Larazotide

What it is

Larazotide (AT-1001) is a synthetic 8-amino-acid peptide that functions as an antagonist of zonulin, the endogenous tight junction regulator that modulates intestinal paracellular permeability. Zonulin is a pre-haptoglobin 2 protein that, when secreted in response to gliadin or intestinal bacteria, signals through protease-activated receptor 2 (PAR2) and epidermal growth factor receptor (EGFR) to disassemble tight junction complexes in intestinal epithelial cells, increasing paracellular permeability. Larazotide prevents tight junction opening by multiple mechanisms: (1) blocking zonulin-mediated signaling at the tight junction; (2) inhibiting myosin light chain kinase (MLCK)-dependent myosin light chain-2 phosphorylation, which drives actin cytoskeletal contraction and tight junction disassembly; (3) promoting redistribution of claudin-4 and other tight junction proteins back to the intercellular junction; and (4) antagonizing the Rho GTPase/ROCK pathway that regulates junctional permeability. In vivo, these effects are measured by transepithelial electrical resistance (TEER) and the lactulose-to-mannitol (L:M) urinary excretion ratio as markers of paracellular permeability. In celiac disease, gliadin peptides cross the intestinal epithelium via paracellular routes after tight junction disruption, triggering adaptive immune responses in genetically susceptible individuals (HLA-DQ2/DQ8) — the initiating event of the autoimmune cascade. Larazotide does not target gluten or the immune response directly but rather aims to restore barrier integrity, preventing gliadin translocation and reducing the antigenic load driving intestinal inflammation. Beyond celiac disease, larazotide demonstrates barrier-protective effects in intestinal ischemia-reperfusion injury (restoring TEER and reducing LPS permeability in ex vivo porcine jejunum, PMID 33886649) and acute liver failure models (reducing intestinal damage scores in rats, PMID 34791921). A systematic review identified therapeutic potential across type 1 diabetes, inflammatory bowel disease, Kawasaki disease, and respiratory conditions where zonulin-mediated permeability dysregulation plays a role.

Class: Synthetic 8-amino-acid peptide / zonulin antagonist / intestinal tight junction regulator

What it's studied for

• Celiac disease — tight junction protection and symptom reduction during gluten exposure Phase II/III RCT
  • Phase 2 RCT (n=184 celiac patients on gluten-free diet). Larazotide acetate 1, 4, or 8 mg TID + 2.7 g/day gluten challenge for 6 weeks. Primary endpoint (L:M ratio): no significant difference between groups. Key secondary finding: larazotide 1 mg TID significantly reduced gluten-induced gastrointestinal symptoms vs. pl PMID 23163616 Kelly CP et al. Aliment Pharmacol Ther. 2013.
  • Phase 2 dose-ranging RCT (n=86 celiac patients). Larazotide acetate 0.25, 1, 4, or 8 mg TID ± 2.4 g/day gluten × 14 days. Primary urinary L:M permeability endpoint showed high variability; no definitive permeability benefit. Lower doses showed trend toward limiting symptom worsening. Well-tolerated; most common adverse PMID 22825365 Leffler DA et al. Am J Gastroenterol. 2012.
• Intestinal barrier restoration — ischemia-reperfusion injury Animal studies only
  • Ex vivo porcine ischemia-injured jejunum in Ussing chambers: larazotide 1 µM significantly enhanced TEER and reduced LPS permeability vs. injured controls. Higher doses (10 µM) less effective (fragment inhibition). Claudin-4 redistribution to junctions enhanced with treatment. D-amino acid analog #6 effective at 0.1 µM PMID 33886649 Slifer ZM et al. PLoS One. 2021.
• Acute liver failure — intestinal barrier protection Animal studies only
  • Thioacetamide-induced acute liver failure in rats: larazotide acetate prophylaxis via drinking water or gavage significantly decreased intestinal damage scores vs. untreated controls. Liver damage scores not significantly reduced. Histology: epithelial cell fusion and bridge formation in LA-treated villi. Suggests inte PMID 34791921 Caliskan AR et al. Hum Exp Toxicol. 2021.
• Zonulin-mediated inflammatory conditions — broad therapeutic potential Mixed
  • Systematic review (209 publications): larazotide/AT-1001 shows therapeutic potential across celiac disease, type 1 diabetes, IBD, Kawasaki disease, and respiratory conditions. Substantial role of zonulin demonstrated across multiple chronic and acute inflammatory diseases. New molecular targets identified. Establishes PMID 33397225 Troisi J et al. Curr Med Chem. 2021.
  • Review: zonulin dysregulation contributes to IBD, celiac disease, and multiple sclerosis. Larazotide as zonulin antagonist demonstrates therapeutic potential in preclinical and clinical studies for improving gut barrier integrity and reducing inflammation. Supports zonulin as biomarker and therapeutic target across chr PMID 39252622 Mohammadi-Kordkhayli M et al. Curr Med Chem. 2025.
• Intestinal anoxia-reoxygenation injury — mechanistic barrier protection In vitro only
  • C2BBe1 and IPEC-J2 cell monolayers pretreated with 10 mM larazotide acetate and subjected to anoxia/reoxygenation: significantly increased TEER, preserved tight junction protein organization, markedly reduced myosin light chain-2 phosphorylation (ROCK pathway), enhanced cellular proliferation. RNA-seq identified barrie PMID 41153766 Kim J et al. Biomedicines. 2025.

Community-reported dosing

Tier key: Research = PMID-cited study · [C] = scraped community source · [S] = model-synthesized from aggregate community reports (softer evidence). How we source.

Safety signals

• Phase 2 RCT (n=86 celiac patients): larazotide acetate 0.25–8 mg TID for 14 days — most common adverse events were headache and urinary tract infection across all dose groups; no serious adverse events described in abstract; tolerability described as good. PMID 22825365
• Phase 2 trial (n=184 celiac patients) at 1–8 mg TID for 6 weeks: no safety signals beyond those noted in the smaller Phase 2 study; adverse event profile consistent with good tolerability. PMID 23163616
• At high concentrations in ex vivo tissue (10 µM), larazotide generated inhibitory fragments that paradoxically reduced its barrier-protective efficacy — a dose-dependent non-monotonic response observed in tissue but not at clinical oral doses. PMID 33886649

Contraindications

• No formal contraindications established in reviewed literature. Larazotide is an orally administered peptide that is poorly absorbed systemically (acts luminally on intestinal epithelium); systemic contraindications are not established. PMID 33881350
• No approved therapeutic product — use outside clinical trial settings is investigational only. FDA approval has not been granted as of reviewed literature. PMID 23163616