Larazotide Acetate: Evidence, Mechanism & Legal Status

Larazotide acetate (AT-1001, INN-202) is a synthetic eight-amino-acid peptide derived from human zonulin that acts locally in the gut lumen to stabilize the tight junctions between intestinal cells.1 It is the most clinically advanced "non-dietary" celiac candidate ever taken to humans — and a cautionary tale about how a strong Phase 2 signal can evaporate in Phase 3. This monograph separates what is proven from what is hoped.

This article is informational and editorial content for research and educational purposes only. It is not medical advice, not a protocol to follow, and not a sourcing guide. Larazotide acetate is an investigational drug never approved by any regulator; it is sold as a "research chemical not for human use." Dosing figures are reported strictly as seen in the published trial literature for completeness — not as recommendations. Consult a licensed clinician before any health decision.

What is larazotide acetate and how does it work?

Larazotide is a single-chain synthetic octapeptide (sequence Gly-Gly-Val-Leu-Val-Gln-Pro-Gly, molecular formula C₃₄H₅₉N₉O₁₂, MW about 786 g/mol; CAS 881851-50-9 for the acetate), studied clinically as the acetate salt.15 Its sequence is derived from human zonulin and is structurally related to the Vibrio cholerae zonula occludens toxin from which the underlying zonulin biology was first reverse-engineered in Alessio Fasano's laboratory.1

The disease rationale is the zonulin-to-tight-junction axis. In celiac disease, ingested gliadin peptides bind the CXCR3 receptor on the intestinal epithelium, triggering MyD88-dependent release of zonulin, which acts on EGFR/PAR2 to phosphorylate tight-junction proteins and disassemble the paracellular barrier (claudins, occludin, ZO-1).2 The resulting "leaky" junctions let immunogenic gluten peptides reach the lamina propria and drive the HLA-DQ2/DQ8 autoimmune cascade — making intestinal hyperpermeability a plausible upstream, root-cause lever rather than only a downstream consequence.1

Larazotide acts as a zonulin-pathway antagonist in the gut lumen. In vitro it inhibits gliadin- and toxin-fragment-induced actin rearrangement, prevents tight-junction disassembly, and promotes redistribution of ZO-1, claudins, occludin, actin and E-cadherin back to cell-cell junctions, restoring barrier integrity at concentrations as low as about 0.1 mM.1 Critically it addresses only the paracellular pathway; the transcellular route of gliadin entry is unaffected, an inherent limitation.1 The peptide is given orally and engineered to be locally acting with essentially no systemic absorption — plasma concentrations were below the limit of quantification even after a single 36 mg dose — so a conventional plasma half-life is not clinically meaningful.1 A persistent, unexplained feature across trials is an inverse dose-response: lower doses (0.5 mg) consistently outperformed higher ones (1-8 mg).1

What is the evidence by indication?

Celiac disease is the only indication with a mature human-trial program. Human RCTs unequivocally exist; the issue is that the symptom signal was real but modest, the objective permeability endpoint never held, and the pivotal Phase 3 failed. The trial details for the discontinued pivotal study are registered at ClinicalTrials.gov as NCT03569007 (CeDLara).7

The Phase 2 record is the strongest part of the story. An early Phase 1 single-dose gluten challenge (21 patients) showed larazotide blunted the gluten-induced rise in the lactulose-to-mannitol permeability ratio — the first human proof-of-concept for barrier protection.1 In two Phase 2 gluten-challenge trials the primary permeability endpoint was not met, but gastrointestinal symptoms improved at low doses, and in the 184-patient study the 1 mg arm even suppressed anti-tissue-transglutaminase antibody rises.4 The flagship positive trial was the Phase 2b CeliAction study: a 342-adult, multicenter, double-blind trial in patients with persistent symptoms despite a gluten-free diet, in which the 0.5 mg dose met the primary CeD-GSRS symptom endpoint (and 1 mg and 2 mg did not), with 29% of 0.5 mg patients achieving a sustained ≥50% reduction in weekly abdominal symptoms versus 14% on placebo.3

A 2022 systematic review and meta-analysis pooled four RCTs (626 patients) and crystallized the picture: the pooled urinary permeability ratio did not differ significantly between larazotide and placebo, but larazotide was superior for gastrointestinal symptom relief and significantly reduced gluten-related diarrhea (RR 0.420, 95% CI 0.246-0.717, p=0.001), concluding it may complement, not replace, the gluten-free diet.56

Beyond celiac disease, the evidence thins sharply. Larazotide was repurposed for MIS-C — post-COVID multisystem inflammatory syndrome in children — on a gut-hyperpermeability rationale; a four-patient case series reported faster symptom resolution and SARS-CoV-2 spike clearance, and an early Phase 2a launched, but this is open-label, small-n, hypothesis-generating evidence only (Grade C/D).1213 For "leaky gut," IBD, type 1 diabetes and autoimmune indications, the data are entirely preclinical — barrier repair in animal and ex-vivo models such as ischemia-injured porcine jejunum — with no qualifying human efficacy trials.14 The honest read: targeting barrier dysfunction is biologically sound, but larazotide has not been shown to deliver clinical benefit in any non-celiac human population.

