LL-37

Overview

LL-37 is the only human cathelicidin antimicrobial peptide — a 37-amino-acid peptide (starting with two leucines) cleaved from the hCAP-18 precursor. It has broad-spectrum antimicrobial activity and immunomodulatory roles, but is also implicated in the pathogenesis of autoimmune and inflammatory skin diseases including psoriasis, rosacea, and lupus. Not FDA-approved; research-use only.

Mechanism of Action

LL-37 disrupts bacterial, fungal, and some viral membranes through electrostatic interactions with anionic phospholipids. It is chemotactic for neutrophils, monocytes, and T cells via the formyl peptide receptor FPR2 (FPRL1), modulates TLR signaling, promotes angiogenesis and re-epithelialization, and can complex with self-DNA/RNA to activate plasmacytoid dendritic cells — a mechanism linked to autoimmune pathology.

Research Summary

LL-37 was characterized in the mid-1990s as the processed antimicrobial product of hCAP-18 (Gudmundsson et al., 1996). Dürr et al. (2006, Biochim Biophys Acta, PMID 16716248) provided a foundational review of its structure and activity as the sole human cathelicidin. Overhage et al. (2008, Infection and Immunity, PMID 18591225) showed LL-37 prevents Pseudomonas aeruginosa biofilm formation at 0.5 µg/mL — far below its MIC. A randomized, placebo-controlled Phase 1/2 trial (Grönberg et al., 2014, Wound Repair and Regeneration, PMID 25041740) found topical LL-37 safely accelerated healing of hard-to-heal venous leg ulcers at low doses. Its dual role in autoimmunity is well established: Lande et al. (2014, Nature Communications, PMID 25470744) identified LL-37 as a T-cell autoantigen in two-thirds of moderate-to-severe plaque psoriasis patients. No FDA approval exists for any indication. Injectable grey-market protocols for Lyme, biofilm, or mold illness lack controlled clinical evidence and carry theoretical autoimmune risk given LL-37's role in psoriasis, lupus, and rosacea pathogenesis.

Vendors selling LL-37

Scored vendors carrying LL-37, ranked by trust grade. Grades are computed from indexed Certificates of Analysis. Full $/mg pricing is on the comparison page.

Prescribers who offer LL-37

16 prescribers in our directory work with LL-37, each confirmed from their own website. Peptides like LL-37 require a prescription from a licensed provider — telehealth options are available.

Reported Side Effects

• Injection site pain and redness (limited human injection data)
• Theoretical cytokine release with systemic dosing
• Potential to trigger or worsen autoimmune/inflammatory skin disease (psoriasis, rosacea, lupus flares) given LL-37's documented role in their pathogenesis
• Flu-like symptoms

Compare LL-37 with Others

Research References

• LL-37, the only human member of the cathelicidin family of antimicrobial peptides (Dürr et al., 2006) (2006)
• Human host defense peptide LL-37 prevents bacterial biofilm formation (Overhage et al., 2008, Infect Immun) (2008)
• Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial (Grönberg et al., 2014) (2014)
• The antimicrobial peptide LL37 is a T-cell autoantigen in psoriasis (Lande et al., 2014, Nat Commun) (2014)

Frequently asked questions

Has LL-37 been independently lab-tested?

Disclosed Labs has collected 31 Certificates of Analysis (COA) for LL-37 from 8 independent testing labs. 15 vendors have submitted material for testing. Products average 99.2% tested purity across the corpus. Full testing data is available at https://www.disclosedlabs.com/peptides/ll-37/testing.

What is the average purity of LL-37 on the market?

Based on 31 COAs analyzed by Disclosed Labs, LL-37 products average 99.2% (±1.9%) tested purity. Individual vendor results vary; see per-vendor COA data at https://www.disclosedlabs.com/peptides/ll-37/coas.

Which labs have tested LL-37?

Independent labs that have tested LL-37 include: ILS Labs (Grade A). Full lab credibility grades and profiles are at https://www.disclosedlabs.com/labs.

Where can researchers source LL-37?

8 vendors with Disclosed Labs trust grades currently list LL-37, including Ion Peptide, Orbitrex Peptides, Peptidology. Compare live prices and lab-verified COAs at https://www.disclosedlabs.com/prices/ll-37.

Which prescribers offer LL-37 with a prescription?

16 prescribers in the Disclosed Labs directory work with LL-37, each confirmed from their own website, with telehealth options available. LL-37 requires a prescription from a licensed provider. Browse them at https://www.disclosedlabs.com/prescribers?peptide=LL-37.

How does LL-37 work?

LL-37 disrupts bacterial, fungal, and some viral membranes through electrostatic interactions with anionic phospholipids. It is chemotactic for neutrophils, monocytes, and T cells via the formyl peptide receptor FPR2 (FPRL1), modulates TLR signaling, promotes angiogenesis and re-epithelialization, and can complex with self-DNA/RNA to activate plasmacytoid dendritic cells — a mechanism linked to autoimmune pathology.

What does the research say about LL-37?

LL-37 was characterized in the mid-1990s as the processed antimicrobial product of hCAP-18 (Gudmundsson et al., 1996). Dürr et al. (2006, Biochim Biophys Acta, PMID 16716248) provided a foundational review of its structure and activity as the sole human cathelicidin. Overhage et al. (2008, Infection and Immunity, PMID 18591225) showed LL-37 prevents Pseudomonas aeruginosa biofilm formation at 0.5 µg/mL — far below its MIC. A randomized, placebo-controlled Phase 1/2 trial (Grönberg et al., 2014, Wound Repair and Regeneration, PMID 25041740) found topical LL-37 safely accelerated healing of hard-to-heal venous leg ulcers at low doses. Its dual role in autoimmunity is well established: Lande et al. (2014, Nature Communications, PMID 25470744) identified LL-37 as a T-cell autoantigen in two-thirds of moderate-to-severe plaque psoriasis patients. No FDA approval exists for any indication. Injectable grey-market protocols for Lyme, biofilm, or mold illness lack controlled clinical evidence and carry theoretical autoimmune risk given LL-37's role in psoriasis, lupus, and rosacea pathogenesis.