Larazotide vs LL-37
Two peptides sold for gut/barrier health with genuinely different regulatory maturity — one that actually reached Phase 3 and failed, the other still entirely preclinical.
Short answer
The evidence gap decides this one. Larazotide has human clinical data behind it, while LL-37 has only preclinical or minimal evidence, resting mostly on animal or lab work. Someone focused on leaky gut and celiac disease has trial data to go on with larazotide; LL-37, marketed for infection, immunity and healing, is still an early-research option.
Larazotide
AT-1001
A tight-junction regulator with real celiac Phase 2 data — but its pivotal Phase 3 failed, and the supplement use runs far ahead of the evidence.
Full Larazotide evidence reviewLL-37
Cathelicidin
Genuine innate-immunity biology, but its therapeutic use is preclinical — and the same peptide is implicated in driving inflammatory disease.
Full LL-37 evidence reviewLarazotide vs LL-37: head to head
- FDA status / approved use
Larazotide
Investigational and not FDA-approved; pivotal Phase 3 trial halted in 2022LL-37
Unapproved research chemical; not an approved drug for any indication- Marketed for
Larazotide
Leaky gut, celiac diseaseLL-37
Infection, immunity, healing- Outcome areas
Larazotide
Gut healthLL-37
Immune function / inflammation; Injury recovery / tissue repair- Evidence grade
Larazotide
Clinical dataLL-37
Preclinical / minimal- How it works
Larazotide
Zonulin antagonist designed to tighten the junctions between intestinal cellsLL-37
Natural human host-defense peptide that disrupts bacterial membranes- Route and dosing
Larazotide
Oral capsule swallowed before mealsLL-37
Injection- Headline human result
Larazotide
Phase 3 CeDLara trial stopped in 2022 after interim analysis showed it would miss its symptom endpointLL-37
Not established- Strongest evidence
Larazotide
Leffler, Gastroenterology 2015Larazotide evidence reviewPubMed 25683116LL-37
Lande, Nature 2007. Little or no controlled human outcome data for the marketed useLL-37 evidence reviewPubMed 17873860- Key safety signal
Larazotide
Gray-market products carry contamination, mislabeling and mis-dosing risksLL-37
Implicated in rosacea, psoriasis and lupus; gray-market vials carry sterility and purity risks- How it is obtained
Larazotide
Legitimately available only inside clinical trials; vials sold online are gray-market research chemicalsLL-37
Sold gray-market as a research chemical; no approved or legitimately compounded human product
| Larazotide | LL-37 | |
|---|---|---|
| FDA status / approved use | Investigational and not FDA-approved; pivotal Phase 3 trial halted in 2022 | Unapproved research chemical; not an approved drug for any indication |
| Marketed for | Leaky gut, celiac disease | Infection, immunity, healing |
| Outcome areas | Gut health | Immune function / inflammation; Injury recovery / tissue repair |
| Evidence grade | Clinical data | Preclinical / minimal |
| How it works | Zonulin antagonist designed to tighten the junctions between intestinal cells | Natural human host-defense peptide that disrupts bacterial membranes |
| Route and dosing | Oral capsule swallowed before meals | Injection |
| Headline human result | Phase 3 CeDLara trial stopped in 2022 after interim analysis showed it would miss its symptom endpoint | Not established |
| Strongest evidence | Leffler, Gastroenterology 2015Larazotide evidence reviewPubMed 25683116 | Lande, Nature 2007. Little or no controlled human outcome data for the marketed useLL-37 evidence reviewPubMed 17873860 |
| Key safety signal | Gray-market products carry contamination, mislabeling and mis-dosing risks | Implicated in rosacea, psoriasis and lupus; gray-market vials carry sterility and purity risks |
| How it is obtained | Legitimately available only inside clinical trials; vials sold online are gray-market research chemicals | Sold gray-market as a research chemical; no approved or legitimately compounded human product |
marks a row where the two differ. “Not established” marks a cell the available evidence does not answer. Evidence grades come from our evidence matrix, which grades each molecule on the human data for the use it is marketed for.
