Larazotide

Larazotide (AT-1001) is a synthetic octapeptide (sequence GGVLVQPG) originally derived from research into bacterial enterotoxins produced by Vibrio cholerae. It functions as a local tight junction regulator within the gastrointestinal tract, acting at the level of the intestinal epithelium with minimal systemic absorption.

The primary mechanism is competitive antagonism of zonulin, an endogenous signaling protein that increases paracellular intestinal permeability by binding to epidermal growth factor receptor (EGFR) and protease-activated receptor 2 (PAR2). In celiac disease and related conditions, gliadin peptide fragments trigger excessive zonulin release, driving disassembly of tight junction complexes and increased translocation of luminal contents into the lamina propria. Larazotide blocks these receptor sites, interrupting the downstream signaling cascade responsible for tight junction opening.

• Promotes redistribution of structural tight junction proteins — occludin, claudin-3, and ZO-1 — and actin filaments back to their membrane-associated positions. • Inhibits myosin light chain kinase (MLCK), reducing tension on the perijunctional actomyosin ring and facilitating tight junction closure.

Following oral, delayed-release administration, peak concentrations are achieved in the duodenum and proximal jejunum within approximately one hour. Gut-restricted pharmacokinetics with minimal systemic exposure are considered the basis for the compound's tolerability profile.

Larazotide has been evaluated in multiple randomized, placebo-controlled trials in adults with celiac disease, with additional preclinical and early human data in other conditions.

Phase I studies established tolerability from 0.25 mg to 36 mg without severe drug-related adverse events.

A Phase 2 dose-ranging study (n=86; PMID 22825365) tested 0.25 to 8 mg three times daily alongside a 2.4 g/day gluten challenge for 14 days. The urinary lactulose-to-mannitol permeability endpoint proved highly variable in the outpatient setting; lower doses showed trends toward reduced gastrointestinal symptom severity while higher doses did not.

A second Phase 2 trial (Kelly et al., Gut 2013; PMID 23163616; n=184) administered 1, 4, or 8 mg three times daily with 2.7 g/day of gluten for 6 weeks. The 1 mg dose significantly improved Gastrointestinal Symptom Rating Scale scores (P=0.002) and produced the most favorable suppression of anti-tissue transglutaminase antibodies; permeability markers showed no significant difference between groups.

The Phase 2b trial (Leffler et al., Gastroenterology 2015; PMID 25683116; n=342) tested 0.5, 1, and 2 mg three times daily for 12 weeks in celiac patients with persistent symptoms on a gluten-free diet. Only 0.5 mg met the primary endpoint (P=0.022), reducing symptomatic days by 26% (P=0.017) and increasing improved-symptom days by 31% (P=0.034); higher doses offered no advantage.

A Phase 3 trial (CedLara, NCT03569007; target n=525) was discontinued in June 2022 when an interim analysis found the projected sample size required to reach statistical significance to be impractically large. A meta-analysis of 4 RCTs (n=626) found larazotide superior to placebo for GI symptoms during active gluten challenge but not in patients strictly following a gluten-free diet.

In the BioBreeding diabetic-prone rat model, larazotide reduced type 1 diabetes incidence by approximately 70% by preserving intestinal barrier integrity. A small randomized, double-blind trial (Science Translational Medicine, 2025; n=12 children) in COVID-19-associated multisystem inflammatory syndrome found faster GI symptom resolution, viral clearance, and functional recovery versus placebo; a larger long COVID trial is underway.

Typical dosage: 1-8 mg (three times daily).

All dosing data below derive from clinical trials; larazotide is not approved for clinical use and no established therapeutic protocol exists outside of investigational settings.

In Phase 2 gluten challenge studies, doses of 0.25 mg, 1 mg, 4 mg, and 8 mg administered orally three times daily were evaluated. The 1 mg three-times-daily dose produced the most consistent symptom benefit across two Phase 2 trials; 4 mg and 8 mg did not outperform placebo.

In the Phase 2b trial evaluating persistent celiac disease symptoms on a gluten-free diet (Leffler et al. 2015; n=342), 0.5 mg three times daily was the only dose to meet the primary endpoint over a 12-week treatment period. Doses of 1 mg and 2 mg three times daily showed no significant benefit.

The discontinued Phase 3 CedLara trial examined 0.25 mg and 0.5 mg three times daily.

The pediatric MIS-C study employed a four-times-daily schedule for 21 days; the specific milligram dose was not publicly disclosed at time of reporting.

The compound was formulated as an oral, delayed-release preparation, achieving peak intestinal concentrations in the duodenum and proximal jejunum within approximately one hour. The trial data suggest a low-dose efficacy window, with apparent loss of benefit at higher doses.

This information is provided solely for educational reference and does not constitute medical advice. Larazotide is an investigational compound not approved by any regulatory authority; use outside of supervised clinical trials carries risks that are not fully characterized.

No compound-specific stability data has been identified for this peptide. The general lyophilized-peptide handling framework applies — see Storage & handling for temperature, reconstitution diluent, and beyond-use dating principles.

No published clinical trial has formally evaluated larazotide in combination with other pharmacological agents. The celiac disease treatment literature discusses a theoretical rationale for pairing larazotide with gluten-degrading enzyme therapies such as latiglutenase (ALV003) or Aspergillus niger-derived prolyl endopeptidase (AN-PEP). The proposed basis is mechanistic complementarity: enzyme therapies reduce immunogenic gluten peptide load prior to intestinal absorption, while larazotide reinforces the tight junction barrier to limit residual peptide translocation into the lamina propria. This dual-mechanism strategy has not been evaluated in any clinical trial and remains speculative.

In preclinical autoimmune research, zonulin pathway inhibition has been studied independently in rodent models of arthritis and type 1 diabetes, but no human combination data exist for these indications.

Any community or compounding use combining larazotide with other gut-permeability-focused supplements (glutamine, zinc carnosine, or similar) is anecdotal and lacks supportive controlled evidence.

Larazotide is not currently FDA-approved for any indication. It is generally classified as a research compound. Regulatory status varies by country.

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Reported side effects: Generally well-tolerated, possible headache

Across Phase I through Phase 2b clinical trials, larazotide's adverse event profile has been comparable to placebo. Phase I dose-escalation studies confirmed that single and repeated doses up to 36 mg produced no severe drug-related adverse events.

The most commonly reported adverse events in Phase 2 trials were headache and urinary tract infection, each occurring in more than 5% of participants in at least one study. Gastrointestinal symptom rates were similar between treatment and placebo groups. A systematic review of 3 RCTs (n=136) calculated an odds ratio for overall adverse events (GI symptoms, headache, urinary tract infection, fatigue) comparing larazotide to placebo of 0.60 (95% CI 0.28 to 1.28), indicating no statistically significant excess adverse events with active treatment.

In the Phase 2b trial (Leffler 2015; n=342), EKG, urinalysis, hematology, and serum chemistry showed no clinically significant changes across all dose groups. The compound's gut-restricted pharmacokinetics, with minimal systemic absorption, are considered the basis for the absence of systemic toxicity signals.

Safety data beyond 12 weeks of continuous use are limited. No adequate clinical data exist for use during pregnancy, lactation, or in patients with severe renal or hepatic impairment. The pediatric MIS-C trial (n=12) reported no significant increase in adverse events versus placebo over 21 days of treatment.

Larazotide is not approved by any regulatory authority. No formal contraindications have been established given its investigational status, and long-term safety in humans remains inadequately characterized.