LL-37

LL-37 is the only human cathelicidin-derived antimicrobial peptide, a 37-residue amphipathic α-helix released by proteolytic cleavage from the hCAP-18 precursor and named for its two leading leucines. Its cationic, amphipathic structure lets it bind and disrupt anionic microbial membranes, giving broad activity against bacteria, some viruses and fungi. Beyond direct killing, it is a host-defence signalling molecule: it neutralises LPS, chemoattracts and modulates immune cells, and influences wound healing and angiogenesis, partly through the formyl-peptide receptor FPR2/ALX and EGFR-linked pathways. Critically, its effects are concentration- and context-dependent — the same peptide is antimicrobial and immunomodulatory at some levels and cytotoxic or pro-inflammatory at others, and it can promote or suppress tumour growth depending on tissue.

LL-37 is an endogenous human peptide with a very large preclinical literature (in vitro and animal) on innate immunity, LPS neutralisation, wound healing and angiogenesis; foundational reviews are Dürr et al. (2006) and Xhindoli et al. (2016). It is not an approved drug and robust human therapeutic trials are lacking. Importantly, the evidence is genuinely double-edged: Piktel et al. (2016) reviews how LL-37 promotes some cancers (e.g. ovarian, lung, breast) while suppressing others (e.g. colon, gastric), reflecting receptor- and tissue-specific signalling. This ambivalence, together with concentration-dependent cytotoxicity, is central to interpreting it honestly.

Educational overview only — no dosing instructions in the public hub.

In vitro, LL-37 shows clear concentration-dependent cytotoxicity toward host cells and can be pro-inflammatory. Because its biology is double-edged — potentially tumour-promoting in some tissues and linked to inflammatory conditions such as psoriasis and rosacea where it is over-expressed — extrapolating benefit to human use is not supported by current evidence. Long-term human safety is unknown; it is not an approved therapeutic. For material sold as 'research use only', unverified sourcing and purity are the dominant practical risks.

A third-party CoA covering identity, purity (HPLC) and mass confirmation (MS) is the minimum verification. As a 37-mer, LL-37 is synthetically demanding and prone to truncated or deletion sequences and aggregation, so quantification and mass spectrometry — not purity alone — matter for knowing what a sample actually contains.

Research-use-only in most jurisdictions; not approved by the FDA or EMA for human use. It is an endogenous human peptide studied preclinically, not an authorised medicine.