Larazotide Acetate

Background

Larazotide acetate (also known as AT-1001) is an orally administered synthetic octapeptide tight-junction regulator originally developed as an adjunctive therapy for celiac disease (CeD). It is derived from a fragment of the Vibrio cholerae zonula occludens toxin (Zot), designed to antagonize the endogenous human zonulin pathway that modulates intestinal epithelial permeability.[5][8] Larazotide is composed of eight amino acids (H-Gly-Gly-Val-Leu-Val-Gln-Pro-Gly-OH) and is formulated as an acetate salt for oral delivery.[5][8]

The peptide emerged from work demonstrating that zonulin-mediated opening of intestinal tight junctions plays a key role in the pathogenesis of celiac disease by increasing paracellular passage of gliadin peptides and other antigens.[5][8] Larazotide was developed to prevent this abnormal barrier opening without exerting direct immunosuppressive effects.[5]

Since its initial development in celiac disease, larazotide acetate has been explored in other conditions linked to epithelial barrier dysfunction and systemic inflammation, including acute lung injury, SARS-CoV-2 infection, and multisystem inflammatory syndrome in children (MIS-C), largely at preclinical or early clinical stages.[2][7][8]

Mechanism of action

Larazotide acetate is classified as a tight-junction regulator and zonulin antagonist. Zonulin is a modulator of intercellular tight junctions in intestinal and other epithelia, acting via signaling pathways that include epidermal growth factor receptor (EGFR) and protein kinase C, leading to cytoskeletal rearrangement and tight-junction disassembly.[5][8]

Larazotide interferes with zonulin-induced tight-junction opening, thereby restoring or maintaining barrier function and reducing paracellular permeability:

• In vitro, larazotide prevents gliadin-induced actin cytoskeleton rearrangement and preserves tight junction integrity in intestinal epithelial cell monolayers.[5][8]
• It reduces transepithelial flux of macromolecules, including gliadin peptides, across intestinal epithelia in preclinical models.[5]
• The pharmacological effect is local to the intestinal lumen and mucosa: larazotide has minimal systemic absorption, consistent with its peptide nature and the observed low plasma levels in clinical studies.[5][8]

Beyond intestinal barrier effects, larazotide has been investigated in silico and in vitro as a direct inhibitor of the SARS-CoV-2 main protease (Mpro). Molecular modeling and biochemical assays show that AT-1001 can bind the catalytic domain of Mpro and inhibit its enzymatic activity in the micromolar range, suggesting a potential antiviral mechanism distinct from tight-junction modulation.[1][2][3] The clinical relevance of this Mpro interaction remains unproven.

Evidence summary

Celiac disease

Most clinical data for larazotide acetate derive from randomized controlled trials (RCTs) in adults with celiac disease.

• Gluten-challenge studies (early phase trials): Multiple phase 2 studies evaluated larazotide in CeD patients undergoing controlled gluten exposure. In these trials (sample sizes generally in the tens to low hundreds), larazotide reduced gluten-induced increases in intestinal permeability (measured by lactulose/mannitol ratio), decreased gastrointestinal symptoms, and attenuated serologic and cytokine responses compared with placebo.[5][8] These studies established proof-of-mechanism but were limited in duration and size.

• Persistent symptoms on gluten-free diet (GFD): multicenter RCT

  A pivotal multicenter, randomized, double-blind, placebo-controlled trial evaluated larazotide in adults with biopsy-confirmed celiac disease who had persistent symptoms despite ≥12 months on a GFD.[9]

  • Design: 342 adults randomized after a 4-week placebo run-in to receive larazotide acetate 0.5 mg, 1.0 mg, or 2.0 mg three times daily, or placebo, for 12 weeks while maintaining their GFD, followed by 4 weeks of placebo washout.[9]
  • Primary outcome: Change in celiac disease symptom severity as measured by the Celiac Disease Symptom Diary (CDSD) and related symptom scoring; secondary outcomes included quality of life, serologic markers, and safety.[9]
  • Results: The lowest dose (0.5 mg TID) showed the most consistent symptom improvement versus placebo, including reductions in abdominal and extraintestinal symptoms; higher doses did not demonstrate superior efficacy and in some analyses were less effective, suggesting a non-linear dose–response.[9] The treatment was generally well tolerated with adverse event rates similar to placebo.[9]

• Delayed-release formulation and pharmacokinetics

  A porcine model study assessed a delayed-release larazotide formulation designed to release the peptide in the mid-duodenum and jejunum, the primary sites of celiac pathology.[10] This formulation achieved targeted intestinal delivery with minimal systemic exposure, supporting ongoing clinical development.[10]

• Comprehensive pharmacological review

  A recent review summarizes larazotide’s pharmacology, preclinical models, and clinical trial data, noting consistent effects on intestinal permeability and symptom reduction in CeD, with ongoing phase 3 trials as an adjunct to GFD in adults.[8]

COVID-19 and MIS-C

• SARS-CoV-2 Mpro targeting (preclinical): In silico and in vitro studies demonstrate binding of larazotide to SARS-CoV-2 Mpro and inhibition of enzyme activity, and cell-based assays evaluate antiviral effects of AT-1001 derivatives.[1][2][3] These data are exploratory and have not yet translated into controlled clinical trials.

