What it is
LL-37 is different in kind from most peptides tracked on this site. It is not a synthetic research compound designed to mimic or extend a natural signal. It is the natural signal itself, the active 37-residue fragment cleaved from hCAP-18, the only cathelicidin the human body produces. Neutrophils and epithelial cells release it as a front-line antimicrobial defense, and the research literature on it is correspondingly about infection and immunity, not about performance, recovery or anti-aging in the way most vendor-marketed peptides are framed.
What the research covers
A 2005 review by Tjabringa, Rabe and Hiemstra in Pulmonary Pharmacology & Therapeutics laid out LL-37's role in lung defense: a positively charged, amphipathic peptide that disrupts bacterial membranes directly and also functions as a signaling molecule in inflammation and tissue repair, beyond simple antimicrobial killing.[1] Duplantier and van Hoek, writing in Frontiers in Immunology in 2013, reviewed it specifically as a candidate treatment for polymicrobial infected wounds, citing its combined antibacterial and wound-healing activity as the rationale.[2] Separately, Kuroda and colleagues, in Frontiers in Oncology in 2015, reviewed LL-37 and its structural mimics as candidate anticancer agents, based on activity against tumor cell lines in laboratory studies.[3]
The safety picture is genuinely mixed
This is the point worth being direct about. LL-37 is not a peptide with a clean safety profile that simply lacks marketing attention. Its own research literature identifies real limits. A 2019 review by Wang and colleagues in Advances in Experimental Medicine and Biology, focused on antimicrobial peptide design built on the LL-37 scaffold, states plainly that clinical application of LL-37 is constrained by low proteolytic stability, cytotoxicity to host cells at higher concentrations, and high production cost, which is exactly why so much of the published work is aimed at engineering shorter, less toxic analogs rather than using the native peptide directly.[4] Separate work has also identified LL-37 as a growth factor for some cancer cell lines in laboratory conditions, a finding in tension with the anticancer research above and a reminder that this compound's biology cuts more than one way.
None of this is a reason to treat LL-37 as more dangerous than any other unregulated research compound. It is a reason not to treat it as a benign wellness peptide, which is a framing its own literature does not support.
No vendor is currently listing this
LL-37 isn't available from any vendor we currently track. It was last seen at $18.40 per mg on Penguin Peptides, 2 July 2026, listed as a 5 mg vial for $92.00. That figure is included here for reference. It's what the compound was actually selling for the last time we confirmed a listing, not a price you can act on today. If a vendor relists it, this page will reflect the live price the next time our data updates.
References
- [1] Tjabringa GS, Rabe KF, Hiemstra PS. The human cathelicidin LL-37: a multifunctional peptide involved in infection and inflammation in the lung. Pulm Pharmacol Ther. 2005;18(5):321-327. PubMed ↗
- [2] Duplantier AJ, van Hoek ML. The Human Cathelicidin Antimicrobial Peptide LL-37 as a Potential Treatment for Polymicrobial Infected Wounds. Front Immunol. 2013;4:143. PubMed ↗
- [3] Kuroda K, Okumura K, Isogai H, Isogai E. The Human Cathelicidin Antimicrobial Peptide LL-37 and Mimics are Potential Anticancer Drugs. Front Oncol. 2015;5:144. PubMed ↗
- [4] Wang G et al. Design of Antimicrobial Peptides: Progress Made with Human Cathelicidin LL-37. Adv Exp Med Biol. 2019;1117:215-240. PubMed ↗