What TB-500 is, and why its name does not tell you what is in the vial

Thymosin beta-4 is a small 43-amino-acid protein present in practically every mammalian cell and body fluid. Its best-described function is to sequester actin, that is, to hold a reserve of unpolymerised actin inside the cell [1]. From there it has been assigned roles in cell migration, blood vessel formation and tissue repair [2].

The name does not tell you which molecule it is

This is the first thing to understand about this product, and almost nobody says it.

The review by Sosne and colleagues identified several active sites with functions of their own within thymosin beta-4. One is the LKKTETQ sequence, the central actin-binding domain — amino acids 17 to 23 plus one — credited with angiogenesis, wound healing and cell migration [3]. That short fragment is what many suppliers sell under the name "TB-500".

But the name is also used for the whole protein: the 2026 rat study cited below calls the full synthetic thymosin beta-4 "TB-500" [5].

Both circulate under the same trade name. The practical consequence is direct: the product name does not let you know which molecule is inside, and a purity percentage does not either, because it measures something else. The only thing that tells you is an identity confirmation for the batch.

What has been studied, and in which species

What has been published are animal models and cell culture. There is nothing here equivalent to the phase 3 trials of other compounds in this catalogue.

• Tissue repair in animals. A review of the animal models collects work in skin, cornea and heart, and describes reduced inflammatory mediators, cell migration, blood vessel formation and cell survival [4].
• Tendon, in rats. A 2026 study transected and repaired the Achilles tendon of 32 rats and compared four groups: control, BPC-157, TB-500 and the combination of the two. The authors measured a higher maximum load to failure in the TB-500 group, reaching statistical significance, and better histological scores for tendon architecture [5].
• And the awkward figure from the same study. Combining the two peptides conferred no additional benefit over either one alone. The authors themselves propose as a hypothesis that both converge on shared pathways, and say it needs confirming [5]. It is a single exploratory study in rats, but it is the only one comparing them head to head.

What does not exist

There is no approved human indication for thymosin beta-4 or its fragments, in the European Union or in the United States. Clinical trials have been run in dermal, corneal and cardiac repair [4], but none has resulted in an authorised medicine.

This page describes published literature. It is not medical information, it does not describe a therapeutic use, and it does not replace any healthcare professional.

What to look at when comparing suppliers

• Which molecule it is, stated explicitly: the full 43-amino-acid protein or the short fragment. If the supplier does not say, they either do not know or do not want to say.
• Identity confirmation by mass spectrometry for the specific batch. Here this matters more than purity: the two candidates have very different molecular weights, so mass distinguishes them unambiguously.
• HPLC purity for the batch, with a certificate you can read before buying.