- Clinical data:
- Tested in humans — but investigational, discontinued, or proven only on a surrogate marker (not the marketed outcome).
- Preclinical / minimal:
- Evidence is largely animal, in-vitro, or anecdotal. Little or no controlled human outcome data for the marketed use.
Our verdict
Larazotide got further than almost anything on this list: real Phase 2 celiac data, but its pivotal Phase 3 trial failed, and the leaky-gut supplement use runs well ahead of what even the positive early data showed. LL-37 has genuine innate-immunity biology and real mechanism, but its therapeutic use remains entirely preclinical — and the same peptide is also implicated in driving inflammatory disease, a double-edged detail marketing tends to skip.
Larazotide fits if
Celiac-adjacent gut-barrier function specifically is the interest, understanding the pivotal trial for that exact use failed.
LL-37 fits if
You're reading about innate-immunity peptide biology generally — there's no human trial behind any product sold under this name.
Larazotide vs LL-37: common questions
- Is either larazotide or LL-37 FDA-approved?
- No. Larazotide is investigational and not FDA-approved; pivotal Phase 3 trial halted in 2022. LL-37 is an unapproved research chemical; not an approved drug for any indication.
- Which has stronger human evidence, larazotide or LL-37?
- Larazotide. It has human clinical data (key source: Leffler, Gastroenterology 2015), while LL-37 has only preclinical or minimal evidence (key source: Lande, Nature 2007).
- What are the main safety concerns with larazotide and LL-37?
- With larazotide, gray-market products carry contamination, mislabeling and mis-dosing risks. LL-37 is implicated in rosacea, psoriasis and lupus; gray-market vials carry sterility and purity risks.
Key studies behind each
Larazotide
- Paterson BM, Lammers KM, Arrieta MC, Fasano A, Meddings JB. (2007). The safety, tolerance, pharmacokinetic and pharmacodynamic effects of single doses of AT-1001 in coeliac disease subjects: a proof of concept study. Aliment Pharmacol Ther. PubMed 17697209
- Fasano A. (2011). Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer. Physiol Rev. PubMed 21248165
- Kelly CP, Green PH, Murray JA, et al. (2013). Larazotide acetate in patients with coeliac disease undergoing a gluten challenge: a randomised placebo-controlled study. Aliment Pharmacol Ther. PubMed 23163616
- Leffler DA, Kelly CP, Green PH, et al. (2015). Larazotide acetate for persistent symptoms of celiac disease despite a gluten-free diet: a randomized controlled trial. Gastroenterology. PubMed 25683116
LL-37
- Vandamme D, Landuyt B, Luyten W, Schoofs L. (2012). A comprehensive summary of LL-37, the factotum human cathelicidin peptide. Cell Immunol. PubMed 23246832
- Dürr UH, Sudheendra US, Ramamoorthy A. (2006). LL-37, the only human member of the cathelicidin family of antimicrobial peptides. Biochim Biophys Acta. PubMed 16716248
- Gallo RL. (2008). Sounding the alarm: multiple functions of host defense peptides. J Invest Dermatol. PubMed 18071331
- Dzurová L, Holásková E, Pospíšilová H, et al. (2024). Cathelicidins: Opportunities and Challenges in Skin Therapeutics and Clinical Translation. Antibiotics (Basel). PubMed 39858288
The full evidence reviews
- Larazotide: the leaky-gut peptide that failed its Phase 3 trial
An 8-amino-acid tight-junction regulator with real celiac data and a failed pivotal trial — and why the supplement use runs far ahead of the evidence.
Updated August 2026
- LL-37: a real immune peptide, no human proof, and two edges
The human cathelicidin is genuine innate-immunity biology — but its therapeutic use is preclinical, and the same peptide is implicated in inflammatory disease.
Updated August 2026
Where to get it
Where to get peptide therapy
Clinician-led telehealth services that prescribe compounded peptides. The specific peptides offered vary by provider — confirm Larazotide availability before ordering.
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