Research library
TB-500 and Thymosin β4 Research Overview: Actin Sequestration, Repair Models and Evidence Boundaries
- Compiled by:
- Peptide Pilots Scientific Content Team
- Reviewed by:
- Peptide Pilots Quality & Compliance review
- Last revised:
How does TB-500 relate to thymosin β4, and which repair-related findings come from the fragment rather than the full protein?
Thymosin β4 (Tβ4) is a 43-amino-acid intracellular actin-sequestering peptide encoded by TMSB4X, and it is the molecule that has been studied in registered human trials, including corneal and dermal wound programmes. TB-500 as sold for laboratory use is generally a short synthetic fragment containing the central actin-binding motif (commonly the LKKTETQ region). Most published mechanistic and outcome data describe full-length Tβ4; fragment-specific data are far sparser. Any citation of Tβ4 literature in support of TB-500 should state explicitly which molecule was studied.
This page is an educational literature summary for laboratory professionals. It is not medical advice, not a description of product performance, and it does not describe or endorse human or veterinary use. Materials referenced are supplied for controlled laboratory research only.
What is TB-500 (thymosin β4 fragment)?
Thymosin β4 is a highly abundant, unstructured cytosolic peptide that binds monomeric G-actin in a 1:1 complex and buffers the pool available for filament polymerisation, thereby influencing cell motility and cytoskeletal remodelling.
TB-500 refers in practice to a synthetic fragment retaining the actin-binding heptapeptide motif, used in laboratory studies of cell migration, angiogenesis and tissue-repair models. It is not a naturally occurring circulating hormone and should not be described as one.
TB-500 (thymosin β4 fragment) names and identifiers
Also referred to as: Tβ4 fragment; Ac-SDKP-related research peptide; thymosin beta-4 (7-24) fragment; TB4-Frag
| Parent protein | Thymosin beta-4, gene TMSB4X, UniProt P62328 |
|---|---|
| Full-length Tβ4 length | 43 amino acids, ≈4963 g/mol |
| Key functional motif | LKKTETQ (actin-binding region) |
| Common fragment CAS | 77591-33-4 (Tβ4 fragment 17-23 acetate, motif-containing) |
| Related cleavage product | Ac-SDKP, an N-terminal tetrapeptide with separately documented anti-fibrotic literature |
| Registry records | ClinicalTrials.gov registrations for RGN-259 (Tβ4 ophthalmic) and RGN-352 |
TB-500 (thymosin β4 fragment) research background
Thymosin β4 was originally isolated from thymic tissue in the early 1980s and initially misclassified as a thymic hormone; later work established it as a ubiquitous intracellular actin-sequestering peptide rather than a secreted endocrine factor.
Interest in tissue repair arose from reports that Tβ4 promotes endothelial and keratinocyte migration and reduces inflammatory signalling in injury models, followed by cardiac work reporting epicardial cell activation after infarction in mice.
Clinical development has centred on ophthalmic formulations of full-length Tβ4 for dry-eye and neurotrophic keratopathy. The scientific question relevant to TB-500 specifically is whether the isolated motif reproduces the activity of the intact peptide, and published direct comparisons are limited.
Proposed TB-500 (thymosin β4 fragment) mechanisms and pathways
Evidence is separated by study type. In-vitro and animal findings describe model systems and do not establish equivalent behaviour in humans.
TB-500 (thymosin β4 fragment) in-vitro and cell-based evidence
- Full-length Tβ4 binds G-actin and inhibits its polymerisation, altering the free monomer pool and downstream cytoskeletal dynamics.
- Reported increases in endothelial and keratinocyte migration in scratch and Boyden-chamber assays, with associated changes in laminin-5 and matrix metalloproteinase expression.
- Reported downregulation of NF-κB-associated inflammatory signalling in stimulated cell models.
- Fragment studies indicate the LKKTETQ motif carries part of the migratory activity, though intact-peptide comparisons within a single experiment are uncommon.
TB-500 (thymosin β4 fragment) animal-model evidence
- Murine myocardial infarction studies reported epicardial progenitor activation and improved functional endpoints, findings that prompted substantial follow-up work with mixed replication outcomes.
- Rodent and rabbit corneal injury models report faster epithelial closure and reduced inflammatory infiltration.
- Dermal wound and dermal-fibrosis models report altered collagen deposition, with direction of effect varying by model.
Published TB-500 (thymosin β4 fragment) human-study evidence
- Registered human trials have used full-length Tβ4, mainly as topical ophthalmic RGN-259, with reported endpoints in dry-eye and neurotrophic keratopathy studies.
- No registered human efficacy trial of the short TB-500 fragment as sold for research use has been published.
- Tβ4 and its fragment appear on the World Anti-Doping Agency prohibited list, which is a regulatory classification rather than a statement about efficacy.
