Larazotide Acetate: gut-lining sealer for celiac disease (AT-1001)
A synthetic peptide that seals the gut lining so fewer gluten fragments leak through and trigger immune attacks; studied in celiac disease and Long COVID; experimental, not an approved drug.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Larazotide acetate (also known as AT-1001) is a synthetic 8-amino acid peptide that helps keep the spaces between cells in the gut lining properly sealed. It was developed to reduce the excessive intestinal "leakiness" seen in celiac disease — the immune condition triggered by gluten in wheat, barley, and rye. The idea behind larazotide is that by blocking a protein called zonulin from prying open the gut lining, fewer gluten fragments can slip through and trigger the immune attack. Larazotide has been through multiple Phase 2 clinical trials in celiac disease and reached Phase 2/3 evaluation; it is not FDA-approved for any indication.
The peptide's sequence (GGVLVQPG) was derived from the C-terminal domain of zonula occludens toxin (ZOT), a protein made by Vibrio cholerae that opens intestinal tight junctions — larazotide uses the same sequence but acts as a competitive blocker rather than an opener.
History
Celiac disease affects roughly 0.5–1.5% of the global population. The only established treatment is a strict, lifelong gluten-free diet (GFD), which is effective but places a heavy burden on patients and is frequently complicated by inadvertent gluten exposure. A significant proportion of patients — estimated at 7–30% — continue to have persistent gastrointestinal symptoms despite dietary adherence, a pattern sometimes called non-responsive celiac disease. This unmet need drove interest in pharmacological adjuncts.
The mechanistic foundation came from the laboratory of Alessio Fasano and colleagues in the early 2000s, where researchers identified zonulin — an endogenous protein (later identified as complement factor B / CUZD1) — as a physiologic regulator of intestinal tight junctions. They found that gliadin exposure in celiac disease triggers zonulin release, which binds epithelial receptors and opens tight junctions through a signaling cascade, allowing immunogenic gliadin peptides to cross the epithelial barrier and drive the autoimmune response in the lamina propria. V. cholerae's ZOT uses a similar receptor pathway; its C-terminal 8-mer was exploited as a pharmacological lead.
Larazotide acetate was developed by Alba Therapeutics Corporation as a competitive inhibitor at the ZOT/zonulin receptor. Phase 1 safety studies in healthy volunteers established tolerability. Phase 2 efficacy trials followed in celiac disease patients both with and without concurrent gluten challenge, providing the data summarized below. The program was subsequently acquired by Innovate Biopharmaceuticals, which merged into 9 Meters Biopharma. A Phase 3 program for celiac disease was planned; as of 2025–2026 the program appears deprioritized after Phase 2b, and larazotide has no approved indication. A separate Phase 2 investigation in Long COVID — based on evidence that SARS-CoV-2 disrupts intestinal barrier integrity through zonulin-related mechanisms — was recruiting as of 2026.
What it does
Larazotide binds to the ZOT/zonulin receptor on intestinal epithelial cells and competitively blocks zonulin from activating it. In the absence of larazotide, dietary gliadin triggers zonulin release, which activates a signaling cascade (PKCβ → myosin light chain kinase → myosin light chain phosphorylation → contraction of the perijunctional actomyosin ring) that displaces occludin and ZO-1 from tight junction complexes, creating paracellular gaps through which gliadin peptides can enter the lamina propria. By occupying the receptor first, larazotide blocks this sequence.
Beyond receptor-level competition, in vitro and in vivo studies show larazotide also directly promotes reassembly of occludin, ZO-1, and ZO-2 into functional tight junction strands and reduces myosin light chain kinase–driven actin tension. The net result in experimental models is reduced paracellular transport of macromolecules.
Importantly, larazotide does not modify the adaptive immune response once activated, does not affect antigen presentation, does not target HLA-DQ2/DQ8, and does not neutralize gliadin peptides directly. It operates exclusively at the barrier level — reducing the rate of gliadin entry, not eliminating the downstream immune machinery.
Evidence
- Human (Phase 2b persistent CD symptoms on GFD, n=342, 12 weeks): Leffler and colleagues (Gastroenterology, 2015) enrolled celiac disease patients on a gluten-free diet with persistent gastrointestinal symptoms. Larazotide 0.5 mg three times daily significantly reduced CD-specific gastrointestinal symptoms (CD-GSRS) versus placebo (treatment difference −0.27 points, P=0.022). The 1 mg and 2 mg doses did not demonstrate significant benefit — a non-monotonic dose-response pattern that complicated interpretation. The secondary intestinal permeability endpoint (lactulose-to-mannitol ratio) did not improve significantly for any larazotide dose. Adverse event rates were similar across groups; larazotide was well tolerated at all doses (Leffler 2015).
