LL-37
Not FDA-approved
Also known as: Cathelicidin LL-37, Human cathelicidin
LL-37 is the only cathelicidin humans make: a 37-amino-acid peptide that kills microbes and signals to immune cells. White blood cells and the linings of the skin, gut and airways produce it, and vitamin D switches on its gene. Applied to chronic leg ulcers, it looked promising in a small trial but showed no benefit in a larger one.
How it works
- It is cut from a larger, inactive protein called hCAP18. Neutrophils, a type of white blood cell, store hCAP18 and cut LL-37 free once they release it.
- Vitamin D switches on the LL-37 gene in human immune and skin cells. This switch is missing in mice, rats and dogs, so animal results may not carry over.
- In lab studies, it breaks open bacterial membranes. It is not selective, though: it also damages human cells.
- In lab and animal studies, it attracts immune cells and helps new blood vessels grow.
- In cultured human skin, blocking LL-37 slowed skin from regrowing over wounds. That finding led to its testing on ulcers.
Evidence
Venous leg ulcers (applied to the wound)
A first trial in 34 people reported faster healing over four weeks with the lowest strength; the highest strength did no better than placebo. A larger 13-week trial of nearly 150 people found no difference from placebo in ulcer closure.
Diabetic foot ulcers (applied as a cream)
In a four-week trial of 25 people, healthy new tissue filled the wound bed faster than with placebo. Wound size and bacterial counts did not differ.
Injected use for wellness, immunity or recovery
No human trials have tested it for these uses. The case rests on lab findings, and those findings cut both ways.
Caveats
- It is implicated in psoriasis and lupus, where it helps the immune system react to the body's own DNA. Excess, abnormally processed cathelicidin is also found in rosacea.
- Giving it could, in theory, worsen these conditions or provoke an immune reaction against it.
- Some cancers, including ovarian, breast and lung cancer, make extra LL-37. In mice, blocking it slowed the growth of ovarian tumor grafts.
- In a small melanoma study, one patient given weekly injections into tumors developed atypical skin growths resembling a squamous skin cancer. They cleared within two months of stopping.
- Applied to ulcers, it was well tolerated. In the larger trial, no serious side effect was judged to be caused by it.
References
This page is for education only. It is not medical advice. Decisions about any treatment belong with a physician who knows your history.