Larazotide
An orally dosed octapeptide that acts locally in the gut to regulate tight junctions — the most clinically advanced celiac drug candidate until its Phase 3 was stopped at a pre-planned interim analysis in 2022 and its sponsor filed for Chapter 7 liquidation in 2023. Academic work continues, including a completed 107-patient Long COVID trial.
Larazotide is a small peptide you swallow that stays in the gut and tightens the junctions between intestinal cells. It got further than any other celiac drug — all the way to Phase 3 — before the trial was stopped early and the company behind it went bankrupt. It is not approved, not available, and no company is developing it, though hospital researchers are still testing it for Long COVID.
What is Larazotide?
Larazotide acetate is a synthetic octapeptide, sequence GGVLVQPG, designed to regulate intestinal tight junctions. It is taken orally, acts locally in the gut lumen, and is minimally absorbed — which is why its safety profile has been close to placebo across every trial, and why it is one of the few peptides in this directory with a genuinely oral route. It is conventionally described as 'derived from' the Vibrio cholerae zonula occludens toxin (ZOT), and that phrasing does not survive checking. Larazotide's octapeptide does not occur in ZOT's sequence, nor in human haptoglobin, the precursor of the protein called zonulin. By contrast the related permeability-*enhancing* fragment AT-1002 (FCIGRL) genuinely is present in ZOT. 'ZOT-inspired' is accurate; 'derived from' is shorthand that implies a sequence relationship that is not there. A 2021 letter in Gut by two leading celiac immunologists made the same point about larazotide's relationship to zonulin and pre-haptoglobin-2. The programme's status is the single most important thing to know. The Phase 3 CeDLara trial (NCT03569007) was terminated by its sponsor in 2022 after a pre-planned interim analysis. 9 Meters Biopharma then discontinued larazotide in celiac disease, and on 17 July 2023 the company ceased operations and filed for Chapter 7 liquidation. No other company has picked the asset up. What remains is academic: Massachusetts General Hospital ran a Phase 2a in multisystem inflammatory syndrome in children, published in Science Translational Medicine in 2025, and has completed a 107-patient Phase 2 in Long COVID whose results have not yet been reported.
What Larazotide Is Investigated For
Larazotide has the deepest clinical record of any peptide aimed at the intestinal barrier, and it still failed to reach approval. Four randomised trials in celiac disease covering 626 patients produced a consistent but modest picture: symptom benefit concentrated in gluten-challenge settings, a successful Phase 2b at one specific dose, and an excellent safety profile throughout. The pivotal Phase 2b (342 patients on a gluten-free diet) met its primary endpoint at 0.5 mg three times daily, with a 26% decrease in symptomatic days. The detail that shaped everything afterwards is that the 1 mg and 2 mg doses 'were no different than placebo for any end point' — a non-monotonic dose-response in which more drug did nothing, which is why the Phase 3 tested 0.25 mg and 0.5 mg rather than escalating. The mechanistic result is harder to square. The 2022 meta-analysis of all four trials found that the lactulose-to-mannitol ratio — the direct measure of intestinal permeability, and the thing larazotide is supposed to fix — 'did not significantly differ between AT-1001 and placebo groups, irrespective of the gluten status.' Symptoms improved; measured permeability did not. That gap has never been resolved, and it matters more now that the zonulin framework itself is contested. Outside celiac disease the most credible work is in multisystem inflammatory syndrome in children, where a 2025 Science Translational Medicine Phase 2a in 12 children reported faster resolution of gastrointestinal symptoms, faster clearance of viral spike antigen and faster return to usual activities, with no drug-related adverse events. A 107-patient Long COVID trial at Massachusetts General completed in June 2026 with results not yet reported. Generic 'leaky gut' use has no trial behind it at all, and the drug cannot be obtained in any case.
