TB-500 and thymosin beta-4: what the research shows

What thymosin beta-4 is

Thymosin beta-4 (Tβ4) is a small, naturally occurring peptide that plays a role in the repair and regeneration of injured cells and tissues. After an injury it is released by platelets, macrophages and many other cell types. [1]

It binds actin, a structural protein of the cell skeleton, and promotes cell migration, including the mobilisation, migration and differentiation of stem and progenitor cells that form new blood vessels. It also lowers the number of myofibroblasts in wounds, which is associated with less scar formation and fibrosis. [1]

What TB-500 is

TB-500 is a product name, not a defined molecule. When researchers analysed a TB-500 product with high-resolution mass spectrometry, they identified the N-terminally acetylated 17–23 fragment of human thymosin beta-4, the seven-amino-acid sequence Ac-LKKTETQ. They synthesised the fragment and proposed a method to detect it in plasma and urine. [3]

So the name TB-500 alone does not tell you whether a vial holds full-length thymosin beta-4 or a fragment of it: the certificate of analysis should state the sequence that was tested.

What the research covers

Most of the research concerns thymosin beta-4 itself, not TB-500 products. The table summarises the main lines of work. [1] [2] [3] [4]

What is not known

Human evidence is limited to small, specific studies of thymosin beta-4 formulations, such as the nine-patient dry-eye trial; its authors describe it as a small trial. [4] No clinical trial in the sources above tested a product sold as TB-500, and the analysed TB-500 product contained a fragment rather than the full peptide. [3]

Status in sport

The World Anti-Doping Agency's 2026 Prohibited List names ‘thymosin-β4 and its derivatives, e.g. TB-500’ among the growth factors and growth-factor modulators of class S2, prohibited at all times, in and out of competition. [5] Methods to detect the TB-500 fragment in plasma and urine have been described. [3]

Storage and stability in the lab

Peptides can degrade through chemical routes such as oxidation, deamidation and hydrolysis and through physical routes such as aggregation, and they are generally more stable in the dry state than in solution. [6]

Lyophilised vials are therefore normally kept cold, dry and away from light until they are reconstituted. The storage statement on the product page and on the batch certificate takes precedence.

How to check a batch

A useful certificate of analysis names the testing laboratory, the batch number printed on the vial, the test date and the methods used. Identity is usually confirmed by mass spectrometry, where the measured mass should match the expected molecular mass, and purity is measured by HPLC. For TB-500, check which sequence the report says was tested: full-length thymosin beta-4 and the 17–23 fragment have very different masses. [3]

Where the manufacturer supplies a batch report, we link it on the product page; products without one do not claim one.