut permeability and widely invoked in 'leaky gut' marketing. In 2021, Gut published a letter from celiac immunology researchers in Oslo and Leiden titled 'Lack of relationship of AT1001 to zonulin and prehaptoglobin-2: clinical implications', challenging the link between larazotide (AT-1001) and the zonulin pathway it was said to target (correspondence) ⁹. A drug whose mechanism is disputed and whose main biomarker did not move is hard to rescue with symptom subgroups.

Larazotide beyond celiac disease

Research on the peptide has continued in other settings. A 2025 report described children with post-COVID multisystem inflammatory syndrome treated with larazotide alongside standard care, reporting faster resolution of gastrointestinal symptoms and faster clearance of viral spike antigen, with no larazotide-related adverse events (human study) ¹⁰. Animal studies have explored intestinal injury and other conditions ². None of this changes its unapproved status.

Why celiac drug trials are difficult

The sponsor's chief medical officer, announcing the halt, pointed to the challenges and complexities of the disease and of measuring outcomes ⁸. Celiac symptoms come and go, depend on accidental gluten exposure that no trial can fully control, and overlap with other gut complaints. A drug meant to reduce the effect of hidden gluten has to show a difference against a background that changes week to week. That is not an excuse for larazotide; it is a reason to expect early, small trials to overestimate benefit, as they often do.

What it teaches about gut peptides

Larazotide is one of the most carefully studied 'gut barrier' peptides, with five controlled trials and a phase 3. That is far more than BPC-157 or KPV, which are sold online for gut healing with little or no human evidence. Its lessons apply to them:

• A plausible mechanism and a promising pilot study are where drugs start, not where they prove themselves ³.
• The marker a drug is designed to fix may not move, even if symptoms seem to ⁶.
• Results that appear at one dose but not others need a bigger trial before anyone relies on them ⁷.
• Even a company-funded phase 3 can stop when the effect is too small to prove ⁸.

Our guide to reading a peptide study explains these patterns, and our KPV vs BPC-157 page shows how thin the evidence is for the gut peptides sold online.

Approved gut peptides, for contrast

Some peptides do have proven gut benefits, for specific conditions. Teduglutide (Gattex) is approved for short bowel syndrome in patients dependent on intravenous nutrition, and linaclotide (Linzess) for irritable bowel syndrome with constipation and chronic constipation ¹. Both reached approval with phase 3 trials that met their goals, and both treat conditions other than celiac disease. For celiac disease, a gluten-free diet remains the only established treatment.

Questions to ask about any gut peptide claim

• Has it been tested in people with my condition, in a randomised, placebo-controlled trial?
• Did the marker it is supposed to fix actually change, or only symptom scores?
• Did the benefit hold across doses, or appear at only one?
• Was a larger, later trial run, and did it confirm the early result?
• Is the product an approved medicine, or a research powder making a mechanism claim?

What the gluten-challenge trials were testing

Two of the trials deliberately exposed people with well-controlled celiac disease to a measured daily dose of gluten, 2.4 g in one and 2.7 g in the other, to see whether larazotide could blunt the reaction ^{4 5}. That mimics the accidental exposure many people on a gluten-free diet face. In the 2013 trial, all doses blunted the rise in anti-transglutaminase antibodies, a blood marker of celiac activity, even though permeability did not change ⁵. That antibody signal was one of the more intriguing findings, but it was not the endpoint phase 3 was designed to prove, and it did not carry the drug to approval.

The bottom line

Larazotide was a serious attempt to treat celiac disease with a peptide, and it nearly reached the finish line. Its early symptom signals were real enough to justify phase 3, but its main biomarker never moved, its phase 2b result rested on one dose, its mechanism was challenged, and its phase 3 stopped when the effect proved too small. It is not approved. Any 'leaky gut' peptide sold online is starting far further back than larazotide did.

Frequently asked questions

What is larazotide?

An eight-amino-acid oral peptide designed to tighten intestinal tight junctions in celiac disease. It is not approved.

Why did the larazotide phase 3 trial stop?

In June 2022 an interim analysis found the number of additional patients needed to show a significant difference from placebo was too large to justify continuing.

Did larazotide reduce leaky gut?

In trials, its effect on the lactulose-to-mannitol permeability measure did not differ from placebo, although some doses limited symptoms during gluten challenge.

Is larazotide available?

No. As of October 3, 2026 it is not approved anywhere, and its phase 3 trial is listed as terminated.

Is there a drug for celiac disease?

No drug is approved for celiac disease; a strict gluten-free diet remains the only established treatment.

Related on Grey Peptides

• Larazotide
• How to read a peptide study
• KPV vs BPC-157

Sources

1. Grey Peptides encyclopedia entries for larazotide (sequence, status: no Drugs@FDA application, read September 30, 2026; NCT03569007 terminated by the sponsor, record updated July 26, 2022), teduglutide and linaclotide (approved indications). Read October 3, 2026.
2. Slifer, Z. M., et al. (2021). Larazotide acetate: a pharmacological peptide approach to tight junction regulation. Am J Physiol Gastrointest Liver Physiol, 320(6), G983-G989. PMID: 33881350
3. Paterson, B. M., et al. (2007). The safety, tolerance, pharmacokinetic and pharmacodynamic effects of single doses of AT-1001 in coeliac disease subjects: a proof of concept study. Aliment Pharmacol Ther, 26(5), 757-66. PMID: 17697209
4. Leffler, D. A., et al. (2012). A randomized, double-blind study of larazotide acetate to prevent the activation of celiac disease during gluten challenge. Am J Gastroenterol, 107(10), 1554-62. PMID: 22825365
5. Kelly, C. P., et al. (2013). Larazotide acetate in patients with coeliac disease undergoing a gluten challenge: a randomised placebo-controlled study. Aliment Pharmacol Ther, 37(2), 252-62. PMID: 23163616
6. Hoilat, G. J., et al. (2022). Larazotide acetate for treatment of celiac disease: A systematic review and meta-analysis of randomized controlled trials. Clin Res Hepatol Gastroenterol, 46(1), 101782. PMID: 34339872
7. Leffler, D. A., et al. (2015). Larazotide acetate for persistent symptoms of celiac disease despite a gluten-free diet: a randomized controlled trial. Gastroenterology, 148(7), 1311-9.e6. PMID: 25683116
8. 9 Meters Biopharma. 9 Meters Biopharma Announces Interim Analysis of Phase 3 Study of Larazotide for Celiac Disease Does Not Support Trial Continuation. Press release, June 21, 2022 (Exhibit 99.1 to an SEC filing). Read October 3, 2026.
9. Sollid, L. M., et al. (2021). Lack of relationship of AT1001 to zonulin and prehaptoglobin-2: clinical implications. Gut, 70(11), 2211-2212. PMID: 33443022
10. Yonker, L. M., et al. (2025). Viral spike antigen clearance and augmented recovery in children with post-COVID multisystem inflammatory syndrome treated with larazotide. Sci Transl Med, 17(809), eadu4284. PMID: 40737433

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.