History & Discovery
Larazotide came out of Alessio Fasano's work on Vibrio cholerae zonula occludens toxin and the proposal that a human analogue, zonulin, regulates intestinal tight junctions physiologically. Alba Therapeutics developed the peptide as AT-1001, and first-in-human work in coeliac subjects was published in 2007. The asset then travelled: Alba to Innovate Biopharmaceuticals, which reverse-merged into a listed shell, and then to 9 Meters Biopharma — a corporate lineage running Tandon Digital to Monster Digital to Innovate to 9 Meters, visible in the SEC filer history. The clinical programme peaked between 2012 and 2015. A gluten-challenge trial showed benefit, and the 342-patient Phase 2b published in Gastroenterology in 2015 met its primary endpoint at 0.5 mg three times daily while the higher doses did nothing. Larazotide received FDA Fast Track designation and became the most clinically advanced non-dietary celiac candidate in development — the drug most often named when anyone asked what might finally supplement the gluten-free diet. CeDLara, the Phase 3, began in May 2019. On 21 June 2022 the sponsor announced under the headline 'Interim Analysis of Phase 3 Study of Larazotide for Celiac Disease Does Not Support Trial Continuation' that an independent statistician's pre-planned analysis — conducted for group-size re-estimation, not efficacy — indicated the additional enrolment required to demonstrate a significant clinical outcome was too large to justify. On 15 August 2022 the company confirmed it was discontinuing larazotide in celiac disease and shifting resources to vurolenatide. 307 patients had enrolled against a target of 525; no results were ever posted. The ending was abrupt. On 17 July 2023 9 Meters Biopharma ceased operations and filed a voluntary Chapter 7 petition in the Eastern District of North Carolina; the filing states the company had no officers, consultants or employees as of that date, and Nasdaq suspended trading later that month. Describing this as 'corporate restructuring', as an earlier version of this page did, materially understates it — the company was liquidated and no longer exists. A search of SEC filings across all registrants from 2024 onward turns up no acquisition of the asset. What survived is academic and runs through Fasano's own institutional orbit. Massachusetts General Hospital tested larazotide in multisystem inflammatory syndrome in children on the hypothesis that SARS-CoV-2 spike protein translocates from gut reservoirs through a zonulin-compromised barrier; the trial stopped early as MIS-C case numbers declined, but the 12-patient result published in Science Translational Medicine in 2025. The same group then completed a 107-patient Phase 2 in Long COVID in June 2026, results not yet reported. Meanwhile the conceptual foundation came under sustained challenge — the 2018 ELISA finding, the 2021 Gut letters, and the 2026 systematic review on assay specificity — leaving larazotide in the unusual position of a drug whose clinical programme collapsed and whose mechanism was being renegotiated at the same time.
How It Works
The cells lining your intestine are stitched together by structures called tight junctions. In celiac disease those stitches loosen, letting gluten fragments through to immune cells underneath. Larazotide is designed to keep the junctions closed. Because it is a peptide that stays in the gut rather than entering the bloodstream, it acts where the problem is and almost nowhere else — which is why it caused so few side effects.
Larazotide is a tight junction regulator rather than a conventional receptor drug: it promotes tight junction assembly and prevents pathological opening, with the two foundational in vitro papers showing it drives junction assembly in epithelial cells and regulates tight junctions in vitro and in vivo. In celiac disease, gliadin peptides trigger paracellular opening, allowing antigen to reach the lamina propria; blocking that step is the therapeutic rationale. The conventional account names zonulin as the mediator and larazotide as its antagonist. That account is now contested on three fronts, and the page states them plainly because they bear on how much confidence the mechanism deserves. First, the biomarker. Most zonulin research uses commercial ELISA kits, and a 2018 study — with zonulin's own discoverer among the authors — showed those kits do not recognise pre-haptoglobin-2, the protein zonulin was identified as, instead detecting properdin and other structural analogues. A 2026 systematic review found that across eight studies the results were contradictory, with one study producing opposite answers from two assays run on the same samples, and concluded the commercial-ELISA literature simply cannot establish whether pre-haptoglobin-2 is altered in disease. Second, the sequence. Larazotide's octapeptide GGVLVQPG is not present in human haptoglobin and not present in Vibrio cholerae ZOT, though ZOT does contain FCIGRL, the related permeability-enhancing fragment AT-1002. A 2021 Gut letter from Sollid and Koning raised exactly this disconnect between AT1001, zonulin and pre-haptoglobin-2. Third, the target. Protease-activated receptor 2 is increasingly treated as the receptor through which zonulin signals — Fasano's own group has characterised zonulin and PAR2 expression together — and a 2025 paper simply calls the molecule 'the PAR2 antagonist larazotide.' PAR2 antagonism is a more specific and more defensible description than zonulin antagonism. Against all of this sits a clinical result that is harder to explain than any of it: the pooled analysis of all four randomised celiac trials found no significant difference from placebo in the lactulose-to-mannitol ratio, the standard functional measure of intestinal permeability, in either gluten-challenge or gluten-free-diet patients. Symptoms improved in challenge settings while the permeability measure did not move. Either the measure is too insensitive, or larazotide's symptom benefit runs through something other than the permeability change it was designed to produce.
Evidence Snapshot
Human Clinical Evidence
Moderate, and ceilinged by a Phase 3 that never read out. Four randomised controlled trials in celiac disease covering 626 patients, pooled in a 2022 meta-analysis: symptom improvement in gluten-challenge subgroups, no significant effect on lactulose-to-mannitol ratio in any subgroup, and tolerability comparable to placebo. The 342-patient Phase 2b met its primary endpoint at 0.5 mg only. The Phase 3 CeDLara trial enrolled 307 of a planned 525 patients and was terminated at a pre-planned interim sample-size re-estimation with no efficacy result posted or published. Beyond celiac: a 12-patient Phase 2a in MIS-C published in Science Translational Medicine 2025, and a completed 107-patient Phase 2 in Long COVID with results not yet reported.
