TB-500 is a synthetic, N-acetylated seven-residue peptide (Ac-LKKTETQ) that corresponds to amino acids 17–23 of thymosin beta-4. That region is the protein’s actin-binding site. TB-500 supplies 10 mg of a standard 70 mg GLOW vial.
Compound snapshot
| Sequence | Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln (Ac-LKKTETQ) |
| Relationship | Fragment 17–23 of thymosin beta-4 (Tβ4), a 43-residue protein |
| Molecular formula | C₃₈H₆₈N₁₀O₁₄ |
| Molecular weight | ≈889.0 g/mol |
| CAS number | 885340-08-9 |
| Regulatory status | Not approved for human use; on the WADA prohibited list; prescription-only in Australia and New Zealand |
Naming confusion to watch for: some suppliers label full-length thymosin beta-4 (about 4.9 kDa) as “TB-500”. The two are different molecules with very different masses. The mass spectrum on a COA tells you which one you have: about 889 Da for TB-500, about 4,960 Da for full Tβ4.
What the research covers
Most of the evidence comes from studies of the parent protein, thymosin beta-4, not the fragment itself. Tβ4 binds actin, which helps control how cells move. Animal and cell studies have linked it to cell migration, blood-vessel formation and repair in skin, eye and heart-injury models. Reviews by Goldstein and colleagues summarize this work. Some drug-development programs took full-length Tβ4 into early clinical trials for wound and eye indications.
The fragment has much less direct research. Its main documented use is as a doping agent in racehorses, which is why anti-doping laboratories have published detection methods using liquid chromatography–mass spectrometry. No human trials of TB-500 itself have been published.
What is still unknown
- Whether the 17–23 fragment reproduces the effects reported for full-length Tβ4.
- Human safety. There is no clinical data, and elevated Tβ4 has been associated with tumor progression in some cancer research.
- How it behaves when combined with other peptides, such as in the GLOW blend.
Role in the GLOW blend
TB-500 is the cell-migration component of the GLOW stack, alongside GHK-Cu and BPC-157. Because it is the smallest share of the blend by mass, the COA should show it clearly in the mass spectrum. If it doesn’t, ask the supplier for component-level testing. See how to read a peptide COA.
Key references
- Goldstein AL, et al. Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applications. Expert Opin Biol Ther. 2012. PubMed
- Animal studies with thymosin β4, a multifunctional tissue repair and regeneration peptide. Ann N Y Acad Sci. 2010. PubMed
- Advances in the basic and clinical applications of thymosin β4. Expert Opin Biol Ther. 2015. PubMed
This page is educational and summarizes published research. It is not medical advice. TB-500 is not approved for human use and is prohibited in sport. Research-grade material is for laboratory use only.