Larazotide
low riskAlso: AT-1001 · Larazotide Acetate · INN-202
Larazotide acetate (AT-1001) is a synthetic octapeptide derived from the zonula occludens toxin of Vibrio cholerae. It acts as a tight junction regulator — blocking abnormal intestinal permeability by antagonizing the effects of zonulin, the protein that governs tight junction opening. It completed Phase IIb trials in celiac disease with positive results but has not received FDA approval. Development was stalled by ImmunsanT before Phase III completion. It remains the most clinically advanced tight junction-targeting peptide to date.
Reported Benefits
Celiac disease symptom reduction
Phase IIb trial (Leffler et al., 2015) showed 0.5 mg TID significantly reduced gastrointestinal symptoms and celiac disease patient-reported outcome scores versus placebo in patients on a gluten-free diet.
Tight junction / intestinal barrier restoration
Multiple in vitro and animal studies confirm larazotide blocks zonulin-mediated tight junction disruption and reduces lactulose/mannitol ratio (a measure of intestinal permeability).
Gluten-challenge protection
Larazotide reduced symptom severity during intentional gluten challenge in celiac patients, suggesting a role as an adjunctive therapy rather than primary treatment.
Non-celiac intestinal permeability
Animal models support broader application; no human trial data outside celiac disease.
Mechanism of Action
Larazotide is a competitive antagonist of zonulin, the endogenous protein responsible for opening epithelial tight junctions by binding PAR2 and EGFR receptors. By blocking zonulin signaling, larazotide maintains tight junction integrity — specifically preventing PKC-alpha-mediated rearrangement of occludin and zonula occludens-1 (ZO-1) proteins. This directly reduces paracellular permeability to luminal antigens, gliadin peptides, and bacterial products. Larazotide acts locally in the intestinal lumen with minimal systemic absorption.
Key Clinical Studies
Leffler DA et al. (2015)
Randomized, double-blind, placebo-controlled Phase IIb · 342
0.5 mg TID larazotide significantly improved GI symptom scores vs placebo in celiac disease patients on a gluten-free diet over 12 weeks
Paterson BM et al. (2007)
Randomized, double-blind, Phase IIa · 86
Larazotide reduced intestinal permeability during gluten challenge and improved symptom scores
Kelly CP et al. (2013)
Randomized, double-blind, placebo-controlled · 184
1 mg TID larazotide reduced celiac disease symptom scores vs placebo; dose-response relationship observed
Overview
Larazotide acetate is the most clinically advanced compound ever designed specifically to target intestinal tight junctions. Its development grew out of research by Alessio Fasano (then at University of Maryland, now at Harvard/MGH) into zonulin — the protein he identified as the master regulator of intestinal permeability and a key mediator of autoimmune disease. Larazotide represents the clinical translation of that mechanistic work: a peptide designed to block zonulin’s effects and maintain the intestinal barrier against pathological permeability. It reached Phase IIb in celiac disease, generated positive data, and then stalled in development.
Evidence
The Phase IIb trial is the key data point. At the 0.5 mg TID dose, larazotide showed a statistically significant reduction in GI symptom burden in celiac patients on a gluten-free diet — meaning it reduced symptoms even in patients who were already avoiding gluten. The effect size was modest but real, and the safety profile was clean. Earlier Phase IIa data supported the mechanistic story: reduced intestinal permeability during gluten challenge. This is more clinical evidence than the vast majority of research peptides carry.
Regulatory Status / Clinical Use
ImmunsanT, the company that developed larazotide, completed Phase IIb trials but did not advance to Phase III before entering financial difficulties. The compound was not approved by the FDA. It is not commercially available, not on the 503A list, and not available through domestic compounding. The mechanistic concept — zonulin blockade — has influenced broader research into intestinal permeability, but larazotide itself has no approved clinical indication anywhere in the world.
Bottom Line
Larazotide has better clinical evidence than most peptides discussed in research and longevity contexts, but no regulatory approval and no commercial availability. The science is sound, the target is validated, and the Phase II data is encouraging. The gap between Phase IIb success and clinical availability is entirely regulatory and commercial, not scientific. For practitioners focused on intestinal permeability and celiac-adjacent conditions, larazotide represents the state of the science even if it cannot be prescribed.
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Regulatory Status
Research OnlyNot FDA-approved; not 503A-listed; completed Phase IIb trials; Phase III development halted by ImmunsanT
Safety Profile
Side Effects
- •Headache (most commonly reported)
- •Nausea
- •Vomiting (rare)
- •Diarrhea (rare)
Contraindications
- •Known hypersensitivity to larazotide or its components
- •Pregnancy (insufficient data)
Drug Interactions
- •No clinically significant drug interactions identified in Phase II trials
Primary Uses
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