Animal / Preclinical
Moderate. Tight junction assembly demonstrated in vitro and in vivo, with supporting work in porcine ischaemia-injured jejunum, IL-10-deficient colitis, anoxia-reoxygenation injury, arthritis onset, eosinophilic oesophagitis and a 2026 NAFLD model. Consistent in direction, but mostly short-duration barrier-function endpoints rather than disease-modifying outcomes.
Mechanistic Rationale
Contested, and downgraded accordingly. Tight junction biology is well understood and larazotide demonstrably acts on it in vitro. What is unsettled is the framing: the zonulin biomarker literature rests on assays that do not detect the protein they claim to, larazotide's sequence is absent from both zonulin's precursor and ZOT, PAR2 is emerging as the more defensible target, and the one pooled test of the functional permeability endpoint was negative.
Research Gaps & Open Questions
What the current literature has not yet settled about Larazotide:
- 01What the Phase 3 would have shown. CeDLara enrolled 307 of a planned 525 patients and stopped at a pre-planned sample-size re-estimation; no results have been posted to ClinicalTrials.gov and nothing was published. The most consequential dataset about this drug simply does not exist in the public record.
- 02The permeability paradox. The pooled analysis of all four randomised trials found no significant difference from placebo in lactulose-to-mannitol ratio, while symptoms improved in gluten-challenge subgroups. Whether the measure is too insensitive, or larazotide works through something other than measurable permeability change, is unresolved and now unlikely to be resolved.
- 03Whether 'zonulin antagonist' is the right description at all. Commercial zonulin assays do not detect pre-haptoglobin-2; larazotide's sequence is absent from both haptoglobin and ZOT; and recent work describes the molecule as a PAR2 antagonist instead. The mechanism may need renaming rather than merely refining.
- 04Why 0.5 mg worked and 1 mg and 2 mg did not. A non-monotonic dose-response was observed in the largest trial and never explained.
- 05Results of the completed Long COVID trial. NCT05747534 finished with 107 participants in June 2026 with nothing posted or published — the single most informative pending item about this compound.
- 06Whether anyone will develop it further. The asset is unencumbered by an active sponsor following Chapter 7 liquidation, has human safety data in more than 600 patients, and has a plausible mechanism in several barrier-dysfunction conditions. No acquirer has appeared in SEC filings since 2024.
- 07Indications beyond the gut-barrier paradigm. Preclinical signals exist in NAFLD, arthritis onset, eosinophilic oesophagitis and atopic dermatitis keratinocytes, none followed into humans.
Forms & Administration
Oral capsules taken before meals in all trials — a genuinely unusual route for a peptide, made possible because larazotide acts locally in the gut lumen and is minimally absorbed. Phase 2b used 0.5, 1 and 2 mg three times daily; the Phase 3 used 0.25 mg and 0.5 mg three times daily against placebo; the MIS-C study dosed four times daily for three weeks. A delayed-release formulation was developed and studied in vivo. None of this is obtainable: there is no approved product, no company developing it, and no trial enrolling.
Dosing & Protocols
The ranges below reflect protocols commonly discussed in the literature and by clinicians — not a prescription. Actual dosing for any individual should be determined by a qualified healthcare provider who knows the patient.
Typical Range
0.5 mg three times daily was the only dose to meet a primary endpoint, in the 342-patient Phase 2b. The 1 mg and 2 mg doses tested alongside it were no different from placebo on any endpoint. The Phase 3 therefore tested 0.25 mg and 0.5 mg three times daily against placebo. The MIS-C study used four-times-daily dosing over three weeks in children. No dose is established or available for any use.
Frequency
Three times daily, taken before meals, in the celiac trials — timing that follows directly from the mechanism, since the drug is meant to be present in the lumen when gluten arrives rather than to maintain a systemic level.
Timing Considerations
Time of day
No preference — any time of day works.
Relative to meals
Taken before meals in all celiac trials — the drug is intended to be in the lumen when gluten arrives.
Relative to exercise
Not tied to exercise timing.
Three times daily in the celiac programme, four times daily in the paediatric MIS-C protocol.
Cycle Length
Celiac trials ran 12 weeks of treatment, with the Phase 2b adding a 4-week placebo run-in and a 4-week placebo run-out. The MIS-C protocol was three weeks with 24 weeks of safety follow-up. Chronic indefinite use was the intended commercial pattern but was never studied beyond these windows.