- Human (Phase 2b gluten challenge, n=184, 12 weeks): Leffler and colleagues (American Journal of Gastroenterology, 2012) enrolled patients with biopsy-confirmed celiac disease on GFD for ≥12 months, with daily gluten challenge. The primary endpoint — change in lactulose-to-mannitol ratio — did not significantly differ between larazotide and placebo. However, total GSRS and CD-specific GSRS improved significantly in the larazotide arms versus placebo, and gluten-related diarrhea was reduced in the larazotide group. The discrepancy between permeability (non-significant) and symptoms (significant) raised questions about the mechanism of symptomatic benefit (Leffler 2012).
- Human (meta-analysis of 4 Phase 2 RCTs, n=626): A systematic review (Hoilat and colleagues, 2021) pooled data from three gluten-challenge trials and two GFD-only trials. Lactulose-to-mannitol ratio did not significantly improve versus placebo in either subgroup. In the gluten-challenge subgroup, larazotide significantly improved total GSRS (MD −0.26, 95% CI −0.49 to −0.03) and CD-GSRS (MD −0.23, 95% CI −0.39 to −0.07). In the GFD-only subgroup, symptomatic endpoints showed no significant benefit. The review concluded that larazotide is well tolerated and may adjunctively reduce GI symptoms during gluten exposure but is unlikely to substitute for GFD.
- Animal/preclinical: Preclinical studies have demonstrated larazotide's effect on tight junction proteins in intestinal epithelial cell lines and rodent models, including reduction of paracellular FITC-dextran flux and preservation of occludin and ZO-1 localization at tight junctions. Additional preclinical work has explored larazotide in acute pancreatitis, ischemia-reperfusion injury models, and colitis — conditions sharing an intestinal barrier-disruption component.
Myths and misconceptions
- "Larazotide is a zonulin blocker — it will heal the gut lining" — Larazotide reduces gliadin entry through tight junctions, but it does not repair established immune-mediated mucosal damage (villous atrophy, lymphocytosis, crypt hyperplasia) in celiac disease. Histological healing requires time on a gluten-free diet. In clinical trials, villous architecture did not significantly improve beyond GFD alone during the 12-week study periods.
- "Since permeability didn't improve, larazotide doesn't work" — The lactulose-to-mannitol ratio is an indirect and variable measure of tight junction function. Symptomatic improvement at the 0.5 mg dose in the Leffler 2015 trial was statistically significant despite non-significant permeability changes. Whether the symptom benefit operates through barrier-dependent or barrier-independent mechanisms remains an open question. The disconnect between permeability and symptoms is a genuine interpretive challenge, not necessarily proof of inefficacy.
- "Larazotide cures non-responsive celiac disease" — Persistent celiac symptoms on GFD can have multiple causes: continued inadvertent gluten exposure, refractory sprue, irritable bowel syndrome comorbidity, microscopic colitis, or incomplete villous recovery. Larazotide addresses only the gliadin-entry component at the tight junction. In trials, the 0.5 mg dose showed modest symptomatic benefit, but many patients on GFD did not respond, suggesting their symptoms had other drivers. Larazotide is a potential adjunct, not a cure.
Common questions
Why didn't larazotide reach FDA approval despite Phase 2 data? The regulatory pathway for celiac disease pharmacotherapy is challenging: the FDA has historically required histological improvement (villous recovery) as a primary endpoint for approval, which larazotide was not designed to drive. Symptomatic improvement in a disease managed by dietary modification is also difficult to distinguish from GFD optimization effects. The non-monotonic dose response — where 0.5 mg worked and higher doses did not — raised questions about mechanism and optimal dosing. These factors, combined with commercial transitions at Alba Therapeutics (later Innovate Biopharmaceuticals, then 9 Meters Biopharma), complicated the path to a Phase 3 NDA package.
What is the Long COVID rationale for larazotide? Growing evidence suggests SARS-CoV-2 infection disrupts intestinal barrier integrity, potentially including through zonulin pathway activation. Increased intestinal permeability may contribute to post-acute sequelae of COVID-19 by allowing microbial products to translocate into systemic circulation and perpetuate low-grade inflammation. Larazotide has been under evaluation as a tight junction stabilizer in Long COVID — a different mechanistic context from celiac disease, but applying the same barrier-restoration principle.
