Carl read the papersWhat it actually is
Larazotide is a single chain peptide of eight amino acids that acts as a tight junction regulator. It was designed to work in the gut lumen and is described in the literature as locally acting and non-systemic, so it is taken as a capsule and acts on the cells it passes.
The mechanism is framed as blocking zonulin, the protein that opens tight junctions, and it has been linked to redistribution of tight junction proteins and actin, and to inhibition of myosin light chain kinase. The target condition was coeliac disease in people who still had symptoms despite a gluten-free diet.
How it’s thought to work
- Zonulin antagonism — Thought to block zonulin-driven opening of the tight junctions between intestinal cells.
- Tight junction rearrangement — Associated with redistribution of tight junction proteins and actin filaments back into a closed arrangement.
- Myosin light chain kinase — More recent work links it to MLCK inhibition, which likely reduces tension on the actin filaments and lets the junction close.
- Acts locally — Minimal absorption is the design, not a flaw. Whatever it does, it does on the way through.
What the research says
An unusual amount of it, and the ending matters. The largest completed trial randomised 342 adults with coeliac disease and persistent symptoms on a gluten-free diet to larazotide 0.5, 1 or 2 mg three times daily for 12 weeks: only the 0.5 mg dose beat placebo, and the 1 and 2 mg doses were no different from placebo on any endpoint. An earlier gluten challenge study of 184 patients tested 1, 4 and 8 mg three times daily against 2.7 g of gluten a day for 6 weeks, and found a symptom benefit at 1 mg but no difference in the lactulose-to-mannitol permeability measure. A meta-analysis of four randomised trials (626 patients) found no significant effect on that permeability ratio, with symptom benefit only under gluten challenge. The phase 3 trial was stopped in June 2022: an interim analysis after the 12 week double-blind portion in about half the target enrolment concluded that the extra patients needed to show a significant effect were too many to justify continuing. A separate phase 2a in 12 children with post-COVID multisystem inflammatory syndrome reported no larazotide-related adverse events and faster symptom resolution.
- Eight amino acid oral peptide, designed to act in the gut lumen rather than be absorbed.
- 342 patients: 0.5 mg three times daily beat placebo; 1 mg and 2 mg did not, in the same trial.
- Meta-analysis of 4 trials, 626 patients: no significant change in the lactulose-to-mannitol permeability ratio.
- Phase 3 (307 enrolled, 0.25 and 0.5 mg three times daily) terminated in 2022 after a futility-style interim analysis.
- Safety across trials has been unremarkable, which is the one consistently good finding.
Reported protocols
These are the doses the peptide community actually reports running (Reddit & forums), alongside published research — logged for education, not as a recommendation to use.
| Parameter | Commonly reported range |
|---|---|
| Trial dose | 0.5 mg three times daily, as capsules. That is the only dose that beat placebo in the 342-patient trial, and the phase 3 tested 0.25 mg and 0.5 mg three times daily |
| The inverted-U | Higher is worse here, demonstrably: 1 mg and 2 mg three times daily were indistinguishable from placebo on every endpoint in the same trial. The authors suggested peptide aggregation at higher doses as one possible reason |
| Route | Oral capsule. Nothing is injected, which also means nothing is reconstituted |
| Duration | The 342-patient trial ran 12 weeks of treatment between placebo run-in and run-out phases; the phase 3's efficacy portion was also 12 weeks |
| Community dose | Not established from independent sources. The figures online are the trial dose, repeated by vendor pages, and no credible first-hand write-ups turned up |
| Carl's note | The dose-response curve is the single most important thing to know here, and it is the first thing people get wrong when they assume a bigger capsule is a stronger one. |
Common use cases
| Goal | Community protocol notes |
|---|---|
| Coeliac symptoms despite a gluten-free diet | the condition it was built for, where the 342-patient trial found a modest benefit at 0.5 mg and the phase 3 failed to confirm it |
| Gut barrier research | where it earns its keep: a specific tool for a specific junction mechanism |
| General leaky gut use | the reason most people search for it, and the use with the least evidence behind it |
Mixing it (reconstitution)
Freeze-dried peptides must be reconstituted with bacteriostatic water before they can be measured. Carl’s calculator turns “mg in the vial + ml of water + target dose” into “units on the syringe” — and tells you how long the vial lasts.
→ Open the Reconstitution Calculator
Injection & handling
There is nothing to inject, which makes this one of the few entries here you cannot get wrong with a syringe. Larazotide is an oral capsule and the whole design relies on it staying in the gut, so the formulation matters more than the dose does: the phase 3 used enteric-coated beads in gelatin capsules so the peptide survives the stomach and is released where it is meant to work. A raw powder bought as research material has none of that, and dissolving a gut-acting peptide into water and drinking it is not the same product the trials tested. Store capsules as supplied, in a cool dry place.
Stacks it appears in
- With BPC-157 — The obvious pairing in gut discussions, and an entirely theoretical one. Different mechanisms, no combination data in people.
- With KPV — Another gut-inflammation peptide that comes up alongside it. Same caveat: no trial has put them together.
- With a gluten-free diet — The only combination the trials actually tested. Larazotide was always studied as an add-on to the diet, never as a replacement for it.
Sources
- Leffler DA et al. Larazotide acetate for persistent symptoms of celiac disease despite a gluten-free diet: a randomized controlled trial. Gastroenterology 2015 (PMID 25683116, PMC4446229)
- Kelly CP et al. Larazotide acetate in patients with coeliac disease undergoing a gluten challenge. Aliment Pharmacol Ther 2013 (PMID 23163616)
- Hoilat GJ et al. Larazotide acetate for treatment of celiac disease: systematic review and meta-analysis of RCTs. Clin Res Hepatol Gastroenterol 2022 (PMID 34339872)
- Slifer ZM et al. Larazotide acetate: a pharmacological peptide approach to tight junction regulation. Am J Physiol Gastrointest Liver Physiol 2021 (PMID 33881350)
- ClinicalTrials.gov NCT03569007 (CeD-LA-3001, phase 3, terminated)
- 9 Meters Biopharma press release, 21 June 2022 (interim analysis does not support trial continuation), SEC EDGAR
- Yonker LM et al. Viral spike antigen clearance and augmented recovery in children with post-COVID MIS treated with larazotide. Sci Transl Med 2025 (PMID 40737433)
- SAHPRA registered health products register (no larazotide product)
- SAHPRA, Peptide Products public information page (May 2026)
- WADA 2026 Prohibited List, S0 non-approved substances