Protocol Notes
The dose-response here is the most instructive thing in the file and the opposite of the usual peptide intuition. In the Phase 2b, 0.5 mg worked and 1 mg and 2 mg did not — not merely less well, but 'no different than placebo for any end point.' Anyone reasoning that a larger dose of a locally acting, minimally absorbed peptide should produce more effect would have been wrong. The phenomenon was never mechanistically explained, and it is a useful caution against assuming monotonic dosing for peptides acting on a structural rather than a receptor-occupancy target. Route is the other unusual feature. Larazotide is one of very few peptides in this directory given orally, and it works precisely because it is not absorbed — the gut lumen is the site of action. That also means the oral route cannot be generalised to other peptides, which usually need systemic exposure and are destroyed before achieving it. Practically, none of this is actionable. There is no approved product, no compounded supply, no trial enrolling, and no company developing the asset. For celiac disease the gluten-free diet remains the only established treatment, and a 2026 Gut review from Mayo authors surveys what has been tried since and calls for reliable permeability biomarkers — the absence of which is part of why larazotide's own mechanism was never cleanly demonstrated. Anyone with persistent symptoms on a strict gluten-free diet should be evaluated for the things that actually explain it, including inadvertent gluten exposure, refractory celiac disease, microscopic colitis, small intestinal bacterial overgrowth and lactose or fructose intolerance.
Larazotide is not approved in any jurisdiction, its development was discontinued, and the sponsor was liquidated in 2023. Nothing on this page is a dosing recommendation, and no legitimate route exists to obtain it.
Timeline of Effects
Onset
In the Phase 2b, separation from placebo on symptom scores emerged over weeks of consistent dosing rather than immediately, with the trial structured around a 4-week placebo run-in before 12 weeks of treatment. In gluten-challenge designs, the relevant effect is prevention of symptoms following a defined exposure rather than resolution of ongoing ones.
Peak Effect
Maximum measured effect in the celiac programme was the Phase 2b's 12-week endpoint: a 26% decrease in symptomatic days, a 31% increase in improved symptom days, and reductions in headache and tiredness, all at 0.5 mg three times daily. No longer-horizon efficacy data exists, because the Phase 3 was terminated before any endpoint analysis and nothing was published.
After Discontinuation
Effects would be expected to stop with the drug, since larazotide acts locally and transiently in the lumen and modifies no underlying disease process — the Phase 2b's 4-week placebo run-out was designed to observe exactly this. Nothing about celiac autoimmunity is altered, which is why larazotide was always positioned as an adjunct to the gluten-free diet rather than a replacement for it.
Monitoring & Measurement
Bloodwork & Labs
- •Tissue transglutaminase IgA and deamidated gliadin peptide antibodies — the standard serology for celiac diagnosis and adherence monitoring
- •Total IgA, to interpret those results correctly in IgA deficiency
- •Urinary gluten immunogenic peptides — a direct measure of recent gluten exposure, far more informative than symptom recall
- •Haemoglobin, ferritin, vitamin D, B12 and folate, for the deficiencies that accompany untreated or poorly controlled celiac disease
- •Serum zonulin — explicitly not recommended, for the assay-specificity reasons set out above
Functional & Performance Tests
- •Lactulose-to-mannitol ratio — the research measure of intestinal permeability, and the one that showed no larazotide effect in pooled analysis
- •Duodenal biopsy with Marsh grading, which remains the diagnostic reference standard
- •Dietitian-led review of gluten exposure, which identifies the cause of persistent symptoms more often than any laboratory test
When to Test
Celiac serology at diagnosis and periodically thereafter to assess adherence. Urinary gluten immunogenic peptides where inadvertent exposure is suspected. Biopsy where symptoms persist despite documented adherence, to distinguish refractory disease from ongoing exposure.
Interpretation & Notes
The monitoring here is for celiac disease rather than for larazotide, because the drug is not available and the underlying condition is what a reader on this page actually has to manage. The single most useful point is the one about zonulin testing. Serum zonulin is marketed directly to consumers as a leaky-gut biomarker, and the assays used do not detect the protein they are named after. A 2026 systematic review found results across studies were contradictory, including one study that produced opposite answers from two different assays run on the same samples. Money spent on a zonulin panel is better spent on urinary gluten immunogenic peptides, which measure something concrete and actionable. Persistent symptoms on a gluten-free diet are common and usually have a findable cause — inadvertent exposure first, then microscopic colitis, small intestinal bacterial overgrowth, lactose or fructose intolerance, pancreatic insufficiency, and refractory celiac disease. That diagnostic list is what larazotide was competing against, and it remains the right place to start.
Common Questions
Is larazotide still being developed?
No. The Phase 3 celiac trial was terminated by its sponsor in 2022, 9 Meters Biopharma announced it was discontinuing larazotide in celiac disease that August, and on 17 July 2023 the company ceased operations and filed for Chapter 7 liquidation. No other company has acquired the asset. The only ongoing activity is investigator-led academic research, principally at Massachusetts General Hospital.
Did the Phase 3 trial fail?
Not in the way it is usually described, and the distinction is worth preserving. CeDLara was stopped at a pre-planned interim analysis whose purpose was sample-size re-estimation, not efficacy testing — the sponsor concluded that the number of additional patients needed to demonstrate a significant clinical outcome was too large to justify continuing. No efficacy result was ever reported, no results have been posted to ClinicalTrials.gov, and nothing has been published. So 'did not meet its primary endpoint' is not supportable: the trial never reached an endpoint analysis. 307 of a planned 525 patients were enrolled.
