Also known as: Thymosin Beta-4 fragment (17-23), TB4 fragment, TB500, TB 500, Ac-LKKTETQ
TB-500 is the name the market and the FDA use for a short synthetic fragment of thymosin beta-4: the seven-amino-acid, N-acetylated actin-binding sequence Ac-LKKTETQ (residues 17 to 23). Thymosin beta-4 itself is a 43-amino-acid peptide (about 4963 Da acetylated) and one of the most abundant intracellular actin-sequestering molecules in mammalian cells.
Reconstitution Calculator for TB-500
Pre-filled · 5mg vial · 2500mcg dose
Overview
At A Glance
Actin Sequestration and Cytoskeletal Dynamics…
Overview
TB-500 is the name the market and the FDA use for a short synthetic fragment of thymosin beta-4: the seven-amino-acid, N-acetylated actin-binding sequence Ac-LKKTETQ (residues 17 to 23). Thymosin beta-4 itself is a 43-amino-acid peptide (about 4963 Da acetylated) and one of the most abundant intracellular actin-sequestering molecules in mammalian cells. The two are not the same molecule. Analytical work on internet-sold TB-500 found products that did not match their descriptions (PMID: 36482504), and a 2024 metabolite study states that the biological effects of the acetylated TB-500 fragment have not been documented (PMID: 38382158). The sequence and mass on a lot certificate of analysis are the only way to know which form a vial holds. The foundational review by Goldstein et al. (2005) established full-length thymosin beta-4 as a multifunctional regenerative peptide with roles spanning wound healing, angiogenesis, anti-inflammation, and cardiac repair. Unlike many bioactive peptides, thymosin beta-4 is not a hormone or cytokine but rather an intracellular actin-regulatory protein that, when released extracellularly following injury, initiates paracrine signaling cascades that drive tissue repair. Most of what follows is full-length thymosin beta-4 data; the fragment's efficacy data appears only in the wound-healing paragraph. Thymosin beta-4 has been studied extensively in preclinical models of cardiac injury. Bock-Marquette et al. (2004) demonstrated that thymosin beta-4 promotes survival of cardiomyocytes after experimental myocardial infarction in mice, reduces infarct size, and improves cardiac function. The mechanism involves activation of the Akt (protein kinase B) survival pathway and migration of cardiomyocytes and endothelial cells toward the injury. These findings positioned thymosin beta-4 as a candidate cardiac repair agent, though clinical translation has been limited. In wound healing research, thymosin beta-4 accelerates dermal wound closure by promoting keratinocyte and endothelial cell migration, increasing angiogenesis, and reducing inflammation at the wound site. Philp et al. (2003) showed that topical thymosin beta-4 significantly accelerated full-thickness wound closure in diabetic and aged mouse models, and in the same paper the free seven-residue fragment LKKTETQ promoted repair in aged animals comparable to the parent peptide (PMID: 12581423). That one mouse study, plus in-vitro assays, is the fragment record; there is no human data for the fragment. Thymosin beta-4 has also shown efficacy in corneal wound healing models. Sosne et al. demonstrated that thymosin beta-4 eye drops accelerate corneal epithelial wound closure and reduce inflammation after chemical or mechanical injury, leading to ophthalmic clinical trials (Phase 2 and Phase 3, RGN-259) for dry eye and neurotrophic keratopathy. This is the most advanced clinical development program for any thymosin beta-4-based therapeutic, and it is topical. TB-500 is not FDA-approved for any human therapeutic indication. It is a doping-control target in racing horses (PMID: 23084823) and is used in the human peptide biohacking community for musculoskeletal recovery, wound healing, and anti-inflammatory effects, on the strength of the full-length peptide literature rather than any human fragment data.
Potential Research Fields
Chemical Information
IUPAC Name
N-acetyl-L-leucyl-L-lysyl-L-lysyl-L-threonyl-L-alpha-glutamyl-L-threonyl-L-glutamine
CAS Number
77591-33-4
Molecular Formula
C38H68N10O14 (Ac-LKKTETQ); full-length thymosin beta-4 is C212H350N56O78S
Molecular Mass
889.0 g/mol (Ac-LKKTETQ); 846.97 g/mol (LKKTETQ, free); full-length thymosin beta-4 4963.4 g/mol acetylated
Amino Acid Sequence
Dosing & Protocols
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Research
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Interactions
Interaction Matrix
Contraindications
Active cancer (theoretical concern with tissue growth promotion). Pregnancy or breastfeeding. Known hypersensitivity to thymosin beta-4 fragments.
Research Disclaimer
This interaction data is compiled from published research and community reports. It may not be exhaustive. Always consult a healthcare professional before combining compounds.
