Summary

Larazotide acetate (also known as AT-1001) is a synthetic octapeptide derived from a Zot (zonula occludens toxin) fragment of Vibrio cholerae. It modulates intestinal tight junctions by interacting with zonula occludens-1 (ZO-1) and has been investigated primarily as an oral adjunct therapy for celiac disease, with additional research in inflammatory bowel disease and other conditions involving compromised epithelial barriers. Unlike many research peptides, larazotide has completed Phase 3 clinical trials, providing a relatively robust human safety and efficacy dataset.

Overview

Larazotide acetate (AT-1001) is an eight-amino-acid synthetic peptide (sequence: GGVLVQPG) originally derived from a non-cytotoxic fragment of the Vibrio cholerae zonula occludens toxin (Zot). It was developed by Alba Therapeutics (later Innovate Biopharmaceuticals, now 9 Meters Biopharma) as an oral tight-junction modulator intended to reduce intestinal permeability.

The peptide's primary research interest lies in its ability to transiently and reversibly tighten epithelial tight junctions — the intercellular complexes that regulate paracellular permeability. In celiac disease, gluten-derived gliadin peptides trigger zonulin release, which loosens tight junctions and allows gliadin fragments to cross the intestinal barrier, activating an inflammatory immune response. Larazotide is hypothesised to counteract this zonulin-mediated opening, reducing gliadin transit and the associated inflammation.

Mechanism of Action

Larazotide acetate interacts with the tight-junction protein zonula occludens-1 (ZO-1) and is believed to modulate the actin cytoskeleton–tight junction interaction. By stabilising tight-junction complexes, it reduces paracellular permeability in the intestinal epithelium.

The proposed mechanism is distinct from zonulin antagonism: rather than blocking zonulin itself, larazotide appears to prevent the cytoskeletal rearrangement that zonulin triggers, thereby maintaining tight-junction integrity. This effect is described as dose-dependent and reversible.

Key mechanistic points:

  • Tight-junction stabilisation: Reduces paracellular flux of macromolecules across epithelial barriers.
  • ZO-1 interaction: Binds to the ZO-1 scaffolding protein, preventing its dissociation from the tight-junction complex.
  • Zonulin pathway modulation: Counteracts zonulin-mediated tight-junction disassembly without directly antagonising the zonulin receptor.
  • Oral bioavailability: Administered orally; acts locally at the intestinal epithelium with minimal systemic absorption.

Research Summary

Larazotide acetate has one of the more extensive clinical-trial datasets among peptides discussed in research communities, having progressed through Phase 1, Phase 2, and Phase 3 studies.

Phase 1 (2007)

A first-in-human study demonstrated that larazotide was well tolerated in healthy volunteers and reduced gut permeability in response to gliadin challenge. (Paterson et al., 2007)

Phase 2b celiac disease (2009)

A randomised, double-blind, placebo-controlled study in celiac disease patients showed that larazotide reduced gastrointestinal symptoms and decreased intestinal permeability compared with placebo during gluten challenge. (Kelly et al., Gastroenterology, 2009)

Phase 2b (2012)

A further Phase 2 trial evaluated larazotide in patients with active celiac disease on a gluten-free diet. The study showed improvement in symptom scores and a trend toward reduced mucosal damage, though results were mixed across endpoints. (Leffler et al., Clinical Gastroenterology and Hepatology, 2012)

Phase 3 (2019)

A Phase 3 trial (CELIAC3) evaluated larazotide in patients with continuing celiac symptoms despite a gluten-free diet. In 2019, 9 Meters Biopharmaceuticals announced that the trial did not meet its primary endpoint of symptom improvement versus placebo. However, secondary endpoints showed some signals, and the peptide was generally well tolerated. (Syage et al., 2019; presented at DDW 2019)

Evidence grading rationale

Graded as moderate because the peptide has completed multiple human clinical trials including Phase 3, but the Phase 3 primary endpoint was not met, and no regulatory approval has been granted worldwide. The mechanistic rationale and Phase 2 signals are consistent but not definitively confirmed.

Commonly Discussed Protocols

Research use only. No medical advice. The following reflects published clinical-trial designs, not recommendations.

In clinical trials, larazotide acetate was administered as an oral capsule or tablet at doses ranging from 0.25 mg to 3.0 mg taken before meals containing gluten (in gluten-challenge studies) or three times daily (in active-disease studies). Typical trial durations ranged from 2 to 12 weeks.

  • Gluten challenge studies: 0.5–3.0 mg oral, taken 15–30 minutes before gluten ingestion.
  • Active celiac disease studies: 0.5–1.0 mg oral, three times daily before meals for 6–12 weeks.

No standardised research protocol exists outside of clinical-trial contexts. As with all unlicensed peptides, any use outside of approved clinical trials is investigational and not endorsed.

Stacking

Larazotide has not been studied in combination with other peptides in clinical settings. Its oral, locally-acting mechanism and minimal systemic absorption make it mechanistically distinct from injectable research peptides, and there is no published rationale for combining it with growth-hormone secretagogues, healing peptides, or metabolic peptides.

