TB-500
An acetylated fragment of thymosin beta-4 corresponding to residues 17–23. Chemically distinct from full-length thymosin beta-4, a distinction routinely blurred in this industry.
| Total citations | 4 |
|---|---|
| Human clinical studies | 1 |
| Animal models | 1 |
| In vitro studies | 1 |
| Reviews / meta-analyses | 1 |
Mechanism of action
Material sold as TB-500 was chemically characterised by Esposito and colleagues in 2012 and identified as the N-terminally acetylated 17–23 fragment of thymosin beta-4 (Ac-LKKTETQ) — not the full 43-residue protein. This distinction matters: the two are different molecules, and the bulk of the published biology concerns the full-length protein.
Full-length thymosin beta-4 is the principal intracellular G-actin sequestering peptide, buffering the monomeric actin pool and regulating cytoskeletal dynamics and cell migration. In murine cardiac models it activates integrin-linked kinase and Akt, promoting cardiomyocyte and epicardial cell migration and survival after infarction.
Peer-reviewed literature
Study type is tagged on every entry so animal and in-vitro findings are never mistaken for human clinical evidence.
Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500
Analytical chemistry establishing that commercially sold TB-500 is the Ac-LKKTETQ fragment, not full-length thymosin beta-4.
Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair
Full-length thymosin beta-4 improved cardiac function after infarction in mice via integrin-linked kinase and Akt activation. Concerns the full protein, not the TB-500 fragment.
Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial
A phase 2 randomised trial of topical thymosin beta-4 ophthalmic solution in severe dry eye — the furthest the full-length protein has progressed in humans.
Thymosin beta 4 regulation of actin in sepsis
Reviews the actin-sequestering role of thymosin beta-4 and its proposed immunomodulatory activity in sepsis.
Limitations & open questions
Findings from full-length thymosin beta-4 studies cannot be assumed to transfer to the 17–23 fragment. Where the literature below concerns the full protein, that is stated explicitly. Any claim that TB-500 "is" thymosin beta-4 is chemically incorrect.