Published TB-500 (thymosin β4 fragment) studies
| Study | Model / type | Research question | Main observation | Citation |
|---|---|---|---|---|
| Bock-Marquette et al., cardiac repair | Mouse myocardial infarction | Does Tβ4 influence cardiomyocyte survival and cardiac function after infarction? | Reported Akt activation, increased myocyte survival and improved functional measures. | Nature, 2004 |
| Smart et al., epicardial progenitor study | Adult mouse heart | Can Tβ4 activate adult epicardium-derived progenitor cells? | Reported reactivation of embryonic epicardial programmes; later independent work produced mixed replication. | Nature, 2007 |
| Sosne et al., corneal wound healing | Rodent and rabbit corneal injury; subsequent human ophthalmic trials | Does topical Tβ4 accelerate corneal epithelial repair? | Reported faster epithelial closure and reduced inflammation; translated into registered ophthalmic trials. | Clinical Ophthalmology, 2010 |
| Actin-binding structural work | Biophysical and structural studies of Tβ4–actin complexes | How does Tβ4 sequester G-actin? | Defined the 1:1 sequestration mode and the contribution of the central motif to binding. | EMBO Journal, 2004 |
Limitations of the TB-500 (thymosin β4 fragment) evidence
- Most cited evidence concerns full-length Tβ4, not the short fragment marketed as TB-500; equivalence between the two is assumed more often than demonstrated.
- Cardiac progenitor findings have a contested replication history, and later lineage-tracing studies challenged parts of the original interpretation.
- Vendor-supplied fragments vary in exact sequence, N-terminal acetylation and C-terminal amidation, which complicates cross-study comparison.
- As an intracellular actin-binding peptide, the route by which extracellular administration produces the reported effects is not fully explained; a defined cell-surface receptor has not been established.
- Human data are confined to topical ophthalmic use of the intact protein; systemic human efficacy or safety data are absent.
TB-500 (thymosin β4 fragment) laboratory characteristics
Handling and analytical information reported in the literature and in supplier documentation. Values apply to laboratory materials and are not directions for any other use.
| Appearance | White lyophilised powder |
|---|---|
| Solubility | Readily soluble in water and aqueous buffers; the peptide is highly hydrophilic and intrinsically disordered |
| Lyophilised storage | Commonly stored at −20 °C, desiccated |
| Reconstituted handling | Refrigerated, protected from light, freeze–thaw cycling avoided |
| Analytical testing | RP-HPLC purity and MS identity; sequence verification is particularly relevant because fragment definitions differ between suppliers |
| Stability considerations | No cysteine residues; oxidation of methionine and N-terminal degradation are the routes usually monitored in full-length preparations |
Frequently asked TB-500 (thymosin β4 fragment) research questions
Is TB-500 the same as thymosin β4?
No. Thymosin β4 is the full 43-residue peptide. TB-500 as supplied for research is normally a short synthetic fragment containing the LKKTETQ actin-binding motif.
What is the actin-sequestering mechanism?
Full-length Tβ4 forms a 1:1 complex with monomeric G-actin, reducing the monomer pool available for polymerisation and thereby influencing cytoskeletal dynamics and cell migration.
Have human trials been conducted?
Registered human trials used full-length thymosin β4, principally topical ophthalmic formulations. The short fragment has no published registered efficacy trial.
Why does exact sequence matter when citing this literature?
Because fragment length, acetylation and amidation differ between preparations, and those differences affect stability and reported activity. Certificates of analysis should be checked against the sequence used in the cited study.
TB-500 (thymosin β4 fragment) primary references
- Bock-Marquette I, Saxena A, White MD, DiMaio JM, Srivastava D (2004). Thymosin β4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature. https://doi.org/10.1038/nature03000
- Smart N, Risebro CA, Melville AAD, et al. (2007). Thymosin β4 induces adult epicardial progenitor mobilization and neovascularization. Nature. https://doi.org/10.1038/nature05383
- Sosne G, Qiu P, Kurpakus-Wheater M (2010). Thymosin beta 4: a novel corneal wound healing and anti-inflammatory agent. Clinical Ophthalmology. https://doi.org/10.2147/OPTH.S10474
- Irobi E, Aguda AH, Larsson M, et al. (2004). Structural basis of actin sequestration by thymosin-β4: implications for WH2 proteins. EMBO Journal. https://doi.org/10.1038/sj.emboj.7600372
- PubMed literature index (2026). Current indexed literature for thymosin beta 4. US National Library of Medicine. https://pubmed.ncbi.nlm.nih.gov/?term=thymosin+beta+4
Authorship and revision
Compiled from primary literature and public databases. Every factual statement on this page is traceable to a listed reference. Compiled by Peptide Pilots Scientific Content Team; documentation and compliance review by Peptide Pilots Quality & Compliance review. First published ; last revised . Pages are revised when the cited literature changes materially.
Catalogue reference
Peptide Pilots supplies TB-500 as a laboratory reagent with per-lot RP-HPLC and mass-spectrometry documentation. Quantities, testing, packaging and fulfilment details are on the catalogue page.
Related catalogue products
Laboratory reagents supplied by Peptide Pilots from the Recovery, Tissue & Inflammation Research tier. Research use only; not for human or veterinary use.
