What is larazotide? What it does, benefits and what the evidence shows

Larazotide (larazotide acetate, also called AT-1001) is an eight-amino-acid peptide designed to keep the tight junctions between gut lining cells closed, developed as an add-on for celiac disease. We found no approval for larazotide from any regulator, and its only Phase 3 trial, which enrolled 307 adults with celiac disease, was terminated by the sponsor in 2022. Mid-stage human trials gave mixed results, one of them positive on symptoms, and the sponsor stopped its Phase 3 trial in June 2022 after an interim analysis suggested the study would need far more patients than was feasible. The wider "heal leaky gut" claims that sell it on the grey market have no human trial behind them.

What larazotide is and how it works

Larazotide is a synthetic peptide of eight amino acids that acts as a tight junction regulator (Slifer et al., American Journal of Physiology, GI and Liver Physiology, 2021). Tight junctions are the seals between the cells lining your intestine. In celiac disease, gluten sets off an immune reaction, and increased gut permeability is considered a central part of the disease (Damianos et al., Gut, 2026). The idea behind larazotide is to hold those seals shut so that less gluten reaches the immune system.

Its lineage is unusual. AT-1001 is a peptide whose structure is derived from a protein secreted by Vibrio cholerae, the cholera bacterium (Paterson et al., Alimentary Pharmacology & Therapeutics, 2007). In cultured gut cells and in gliadin-sensitized mice, larazotide blocked the disruption of tight junction proteins caused by gliadin fragments and cytokines, and preserved normal junction structure (Gopalakrishnan et al., Peptides, 2012). It is described as a zonulin antagonist, and more recent work links it to inhibition of myosin light chain kinase, which reduces tension on the cell skeleton and lets junctions close (Slifer et al., 2021).

Two cautions on the mechanism. First, the "zonulin" story is itself contested: an independent group found that commercial kits sold to measure serum zonulin were not detecting the actual protein, and advised caution about using serum zonulin as a marker of gut barrier integrity (Ajamian et al., PLoS One, 2019). Second, a search for "AT-1001" can return a different drug: Amicus Therapeutics used the same code for migalastat, a Fabry disease treatment, in its ClinicalTrials.gov records (ClinicalTrials.gov, NCT00214500). Larazotide and migalastat are unrelated.

What people use it for

What the research actually shows

Symptoms in people on a gluten-free diet

The most-cited trial enrolled 342 adults with celiac disease who still had symptoms despite a gluten-free diet of a year or more. It was randomized, double-blind and placebo-controlled, with about three months of treatment. The primary endpoint, the average celiac-specific symptom score, was met, but only at the lowest of the three doses tested; the two higher doses were no different from placebo on any endpoint. Safety was comparable with placebo, and the authors themselves called the results "mixed" (Leffler et al., Gastroenterology, 2015).

That odd dose pattern has a possible explanation from lab work. In pig intestine, larazotide worked at one concentration but not at a lower or a higher one, and the researchers found that enzymes in the gut lining chop the peptide into fragments, one of which blocked the barrier-repair effect (Slifer et al., PLoS One, 2021). That is a hypothesis from tissue experiments, not something shown in patients, but it is a reminder that "more" did not mean "better" in the human trial.

Gluten challenge studies

Several smaller trials deliberately gave people with celiac disease gluten while on larazotide or placebo. In a 2007 proof-of-concept study, permeability rose in the placebo group after gluten and not in the larazotide group, and symptoms were reported more often on placebo; the study was small, and the authors described it as exploratory (Paterson et al., 2007). A 2012 dose-ranging study of 86 patients found that the permeability test (urinary lactulose-to-mannitol ratio) was too variable in outpatients to measure the effect accurately, though some lower doses appeared to prevent gluten-induced symptom worsening (Leffler et al., American Journal of Gastroenterology, 2012). A 2013 study of 184 patients over several weeks of gluten exposure again saw no significant difference in that permeability ratio, but found fewer gluten-induced symptoms at the lowest dose and smaller rises in anti-tissue transglutaminase antibodies at every dose tested, with similar adverse event rates to placebo (Kelly et al., Alimentary Pharmacology & Therapeutics, 2013).