$29.00
up to $64.99
$4.9000
4
8
vial
Tracking since Mar 13, 2026 · 8 data points
Price History
4 data pointsVendors Selling TB-500
Ion Peptide
BioMyst Labs
VANDL Labs
Disguised Alpha
How we score these vendors
Every supplier above is graded 0 to 100 on COA verification, payment transparency, shipping, reviews, and active listings. Methodology published, no pay-to-rank.
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5/18/2026Research Score
1,039 PubMed results
Quality Indicators
Data Completeness
100%Research Volume
Well-researched compound
Quick Facts
Half-Life
Plasma half-life is short - full-length thymosin beta-4 clears on the order of hours, while the short LKKTETQ actin-binding fragment clears within minutes. Tissue-level regenerative effects persist substantially longer than plasma exposure.
Molecular Weight
889.0 g/mol (Ac-LKKTETQ); 846.97 g/mol (LKKTETQ, free); full-length thymosin beta-4 4963.4 g/mol acetylated
Administration
Subcutaneous, Intramuscular
CAS Number
77591-33-4
Trial Phase
Phase 2
Safety Profile
Common Side Effects
- • Injection site discomfort (subcutaneous administration)
- • Mild fatigue or lethargy in the days following initial doses
- • Temporary head rush or flushing reported anecdotally
Research Disclaimer
This information is for educational and research purposes only. Not intended as medical advice. Consult a healthcare professional before use.
The Wolverine Stack: BPC-157 + TB-500 Protocol Guide
Complete synergistic recovery protocol: dosing tables, cycling, reconstitution, and 9 PubMed citations.
Frequently Asked Questions
What is TB-500 used for in research?
TB-500 is the name the market and the FDA use for a short synthetic fragment of thymosin beta-4: the seven-amino-acid, N-acetylated actin-binding sequence Ac-LKKTETQ (residues 17 to 23). Thymosin beta-4 itself is a 43-amino-acid peptide (about 4963 Da acetylated) and one of the most abundant intracellular actin-sequestering molecules in mammalian cells. The two are not the same molecule. Analytical work on internet-sold TB-500 found products that did not match their descriptions (PMID: 36482504), and a 2024 metabolite study states that the biological effects of the acetylated TB-500 fragment have not been documented (PMID: 38382158). The sequence and mass on a lot certificate of analysis are the only way to know which form a vial holds.
The foundational review by Goldstein et al. (2005) established full-length thymosin beta-4 as a multifunctional regenerative peptide with roles spanning wound healing, angiogenesis, anti-inflammation, and cardiac repair. Unlike many bioactive peptides, thymosin beta-4 is not a hormone or cytokine but rather an intracellular actin-regulatory protein that, when released extracellularly following injury, initiates paracrine signaling cascades that drive tissue repair. Most of what follows is full-length thymosin beta-4 data; the fragment's efficacy data appears only in the wound-healing paragraph.
Thymosin beta-4 has been studied extensively in preclinical models of cardiac injury. Bock-Marquette et al. (2004) demonstrated that thymosin beta-4 promotes survival of cardiomyocytes after experimental myocardial infarction in mice, reduces infarct size, and improves cardiac function. The mechanism involves activation of the Akt (protein kinase B) survival pathway and migration of cardiomyocytes and endothelial cells toward the injury. These findings positioned thymosin beta-4 as a candidate cardiac repair agent, though clinical translation has been limited.
In wound healing research, thymosin beta-4 accelerates dermal wound closure by promoting keratinocyte and endothelial cell migration, increasing angiogenesis, and reducing inflammation at the wound site. Philp et al. (2003) showed that topical thymosin beta-4 significantly accelerated full-thickness wound closure in diabetic and aged mouse models, and in the same paper the free seven-residue fragment LKKTETQ promoted repair in aged animals comparable to the parent peptide (PMID: 12581423). That one mouse study, plus in-vitro assays, is the fragment record; there is no human data for the fragment.
Thymosin beta-4 has also shown efficacy in corneal wound healing models. Sosne et al. demonstrated that thymosin beta-4 eye drops accelerate corneal epithelial wound closure and reduce inflammation after chemical or mechanical injury, leading to ophthalmic clinical trials (Phase 2 and Phase 3, RGN-259) for dry eye and neurotrophic keratopathy. This is the most advanced clinical development program for any thymosin beta-4-based therapeutic, and it is topical.
TB-500 is not FDA-approved for any human therapeutic indication. It is a doping-control target in racing horses (PMID: 23084823) and is used in the human peptide biohacking community for musculoskeletal recovery, wound healing, and anti-inflammatory effects, on the strength of the full-length peptide literature rather than any human fragment data.
What forms does TB-500 come in?
TB-500 is available in vial form.
How much does TB-500 cost?
Prices start at $29.00 across 4 vendors.
How do I compare TB-500 vendors?
Compare prices, payment methods, shipping, and COA scores across 4 vendors.
Research Tools
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Research Benches
Reference pages that put TB-500 next to the compounds people pair it with: roles, evidence, overlap and conflicts. No dosing. Research use only.
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