TB-500: what the current research shows
TB-500 is usually discussed as if it were Thymosin β4. It is not — it is a short fragment of it, and the distinction shapes how the research on each should be read.
What TB-500 is
TB-500 is a synthetic peptide corresponding to the actin-binding region of Thymosin β4, a 43-amino-acid protein found in most mammalian cells and present at high concentration in platelets and wound fluid.
Material sold as TB-500 is most commonly the acetylated seven-residue fragment Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln, which contains the sequence associated with actin binding.
| Class | Synthetic peptide fragment |
|---|---|
| Sequence | Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln |
| Molecular formula | C₄₃H₇₅N₁₃O₁₄ |
| Molecular weight | 889.02 g/mol |
| CAS number | 885340-08-9 |
| Supplied as | Lyophilised powder, 5 mg per vial |
TB-500 is not Thymosin β4
A great deal of research described online as “TB-500 research” was performed using full-length Thymosin β4, not the fragment. The two are related but not interchangeable, and findings for one are not automatically findings for the other.
Full-length Tβ4 has functions beyond actin sequestration, including interactions that the seven-residue fragment cannot reproduce simply because the relevant structure is absent. When reading a study, the first thing to establish is which molecule was actually used.
The research landscape
Published work relevant to this area falls into three groups.
Actin regulation, in vitro
Tβ4 is a well-characterised actin-sequestering protein. Its role in maintaining the pool of unpolymerised actin monomers within cells is established cell biology, and is not controversial.
Cell migration and angiogenesis models
Laboratory work has reported effects on endothelial cell migration, tube formation and keratinocyte migration in culture systems.
Animal injury models
Rodent and some larger-animal models have examined Tβ4 in dermal wound, corneal injury and cardiac injury contexts. Much of this used full-length Tβ4.
Proposed mechanisms
The mechanism with the strongest support is actin sequestration — binding monomeric G-actin and influencing the equilibrium between monomeric and filamentous actin, which in turn affects cytoskeletal remodelling and therefore cell motility.
Secondary mechanisms proposed in the literature include effects on the expression of matrix metalloproteinases and modulation of inflammatory signalling. These are less well established.
Human data
Full-length Thymosin β4 has been investigated in early-phase human clinical trials, including for dermal wound healing and corneal injury. Those trials relate to Tβ4, not to the TB-500 fragment.
There is no established human efficacy evidence base for the TB-500 fragment itself.
Regulatory context
- Not an approved drug. Neither TB-500 nor Thymosin β4 is approved for general therapeutic use.
- Prohibited in sport. TB-500 is prohibited at all times under the World Anti-Doping Agency’s list, within the peptide hormones, growth factors and related substances category.
- Sold as a research chemical. Supplied for laboratory research use only.
Frequently asked questions
Is TB-500 the same as Thymosin β4?
No. TB-500 is normally a seven-residue fragment containing the actin-binding sequence; Thymosin β4 is the full 43-residue protein. Research on one should not be read as research on the other.
Which molecule does Verolyn Labs supply?
The acetylated seven-residue fragment, Ac-LKKTETQ, with identity confirmed by LC-MS against the expected mass of 889.02 g/mol. The observed mass is stated on the certificate for each batch.
Has TB-500 been studied in humans?
Not in any established efficacy evidence base. Early-phase human trials in this area used full-length Thymosin β4.
Why is TB-500 often compared with BPC-157?
Mostly because both are discussed in tissue-repair contexts, not because they are structurally or mechanistically similar. They are unrelated peptides with different proposed mechanisms.
TB-500 reference material
5 mg lyophilised, 99.3% by RP-HPLC, identity confirmed by LC-MS against the expected fragment mass.