A pooled analysis of the four randomized trials (626 patients) reached the same shape of answer: no significant change in the permeability ratio, better symptom scores in people undergoing gluten challenge, and no significant symptom difference in people simply staying on a gluten-free diet (Hoilat et al., Clinics and Research in Hepatology and Gastroenterology, 2022). In plain terms: the drug was built to reduce gut permeability, and the trials could not show that it does, yet symptoms sometimes improved. Nobody has cleanly explained why.

The Phase 3 trial was stopped

The company that developed larazotide, 9 Meters Biopharma, ran a Phase 3 trial in adults with persistent celiac symptoms on a gluten-free diet. On June 21, 2022 it announced a pre-specified interim analysis covering roughly the first half of the target enrollment. An independent statistician found that the number of additional patients needed to show a significant difference between larazotide and placebo was too large to support continuing, and the company halted the trial (9 Meters Biopharma press release, June 21, 2022, filed with the SEC). ClinicalTrials.gov lists the study as terminated by the sponsor, with 307 participants enrolled and no posted results (ClinicalTrials.gov, NCT03569007). A 2026 review in Gut still lists larazotide among experimental medications for restoring barrier function (Damianos et al., 2026). We found no later Phase 3 program.

Everything outside celiac disease

Beyond celiac disease, the evidence is mostly lab-based, with a few small early human studies in post-COVID conditions. Larazotide improved barrier function in ischemia-injured pig intestine in a tissue chamber (Slifer et al., 2021), and in cultured cell layers it stabilized tight junctions after oxygen deprivation and reoxygenation (Kim et al., 2025). Those are experiments on tissue and cells. The exception is a Phase 2a randomized, placebo-controlled trial in 12 children with post-COVID multisystem inflammatory syndrome (MIS-C), published in Science Translational Medicine in 2025, which reported no larazotide-related adverse events and faster symptom resolution (Science Translational Medicine, 2025). ClinicalTrials.gov also lists a completed Phase 2 long COVID study of 107 participants with no posted results (ClinicalTrials.gov, NCT05747534). We found no human trial for ulcerative colitis, Crohn's disease, irritable bowel or general "leaky gut".

Side effects and risks

• In trials. Safety was comparable with placebo in the trials above. In the 2012 study the most common adverse events were headache and urinary tract infection, with no serious adverse events (Leffler et al., 2012). The pooled analysis found other adverse events comparable between larazotide and placebo (Hoilat et al., 2022).
• Short studies. The trials ran for weeks to a few months. We found no long-term safety data.
• Not a treatment for celiac disease. Even in the best trial, participants stayed on a gluten-free diet; nothing in the evidence suggests larazotide makes gluten safe to eat.
• Theory versus evidence. Loosening or tightening tight junctions affects what crosses the gut wall, and no one has studied larazotide in people with other gut conditions. That is unknown, not proven harmful.
• Regulatory status. We found no approval for larazotide from any regulator, and no listing for it on FDA's page of bulk drug substances with significant safety risks (FDA, page current as of April 22, 2026). That absence tells you nothing about safety; it just means FDA has not evaluated it there.

What the lab tests show

As of September 29, 2026, VendorVerify's database has no lab results for larazotide. That doesn't mean the vials are good or bad; it means no report has been submitted that we can count. If you have had a larazotide vial tested, submitting the report is the fastest way to change that.

Because we don't have enough lab data on this compound to rank vendors for it, here are the highest-ranked vendors across all compounds right now. A vendor's overall record is a signal, not a guarantee for a compound they have never had tested.

Buying smarter

With no compound-specific data, lean on the general checks. Look at each vendor's full record and how many reports sit behind the score. Treat a vendor-posted COA as a starting point (how to read a peptide COA, fake peptide COAs). Larazotide is a short peptide sold with no track record in our data, so paying for identity, purity and quantity testing on your own vial is worth it; how to get a peptide tested walks through it, and endotoxin in research peptides covers when to add that test.

If a report comes back with a fail, stop using that batch, tell anyone who bought from the same run, bring the report to the vendor, and submit it to VendorVerify. Buyers researching gut-barrier peptides often also read about KPV, BPC-157 and LL-37; the peptide hub lists every compound we track.

Database figures are from VendorVerify as of September 29, 2026. This isn't medical advice; larazotide has no approval anywhere we could find, and its Phase 3 trial was stopped in 2022.