Larazotide

What Is Larazotide?

Larazotide is a synthetic octapeptide studied as an antagonist of zonulin, a regulator of the tight junctions that seal the spaces between intestinal epithelial cells ^[1]. It is described as a gut permeability regulator and is most often tested as larazotide acetate under the development code AT-1001 ^[2].

The interest in larazotide follows from research linking zonulin-driven increases in epithelial and endothelial permeability to several acute and chronic inflammatory diseases ^[1]. Celiac disease has been the main clinical target, because increased intestinal permeability is considered a central part of its pathophysiology ^[3].

Beyond celiac disease, larazotide has been examined in research on type 1 diabetes, other autoimmune diseases, inflammatory bowel disease, Kawasaki disease, and respiratory diseases ^[1], and in a pediatric trial in post-COVID multisystem inflammatory syndrome ^[4].

Chemical Structure and Molecular Identity

Larazotide is a linear peptide of eight standard amino acids, Gly-Gly-Val-Leu-Val-Gln-Pro-Gly, with a free N-terminal amine and a free C-terminal carboxylic acid. PubChem (CID 9810532) lists its molecular formula as C32H55N9O10, its molecular weight as 725.8 g/mol, and its CAS number as 258818-34-7 for the free base.

The peptide is small and largely hydrophobic in its central Val-Leu-Val segment, with no aromatic, acidic, or basic side chains. The acetate salt form used in most studies has a different total mass than the free peptide, so analytical values should be compared with the matching form.

A systematic review of the literature searched under the names larazotide, larazotide acetate, AT-1001, FZI/0, and INN-202, reflecting the several designations used across studies ^[1].

Research History and Development

Larazotide’s clinical development centered on celiac disease, and research later extended to other conditions linked to zonulin and barrier dysfunction ^[1]. By 2020, four randomized controlled trials had studied it in patients with celiac disease ^[2].

Those trials enrolled a combined 626 patients, 465 receiving larazotide acetate and 161 receiving placebo, and tested it both during gluten challenge and in patients following a gluten-free diet ^[2]. Recent reviews of celiac therapeutics still group larazotide acetate with experimental permeability-modulating medications such as IMU-856 ^[3][5].

Preclinical research has broadened to autoimmune arthritis ^[6], vascular disease ^[7], and colitis, including a hydrogel built for sustained local release of larazotide acetate ^[8]. In 2025, a phase 2a randomized, double-blind, placebo-controlled trial reported results in children with multisystem inflammatory syndrome after SARS-CoV-2 infection ^[4].

Mechanisms Studied in Research

Larazotide is studied as a zonulin antagonist that limits tight-junction disruption and so reduces paracellular permeability across epithelial and endothelial barriers ^[1].

Zonulin and tight junctions

Zonulin is a regulator of intestinal tight junctions, and its modulation of junction competency has been described in many inflammatory diseases ^[1]. In coeliac disease, mechanisms of barrier disruption include zonulin, inflammatory cytokines, microbial changes, and immune responses to gliadin peptides ^[3].

Cellular signaling

In LPS-injured Caco-2 intestinal cells, sustained-release larazotide acetate inhibited zonulin-mediated tight-junction disruption by acting against MLCK and phosphorylated myosin light chain signaling, restoring epithelial integrity ^[8]. In a mouse aortic disease model, the authors described AT-1001 as a protease-activated receptor 2 inhibitor that seals tight junctions in vascular endothelium ^[7].

Gut barrier and systemic inflammation

In mouse autoimmune arthritis, rising serum zonulin accompanied a leaky intestinal barrier, dysbiosis, and inflammation, and predicted the transition from autoimmunity to arthritis ^[6]. In children with MIS-C, investigators tested larazotide because of a suggested route in which SARS-CoV-2 spike protein moves from gastrointestinal reservoirs into the blood through zonulin-mediated trafficking ^[4].

Key Findings From Published Studies

Human data show mixed results in celiac disease and early signals in a small pediatric MIS-C trial, while animal studies report reduced barrier damage and inflammation across several models.

Celiac disease meta-analysis

A 2022 meta-analysis of four randomized trials found that the change in lactulose-to-mannitol ratio, a measure of intestinal permeability, did not differ significantly between larazotide acetate and placebo, regardless of gluten status ^[2]. In patients undergoing gluten challenge, larazotide acetate was associated with greater improvement in total and celiac-specific gastrointestinal symptom rating scale scores and with less gluten-related diarrhea; no significant difference was seen in patients on a gluten-free diet ^[2]. Other adverse events were comparable to placebo ^[2].

Phase 2a trial in MIS-C

In a randomized, double-blind, placebo-controlled trial in 12 children with MIS-C (median age 5.7 years), larazotide was tested as an adjunctive therapy, and no larazotide-related adverse events were reported over 24 weeks of follow-up ^[4]. Across participants, blood spike antigen levels correlated with interferon-gamma, interleukin-6, and gastrointestinal symptom scores ^[4]. Treated children showed faster resolution of gastrointestinal symptoms, faster clearance of spike antigen from blood, and a faster return to usual activities ^[4].

Animal studies

• Arthritis (mouse): treatment with larazotide acetate in the pre-phase of disease reduced the onset of arthritis, supporting impaired gut barrier function as a checkpoint between autoimmunity and inflammation ^[6].
• Thoracic aortic aneurysm and dissection (mouse): in a beta-aminopropionitrile model, AT-1001 alleviated endothelial tight-junction impairment, attenuated vascular inflammation and edema, and reduced disease incidence; endothelial-specific ZO-1 knockout had the opposite effect, increasing incidence ^[7].
• Colitis (mouse): in dextran sulfate sodium colitis, a hyaluronic acid hydrogel releasing larazotide acetate and an antimicrobial reduced disease activity, suppressed pro-inflammatory cytokines while raising IL-10, repaired the tight-junction proteins ZO-1, occludin, and claudin-5, restored MUC2 mucus production, and rebalanced gut microbiota ^[8]. Because the hydrogel also carried an antimicrobial, this result does not isolate larazotide’s own contribution.

Limits of the evidence

The celiac meta-analysis pooled only four trials, and its main permeability endpoint was negative ^[2]. The MIS-C trial enrolled 12 children, so its findings are preliminary and were framed by the authors as suggesting that larazotide may be safe and may speed symptom resolution ^[4].

Because larazotide is usually supplied as an acetate salt whose mass differs from the free peptide, HPLC and mass-spectrometry certificates of analysis help confirm identity.

Regulatory and Research Status

Larazotide is an investigational peptide and is not approved by the US Food and Drug Administration for any indication. Reviews of celiac disease therapies note that, despite encouraging preclinical and clinical results, no treatment has yet been conclusively proven as an effective alternative to the gluten-free diet ^[5].

Most of the human evidence concerns celiac disease, where the four randomized trials studied patients both under gluten challenge and on a gluten-free diet, with different results in each setting ^[2]. Outside celiac disease, randomized human data include the small pediatric MIS-C trial ^[4].

The authors of the celiac meta-analysis described larazotide acetate as largely well tolerated and somewhat superior to placebo for symptoms during gluten challenge ^[2]. Researchers in the field continue to call for reliable biomarkers of intestinal permeability and for further study of barrier-restoring therapies ^[3].

In the laboratory, larazotide is used as a tool to test whether restoring tight-junction function changes the course of inflammatory, autoimmune, and vascular disease models ^[6][7].