LL-37

cathelicidin LL-37

Grade C: Preliminary or limited human evidence

TL;DR: Human clinical evidence for LL-37 is limited to topical wound healing; there is no published human trial of systemic or injectable LL-37, which is the form sold to consumers. An early phase I/II randomized, placebo-controlled trial in hard-to-heal venous leg ulcers was positive (PMID 25041740, 2014), but the larger phase IIb randomized, placebo-controlled trial did not meet its primary endpoint of confirmed wound closure (PMID 34687253, 2021). Grade C reflects that human randomized data exists, but the most advanced trial failed and the data is topical only; it does not transfer to the injectable use, for which there is no human evidence.

Key Takeaways

Grade C: Preliminary or limited human evidence
Not FDA approved: Not FDA-approved for any indication. As of 2026 it sits in the FDA's restricted (Category 2) compounding bucket and has not yet been reviewed by the Pharmacy Compounding Advisory Committee.
Compounding: Not an FDA-approved drug. The compounding status of these peptides is unsettled and changing; confirm current legality with a licensed pharmacist or physician before any use.

LL-37 chemical structure — Structure via PubChem CID 16198951

Mechanism

LL-37 is the only human cathelicidin antimicrobial peptide. It disrupts microbial membranes and modulates innate immune signaling; in wound healing it is proposed to promote keratinocyte migration and angiogenesis.

Evidence

Human clinical evidence for LL-37 is limited to topical wound healing; there is no published human trial of systemic or injectable LL-37, which is the form sold to consumers. An early phase I/II randomized, placebo-controlled trial in hard-to-heal venous leg ulcers was positive (PMID 25041740, 2014), but the larger phase IIb randomized, placebo-controlled trial did not meet its primary endpoint of confirmed wound closure (PMID 34687253, 2021). Grade C reflects that human randomized data exists, but the most advanced trial failed and the data is topical only; it does not transfer to the injectable use, for which there is no human evidence.

Safety and risks

Beyond topical wound-care trials, human safety data for systemic or injectable LL-37 does not exist. A documented laboratory concern is tumor biology: elevated LL-37 expression promotes proliferation and invasion in several cancers, including ovarian (PMID 17960624), breast, and lung, although it can suppress tumor growth in colon and gastric cancer, so the effect is tissue-specific (review: PMID 26395996). Whether exogenous administration reproduces this in humans has not been studied. People with a personal or family history of cancer face particular unknowns, and systemic use outside a clinical trial carries uncharacterized risk.

Interactions

No systemic human pharmacokinetic or interaction data exist. Its immunomodulatory activity raises a theoretical concern alongside immunosuppressants or biologics.

Federal compounding status

Nomination withdrawn (was Category 2) as of 2026-06-02.

This substance was nominated for the FDA 503A or 503B bulk-substances list and previously sat in the Category 2 (significant safety risk) group; the nomination was later withdrawn, so it is not on an active FDA bulks list and is not eligible for routine pharmacy compounding. FDA source

Federal status only, from public FDA records. State pharmacy-board rules vary and are not covered here. This is regulatory reporting, not legal advice. All compounds.

Compounding legality

Not an FDA-approved drug. The compounding status of these peptides is unsettled and changing; confirm current legality with a licensed pharmacist or physician before any use.

Sources

LL-37 is Not FDA approved. PeptideGrids presents evidence and regulatory status for informational purposes only. We do not sell, supply, source, or help anyone obtain this compound, and we provide no dosing or administration guidance. This is not medical advice; consult a licensed clinician. Full disclaimer.

Last reviewed June 2, 2026 by PeptideGrids editorial team (independently audited).