PwPepwise

Larazotide

Healing & Recovery

a.k.a. AT-1001

Tight-junction modulator

Larazotide (also known as AT-1001 or larazotide acetate) is a short, orally administered peptide that works.

§Dosing at a glance

3 protocols · from the research
What it's forDoseHow oftenHowFor how long
Celiac Disease — Persistent Symptoms on a Gluten-Free Diet0.5 mg3× dailyOralTaken by mouth.12 wks
Celiac Disease — During Gluten Challenge0.25 mg—OralTaken by mouth.—
Preclinical / Animal Models0.01 mg/mL—OralTaken by mouth.7 days

Approximate values pulled from the research — double-check before dosing.

§01Summary

Larazotide (also known as AT-1001 or larazotide acetate) is a short, orally administered peptide that works by tightening the microscopic junctions between cells lining the intestine. These "tight junctions" normally act as a selective barrier, and in conditions like celiac disease they can become leaky — allowing harmful fragments of gluten and other molecules to pass into the body and trigger immune reactions and inflammation. By blocking a signaling protein called zonulin, larazotide helps restore this barrier and reduce the resulting symptoms.10,16

In celiac disease patients who continue to experience gastrointestinal symptoms despite following a strict gluten-free diet, larazotide acetate at 0.5 mg taken three times daily reduces overall symptom burden, decreases the number of symptomatic days, and may reduce non-digestive symptoms such as headache and tiredness.1 It appears to attenuate gastrointestinal symptom worsening during accidental or deliberate gluten exposure.3,9 Beyond celiac disease, larazotide is being investigated for conditions involving gut barrier dysfunction, including inflammatory bowel disease, acute pancreatitis, and post-COVID syndromes, with early evidence suggesting broader barrier-protective activity across multiple organ systems.5,11,18

This is the layperson summary. Mechanism, dosing, the evidence base, and the published literature are in the sections below — every claim links to its source.

§02In depth

Larazotide acetate (AT-1001) is a synthetic 8-amino acid peptide derived from a sequence originally identified in the accessory colonization factor (AcfB) protein of Vibrio cholerae.10 It acts primarily as an antagonist of zonulin, an endogenous protein that regulates the assembly of tight junction complexes in the intestinal epithelium. Zonulin — now identified as prehaptoglobin 2 — modulates paracellular permeability by triggering disassembly of the apical junctional complex, and is pathologically upregulated in response to luminal gliadin (gluten) exposure in celiac disease.14,15 By occupying the zonulin receptor, larazotide prevents downstream signaling cascades that lead to actin cytoskeletal rearrangement and redistribution of tight junction scaffold proteins including ZO-1, occludin, claudin-4, and claudin-5.13,16,17

A secondary mechanism involves inhibition of myosin light chain kinase (MLCK), an enzyme that phosphorylates the myosin light chain (p-MLC), causing actomyosin contraction and physical widening of the paracellular space.15,17 By blocking both the zonulin receptor pathway and MLCK/p-MLC signaling, larazotide provides complementary upstream and downstream protection of epithelial barrier integrity. In vitro, apically applied larazotide is able to counteract basolaterally applied cytokine-induced permeability increases, suggesting that luminal application exerts effects on both sides of the epithelial layer.16

Beyond the gut, zonulin has been identified as a serine protease-related complement activator capable of generating C3a and C5a in vivo, and larazotide has demonstrated dose-dependent attenuation of albumin leak, neutrophil accumulation, and proinflammatory cytokines in murine acute lung injury models.14 This complement-modulating activity broadens the theoretical therapeutic scope of larazotide to pulmonary and systemic inflammatory conditions.

Pharmacologically, larazotide is designed for luminal topical activity with minimal systemic absorption, which is consistent with its favorable safety profile. An oral delayed-release formulation has been developed to target drug delivery to the distal duodenum and proximal jejunum — the anatomical sites of maximal celiac disease pathology — achieving peak luminal concentrations of 0.32–1.76 µM at approximately 1 hour post-dosing in a porcine pharmacokinetic model.20 A non-linear dose-response relationship has been observed in both clinical and ex vivo settings, with an optimal therapeutic window identified at lower doses; at higher concentrations, brush-border aminopeptidase M generates inhibitory N-terminally truncated peptide fragments that appear to counteract the barrier-restoring activity of the parent molecule.13

