- Generic name: Larazotide acetate · Code: AT-1001
- CAS: 343306-79-6
- Sequence: 8-amino acid synthetic peptide
- Mechanism: Zonulin receptor antagonist / tight junction stabiliser
- Developer: Alba Therapeutics
- Phase 2b: Significant symptom reduction at 0.5 mg tid in celiac disease
01 What Is Larazotide?
Larazotide acetate (AT-1001) is a synthetic octapeptide that functions as a tight junction regulator by antagonising the zonulin signalling pathway. Zonulin is the endogenous mediator of intestinal tight junction permeability — its activation by gliadin or bacteria opens paracellular channels, increasing gut permeability to macromolecules.
Larazotide was developed as a treatment adjunct for celiac disease, targeting the upstream permeability mechanism rather than the downstream immune response. Unlike immunosuppressive approaches, larazotide aims to prevent antigenic challenge by maintaining tight junction integrity — keeping immunogenic gliadin peptides in the intestinal lumen rather than allowing paracellular transit to the lamina propria.
02 Tight Junction Biology
Tight junctions are multiprotein complexes located at the apical aspect of the lateral membrane between adjacent epithelial cells. Key structural proteins include:
- Claudins (CLDN1-24): Major structural backbone of the tight junction strand; claudin-2 specifically forms cation-selective channels
- Occludin: Regulatory protein; phosphorylation controls junction opening/closing
- Junctional adhesion molecules (JAMs): Regulate leukocyte transmigration and junction assembly
- ZO-1, ZO-2, ZO-3: Scaffold proteins linking transmembrane proteins to the actin cytoskeleton
Tight junction disruption can be acute (occurring in minutes via actomyosin contraction) or chronic (via altered claudin expression). Research models for larazotide typically use Caco-2 or T84 intestinal epithelial monolayers with transepithelial electrical resistance (TEER) as the primary readout of barrier integrity.
03 The Zonulin Pathway
Zonulin was identified by Fasano and colleagues as the human homologue of the Vibrio cholerae toxin Zot (zonula occludens toxin), which opens gut tight junctions to facilitate bacterial colonisation. Endogenous zonulin is activated by:
- Gliadin/gluten: The α-gliadin fragment binds CXCR3 and PAR-2 receptors on intestinal epithelial cells, triggering MyD88-dependent zonulin release
- Gram-negative bacteria: LPS and flagellin activate pattern recognition receptors that converge on the zonulin pathway
- Inflammatory cytokines: IFN-γ, TNF-α, and IL-1β can upregulate zonulin-mediated permeability
Larazotide competes with zonulin at its receptor — preventing the downstream signalling cascade that leads to tight junction disassembly. In vitro studies using Caco-2 monolayers show larazotide maintains TEER and reduces fluorescein dextran (FD4) paracellular flux in the presence of gliadin challenge.
04 Phase 2b Clinical Data
- Population: Celiac disease patients on GFD + intentional gluten challenge (2.7 g/day)
- 0.5 mg tid: Significant reduction in CeD-PRO abdominal symptoms vs placebo (p=0.022)
- 1 mg and 2 mg: No consistent significant benefit (bell-shaped dose response)
- Anti-tissue transglutaminase (anti-tTG IgA): Reduced in 0.5 mg group
- Intestinal permeability (lactulose/mannitol ratio): Trend toward improvement
The non-linear dose-response (0.5 mg effective, higher doses not) is characteristic of receptor-mediated tight junction biology — where partial antagonism may be sufficient to prevent pathological permeability without completely abolishing physiological tight junction regulation. This has been observed in other zonulin-pathway studies.
05 Research Applications Beyond Celiac Disease
Larazotide's utility as a research tool extends beyond celiac disease. The compound is used to study intestinal barrier function in models of:
- Inflammatory bowel disease: Tight junction disruption in Crohn's disease and ulcerative colitis models
- Non-alcoholic fatty liver disease (NAFLD): Gut-liver axis; LPS translocation via leaky gut as a trigger for hepatic inflammation
- Type 1 diabetes: Intestinal permeability precedes autoimmune insulitis in NOD mouse model; larazotide reduced T1D incidence in early preclinical data
- Autism spectrum disorder: Elevated intestinal permeability observed in some ASD cohorts; larazotide studied as a tool for permeability normalisation
06 Frequently Asked Questions
What is Larazotide?
Larazotide acetate (AT-1001) is an 8-amino acid synthetic peptide that acts as a tight junction regulator — specifically a zonulin antagonist. Zonulin is the only known modulator of intestinal tight junctions; it increases paracellular permeability when activated (as occurs with gluten exposure in celiac disease). Larazotide blocks zonulin receptor signalling, stabilising tight junctions and reducing intestinal permeability. It was developed by Alba Therapeutics and studied in celiac disease clinical trials.
What are tight junctions and why do they matter for gut health research?
Tight junctions are protein complexes (involving claudins, occludin, zonula occludens proteins) that seal adjacent intestinal epithelial cells, controlling paracellular (between-cell) transport. When tight junctions are disrupted, larger molecules — including dietary antigens, bacterial endotoxins (LPS), and undigested proteins — can traverse the epithelium and trigger immune responses. This 'intestinal permeability' or 'leaky gut' has been studied in the context of celiac disease, inflammatory bowel disease, type 1 diabetes, non-alcoholic fatty liver disease, and autoimmune conditions.
What did the larazotide Phase 2b clinical trial show?
The Phase 2b trial (ClinicalTrials.gov NCT01396213, n=342) studied larazotide 0.5 mg, 1 mg, and 2 mg tid vs placebo in celiac disease patients on a gluten-free diet. The 0.5 mg dose showed statistically significant reduction in celiac disease patient-reported outcome (CeD-PRO) symptom scores, particularly abdominal pain and bloating, during intentional gluten challenge. The higher doses did not show consistent benefit, suggesting a non-linear dose-response consistent with tight junction biology.
What is zonulin and how does it relate to larazotide?
Zonulin is a protein identified by Alessio Fasano's laboratory as the physiological modulator of intestinal tight junction permeability. It is activated by gliadin (the immunogenic component of gluten) and gram-negative bacteria via protease-activated receptor 2 (PAR-2). Zonulin binding opens tight junctions, increasing paracellular permeability. Larazotide acetate is designed to block this pathway by acting as a competitive antagonist at the zonulin receptor, preventing tight junction disassembly.
Is larazotide approved for use in celiac disease?
No. As of April 2026, larazotide has not received FDA or EMA approval. Despite promising Phase 2b data at the 0.5 mg dose, a Phase 3 programme was not completed. The compound remains of significant research interest as a tool for studying intestinal permeability and tight junction biology in vitro and in vivo models. Rainbow Peptide supplies larazotide For Research Use Only.
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