Is the zonulin mechanism real?
It is genuinely contested, which the drug's usual description does not convey. The commercial ELISA kits used in most zonulin research do not detect pre-haptoglobin-2, the protein zonulin was identified as — a 2018 study established this, with zonulin's own discoverer Alessio Fasano as a co-author, and found the assay instead recognises properdin and other analogues. A 2026 systematic review concluded that 'the existing literature based on commercial ELISAs cannot determine whether pre-HP2/zonulin is altered' in the conditions studied. Meanwhile larazotide is increasingly described by a different target: a 2025 paper calls it, flatly, 'the PAR2 antagonist larazotide.' The peptide does something real at the tight junction; whether 'zonulin antagonist' is the right name for it is unsettled.
Why did the higher doses not work better?
Nobody knows, and it is one of the odder features of this drug. In the 342-patient Phase 2b, 0.5 mg three times daily met the primary endpoint while 1 mg and 2 mg were indistinguishable from placebo on every measure. Non-monotonic dose-response is not unheard of for peptides acting at a structural target, but it was never mechanistically explained, and it narrowed the Phase 3 to 0.25 mg and 0.5 mg.
Can I get larazotide for leaky gut?
No. There is no approved product, no company developing it, no compounding pathway, and nothing currently enrolling. 'Leaky gut' as a consumer concept is also not the indication larazotide was tested for — the trials studied celiac disease, a specific autoimmune condition with objective diagnostic criteria. Anything sold online as larazotide is outside any legitimate supply chain.
What about the Long COVID trial?
Massachusetts General Hospital ran a Phase 2 randomised placebo-controlled trial of larazotide in Long COVID (NCT05747534) in 107 participants aged 7 to 50, which completed in June 2026. No results have been posted to ClinicalTrials.gov and nothing has been published, so the outcome is genuinely unknown — this page will not speculate on it. The rationale follows the MIS-C work: persistent viral antigen translocating from gut reservoirs through a compromised barrier.
Was larazotide safe?
Yes, consistently. Across four randomised celiac trials totalling 626 patients, adverse events were comparable to placebo, and the pooled analysis found larazotide actually reduced gluten-related diarrhoea in challenge settings. The MIS-C trial reported no larazotide-related adverse events in children followed for 24 weeks. This is a drug that was abandoned for commercial and efficacy reasons, not safety ones — minimal systemic absorption is the likely reason its tolerability was so unremarkable.
Who Larazotide Is NOT For
- •Not obtainable — development discontinued, sponsor liquidated, nothing enrolling.
- •Known hypersensitivity to larazotide acetate or to capsule excipients.
- •Use as a substitute for a gluten-free diet in celiac disease — larazotide was only ever tested as an adjunct, in patients maintaining their diet.
- •Undiagnosed gastrointestinal symptoms — persistent symptoms attributed to 'leaky gut' warrant evaluation for celiac disease, inflammatory bowel disease, microscopic colitis, small intestinal bacterial overgrowth and carbohydrate malabsorption before any peptide is considered.
- •Pregnancy and breastfeeding — not studied in either population.
- •Paediatric use outside a trial — the only paediatric data come from a 12-patient MIS-C study under research conditions.
Drug & Supplement Interactions
Larazotide has an unusually clean interaction profile, and for a structural reason rather than an absence of study: it acts in the gut lumen and is minimally absorbed, so it does not reach systemic concentrations at which pharmacokinetic interactions occur. No cytochrome P450 or transporter interactions have been reported across a programme spanning more than 600 trial patients. The plausible interactions are local and mechanistic rather than metabolic. Any drug whose absorption depends on paracellular transit could in principle be affected by a compound that tightens tight junctions — this is a theoretical concern that the published record does not address, and it would matter most for narrow-therapeutic-index drugs absorbed by that route. It was never formally studied. In the opposite direction, agents that increase intestinal permeability work against larazotide's mechanism. NSAIDs are the clearest example, and there is a published report that a potassium-competitive acid blocker increases ileal permeability and exacerbates ileal inflammation — relevant context for anyone combining barrier-directed therapy with acid suppression. No interaction concerns were documented with the drugs celiac patients commonly take, and the MIS-C protocol gave larazotide alongside standard hyperinflammatory treatment without drug-related adverse events. With the programme discontinued, no further interaction work will be done.
