What is TB-500?
TB-500 (also written TB500 or TB 500) is a research name tied to thymosin beta-4, a 43-residue actin-binding peptide found throughout mammalian tissue (Philp et al., 2003). The name does not point to one molecule. Analysis of material sold as TB-500 identified a seven-residue fragment, residues 17 to 23 of thymosin beta-4 with an acetylated N-terminus, Ac-LKKTETQ (Esposito et al., 2012), and a racing laboratory's detection method targets the same fragment (Ho et al., 2012).
Most biological data, however, concern the full-length protein. This guide keeps the two apart, naming the molecule and model behind every finding. Disguised Alpha supplies TB-500 (Thymosin Beta-4) as a lyophilized powder for laboratory research use only. Nothing on this page is guidance for use in people.
TB-500 reference data
| Property | Value |
|---|---|
| Name on the product page | TB-500 (Thymosin Beta-4) |
| Peptide class listed | Thymosin β-4 / fragment |
| Formula, weight and CAS listed | C212H350N56O78S, 4963 g/mol, CAS 77591-33-4 |
| What those values describe | Full-length thymosin beta-4, 43 residues: Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES (PubChem CID 16132341; UniProt P62328) |
| Fragment identified in TB-500 | Ac-LKKTETQ, residues 17 to 23 with an acetylated N-terminus: C38H68N10O14, 889.0 g/mol, CAS 885340-08-9 (PubChem CID 62707662) |
| Amount per vial | 10mg label claim, shown with the certificates on the product page |
| Form | Lyophilized powder |
| Testing | Third-party tested, with the certificate for each lot published on the product page and in the COA portal |
Name, class, formula, weight, CAS number, label amount and storage are from the product page; the sequence is from UniProt and the fragment data from PubChem. The page pairs full-protein data with a "fragment" class, and published analyses of TB-500 found the fragment, so this guide does not assume which molecule a vial holds. The two differ about 5.6-fold in molecular weight, which changes any molarity calculation: confirm identity and measured content on your lot's certificate.
What the research covers
Published work falls into five areas. Each summary names the model and the molecule tested.
What the name TB-500 refers to
A doping-control laboratory analyzed a TB-500 preparation by liquid chromatography and high-resolution mass spectrometry, identified Ac-LKKTETQ, and confirmed it by independent synthesis (Esposito et al., 2012). A racing laboratory described TB-500 as a veterinary preparation whose key ingredient is LKKTETQ with an artificially acetylated N-terminus (Ho et al., 2012). The name is not a reliable guide to content.
Analysis of internet products sold as TB500 and TB1000 found contents not systematically consistent with their descriptions (Delcourt et al., 2023); a 2025 hydrogel study in human corneal cells and an alkali burn model used "TB500" for the unacetylated sequence (Lu et al., 2025); and a 2026 rat study described its TB-500 as synthetic thymosin beta-4 (Biçer et al., 2026).
Metabolism of the acetylated fragment
In vitro incubations identified likely metabolites of Ac-LKKTETQ, and the parent peptide and its metabolites were then detected in urine and plasma from horses that had received TB-500 (Ho et al., 2012). A later study followed TB-500 in human serum, in vitro enzyme systems and rats: in rat urine Ac-LK was the main metabolite over the first six hours, and Ac-LKK remained detectable for up to 72 hours (Rahaman et al., 2024). Models: in vitro enzyme systems, horses and rats.
The 17 to 23 actin-binding motif
Comparing natural protein, fragments and synthetic peptides, one group reported that the seven-residue motif matched the full protein in endothelial cell migration and chick aortic arch sprouting assays at about 50 nM, while peptides lacking part of it were inactive (Philp et al., 2003).
In a second report the same year, a synthetic LKKTETQ peptide promoted repair of full-thickness skin wounds in aged mice comparably to the parent molecule (Philp et al., 2003). In human hepatic stellate cells, the 17 to 23 peptide, but not the 1 to 15 peptide, reduced PDGF-BB driven proliferation and migration (Shah et al., 2018). Models: human and chick cell and tissue assays, mice.
According to a 2024 study, such activities were reported for the unacetylated form, and biological effects of acetylated TB-500 itself had not been documented. In fibroblast culture that study found no cytotoxicity, and a significant scratch-wound effect only for the metabolite Ac-LKKTE (Rahaman et al., 2024).
Full-length thymosin beta-4
Thymosin beta-4 was sequenced from calf thymus in 1981 as a 43-residue peptide with an acetylated N-terminus (Low et al., 1981), and later identified as the peptide holding most unpolymerized actin in resting human platelets, binding actin monomers 1:1 and inhibiting their polymerization (Safer et al., 1991). In a rat full-thickness wound model it increased re-epithelialization, contraction, collagen deposition and angiogenesis, and it stimulated keratinocyte migration in a chamber assay (Malinda et al., 1999).