What doses appear in the literature?

Reported strictly as information, not a protocol. Larazotide is unapproved and there is no validated human dose, formulation, or indication.1 The route is oral, locally acting in the gut lumen.1 The "headline" dose is 0.5 mg three times daily, taken before meals — the only dose that met endpoints in the 342-patient Phase 2b CeliAction trial.3 Across the program, efficacy trials studied 0.25, 0.5, 1, 2, 4 and 8 mg three times daily, with single PK doses up to 36 mg; the Phase 3 used 0.25 mg and 0.5 mg.7 Two caveats dominate: higher doses were not more effective and often showed no benefit at all (the inverse dose-response), and pre-meal three-times-daily timing aligns the peptide's short functional window of roughly 2-3 hours with gluten exposure.1 Reconstitution is not applicable to the clinical product (an oral capsule or solution, not an injectable); research-chemical powder sold by vendors is not for human use and carries no identity, sterility or dosing assurance.15

How safe is larazotide acetate?

Across the full development program — roughly 600 to 900 subjects dosed at 0.25 to 36 mg — larazotide was consistently well tolerated, with adverse-event rates comparable to placebo and no severe drug-attributable events; the most common complaint in healthy volunteers was headache.13 The meta-analysis confirmed a well-endured safety profile and even fewer gluten-related diarrhea events than placebo.5 Systemic toxicity risk is low because absorption is negligible: animal toxicology (rats to 1000 mg/kg oral; dogs to 40 mg/kg) showed no significant toxicity.1 The principal theoretical concern is disruption of normal barrier homeostasis or antigen handling with chronic use, but no such signal emerged in trials and there is no human experience beyond trial durations of 24 weeks or less. Pregnancy and lactation were not studied — default to avoidance — and pediatric exposure is limited to the small MIS-C case series.12 No formal contraindications exist because there is no approved label; the only categorical one is the overriding fact that larazotide is investigational and not authorized for human use outside a clinical trial.

What is the FDA and WADA status in 2026?

Larazotide acetate is not approved for celiac disease or any other indication anywhere in the world; the standard of care for celiac disease remains a lifelong gluten-free diet, and there is no FDA-approved celiac drug therapy as of 2026.8 It held FDA Fast Track designation during development — an expedited-review status, not approval — which became moot after the Phase 3 CeDLara failure.9 Its program lineage ran Alba Therapeutics to Innovate Biopharmaceuticals to 9 Meters Biopharma, which redirected resources after the June 2022 discontinuation; there is no active sponsor-led pivotal celiac program as of 2026.7 On compounding, larazotide does not appear on FDA's 503A or 503B bulk-substances lists as an authorized substance, and most peptides without a USP monograph that are not components of approved drugs cannot lawfully be compounded under 503A — so it sits in a gray zone with no clear authorized pathway, and the July 23-24, 2026 PCAC meetings reviewing other peptides did not include it.1617 It is sold by chemical suppliers strictly as research-use-only material not for human use.15

For athletes, larazotide is not named on the 2026 WADA Prohibited List, but as a non-approved pharmacological substance it falls under category S0 (Non-Approved Substances), prohibited at all times, and tested athletes are strictly liable.18 The safe assumption is that it is banned; athletes should verify via Global DRO or USADA.19

Bottom line. Larazotide acetate is an elegant, root-cause idea backed by the strongest non-dietary celiac human-trial record ever assembled — and it still fell short. Proven: modest, replicated symptom relief and good tolerability as a gluten-free-diet adjunct at 0.5 mg three times daily (Grade B). Not proven or failed: the objective permeability endpoint was never significantly beaten, no mucosal-healing or curative effect was shown, and the confirmatory Phase 3 failed and was discontinued in June 2022. All leaky-gut, IBD, autoimmune and longevity claims rest on preclinical data or marketing. As of 2026, larazotide is an investigational drug whose pivotal trial failed — not an evidence-backed therapy. Regulatory facts are current as of June 2026 and should be re-verified after the July 2026 PCAC meetings.