Safety Profile
Common Side Effects
Cautions
- • Development discontinued; sponsor liquidated in 2023 and no product exists
- • Nothing is currently enrolling — the Long COVID and MIS-C trials are both closed
- • Never approved by any regulator anywhere
- • Not a substitute for a gluten-free diet, which remains the only established celiac treatment
- • Anything sold as larazotide outside a trial is outside any legitimate supply chain
What We Don't Know
The safety picture is one of the better-characterised things about this drug, which makes the gaps elsewhere more conspicuous. What was never established is efficacy at a confirmatory standard: the Phase 3 stopped before any endpoint analysis and no results were ever posted or published, so the strongest evidence remains a single positive Phase 2b dose arm. Long-term safety beyond trial durations is uncharacterised, and with the sponsor liquidated no pharmacovigilance programme exists. The results of the completed 107-patient Long COVID trial are unknown. And because the mechanism itself is contested — the zonulin assay problem, the negative permeability finding in meta-analysis, the emerging PAR2 framing — it is not settled what larazotide's symptom benefit in gluten challenge was actually attributable to.
Legal Status
United States
Never approved by the FDA for any indication. Larazotide held Fast Track designation for celiac disease, which is a review-process designation and not any form of approval or efficacy finding. Development was discontinued in August 2022 and the sponsor, 9 Meters Biopharma, filed for Chapter 7 liquidation on 17 July 2023; no acquirer has emerged. There is no approved product, no compounding pathway, and no trial enrolling — both remaining academic studies, in MIS-C and Long COVID, are closed. Material sold online under this name has no legitimate source.
International
Not approved in the European Union, United Kingdom, Canada, Australia, Japan or any other jurisdiction, and no marketing authorisation application is known to have been filed anywhere. All registered trials were conducted in the United States and Canada.
Sports & Competition
Not named anywhere on the WADA 2027 Prohibited List. S0 nonetheless applies and does so explicitly: the clause covers 'any pharmacological substance which is not addressed by any of the subsequent sections of the List and with no current approval by any governmental regulatory health authority for human therapeutic use,' and names 'drugs under pre-clinical or clinical development or discontinued' and 'peptides' among its examples. Larazotide is a discontinued investigational peptide with no approval anywhere, so it sits squarely inside S0 and is prohibited at all times. S0 substances are Specified Substances, which affects sanction length but not whether a violation is found. There is in any case no performance rationale — a gut-restricted tight junction regulator does nothing ergogenic.
Regulatory status changes over time. Verify current local rules with a qualified professional.
Myths & Misconceptions
Myth
Larazotide's Phase 3 trial failed to meet its primary endpoint.
Reality
The trial never reached an endpoint analysis. CeDLara was stopped at a pre-planned interim whose stated purpose was sample-size re-estimation, after which the sponsor judged that the additional enrolment required was too large to justify continuing. No efficacy result was reported, no results were posted to ClinicalTrials.gov, and nothing was published. 'Stopped early for feasibility' is accurate; 'failed its primary endpoint' asserts a result that does not exist.
Myth
The company behind larazotide restructured and the drug may return.
Reality
9 Meters Biopharma ceased operations and filed a voluntary Chapter 7 petition on 17 July 2023 — liquidation, not reorganisation. Its own filing states it had no officers, consultants or employees as of that date, and Nasdaq suspended trading within weeks. A search of SEC filings across all registrants from 2024 onward finds no acquisition of the asset.
Myth
Larazotide is derived from cholera toxin.
Reality
Not at the sequence level. Larazotide is GGVLVQPG, which appears neither in Vibrio cholerae zonula occludens toxin nor in human haptoglobin. The related fragment AT-1002 (FCIGRL) genuinely is present in ZOT — but that one increases permeability rather than decreasing it. 'ZOT-inspired' describes the intellectual lineage honestly; 'derived from' implies a sequence relationship that is not there.
Myth
Larazotide is a proven treatment for leaky gut.
Reality
It was tested in celiac disease, a specific autoimmune condition, not in the consumer concept of leaky gut. Even in celiac disease the pooled analysis found no significant change in measured intestinal permeability versus placebo. A drug that did not demonstrably change permeability in the disease it was built for is not evidence for a syndrome defined by permeability.
Myth
Serum zonulin tests can tell you whether you need something like larazotide.
Reality
The commercial zonulin ELISAs do not detect pre-haptoglobin-2, the protein zonulin was identified as — demonstrated in 2018 with zonulin's own discoverer among the authors, and reinforced by a 2026 systematic review finding that different assays produced opposite results on the same samples. A test that does not measure the molecule it names cannot guide treatment with a drug aimed at that molecule.
Myth
Larazotide was abandoned because it was unsafe.
Reality
The opposite. Across four randomised trials in 626 patients, adverse events were comparable to placebo, gluten-related diarrhoea was reduced in challenge settings, and the paediatric MIS-C trial reported no drug-related adverse events over 24 weeks of follow-up. It was discontinued because the Phase 3 could not realistically demonstrate efficacy at a feasible sample size, and then its sponsor ran out of money.
Published Research
42 studiesCirculating Zonulin in Irritable Bowel Syndrome: A Systematic Review of Conflicting Evidence and the Critical Impact of Assay Specificity.