Is larazotide the same as "AT1001" for Fabry disease? No. The compound code "AT1001" has been used for two completely unrelated compounds by different companies: larazotide acetate (the 8-amino acid peptide discussed here, for celiac disease) and migalastat hydrochloride (a pharmacological chaperone for α-galactosidase A, for Fabry disease, small molecule approved by EMA in 2016 as Galafold and by FDA in 2018). They share only a development code assigned independently.
Safety signals
Across Phase 1 and Phase 2 trials, larazotide was generally well tolerated. The most commonly reported adverse events were headache, upper respiratory tract infections, and nausea, occurring at rates comparable to placebo. No severe drug-related adverse events were identified in Phase 1 single- and multiple-dose studies in healthy volunteers. In Phase 2 trials, overall adverse event rates were similar between larazotide and placebo groups across dose levels from 0.25 mg to 2 mg three times daily. Long-term safety data beyond 12–52 weeks of trial exposure is limited, as the drug has not entered broad clinical use (Leffler 2015; Leffler 2012).
Regulatory status
- US: Not FDA-approved for any indication. Larazotide received FDA Fast Track designation during the celiac disease development program, which confers expedited review but not approval. The Phase 2b program produced a positive symptomatic signal at 0.5 mg TID; however, a Phase 3 pivotal trial package was not completed, and the regulatory pathway in celiac disease is uncertain as of 2026.
- EU / International: No marketing authorization in any major jurisdiction.
- WADA: Not named on the WADA Prohibited List. As a locally acting intestinal peptide with no plausible performance-enhancing mechanism, sports regulatory risk is limited, though the broad S0 category (unapproved investigational agents) technically applies.
Related peptides
- BPC-157 — gastric and mucosal repair peptide frequently discussed in gut-health contexts; no shared zonulin mechanism
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Why does a lower dose of larazotide sometimes protect the gut better than a higher dose, and does this tell us something important about how it works?
Solving this paradox could rescue larazotide as an effective celiac treatment by identifying exactly the right dose, potentially giving the millions of celiac patients who cannot maintain a gluten-free diet an effective pharmaceutical option.
Could larazotide, designed for celiac disease, also seal the leaky gut that helps trigger Crohn's disease flares?
If larazotide can reduce the gut leakiness that drives Crohn's flares, patients could potentially stay in remission longer without increasing their immunosuppressive drugs, which carry serious infection and cancer risks.
Does larazotide work only in the gut because it gets destroyed too quickly to reach other organs, and is this limited reach actually a safety benefit?
A drug that acts only where the problem is, without reaching the rest of the body, is less likely to cause unwanted side effects elsewhere; understanding this could help design the optimal formulation and dosing to maximize gut protection while remaining safe.
If larazotide stops gluten fragments from leaking through the gut wall, could it also prevent the brain symptoms some celiac patients get even while on a strict gluten-free diet?
Neurological symptoms like ataxia and brain fog are a hidden burden of celiac disease that a gluten-free diet alone often fails to resolve; a treatment that blocks the leakage triggering these symptoms could dramatically improve quality of life.
Which of larazotide's eight building blocks are essential for its gut-sealing action, and could that core be designed into a more stable oral drug?
Finding the essential core of larazotide could allow chemists to build a pill-form version that survives digestion better, making a gut-sealing treatment far more practical for the millions of celiac patients who need it daily.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.8385142087936401 | openfold3-mlx |
| ranking score | 0.8986321091651917 | openfold3-mlx |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.428 | global PDE — lower = better |
| disorder | 0.104 | fraction disordered |
| chain pair ipTM (A, B) | 0.839 | interface quality |
▸3-letter notation
▸recipeopenfold3-mlx 0.3.1
| parameter | value |
|---|---|
| model | openfold3-mlx 0.3.1 |
| weights | aedd8f3eb814e392… |
| hardware | apple_m4_base_16gb |
| mlx version | 0.31.1 |
| python | 3.14.3 |
| random seed | 42 |
| msa strategy | colabfold |
| diffusion samples | 1 |
| runtime | 80s |
| predicted by | mlx@peptide |
| predicted at | 2026-05-03 |
python3 openfold3/run_openfold.py predict --query_json {query.json} --runner_yaml examples/example_runner_yamls/mlx_runner.yml --output_dir {output_dir} --num_diffusion_samples 1 ▸citationbibtex
@peptide{pep10900,
sequence = {GGVLVQPG},
target = {tissue-repair},
author = {peptidemodel},
year = {2026},
status = {computed}
}