• Acute lung injury and barrier dysfunction (preclinical): Prior work cited in COVID-19–focused analyses describes larazotide reducing mucosal permeability, neutrophil extravasation, and mortality in mouse models of acute lung injury, supporting the concept of barrier-protective effects beyond the gut.[2][4]

• MIS-C case series: A small case series evaluated larazotide as adjunctive therapy in children with multisystem inflammatory syndrome in children (MIS-C) associated with SARS-CoV-2.[7]

  • Design: Children with MIS-C received larazotide in addition to standard-of-care therapy (steroids and intravenous immunoglobulin). Exact sample size is modest; the report focuses on clinical trajectories and biomarker changes rather than controlled comparisons.[7]
  • Outcomes: The series reported improvements in gastrointestinal symptoms, reductions in SARS-CoV-2 antigenemia, and favorable clinical courses, but lacked a control group and standardized dosing comparisons.[7]

  Overall, evidence in COVID-19–related conditions remains preliminary and hypothesis-generating.

Clinical and research uses

Celiac disease

• Investigational indication: Larazotide acetate is under active investigation as an adjunctive oral therapy for adults with celiac disease, intended to be used together with a gluten-free diet to reduce symptoms and potentially mitigate damage from inadvertent gluten exposure.[5][8][9]
• Target population: Adults with biopsy-confirmed CeD who continue to experience symptoms or inflammation despite adherence to a GFD, or who are undergoing controlled gluten challenge in research settings.[5][8][9]
• Clinical trial status: Phase 2 trials have been completed, and phase 3 trials for CeD are ongoing.[6][8] No regulatory approvals for celiac disease have been granted as of the latest reports.[8][10]

Other potential uses (early-stage)

• COVID-19 and MIS-C: Larazotide is being explored as an adjuvant therapy to restore mucosal barrier integrity, reduce antigen translocation, and potentially modulate systemic inflammation in COVID-19 and MIS-C.[2][7][8] Evidence consists of small case series and preclinical work; large controlled trials are lacking.
• Barrier-related disorders: Given its mechanism, larazotide has been proposed for other diseases involving intestinal or epithelial barrier dysfunction and systemic inflammation, but human data remain sparse.[5][8]

Dosing context

Larazotide acetate dosing in the literature is investigational and should not be interpreted as prescribing guidance.

• Celiac disease trials:

  • In the multicenter CeD RCT for persistent symptoms on GFD, oral doses of 0.5 mg, 1.0 mg, and 2.0 mg three times daily were evaluated over 12 weeks, administered before meals.[9]
  • Earlier gluten-challenge trials used similar low-milligram oral doses, typically multiple times per day, with total daily doses ranging from approximately 1 to 8 mg.[5][8]

• Formulation:

  • Immediate-release and delayed-release oral formulations have been developed. The delayed-release capsules are designed to release larazotide in the mid-duodenum and jejunum based on in vitro dissolution and in vivo porcine data.[10]

• Pharmacokinetics:

  • Larazotide exhibits minimal systemic absorption with low or undetectable plasma concentrations in human studies, consistent with local action in the gut lumen and mucosa.[5][8]

Dosing regimens in non-celiac indications (e.g., MIS-C) have not been standardized and are reported only in small exploratory studies.[7]

Safety profile

Across celiac disease trials, larazotide has demonstrated a generally favorable short- to medium-term safety profile.

• Adverse events in CeD RCTs:

  • In the 342-patient RCT of persistent CeD symptoms, overall adverse event (AE) rates were similar between larazotide and placebo groups.[9]
  • Common AEs included gastrointestinal symptoms (e.g., abdominal pain, diarrhea, nausea), which often overlapped with underlying disease manifestations.[5][8][9]
  • No significant increase in serious adverse events or treatment discontinuations versus placebo was reported.[9]

• Systemic safety:

  • Given limited systemic exposure, no consistent systemic toxicity signals (e.g., organ toxicity, immunosuppression) have been identified in clinical studies to date.[5][8]

• Long-term safety:

  • Long-term data are limited; most trials have treatment durations of weeks to a few months. Long-term safety, especially in chronic use, remains to be fully characterized.[5][8]

• Special populations:

  • Pediatric use is largely restricted to MIS-C case-series and early investigations; robust pediatric safety data are lacking.[7][8]

Overall, larazotide is considered well tolerated in trial populations, but comprehensive post-marketing safety data are unavailable because the drug is not yet approved.[8]

Regulatory status

• United States:

  • Larazotide acetate is an investigational drug and is not approved by the U.S. Food and Drug Administration (FDA) for any indication.[8][10]
  • It has been evaluated under investigational new drug (IND) applications in phase 2 and phase 3 clinical trials for celiac disease, primarily as an adjunct to a gluten-free diet.[6][8]

• European Union:

  • As of current published reports, larazotide has no marketing authorization from the European Medicines Agency (EMA) for celiac disease or any other condition.[8]
  • Clinical development activities, including multinational trials, are ongoing, but no centralized EU approval has been reported.[6][8]

• Other regions:

  • No national regulatory authority has publicly reported approval of larazotide for clinical use. Its use remains confined to clinical trials and small compassionate or exploratory uses (e.g., MIS-C case series).[7][8]

Consequently, larazotide acetate is currently categorized as an investigational tight-junction regulator with the most advanced development in celiac disease, and exploratory applications in COVID-19–related conditions and other barrier dysfunction disorders.