TB-500: Scientific Profile

Publicado el 28 de diciembre de 2025 · Actualizado el 18 de septiembre de 2026

Thymosin β4 (TB-500), a 43-amino-acid N-acetylated peptide of the beta-thymosin class that sequesters G-actin. Its LKKTETQ motif (residues 17-23) modulates the actin cytoskeleton, cell migration and angiogenesis. Reagent for research (CAS 77591-33-4).

TB-500 (English name TB-500) is a synthetic peptide that corresponds to the active region of thymosin beta-4 (Tβ4), a naturally occurring 43-amino-acid protein present in virtually all tissues and fluids. TB-500 reproduces the functional fragment containing the actin-binding domain (the central sequence LKKTETQ), which is the key element of thymosin beta-4's biological activity in research models.

From a structural standpoint, being a synthetic fragment rather than the complete protein, TB-500 is smaller, more stable, and easier to handle in the laboratory, while retaining the motif responsible for actin regulation.

The studied mechanism of action of TB-500 centers on the regulation of actin, one of the fundamental proteins of the cytoskeleton. By sequestering actin monomers (G-actin) and modulating their polymerization, in preclinical models it has been described as influencing cell migration, angiogenesis, and tissue repair and remodeling processes. Because of these properties, it has been studied as a tool in models of wound healing, tissue recovery, and injury response.

In research, TB-500 is used as a tool for studying actin and cytoskeleton dynamics, cell migration, angiogenesis, and tissue repair models. It is frequently used alongside BPC-157 in recovery studies because of their complementary mechanisms.

TB-500 is supplied as a lyophilized powder for reconstitution. Frozen storage protected from light is recommended, along with reconstitution using the sterile diluent indicated in the protocol. This product is offered exclusively as a research reagent (research use only): it is not intended for the diagnosis, prevention or treatment of any disease, nor for human or veterinary consumption.

Mechanism of action

TB-500/Thymosin β4 exerts its effects through multiple mechanisms: (1) G-actin sequestration: Tβ4 is the main monomeric-actin-sequestering protein in mammalian cells, maintaining a pool of G-actin available for dynamic cytoskeletal polymerization during cell migration; (2) Promotion of cell migration: it facilitates migration of endothelial progenitor cells (EPCs), keratinocytes, muscle satellite cells, and cardiac stem cells toward injury sites; (3) Induction of angiogenesis: it increases blood vessel formation through upregulation of VEGF and activation of endothelial cells; (4) Inflammatory modulation: it reduces expression of proinflammatory cytokines (TNF-α, IL-6) and increases anti-inflammatory markers; (5) Inhibition of apoptosis: via downregulation of caspase-9 and upregulation of Bcl-2 in ischemic cardiomyocytes; (6) Stem cell stimulation: it activates epicardial Sca-1+ stem cells in murine infarction models. The LKKTETQ structure is the actin-binding motif; the N-acetyl group at serine 1 is crucial for stability. Plasma half-life: ~2 hours (TB-500), 0.5-1 hour (full Tβ4). Elimination via proteolytic catabolism. Subcutaneous bioavailability: ~70%.

Mechanism summary

It sequesters monomeric G-actin through the LKKTETQ motif (residues 17-23), inhibiting actin polymerization; in preclinical and in vitro models it promotes cell migration, angiogenesis, MMP modulation and anti-inflammatory tissue repair.

Estudios Clínicos (9)

Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applications (Goldstein AL, et al. · Expert Opinion on Biological Therapy · 2012) — Review of thymosin beta-4 (TB-500) in tissue repair and regenerative medicine. PMID 22074294.
Thymosin β4 activates ILK and promotes cardiac migration, survival, and repair (Bock-Marquette I, Saxena A, White MD, et al. · Nature · 2004) — Study in murine infarction models demonstrating that Tβ4 activates integrin-linked kinase and promotes cardiomyocyte survival. PMID 15565145.
Thymosin β4 accelerates wound healing (Malinda KM, Sidhu GS, Mani H, et al. · Journal of Investigative Dermatology · 1999) — Study in rat dermal wound-healing models, evaluating topical and systemic application of Tβ4. PMID 10469335.
Thymosin beta 4 promotes corneal wound healing and decreases inflammation in vivo following alkali injury (Sosne, et al. · Experimental Eye Research · 2002) PMID 11950239.
A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers. (Ruff D, et al. · Ann N Y Acad Sci · 2010) PMID 20536472.
The effect of thymosin treatment of venous ulcers. (Guarnera G, et al. · Ann N Y Acad Sci · 2010) PMID 20536470.
Thymosin beta-4 and venous ulcers: clinical remarks on a European prospective, randomized study on safety, tolerability, and enhancement on healing. (Guarnera G, et al. · Ann N Y Acad Sci · 2007) PMID 17495250.
Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential (Esposito, et al. · Drug Testing and Analysis · 2012) PMID 22962027.
Solid-phase extraction of small biologically active peptides on cartridges and microelution 96-well plates from human urine (Semenistaya, et al. · Drug Testing and Analysis · 2016) PMID 26472487.

Warnings

TB-500 is a compound exclusively for research use (RUO); the following warnings and handling considerations apply to its use in the laboratory:

Experimental agent without regulatory approval
Theoretical risk of promoting tumor angiogenesis
Human clinical data limited to phase 2 trials with mixed results
No chronic toxicity studies in humans
Does not replace conventional medical care
Use exclusively in validated research protocols
Active neoplasms (theoretical risk of tumor promotion)
Hypersensitivity to the peptide
Pregnancy and lactation (no data)

Technical data

CAS: 77591-33-4
Molecular formula: C212H350N56O78S
Molecular weight: 4963.44 Da
Compound type: peptide
Storage: -20 °C liofilizado; 2-8 °C reconstituido
Shelf life (lyophilized): 24 months at 2-8°C
Shelf life (reconstituted): 14-21 days at 2-8°C with bacteriostatic preservative
Light-sensitive: No

Available for research

TB-500 is available as a research-use-only (RUO) reagent with HPLC-verified purity and a per-batch COA:

Frequently asked questions about TB-500

What is TB-500?

Thymosin β4 (TB-500), an N-acetylated 43-amino-acid peptide of the beta-thymosin class that sequesters G-actin. Its LKKTETQ motif (residues 17-23) modulates the actin cytoskeleton, cell migration, and angiogenesis.

What is the mechanism of action of TB-500?

What is TB-500 investigated for?

In preclinical research, TB-500 is studied primarily in: Research on muscle repair; Dermal wound-healing models; Studies of cardiac regeneration. Material exclusively for scientific research.

What are the chemical properties of TB-500?

Molecular formula C212H350N56O78S; molecular weight 4963.44 Da; CAS number 77591-33-4.

How is TB-500 stored?

Condiciones de conservación: -20 °C liofilizado; 2-8 °C reconstituido; estabilidad liofilizado: 24 meses a 2-8°C; una vez reconstituido: 14-21 días a 2-8°C con conservante bacteriostático.

What routes of administration are studied for TB-500?

In research models the following are described: Subcutaneous, Intramuscular. Use is exclusively for scientific research.