TB-500 (Thymosin Beta-4) Research Peptide

At Crown Peptides, TB-500 means synthetic thymosin beta-4 matching the complete 43-amino-acid sequence (C212H350N56O78S, 4963.49 g/mol), sold as freeze-dried powder in 5mg and 10mg vials. Listings also spell it TB 500 or TB500, and each batch’s mass spectrometry result confirms the full-length chain.

Allan Goldstein’s laboratory pulled it out of thymosin fraction 5, a calf thymus extract, and Low, Hu and Goldstein published the full bovine sequence in 1981. At that stage it was assumed to be a thymic hormone. The actin connection came a decade later, when a platelet peptide named Fx, already known to sequester actin, proved to be the same molecule.

It describes binding that takes actin subunits out of circulation without destroying them. Thymosin beta-4 locks each monomer away so that it cannot join a filament, then gives it up when profilin or filament-building machinery competes for it. Microinjected into cultured cells in 1992, the synthetic peptide thinned stress fibres in proportion to the amount added.

The evidence says it does, even though it has no signal sequence for conventional secretion. Released peptide has been linked in experimental studies to the integrin-linked kinase pathway in heart cells, to endothelial migration, and to production of Ac-SDKP from its first four residues. How it leaves cells remains an open question.

Angiotensin-converting enzyme is the main enzyme that breaks Ac-SDKP down. Blocking it lets the tetrapeptide accumulate, and a 1996 crossover study in healthy volunteers recorded a rise of around 5.5-fold after captopril. Kidney experiments later showed that blocking meprin-α, the enzyme that makes the first cut in thymosin beta-4, stopped captopril from raising Ac-SDKP, tying the fragment back to its parent peptide.

The results were mixed rather than clear-cut. Across the three ARISE dry-eye trials the pre-specified co-primary endpoints were missed, while individual measures such as ocular grittiness reached significance at certain time points. In the small SEER-1 neurotrophic keratopathy trial, healing rates favoured the peptide, but too few patients enrolled to settle the question.

Only under narrow conditions, according to current evidence. Riley’s group saw a modest number of new cardiomyocytes from Wt1-positive epicardial cells in mice treated before the infarct. When Pu’s team gave the peptide after the injury, lineage tracing found more capillaries and a thicker epicardium but no epicardial cells becoming heart muscle.

Surprisingly, they can. Global knockout mice made in 2012 were born at expected ratios with normal hearts and coronary vessels, and mice lacking the gene only in the heart also showed no defect. Earlier RNA-knockdown mice had died mid-gestation with vessel problems, so the gap between the two approaches has become a debate in its own right, and a reminder to check how a model was made.

WADA’s growth factor section names thymosin beta-4 and its derivatives, with TB-500 given as an example, and they are prohibited at all times. The best-known case followed the Essendon supplements affair: in 2016 the Court of Arbitration for Sport found 34 current and former AFL players guilty over thymosin beta-4 use in 2012. In racing, a 2012 Hong Kong LC-MS method detected the acetylated LKKTETQ fragment and its metabolites in horse urine and plasma.

Length is the challenge. A chain this long is assembled one coupling at a time, and every step offers a chance to skip a residue or stop early, so deletion and truncated sequences are the impurities to look for. They elute close to the main HPLC peak and betray themselves by mass: a missing lysine leaves a product 128 Da light. Purity and identity results for each batch are on the Lab Reports page.

In content, it is: the same peptide and specification, twice the weight. The 5mg fill suits cell migration or tube-formation assays run at nanomolar concentrations, while the 10mg fill means fewer reconstitutions for longer animal series. Both are sold singly or in boxes of 5 and 10, saving 15% and 25% per vial, and the peptide calculator gives the concentration for any diluent volume.

GLOW and KLOW each contain 10mg alongside a larger share of GHK-Cu, and the Wolverine Stack pairs 5mg or 10mg with an equal weight of BPC-157. Standalone vials remain the right choice for single-peptide control arms. Our BPC-157 vs TB-500 guide and the TB-500 research guide go further.