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LL-37

Cathelicidin, hCAP18

Tier 4 · Preclinical Only
Class
Antimicrobial host-defence peptide
Molecular target
Bacterial membranes; FPR2 receptor
Sequence / structure
37-aa cationic amphipathic alpha-helix
Evidence tier
Tier 4 — Preclinical Only
Category
Tissue Repair & Cytoprotection

Biology & mechanism

The only human cathelicidin. It is cationic and amphipathic, so it inserts into and disrupts negatively charged bacterial membranes directly — a physical mechanism to which resistance develops poorly. It also acts as a signalling molecule via FPR2, recruiting immune cells and modulating wound repair. Vitamin D upregulates its expression, which is a substantial part of the vitamin D-immunity story.

What the research actually shows

Large preclinical and mechanistic literature. Early human work in venous leg ulcers exists. Systemic therapeutic use is constrained by a real problem: the same membrane-disrupting property that kills bacteria is cytotoxic to host cells at higher concentrations.

Regulatory status

Not FDA-approved.

Safety signals

Cytotoxicity and haemolysis at elevated concentrations are intrinsic to the mechanism, not an incidental impurity effect. Also implicated in the pathology of rosacea and in autoimmune processes in psoriasis and lupus — more of this peptide is not straightforwardly better.

No usage guidance is published here

Forge Bioenergy does not publish dosing, reconstitution, or administration protocols for any peptide. See our editorial policy for why. If you are considering any substance on this page, that conversation belongs with a licensed physician.

References & further reading

Regulatory status changes. This page reflects our reading of public sources as of July 2026 and should be independently verified before it is relied upon.

Important notice Forge Bioenergy publishes scientific reference information only. Nothing on this site is medical advice, a therapeutic claim, or a recommendation to use any substance in humans. Many peptides described here are not approved by the FDA for any use, and several are approved only for narrow indications under prescription. We do not publish dosing, administration, or usage protocols. Consult a licensed physician before making any medical decision.