LL-37
Clinical reviewer: Jacob Moore, MD · Last checked September 17, 2026
What is LL-37?
LL-37 is a 37-residue antimicrobial peptide made only by humans, released from the precursor protein hCAP-18 by neutrophils. It is studied mainly in the laboratory. Its compounding nomination was withdrawn by the nominator, and FDA's entry cites nonclinical findings on male reproduction and tumor-promoting effects. It is not FDA-approved.
What is LL-37 and what has it been studied for?
LL-37 is a 37-residue, amphipathic, helical peptide found only in humans and expressed throughout the body [1]. It is the C-terminal antimicrobial fragment released from the precursor hCAP-18, stored in neutrophil granules [2]. It is described as an antimicrobial peptide and studied for neovascularization and vascular endothelial growth factor expression, evidence drawn from laboratory work rather than clinical trials [1][2].
Is LL-37 FDA-approved?
No. FDA's compounding page lists cathelicidin LL-37 among nominations withdrawn by their nominators, stating the agency lacks sufficient safety-related information to know whether it would cause harm in humans, and that nonclinical research suggests detrimental effects on male reproduction and protumorigenic effects in some tissues [4]. FDA has said it will host an advisory committee meeting before the end of February 2027 to consider cathelicidin LL-37 for the 503A list [3]. It is not an FDA-approved drug.
Related terms
Sources
- LL-37 review, Life (Basel), 2022
- Cathelicidins review, Current Opinion in Hematology, 2002
- FDA, Meeting of the Pharmacy Compounding Advisory Committee (upcoming), content current as of April 15, 2026
- FDA, Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (Category 2), current as of April 22, 2026
This entry is for education and is not medical advice. Talk with a licensed clinician about your own situation before starting, stopping, or changing any treatment.
