LL-37

LL-37 is a 37-amino-acid active peptide processed from the human cathelicidin precursor hCAP18, encoded by the CAMP gene. The historically predicted FALL-39 is a related but distinct 39-residue peptide, not another name for mature LL-37. LL-37’s presence in human granulocytes and wound tissue supports a host-defense role, but endogenous expression is not a treatment result. Gudmundsson et al., 1996, PMID 8681941 · Heilborn et al., 2003, PMID 12603850

What human treatment studies found

A randomized pilot in 34 people with hard-to-heal venous leg ulcers reported improved healing measures at lower topical LL-37 concentrations over a short treatment period. A later phase IIb trial in 148 people with the same broad condition found no significant improvement in its full population versus placebo with compression care. Its favorable large-ulcer analysis was post hoc and needs a trial designed to test that subgroup. These are two independent treated populations, not two confirmations of benefit. Grönberg et al., 2014, PMID 25041740 · Mahlapuu et al., 2021, PMID 34687253

A randomized trial of LL-37 cream in mildly infected diabetic foot ulcers reported greater granulation-index improvement at measured visits. It did not find a significant reduction in inflammatory markers or aerobic bacterial colonization. The paper and NCT04098562 describe the same population; the registry is not another efficacy study. Miranda et al., 2023, PMID 37480520 · NCT04098562

An open-label randomized study in mild Omicron COVID-19 investigated engineered Lactococcus lactis expressing LL-37, not purified peptide. Its overall comparison for time to negative viral test was not significant; an early-treatment subgroup had a signal. The formulation, disease, and outcome do not transfer to topical or injected LL-37. Zhao et al., 2023, PMID 37605995

ClinicalTrials.gov also records a completed, single-group intratumoral LL-37 melanoma study. It enrolled four people and posted results in 2021; its outcome tables report groups of only two and one people. These registry results are distinct from a journal paper, which was not identified for this cohort. They cannot establish antitumor efficacy or general safety for this route, let alone for topical or systemic use. NCT02225366

Why context matters

LL-37 can bind self-DNA and stimulate immune signaling in laboratory experiments; abnormal cathelicidin processing was implicated in human rosacea tissue. A 2026 human bronchial epithelial-cell study found that citrullination changed LL-37-linked inflammatory signaling. These findings show why an antimicrobial effect in one assay cannot be generalized to all tissues or routes. Lande et al., 2007, PMID 17873860 · Yamasaki et al., 2007, PMID 17676051 · Ramotar et al., 2026, PMID 41535907

FDA lists cathelicidin LL-37 among withdrawn bulk-drug nominations. It says safety information is insufficient for compounded LL-37 and cites potential immunogenicity, peptide-characterization concerns, and nonclinical findings about male reproduction and pro-tumor effects in some tissues. Those findings do not prove that every tested topical formulation has the same risk. FDA compounding safety page

No systemic or broad infection use is established by these data. This dossier is a research summary, not medical advice or self-treatment guidance.