LL-37
Also known as: Cathelicidin antimicrobial peptide, hCAP-18 fragment, CAMP, Cathelicidin LL-37
The human body's own cathelicidin antimicrobial peptide, and a genuine subject of immunology research. As a marketed compound, however, it is an unapproved research chemical with no controlled human evidence for its advertised uses — and it is directly toxic to human cells at higher concentrations.
LL-37 is an endogenous human peptide, but it is not FDA-approved as a therapeutic for any indication. Products sold for self-administration are unregulated research chemicals, not medicines.
What it is
LL-37 is the only human cathelicidin antimicrobial peptide — a 37-residue peptide (beginning with two leucines, hence the name) cleaved from the precursor protein hCAP-18. It is a real and important part of human innate immunity: it disrupts the membranes of bacteria, fungi, and viruses, binds and neutralizes bacterial endotoxin, and modulates immune-cell behavior. Unlike most compounds on this site, LL-37 is a molecule the body already makes, and it is the subject of a large, legitimate immunology literature.
What it’s approved or studied for
As a therapeutic, nothing. LL-37 is not FDA-approved for any indication. Its established “uses” describe its endogenous biology — what it does as part of the immune system — not a validated treatment. Products sold for self-administration (marketed for infection, wound healing, gut health, or “immune support”) are unregulated research chemicals with no approved indication behind them.
What human evidence exists
For administered LL-37 as a drug: effectively none of the controlled kind. The research record — antimicrobial activity, wound healing, immunomodulation, and a genuinely mixed anticancer/pro-tumor picture — is Grade D preclinical, based on cell and animal studies. Its role in host defense is well characterized as biology, but that is not the same as evidence that injecting or applying LL-37 treats disease in humans. Human therapeutic effectiveness and long-term safety are both Grade U: unknown.
The major unknowns
Whether administered LL-37 does anything useful in humans, at what dose and route, and with what safety margin are all unresolved. The anticancer data cut both ways depending on tissue, and LL-37 has been implicated in driving inflammation in autoimmune and inflammatory conditions — so “boosting” it is not obviously beneficial. Research-chemical product identity and purity are unregulated and uncertain.
Most important safety considerations
LL-37 is directly cytotoxic to human cells at higher concentrations (on the order of 1–10 µM in laboratory studies), it can be pro-inflammatory, and it has been linked in research to autoimmune and inflammatory disease processes. There is no controlled human safety data for administering it, product quality is uncontrolled, and it is not a legal therapeutic. This page summarizes the research record; it is not medical advice or an endorsement of use.
Evidence by outcome
Each outcome is graded on its own evidence — a compound can be strong for one use and unproven for another. See how we grade.
Well-established biology, but as endogenous function — not as an administered drug. — LL-37 is a real component of human innate immunity with broad activity against bacteria, fungi, and viruses and clear immunomodulatory roles. This describes what the peptide does in the body, not proof that supplementing it treats infection in humans.
Animal and cell data; not established in humans as a therapy. — LL-37 promotes re-epithelialization and angiogenesis in preclinical models; controlled human trials of administered LL-37 for wound healing are lacking.
Preclinical and context-dependent (can be pro- or anti-tumor). — Laboratory work shows both anticancer and, in some tissues, tumor-promoting effects depending on cancer type — an unresolved, dose- and context-dependent picture. No human therapeutic use.
Unknown — no approved indication and no controlled human efficacy data.
Unknown — no controlled human safety data for administered LL-37.
Safety
Common adverse effects
- Not established in humans
Serious risks
- Direct cytotoxicity to human cells at higher concentrations (roughly 1–10 µM in vitro); pro-inflammatory effects and a suggested role in autoimmune and inflammatory conditions; unregulated product quality and contamination risk
Contraindications
- No human contraindication data; not approved for human use; caution given links to inflammatory/autoimmune disease in research
References