LL-37

LL-37 is a 37-amino-acid cationic amphipathic peptide representing the C-terminal cleavage product of hCAP-18 (human cationic antimicrobial protein 18 kDa), encoded by the CAMP gene. It is the only cathelicidin produced in humans and functions as a key effector of innate immune defence at epithelial surfaces. LL-37 is produced by neutrophils, macrophages, mast cells, natural killer cells, keratinocytes, and epithelial cells of the respiratory, gastrointestinal, and genitourinary tracts. LL-37 has three broad functional domains that make it a subject of ongoing research: direct broad-spectrum antimicrobial activity (membrane disruption against bacteria, fungi, enveloped viruses, and some parasites), immunomodulation (chemokine and cytokine induction, immune cell recruitment, modulation of toll-like receptor signalling), and tissue repair (promotion of wound healing, angiogenesis, and re-epithelialisation). Clinical interest in synthetic LL-37 as a therapeutic agent has grown from these observations. Small but genuine randomised controlled trials have evaluated topical LL-37 cream for chronic venous leg ulcers and diabetic foot ulcers, with encouraging wound-healing signals in early-phase work, though a larger Phase 2b trial in venous leg ulcers did not reach primary endpoint significance in the full cohort. Endogenous LL-37 dysregulation is also implicated in inflammatory skin diseases: overexpression in psoriasis and abnormal processing in rosacea contribute to their pathophysiology. Synthetic LL-37 is available from research suppliers. Its use outside approved clinical trials or medical supervision is for research purposes only, and it is not an approved drug in any jurisdiction.