Ll-37

Overview

LL-37 is a human antimicrobial peptide in the cathelicidin family and a key piece of innate immunity. It carries antibacterial, antiviral, and antifungal activity and also influences inflammation and wound healing. Like other peptides on offer here, it is sold as a research chemical that requires reconstitution and subcutaneous injection, so purity and storage are important.

The Bottom Line

LL-37 has genuinely interesting biology, but the gap between the lab and the syringe is wide. Its research grade is only B+, and the human evidence is thin, just two RCTs, with the citation list dominated by in vitro and review papers. Notably, the literature also carries flags: one retracted study and one criticised study. The community enthusiasm, including claims that it 'stopped COVID in its tracks,' runs well ahead of what controlled human data can support.

Evidence Quality

The B+ rating is weighted across 142 peer-reviewed studies (2 RCTs, 16 observational, 23 animal, 55 in vitro, 46 reviews). Findings lean supportive (86 supporting) but include a meaningful 19 refuting, plus the 1 retracted and 1 criticised flags, all reasons to keep expectations modest.

What the Research Shows

Structural work shows LL-37 forming a narrow tetrameric channel in bacterial cell walls, damaging the wall and killing the cell. In a mouse model of polybacterial sepsis it improved survival by suppressing macrophage pyroptosis and inflammatory cytokines. Reviews describe broad-spectrum antibiotic activity along with chemotactic and immunomodulatory properties. Several in vitro studies explore possible anticancer effects, including against pancreatic cancer cells via autophagy suppression and reprogramming of the tumor immune microenvironment. The throughline is that nearly all of this is preclinical.

Community Sentiment

The community sample is very small: across 10 reports, sentiment ran 67% positive and 33% neutral, with no negative reports recorded. Reported effects included wound healing, antimicrobial action, and a few dramatic anecdotes about halting COVID and large symptom reductions. The only side effect mentioned was 'stronger reactions.' With numbers this low, none of it should be read as reliable evidence.

Dosage

A typical range is 100-500 mcg subcutaneously, often daily or every other day during acute use, with cycle length varying by indication.

Effectiveness and Availability

Fans cite broad-spectrum activity against many pathogens and potential help with chronic or recurring infections, and it is sometimes paired with other antimicrobial peptides. It is a relatively niche research chemical available from peptide suppliers and less common than many others, so injectable purity is especially important.