Antimicrobial peptide

LL-37 is the only cathelicidin humans make - a 37-residue antimicrobial peptide released from the precursor hCAP18 in skin, neutrophils and epithelia, which kills bacteria, recruits immune cells and drives re-epithelialisation. It has been through three randomised trials in chronic wounds, and the results run in exactly the direction that should make anyone cautious. A 2014 trial in hard-to-heal venous leg ulcers found the peptide safe and reported a marked effect, with mean ulcer area down 68% at the lower concentration. A 2021 multicentre trial in 148 patients then found no significant improvement in healing across the whole cohort, with benefit only in a post-hoc subgroup with large ulcers. A separate randomised trial in diabetic foot ulcers reported benefit.