LL-37 vs Thymosin Beta-4
A neutral, side-by-side comparison of two healing & recovery peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
LL-37
LL-37 is the only human cathelicidin — a host defense peptide produced by neutrophils, epithelial cells, and macrophages in response to infection and inflammation. It functions simultaneously as a broad-spectrum antimicrobial agent and an immune-modulatory signaling molecule. Research interest has expanded dramatically since COVID-19 studies linked low LL-37 levels to severe outcomes, and gut health research identified it as a key regulator of intestinal barrier integrity.
Full profileThymosin Beta-4
Thymosin Beta-4 (TB4) is the full-length 43-amino acid peptide produced naturally in high concentrations in platelets, wound fluid, and regenerating tissue. It is the parent molecule from which the popular TB-500 research peptide (the 17-23 fragment Ac-LKKTETQ) is derived. TB4 promotes actin polymerization, accelerates wound healing, reduces inflammation, and supports cardiac and neurological repair in preclinical models.
Full profile| LL-37 | Thymosin Beta-4 | |
|---|---|---|
| Category | Healing & Recovery | Healing & Recovery |
| Also known as | Cathelicidin LL-37, hCAP-18 C-terminal fragment, CRAMP (murine equivalent) | TB4, Tβ4, Tβ4 full-length |
| Evidence | Research-stage | Investigational (in trials) |
| Dosing range | 100mcg–500mcg mcg, Daily or 3–5x weekly | 500mcg–2000mcg mcg, 2–3x weekly |
| Administration | Subcutaneous injection, Intranasal (for respiratory applications), Topical (wound care) | Subcutaneous injection, Intramuscular injection, Intravenous (clinical studies only) |
| Key side effects | Injection site redness and irritation (common — pro-inflammatory at injection site), Transient flu-like symptoms (immune activation), Local induration, High doses may be cytotoxic — dose-response curve is non-linear | Injection site discomfort (mild), Transient fatigue post-injection, Headache (uncommon), Theoretically may accelerate growth of pre-existing malignant tumors (promotes angiogenesis and cell migration — use with caution) |
| Cited sources | 3 references | 3 references |
Key differences
- Evidence level differs: LL-37 is research-stage, while Thymosin Beta-4 is investigational (in trials).
- Administration: LL-37 — Subcutaneous injection, Intranasal (for respiratory applications), Topical (wound care); Thymosin Beta-4 — Subcutaneous injection, Intramuscular injection, Intravenous (clinical studies only).
- Frequency: LL-37 is typically Daily or 3–5x weekly; Thymosin Beta-4 is 2–3x weekly.
How each works
LL-37
LL-37 exerts antimicrobial activity by disrupting bacterial membranes via electrostatic interaction with negatively charged lipopolysaccharide — effective against gram-positive and gram-negative bacteria, fungi, and enveloped viruses including SARS-CoV-2 in vitro. Beyond direct antimicrobial action, LL-37 modulates innate immunity through TLR4 signaling, promotes wound healing via EGFR and FPRL1 receptor activation, and has demonstrated anti-biofilm activity against P. aeruginosa and S. aureus. Vitamin D is the primary driver of endogenous LL-37 production.
Thymosin Beta-4
TB4's primary mechanism involves sequestering G-actin monomers (via its LKKTET actin-binding domain) to regulate actin cytoskeleton dynamics — critical for cell migration, wound closure, and tissue remodeling. Clinical trials have evaluated TB4 for corneal wound healing (Phase 2), pressure ulcers, and cardiac repair after MI. The FACT trial investigated TB4 in patients with ischemic heart failure, showing trends toward improved cardiac function. Anti-inflammatory effects are mediated partly through NF-κB pathway downregulation.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.