Side-by-side · Research reference

LL-37vsMelanotan-II

Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.

AHuman-MechanisticHUMAN-REVIEWED15/35 cited

BPhase 1HUMAN-REVIEWED9/43 cited

LL-37

Cathelicidin · Human AMP

Broad-spectrumAntimicrobial activity

Membrane disruptionPrimary mechanismLu 2026 He 2026

Innate immunityHost defense rolePinheiro 2026 Zhang 2026

Endogenous · Secreted at inflammation sites

Melanotan-II

MC1R + MC4R agonist · Tanning + sexual response

0.25–1.0 mgPer doseDorr 1996

Phase 1Evidence levelDorr 1996

~1 hrHalf-life

SQ · Abdomen · Loading 5–7 days, then maintenance

01Mechanism of Action

Parameter

LL-37

Melanotan-II

Primary target

Bacterial membranes · Phosphatidylserine-exposed cellsHe 2026 Lu 2026

MC1R (skin) + MC3R + MC4R (CNS sexual / appetite)Dorr 1996

Pathway

hCAP-18 precursor → Proteinase-3 cleavage → LL-37 release → Membrane insertion/disruption

MC1R agonism → melanocyte tyrosinase → eumelanin synthesis. MC4R → autonomic sexual arousal centresDorr 1996 Simerly 2023

Downstream effect

Membrane permeabilization, cytokine induction, autophagy, phagosome-lysosome fusion, chemotaxisAhmad 2026 Zhang 2026

Skin darkening, photo-protection, increased sexual desire / spontaneous erectionDorr 1996

Feedback intact?

—

Origin

Endogenous human cathelicidin (37-AA fragment, residues 134–170 of hCAP-18)

Cyclic 7-AA modified α-MSH analog; designed at University of ArizonaDorr 1996

Antibody development

—

02Dosage Protocols

Parameter

LL-37

Melanotan-II

Endogenous expression

Constitutive in neutrophils, epithelial tissues

Upregulated during infection and inflammation.Pinheiro 2026

—

Exogenous (experimental)

Dose varies by study; antimalarial ~10–50 μM in vitro

No FDA-approved exogenous formulation.

—

Plasma levels (malaria)

Elevated in infected patients and miceHe 2026

Exogenous administration reduced parasitemia in murine models.He 2026

—

Evidence basis

In vitro, animal models, human observational

Phase 1 + anecdotalDorr 1996

Loading phase

—

0.25–0.5 mg/day SQ × 5–7 daysDorr 1996

Builds up to visible tan.

Maintenance

—

0.5–1.0 mg 1–2×/week

After visible tan develops; supports with UV exposure.

Frequency

—

Daily during loading; 1–2× per week maintenance

Lower / starter dose

—

0.1 mg / day

Conservative starter — assess tolerability for nausea.

Duration

—

8–12 weeks per cycle

Reconstitution

—

Bacteriostatic water; protect from light

Timing

—

Evening preferred (24h tan-development cycle)

Half-life

—

~1 hour plasma; effects on melanocytes persist days

04Side Effects & Safety

Parameter

LL-37

Melanotan-II

Cytotoxicity (high dose)

Membrane disruption in host cells at supraphysiological concentrations

—

Pro-inflammatory signaling

Can exacerbate inflammation in certain contexts (context-dependent)Pinheiro 2026

—

Biofilm formation risk

LL-37-DNA complexes may stabilize dental plaque biofilmsTanabe 2026

—

Theoretical cancer risk

Immunomodulatory roles in tumor microenvironment under investigation

—

Nausea

—

Common, especially loading phase

Flushing

—

Common transient

Spontaneous erection

—

Common in men — MC4R cross-effectDorr 1996

Increased mole / freckle pigmentation

—

Existing moles darken; new lesions possible

Melanoma risk

—

Theoretical concern — increased melanocyte activity; CAUTION in melanoma history

Appetite suppression

—

MC4R-mediated; mild

Pregnancy / OB

—

Contraindicated

Absolute Contraindications

LL-37

—

Melanotan-II

·History of melanoma or atypical mole syndrome
·Pregnancy / breastfeeding
·Active uncontrolled hypertension

Relative Contraindications

LL-37

·Active autoimmune disease (theoretical immune dysregulation)

Melanotan-II

·Significant freckling / dysplastic nevus
·Personal or family melanoma history

05Administration Protocol

Parameter

LL-37

Melanotan-II

1. Natural secretion

LL-37 is constitutively expressed in neutrophils and epithelial cells, cleaved from hCAP-18 by proteinase-3 at sites of infection or inflammation.

Add 2 mL bacteriostatic water to 10 mg vial → 5 mg/mL = 500 mcg per 0.1 mL. Light-protected.

2. Experimental formulations

Synthetic LL-37 and derivatives (e.g., SAMP-12aa) tested in vitro and animal models. Administered via topical, intraperitoneal, or intravenous routes in research settings.

SQ — abdomen. Rotate sites.

3. Stability considerations

LL-37 is resistant to pepsin degradation at gastric pH. Synthetic short peptides designed to retain this stability while reducing toxicity.Lu 2026

Evening preferred. UV exposure (sunlight or tanning bed) helps develop tan.

4. Storage

—

Lyophilised: refrigerate, light-protected. Reconstituted: refrigerate ≤30 days.

5. Needle

—

29–31G insulin syringe.