TB-500 (Ac-LKKTETQ) and thymosin β4: what the research separates

“TB-500” is a supplier label, not a defined molecule. It is most often applied to a short acetylated sequence taken from the N-terminal region of thymosin β4 — commonly written Ac-LKKTETQ. Thymosin β4 itself is a 43-residue peptide. The fragment is part of that sequence; it is not the same molecule, and a result reported for the 43-residue peptide is not a result about the fragment.

Which of the two is in a given vial is a question about that vial’s own certificate of analysis, not about this literature. Where the certificate does not name the sequence, the identity of the material is unestablished and nothing below should be read as describing it.

Sosne et al. (2010), in FASEB J, examined short peptide sequences drawn from thymosin β4 and reported that particular activities of the parent peptide could be located to defined short regions rather than requiring the whole molecule. That paper is about the short sequences themselves, which is why it is cited here and the full-length work below is not folded into it.

Ho et al. (2012), in J Chromatogr A, is an analytical study: it developed liquid chromatography–mass spectrometry detection of TB-500, described as a synthetic version of an active region of thymosin β4, in equine urine and plasma. It establishes how the compound is identified in a sample. It reports no biological outcome and is cited only for the analytical point.

Miret-Casals et al. (2021), in Chem Commun, cross-linked thymosin β4 to actin to trap the interaction between them. This is a biochemical study of the full-length peptide binding monomeric actin.

Crockford et al. (2010), in Ann N Y Acad Sci, is a review of the structure, function and reported biological properties of thymosin β4. A review restates existing work; it is not an additional experiment, and it does not extend those findings to the short fragment.

It does not establish that Ac-LKKTETQ reproduces what full-length thymosin β4 does. Belonging to a sequence is not equivalence of function, and the two should not be swapped for one another when reading any claim.

It does not establish an outcome in humans. No dose, schedule, route or human use is described here, and none should be inferred from it.

It does not establish anything about a multi-component preparation. Where this compound is one part of a blend, none of the cited work evaluated that blend or its ratios, and no combined effect is claimed.

It does not substitute for lot evidence. The sequence, purity and identity actually present in a specific vial are settled only by that lot’s certificate of analysis.

Thymosin β4 and related substances appear on the WADA Prohibited List under section S2. That is a competition-eligibility designation, stated here as a fact of that list — not a safety, efficacy or human-use statement.

Material in this catalogue is supplied for laboratory research use only.