Side-by-side · Research reference

LL-37vsSS-31

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 3HUMAN-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

SS-31

Cardiolipin-binding · Mitochondrial protective

40 mgDaily doseSzeto 2014

Phase 3Evidence levelSzilagyi 2009 Szeto 2014

~3 hrHalf-life

SQ · Abdomen · Once daily

01Mechanism of Action

Parameter

LL-37

SS-31

Primary target

Bacterial membranes · Phosphatidylserine-exposed cellsHe 2026 Lu 2026

Cardiolipin in inner mitochondrial membraneSzeto 2014

Pathway

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

Cardiolipin binding → cristae stabilisation → ETC integrity → reduced ROS + preserved ATP synthesisSzeto 2014 Szilagyi 2009

Downstream effect

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

Mitochondrial bioenergetic preservation; cardio-, neuro-, and reno-protective effects in animal + clinical studiesSzeto 2014

Feedback intact?

—

Origin

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

Synthetic tetrapeptide D-Arg-Dmt-Lys-Phe-NH₂; cell-permeable, mitochondrial-selectiveSzeto 2014

Antibody development

—

02Dosage Protocols

Parameter

LL-37

SS-31

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

Multiple Phase 3 trials (Barth, AMD, ischemia-reperfusion)Szeto 2014 Szilagyi 2009

Standard dose

—

40 mg / day SQ (clinical trials)Szeto 2014

Anecdotal community range 5-10 mg/day. Phase 3 trials use 40 mg.

Frequency

—

Once daily

Lower / starter dose

—

5 mg / day (anecdotal)

Duration

—

Indefinite for mitochondrial disease; cycled for healthspan use

Reconstitution

—

Bacteriostatic water

Timing

—

Morning fasted preferred; pre-workout for exercise-induced mitochondrial stress

Half-life

—

~3 h plasma; tissue uptake longer

04Side Effects & Safety

Parameter

LL-37

SS-31

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

—

Injection site reaction

—

Erythema, mild pruritus

GI symptoms

—

Nausea (uncommon)

Headache

—

Reported in some Phase 3 trials

Cardiovascular

—

Cardio-protective in studies; no signal of harm

Long-term safety

—

Phase 3 data over 24+ months; no major safety signalsSzeto 2014

Pregnancy / OB

—

Avoid — insufficient data

Absolute Contraindications

LL-37

—

SS-31

·Pregnancy / breastfeeding
·Hypersensitivity to peptide

Relative Contraindications

LL-37

·Active autoimmune disease (theoretical immune dysregulation)

SS-31

·None established

05Administration Protocol

Parameter

LL-37

SS-31

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 bacteriostatic water per label. Light-protected handling.

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 or thigh. 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

Morning fasted; pre-workout for exercise-augmented mitochondrial stress.

4. Storage

—

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

5. Needle

—

29–31G, 4–8 mm insulin syringe.

06Stack Synergy

LL-37

— no documented stacks

SS-31

+ MOTS-c

Moderate

View MOTS-c →

SS-31 and MOTS-c address mitochondrial decline through complementary axes. SS-31 protects existing mitochondrial structure (cardiolipin binding, cristae stabilisation). MOTS-c upregulates AMPK/PGC-1α, triggering biogenesis of new mitochondria. Together they pair preservation with renewal — anecdotally favoured in healthspan and post-cardio-event recovery protocols.

SS-31: 5–10 mg SQ · daily morning
MOTS-c: 5 mg SQ · 2× per week pre-workout
Primary benefit: Mitochondrial preservation + biogenesis