Marginean et al. (Biomedicines 2026) — the most current synthesis of the assay problem, and the clearest statement of what it means. 'Independent validation studies have demonstrated that the most frequently used commercial kits do not recognise the pre-haptoglobin-2 molecule claimed to be zonulin, but instead detect haptoglobin, complement C3, or properdin.' Across 8 IBS studies the results were contradictory, with one study giving opposite answers from two assays on the same samples. Essential reading before treating any serum zonulin result as meaningful.
Innate immune dysregulation in celiac disease and refractory celiac disease: mechanisms, management and emerging therapies.
Serum Zonulin and Chitinase (CHI3L1) as Biomarkers of Intestinal Permeability and Disease Activity in Pediatric Celiac Disease.
Potassium-Competitive Acid Blocker Increases Ileal Permeability and Exacerbates Ileal Inflammation under Stress Conditions in a Mouse Model of Eosinophilic Enteritis
Larazotide Acetate Protects the Intestinal Mucosal Barrier from Anoxia/Reoxygenation Injury via Various Cellular Mechanisms
Is There a Future Without Gluten Restrictions for Celiac Patients? Update on Current Treatments.
Antibacterial hyaluronic acid hydrogel with sustained release of larazotide as effective colitis treatment
Viral spike antigen clearance and augmented recovery in children with post-COVID multisystem inflammatory syndrome treated with larazotide
Yonker et al. (Sci Transl Med 2025) — the most rigorous recent larazotide trial and the strongest evidence for an indication outside coeliac disease. A Phase 2a randomised, double-blind, placebo-controlled study in 12 children with multisystem inflammatory syndrome, dosed four times daily for 3 weeks with 24 weeks of safety follow-up. No larazotide-related adverse events; treated children showed faster resolution of gastrointestinal symptoms, faster clearance of SARS-CoV-2 spike antigen, and faster return to usual activities. Note the size and that Alessio Fasano, co-founder of larazotide's originating company Alba Therapeutics, is senior author.
Characterizing zonulin and par2 Expression in Zonulin Transgenic and Zonulin Inhibition Mouse Models of Motility and Inflammation.
Coeliac disease and the intestinal barrier: mechanisms of disruption and strategies for restoration.
Damianos et al. (Gut 2026) — a current Mayo Clinic review of the coeliac barrier field that situates larazotide among the strategies that have been tried and calls for reliable permeability biomarkers. The most useful single reference for a reader asking what, if anything, replaced larazotide after the programme collapsed.
Preventive effects of Larazotide acetate (AT-1001) on non-alcoholic fatty liver diseases (NAFLD) in a mouse model.
The PAR2 Antagonist Larazotide Can Mitigate Acute Histamine-Stimulated Epithelial Barrier Disruption in Keratinocytes: A Potential Adjunct Treatment for Atopic Dermatitis
Glinka and MacGregor (JID Innov 2025) — notable less for its atopic dermatitis finding than for its title, which calls larazotide a PAR2 antagonist rather than a zonulin antagonist. Protease-activated receptor 2 is increasingly treated as the receptor through which zonulin acts, and describing larazotide by that target is both more specific and more defensible than the zonulin framing the page previously used throughout.
Ameliorative Effects of Larazotide Acetate on Intestinal Permeability and Bacterial Translocation in Acute Pancreatitis Model in Rats
Zonulin Antagonist, Larazotide (AT1001), As an Adjuvant Treatment for Multisystem Inflammatory Syndrome in Children: A Case Series
Effects of larazotide acetate, a tight junction regulator, on the liver and intestinal damage in acute liver failure in rats
Peptide Derivatives of the Zonulin Inhibitor Larazotide (AT1001) as Potential Anti SARS-CoV-2: Molecular Modelling, Synthesis and Bioactivity Evaluation
Larazotide acetate for treatment of celiac disease: A systematic review and meta-analysis of randomized controlled trials
Hoilat et al. (Clin Res Hepatol Gastroenterol 2022) — the pooled analysis of all four randomised trials, 626 patients, and the single most important caveat on this page. Symptom scores improved in gluten-challenge subgroups, but 'for change in lactulose-to-mannitol ratio, the endpoint did not significantly differ between AT-1001 and placebo groups, irrespective of the gluten status.' That ratio is the direct measure of intestinal permeability — the thing larazotide is designed to fix. Symptom benefit without a demonstrated permeability change is the central puzzle of this drug.
Multisystem inflammatory syndrome in children is driven by zonulin-dependent loss of gut mucosal barrier.
The mechanistic paper behind the MIS-C work: multisystem inflammatory syndrome in children is driven by zonulin-dependent loss of the gut mucosal barrier, with viral antigen translocating from gastrointestinal reservoirs into the circulation. Whatever the unresolved questions about zonulin as a measurable biomarker, this is a coherent and testable disease model, and it is what motivated giving a gut-restricted tight-junction drug for a systemic inflammatory syndrome.
