LL-37

Immune support Research compound (not approved for human use)

Human cathelicidin antimicrobial peptide · also known as Cathelicidin LL-37, hCAP-18 (37-residue fragment)

For reference only — not medical advice. Figures are commonly reported values compiled from published sources and may be wrong or out of date. Many compounds listed are not approved for human use. Talk to a licensed clinician before using any compound.

LL-37 is the 37-residue peptide released from the human protein hCAP-18. It is part of the innate immune system, with direct antimicrobial activity and a broad set of immunomodulatory effects. It is categorized here as immune because its best-documented role is host defense, even though some of its clinical work concerns wound healing.

Commonly reported dosing (5 mg vial)

Reconstituted with 3 mL → 1.667 mg/mL.

Phase	Dose	Volume	U-100 units
Starting	50 mcg	0.03 mL	3
Standard	200 mcg	0.12 mL	12
Higher	400 mcg	0.24 mL	24

Frequency: Once daily, subcutaneous (sometimes 5 days on, 2 off) · Half-life: Short; not well characterized for subcutaneous use

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Commonly reported dose escalation

Weeks	Dose	Volume	U-100 units
Weeks 1-1	50 mcg	0.03 mL	3
Weeks 2-2	100 mcg	0.06 mL	6
Weeks 3-3	150 mcg	0.09 mL	9
Weeks 4-4	200 mcg	0.12 mL	12
Weeks 5-5	250 mcg	0.15 mL	15
Weeks 6-6	300 mcg	0.18 mL	18
Weeks 7-7	350 mcg	0.21 mL	21
Week 8+	400 mcg	0.24 mL	24

Higher steps may need a larger vial or more than one draw. Escalation schedules vary; dosing decisions belong to a licensed clinician.

Commonly reported reconstitution steps

Vials are usually brought to room temperature (about 15-20 minutes) first.
3 mL of bacteriostatic water is added slowly down the inside wall of the 5 mg vial.
The vial is swirled gently until clear, not shaken.
This gives 1.67 mg/mL. Mixed vials are typically labeled with the date and refrigerated.

Storage

Before mixing: Sealed vials are commonly stored refrigerated (2-8 °C) and protected from light, or frozen (about -20 °C) for long-term storage.

After mixing: Reconstituted solution is commonly kept refrigerated (2-8 °C), protected from light, and not frozen.

Commonly used within 28 days of mixing.

How it works

Beyond disrupting microbial membranes, LL-37 acts as a chemoattractant for neutrophils, monocytes and some T cells and engages several receptors on immune and epithelial cells. These actions are linked in laboratory work to cytokine release, neutralizing bacterial endotoxin and stimulating cell migration and new-vessel formation.

Researched for

Studied for antibacterial and antibiofilm activity in laboratory models.
Investigated topically in a randomized phase 2 trial in hard-to-heal venous leg ulcers.
Examined for roles in skin barrier defense, inflammation and angiogenesis in preclinical work.

Notes

Published human clinical work used topical ulcer applications, not subcutaneous injection; the escalating schedule shown reflects peptide-protocol charts, not a clinical trial.
LL-37 is described as pleiotropic: it can promote or dampen inflammation depending on context, and its role in some cancers is debated in the literature.
Injection-site reactions and inflammatory responses are reasons for caution commonly raised in the research discussion.