Storage & Reconstitution

Larazotide acetate in clinical-trial formulations was supplied as an oral capsule or tablet. For bulk research-grade material supplied as a lyophilised powder, general peptide storage principles apply:

  • Lyophilised: Store at –20°C in a sealed, desiccated container. Protect from light and moisture.
  • Reconstituted: If solubilised for in vitro research, use sterile bacteriostatic water or an appropriate buffer. Stability data for reconstituted larazotide is limited; follow compound-specific handling guidance from the supplier.
  • Handling: As with all research peptides, use appropriate personal protective equipment and follow institutional laboratory safety protocols.

Note: Clinical formulations were oral solids, not injectable. Research-grade material should not be assumed to be suitable for any route without supplier and protocol guidance.

Blood Work

No specific blood-work monitoring protocol was established for larazotide in clinical trials beyond standard safety panels (liver function, renal function, complete blood count). Because larazotide acts locally in the gut with minimal systemic absorption, significant systemic biomarker changes would not be expected. In trial settings, anti-tissue transglutaminase (anti-tTG) IgA antibodies and deamidated gliadin peptide (DGP) antibodies were monitored as disease-activity markers.

UK Legal Status

Larazotide acetate is an investigational medicinal product that has not received marketing authorisation from the MHRA, EMA, FDA, or any other regulatory body. It is not a licensed medicine in the UK.

As a synthetic peptide sold by some research chemical suppliers, it falls into the UK grey area: legal to purchase and possess for bona fide research purposes (in vitro or laboratory use), but not licensed for human consumption, medical use, or administration outside of approved clinical trials. The MHRA has not issued specific guidance on larazotide.

Researchers should be aware that importing or supplying unlicensed peptides for human use without appropriate regulatory approvals may constitute an offence under UK medicines legislation.

Vetted UK Vendors

Larazotide acetate is not commonly stocked by mainstream UK peptide vendors, reflecting its oral, locally-acting nature and its status as a discontinued clinical-stage asset (Phase 3 failed to meet primary endpoint in 2019). Researchers seeking the compound may need to contact specialist research chemical suppliers directly. As always, verify that any supplier provides a certificate of analysis (CoA) confirming peptide content and purity.

No vetted UK vendors currently stock larazotide acetate as a standard catalogue item.

References

  1. Paterson BM, Lammers KM, Arrieta JA, et al. "Safety, tolerance, and symptom response to a single-dose of AT-1001, a zonulin receptor antagonist, in celiac disease subjects on a gluten-free diet." Clinical Gastroenterology and Hepatology. 2007;5(4):466-472. doi:10.1016/j.cgh.2007.01.003
  2. Kelly CP, Green PH, Murray JA, et al. "Larazotide acetate in patients with coeliac disease undergoing a gluten challenge: a randomised placebo-controlled study." Gastroenterology. 2009;136(5 Suppl 1):A-376. Presented at DDW 2009.
  3. Leffler DA, Kelly CP, Green PH, et al. "Larazotide acetate for persistent symptoms of celiac disease despite a gluten-free diet: a randomized controlled trial." Gastroenterology. 2012;143(3):657-666.e1. doi:10.1053/j.gastro.2012.06.058
  4. Paterson BM, Bhatt D, Lammers KM, et al. "Role of zonula occludens toxin and its derivative, AT1002, in modulation of tight junctions and epithelial barrier function." Annals of the New York Academy of Sciences. 2012;1258:139-148. doi:10.1111/j.1749-6632.2012.06523.x
  5. Syage AR, Kelly CP, Dickason MA, et al. "Determination of gluten metabolism after Larazotide Acetate administration in patients with celiac disease: a randomized, double-blind, placebo-controlled study." Presented at Digestive Disease Week (DDW). 2019.
  6. Fasano A. "Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer." Physiological Reviews. 2011;91(1):151-175. doi:10.1152/physrev.00003.2008

References

  1. Paterson BM, Lammers KM, Arrieta JA, et al. "Safety, tolerance, and symptom response to a single-dose of AT-1001, a zonulin receptor antagonist, in celiac disease subjects on a gluten-free diet." Clin Gastroenterol Hepatol. 2007;5(4):466-472. doi:10.1016/j.cgh.2007.01.003
  2. Kelly CP, Green PH, Murray JA, et al. "Larazotide acetate in patients with coeliac disease undergoing a gluten challenge: a randomised placebo-controlled study." Gastroenterology. 2009;136(5 Suppl 1):A-376.
  3. Leffler DA, Kelly CP, Green PH, et al. "Larazotide acetate for persistent symptoms of celiac disease despite a gluten-free diet: a randomized controlled trial." Gastroenterology. 2012;143(3):657-666.e1. doi:10.1053/j.gastro.2012.06.058
  4. Fasano A. "Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer." Physiol Rev. 2011;91(1):151-175. doi:10.1152/physrev.00003.2008
  5. Syage AR, Kelly CP, Dickason MA, et al. "Determination of gluten metabolism after Larazotide Acetate administration in patients with celiac disease." Presented at DDW. 2019.