§04Evidence & efficacy

Evidence base
247Studies
171Human
28Animal

In celiac disease patients experiencing persistent gastrointestinal symptoms despite adherence to a gluten-free diet, larazotide acetate at 0.5 mg TID reduces overall symptom scores compared to placebo, decreases symptomatic days by approximately 26%, increases improved symptom days by approximately 31%, and may reduce non-gastrointestinal symptoms including headache and tiredness.1 A meta-analysis of available RCTs confirmed that larazotide appears to improve gastrointestinal symptom scores in patients undergoing active gluten challenge, with particular benefit for gluten-related diarrhea.9

During controlled gluten challenges, lower doses of larazotide (0.25–1 mg TID) appear to attenuate symptom worsening compared to placebo, with the effect less apparent at higher doses.3 In a proof-of-concept RCT, a single 12 mg dose prevented the 70% rise in intestinal permeability observed with placebo following acute gluten exposure and reduced the proportion of patients with elevated IFN-gamma responses (29% vs. 57%).10

In preclinical models, larazotide appears to reduce intestinal barrier disruption and downstream inflammation in colitis12, acute pancreatitis18, acute liver failure19, and ischemia-injured intestine13, supporting its barrier-protective mechanism across multiple disease contexts. In a pediatric MIS-C study, larazotide treatment was associated with clearance of circulating SARS-CoV-2 spike protein antigen and augmented clinical recovery.11 The compound is currently being investigated for Long COVID in a registered Phase 2a trial.5

§05Safety

Larazotide acetate has demonstrated a consistently favorable tolerability profile across multiple human clinical trials spanning Phase 1 through Phase 3 development. In a Phase 1 multi-dose study in healthy volunteers, safety and tolerability were primary objectives and no concerning signals were identified.7 In the pivotal Phase 2 RCT, the safety profile of all three active dose groups (0.5 mg, 1 mg, and 2 mg TID) was comparable to placebo, with no clinically concerning adverse events highlighted.1 The most commonly noted adverse events across trials were headache and urinary tract infection, neither of which occurred at higher rates than placebo.3 In a proof-of-concept RCT, a single 12 mg dose — substantially higher than the therapeutic range — was well-tolerated with no increase in adverse events versus placebo.10

In the pediatric MIS-C study, no larazotide-related adverse events were reported over a 3-week treatment period and a 24-week safety follow-up in children with a median age of 5.7 years.11 In preclinical rat studies, animals receiving larazotide without the disease-inducing agent showed no notable pathological changes, suggesting tolerability in healthy animals at tested doses.18,19

No drug interactions, contraindications, or organ-specific toxicity signals have been reported in the available evidence base. Long-term safety data beyond 24 weeks is an area of active clinical investigation.

§06History

Larazotide acetate originated from research into the molecular mechanisms by which Vibrio cholerae disrupts intestinal barrier function. The peptide sequence was identified in the bacterium's accessory colonization factor protein AcfB and found to act as a competitive antagonist of zonulin — the endogenous gut permeability regulator identified by Alessio Fasano and colleagues in the late 1990s.10 This discovery positioned larazotide as a first-in-class tight junction regulator with potential to address the pathological increase in intestinal permeability central to celiac disease.

Clinical development began in earnest in the mid-2000s. A foundational Phase 1 multi-dose safety and pharmacokinetics study in healthy volunteers was registered in 2006.7 A proof-of-concept single-dose RCT in celiac disease patients, published in 2007, demonstrated prevention of gluten-induced intestinal permeability increases and significant reduction in gastrointestinal symptoms.10 This was followed by a series of Phase IIb dose-ranging trials evaluating larazotide during controlled gluten challenges and in patients with active celiac disease.4,6,8 A key Phase 2 RCT published in 2015 in Gastroenterology established 0.5 mg TID as the effective dose for managing persistent symptoms in gluten-free diet-adherent patients.1 The compound advanced to Phase 3 development under 9 Meters Biopharma, with the pivotal trial registered in 2019.2 More recently, the therapeutic rationale has expanded to include Long COVID and pediatric inflammatory syndromes linked to gut barrier dysfunction and SARS-CoV-2 antigenemia, with active clinical investigation ongoing.5,11

§07References