It formed a complex with PINCH and integrin-linked kinase that activates Akt, and after coronary artery ligation in mice the study reported greater early myocyte survival and improved cardiac function (Bock-Marquette et al., 2004). Models: purified protein, cell culture, rats and mice. None of these used the fragment, and results for the full protein should not be assumed to carry over to it.
Human studies of full-length thymosin beta-4
A randomized, placebo-controlled study in 40 healthy volunteers, with single and then repeated administration over 14 days, reported infrequent mild or moderate adverse events, none serious, and pharmacokinetics proportional to the amount given (Ruff et al., 2010). In a small phase 2 randomized trial in nine patients with severe dry eye, a thymosin beta-4 eye drop reduced ocular discomfort and corneal staining against vehicle (Sosne et al., 2015). Models: healthy volunteers and a phase 2 trial. We found no published human study of the acetylated fragment.
Key studies
- Esposito S, et al. Drug Test Anal. 2012. PMID 22962027. Identification of Ac-LKKTETQ in a TB-500 product, confirmed by synthesis.
- Ho EN, et al. J Chromatogr A. 2012. PMID 23084823. Fragment metabolites in vitro and in equine urine and plasma.
- Rahaman KA, et al. J Chromatogr B Analyt Technol Biomed Life Sci. 2024. PMID 38382158. Metabolites in serum, enzyme systems and rats; fibroblast assays.
- Philp D, et al. FASEB J. 2003. PMID 14500546. Endothelial migration and aortic sprouting assays: the actin-binding motif.
- Philp D, et al. Wound Repair Regen. 2003. PMID 12581423. Diabetic and aged mouse wound models: full protein and LKKTETQ.
- Malinda KM, et al. J Invest Dermatol. 1999. PMID 10469335. Rat wound model and keratinocyte migration (full protein).
- Bock-Marquette I, et al. Nature. 2004. PMID 15565145. Mouse heart: PINCH, integrin-linked kinase and Akt (full protein).
Handling and storage of lyophilized TB-500
General laboratory practice for this material:
- Store the lyophilized powder at -20°C, protected from light, until use (storage guidance on the product page).
- Let the sealed vial reach room temperature before opening so moisture does not condense on the powder.
- Reconstitute in a sterile solvent or buffer suited to the assay, added gently down the vial wall; swirl rather than shake.
- Peptides adsorb to labware, which matters at low concentrations. In recovery tests with TB-500 and three other peptides, low-binding consumables did not help in every case, so check recovery in your own tubes and plates (Judák et al., 2017).
- Full-length thymosin beta-4 carries one methionine (position 6), which can oxidize; Ac-LKKTETQ has none. Limit air, light and oxidizer exposure either way.
- After reconstitution, keep solutions at 2 to 8°C and protected from light, and split stock into single-use aliquots to avoid freeze/thaw cycles.
- Record the lot number, and take identity and molecular weight from the certificate for molarity.
Frequently asked questions
What is the TB-500 peptide?
In published analyses, Ac-LKKTETQ: the acetylated 17 to 23 fragment of thymosin beta-4 (Esposito et al., 2012). The name is also applied to full-length thymosin beta-4, as in a 2026 rat study (Biçer et al., 2026).
Is TB-500 the same as thymosin beta-4?
Not by the published analyses. Thymosin beta-4, also written Tβ4 or TB-4, is the full 43-residue peptide at about 4963 g/mol; the fragment found in TB-500 is about 889 g/mol. Our product page lists the full protein's formula, weight and CAS number with a "fragment" class, so confirm identity on each lot's certificate.
TB-500 vs BPC-157: what is the difference?
They are unrelated in structure: BPC-157 is a synthetic 15-residue peptide; TB-500 relates to thymosin beta-4. One rat Achilles repair study compared them and reported a significant biomechanical advantage for TB-500 at four weeks and no additive effect from the combination; its abstract calls the TB-500 used synthetic thymosin beta-4 (Biçer et al., 2026). The BPC-157 vs TB-500 comparison sets the two side by side.
Is TB-500 an approved drug?
No. A 2023 analysis of products sold online as TB500 described them as lacking EMA or FDA approval for human or veterinary use (Delcourt et al., 2023). Disguised Alpha sells TB-500 strictly for laboratory research.
How should TB-500 powder be stored?
Keep the lyophilized powder at -20°C and protected from light. After reconstitution, store the solution at 2 to 8°C, protected from light, and avoid freeze/thaw cycles, as listed on the product page.
Where can researchers buy TB-500?
Disguised Alpha sells it for laboratory research, third-party tested with the certificate published on the product page: TB-500 (Thymosin Beta-4). It is also a component of the Wolverine, GLOW and KLOW blends.
Related compounds and guides
- BPC-157 vs TB-500 comparison
- Wolverine (BPC-157 / TB-500) research guide
- KLOW research guide
- BPC-157 research guide
- Thymosin Alpha-1 research guide (a different thymic peptide)
- COA portal: every published certificate, by lot
This product is for research use only. It has not been evaluated for safety or effectiveness in humans. Not for human consumption. All products are intended for laboratory research purposes only.