Educational reference only. Not medical advice. Consult a healthcare provider before starting any protocol.
LL-37
LL-37 (Cathelicidin Antimicrobial Peptide / hCAP18 C-terminal fragment)
What it is
The sole human member of the cathelicidin family of antimicrobial peptides, cleaved from the 18 kDa precursor protein hCAP18. LL-37 is a cationic, amphipathic α-helical peptide with broad-spectrum antimicrobial activity against bacteria (including MRSA), fungi, and viruses, as well as immunomodulatory and wound-healing properties. It has been studied in Phase I/IIb human trials for topical wound healing (venous leg ulcers, diabetic foot ulcers) and intratumoral melanoma injection. Its expression is transcriptionally regulated by vitamin D. No clinical trials have evaluated subcutaneous systemic injection — the route most discussed in biohacking communities.
Community-reported ranges
Subcutaneous dose ranges sourced from community forums and peptide information sites. Topical dose ranges from published clinical trials. Not dosing guidance.
Reported dose range
100–400 mcg
Estimated half-life
Very short (minutes in plasma)
Source: Preclinical data; no formal human systemic PK characterization. Rapid enzymatic degradation by serine proteases is a known development barrier.
Reported cycle length
4–6 weeks on
2-4 weeks off
Route
subcutaneous, topical
Common vial sizes
5mg, 10mg
Reported timing
AM & PM (subcutaneous); 5-days-on/2-days-off schedule discussed in community forums
Reported frequency
1-2x daily
Frequently discussed alongside
Based on community forum discussions. Not a recommendation to combine compounds.
Published research
LL-37 has demonstrated clinical efficacy in topical wound healing: a Phase I/IIa trial (Grönberg et al., 2014) in 34 venous leg ulcer patients showed a ~6-fold higher healing rate at 0.5 mg/mL versus placebo. A Phase IIb (HEAL) trial in 148 patients confirmed benefit in ulcers >10 cm². A diabetic foot ulcer RCT (2023) showed enhanced granulation tissue formation with LL-37 cream. A Phase I melanoma trial tested intratumoral injection at MD Anderson. Preclinically, LL-37 demonstrates antimicrobial activity against >38 bacterial species, anti-biofilm properties, immunomodulatory effects (FPRL-1 chemotaxis, pDC activation), and context-dependent pro/anti-tumor activity. All human trial data involves topical or intratumoral administration; subcutaneous systemic dosing has zero clinical trial support.
Reported side effects
From community self-reports. Not from controlled studies.
Clinical trials (topical, up to 3.2 mg/mL) reported mild injection site reactions. Community users report injection site pain and burning (described as more uncomfortable than most peptides), mild flu-like symptoms during initial days, and potential worsening of autoimmune symptoms. LL-37-DNA complexes can activate type I interferon pathways — elevated LL-37 is associated with psoriasis and rosacea. Concentrations above ~25 µM are cytotoxic to normal human cells in vitro.
Regulatory status
FDA (United States)
Not approved. Placed on Category 2 bulk drug substance list (prohibited for compounding) in late 2023. Status under review following HHS announcement in February 2026 regarding potential reclassification of some Category 2 peptides, but no formal change published as of March 2026.
Health Canada
Not authorized as a therapeutic product. No DIN assigned.
WADA (Competitive Athletes)
Not explicitly named on the 2024–2025 Prohibited List. However, could fall under the S2.3 catch-all clause (substances affecting regenerative capacity) or S0 (Non-Approved Substances). Athletes should treat its status as ambiguous and high-risk.
Requires free account · 7-day trial included