Larazotide acetate induces recovery of ischemia-injured porcine jejunum via repair of tight junctions
Larazotide acetate: a pharmacological peptide approach to tight junction regulation
In vivo assessment of a delayed release formulation of larazotide acetate indicated for celiac disease using a porcine model
Tight junction regulation in celiac disease: role of larazotide acetate
In silico Analysis Revealed Potential Anti-SARS-CoV-2 Main Protease Activity by the Zonulin Inhibitor Larazotide Acetate
Lack of relationship of AT1001 to zonulin and prehaptoglobin-2: clinical implications.
Sollid and Koning (Gut 2021) — a direct challenge to the premise that larazotide relates to zonulin at all, from two of the leading coeliac immunologists, with no declared competing interests. The letter is paywalled and this page does not quote its text, but its central claim is independently checkable and checks out: larazotide's octapeptide GGVLVQPG does not occur in human haptoglobin or in Vibrio cholerae ZOT, while the related permeability-enhancing fragment AT-1002 (FCIGRL) genuinely is present in ZOT.
The Therapeutic use of the Zonulin Inhibitor AT-1001 (Larazotide) for a Variety of Acute and Chronic Inflammatory Diseases
Blurring the picture in leaky gut research: how shortcomings of zonulin as a biomarker mislead the field of intestinal permeability.
Targeting zonulin and intestinal epithelial barrier function to prevent onset of arthritis.
Widely Used Commercial ELISA Does Not Detect Precursor of Haptoglobin2, but Recognizes Properdin as a Potential Second Member of the Zonulin Family.
Scheffler et al. (Front Endocrinol 2018) — the study that undermined the zonulin biomarker field from the inside, since Alessio Fasano, who proposed zonulin, is a co-author. Found that the widely used commercial ELISA 'does not recognize pre-haptoglobin2' and instead detects structural analogues, identifying properdin as another candidate family member. A concession rather than an attack, which is what makes it persuasive.
[Larazotide as an option in case of failure of a gluten-free diet]
The potential utility of tight junction regulation in celiac disease: focus on larazotide acetate
Larazotide acetate for persistent symptoms of celiac disease despite a gluten-free diet: a randomized controlled trial
Leffler et al. (Gastroenterology 2015) — the largest and most informative larazotide trial, 342 adults on a gluten-free diet for 12+ months. The 0.5 mg dose met the primary endpoint on the Celiac Disease GI Symptom Rating Scale (P=.022), with a 26% decrease in symptomatic days and reduced headache and tiredness. The finding that matters for dosing: 'The 1- and 2-mg doses were no different than placebo for any end point.' A non-monotonic dose-response in which the lowest dose works and higher doses do not is unusual and is the reason the Phase 3 tested 0.25 and 0.5 mg rather than escalating.
Commentary: larazotide acetate - an exciting new development for coeliac patients? Authors' reply
Commentary: larazotide acetate - an exciting new development for coeliac patients?
Larazotide acetate in patients with coeliac disease undergoing a gluten challenge: a randomised placebo-controlled study
Kelly et al. (Aliment Pharmacol Ther 2013) — the gluten-challenge design that produced larazotide's cleanest signal, and the setting where the later meta-analysis found benefit concentrated. Worth reading alongside Leffler 2015, since the two populations differ: deliberate gluten exposure versus persistent symptoms on a strict gluten-free diet.
A randomized, double-blind study of larazotide acetate to prevent the activation of celiac disease during gluten challenge
Larazotide acetate promotes tight junction assembly in epithelial cells
One of the two foundational in vitro mechanism papers, showing larazotide promotes tight junction assembly in epithelial cells. Together with its companion on tight junction regulation in vitro and in vivo, it establishes that the molecule does something real at the junction — the question the clinical record leaves open is whether that translates to measurable permeability change in patients.
Larazotide acetate regulates epithelial tight junctions in vitro and in vivo
Reducing small intestinal permeability attenuates colitis in the IL10 gene-deficient mouse.
The safety, tolerance, pharmacokinetic and pharmacodynamic effects of single doses of AT-1001 in coeliac disease subjects: a proof of concept study
The first-in-human study of AT-1001 in coeliac subjects — single doses, safety, tolerability, pharmacokinetics and pharmacodynamics. Establishes the property that makes larazotide unusual among peptides: it acts locally in the gut lumen with minimal systemic absorption, which is why its safety profile has consistently resembled placebo across trials.
ClinicalTrials.gov: Efficacy and Safety of Larazotide Acetate for the Relief of Celiac Disease Symptoms (CeDLara), NCT03569007
ClinicalTrials.gov: AT1001 for the Treatment of Long COVID, NCT05747534
9 Meters Biopharma Form 8-K: Chapter 7 petition and cessation of operations (17 July 2023)
Quick Facts
- Class
- Tight Junction Regulator
- Tier
- C
- Evidence
- Moderate
- Safety
- Well-Studied
- Updated
- Oct 2026
- Citations
- 42PubMed
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View Clinical TrialsLinks to ClinicalTrials.gov for reference. Listing does not imply endorsement.