Thymosin Beta-4
Also known as: TB4, Tβ4, Tβ4 full-length
Thymosin Beta-4 is a research compound not approved for human use. For informational purposes only.
Overview
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.
Research Summary
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.
Dosing Range
low
500mcg
moderate
1000mcg
high
2000mcg
Units: mcg · Frequency: 2–3x weekly
Dosing ranges are aggregated from preclinical research and community protocols. Not medical dosing guidance.
Administration Routes
Reconstitution Notes
Reconstitute with bacteriostatic water. Common concentration: 5mg per 2mL BAC water (2.5mcg/µL). Highly sensitive to heat — store lyophilized powder refrigerated; stable 28 days after reconstitution when refrigerated.Step-by-step reconstitution guide →
Supplies you'll need
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Reported Side Effects
- 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)
Research Papers
3 peer-reviewed sourcesCommunity Experiences
Aggregated from public forums. Anecdotal — not clinical evidence.
Community comparisons of TB4 (full-length) vs TB-500 (fragment), injury repair protocols.
View original threadOverview
Thymosin Beta-4 is one of the most abundant intracellular peptides in the body, found at high concentrations wherever tissue repair is occurring. The name "TB-500" that circulates in research communities refers specifically to the active fragment (residues 17–23: Ac-LKKTETQ), which preserves much of TB4's healing activity in a shorter, more bioavailable form.
TB4 vs TB-500: The Key Distinction
| | TB4 (Full-length) | TB-500 (Fragment 17-23) | |-|------------------|------------------------| | Length | 43 amino acids | 7 amino acids | | Sequence includes | Full actin-binding domain + immune modulatory regions | Core actin-binding LKKTET motif | | Half-life | Shorter (larger molecule) | Longer effective duration | | Research availability | Less common, higher cost | More widely available | | Activity | Broader (cardiac, neural, wound) | Primarily musculoskeletal |
For most musculoskeletal repair protocols, TB-500 is used. For cardiac and neurological applications, full-length TB4 is the research focus.
Mechanism
TB4's primary function is G-actin sequestration. It binds to unpolymerized actin monomers (G-actin), regulating the pool available for cytoskeletal assembly. This controls:
- Cell migration speed (essential for wound closure)
- Tissue remodeling after injury
- Angiogenesis (new blood vessel formation in healing tissue)
Secondary mechanisms include:
- Anti-inflammatory: Downregulates NF-κB; upregulates anti-inflammatory peptide thymosin beta-4 sulfoxide in the presence of glucocorticoids
- Cardiac stem cell activation: Promotes epicardial progenitor cell mobilization
- Neuroregeneration: Promotes oligodendrocyte survival and axonal repair in CNS injury models
Clinical Development
TB4 has been evaluated in human trials more than most peptides in this class:
- DryEye corneal wound healing (Phase 2 — positive data)
- Pressure ulcers — Phase 2 completed
- Ischemic heart failure (FACT trial) — Phase 2 trends toward benefit
RegeneRx Biopharmaceuticals has held TB4 IND applications — making it one of few research peptides with genuine Phase 2 human safety data.
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