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Terminus Peptides
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Research profile · Peptide

TB-500

Also known as TB500, Thymosin beta-4 fragment, Ac-LKKTETQ

In vitro — evidence level 1 of 4: In-vitro evidenceExperimental — UK regulatory status: Experimental — not authorised for human use in the UK

Overview

A synthetic seven-residue fragment of thymosin beta-4, containing the actin-binding motif. It is a different molecule from the full-length protein.

Category
Peptide
Highest evidence level identified
In-vitro evidence
Last scientifically reviewed
19 August 2026
Last regulatory review
19 August 2026

Mechanism under investigation

TB-500 is a synthetic short peptide corresponding to the N-terminally acetylated 17–23 fragment of human thymosin beta-4, the region containing the actin-binding motif. Thymosin beta-4 itself is a 43-amino-acid protein that binds monomeric actin and sequesters it from polymerisation, and is proposed to influence cell migration, angiogenesis and inflammatory signalling. TB-500 is proposed to reproduce the actin-binding portion of that activity, but it is a chemically distinct molecule from the parent protein and its own pharmacology is far less characterised.

Research areas

  • Cytoskeletal biology
  • Tissue repair models

These are fields in which the compound has been investigated. Listing a field is not a statement that anything was demonstrated within it.

Current evidence

In-vitro evidence

Cells, tissues or biochemical systems outside a living organism.

The actin-sequestering mechanism is well established for full-length thymosin beta-4, including structural work showing a one-to-one complex with monomeric actin. Analytical chemistry work synthesised and characterised the acetylated 17–23 fragment specifically in order to develop anti-doping detection methods, confirming what products marketed under this name actually contain. Cell-culture work on the fragment itself, as distinct from the parent protein, is sparse.

Animal evidence

Studies in living non-human animals.

Animal data attach mainly to full-length thymosin beta-4, across models of corneal injury, dermal wound healing, cardiac injury and neurological injury. Published rodent data specifically on the acetylated fragment are limited, and much of what circulates as animal research for this compound is in fact extrapolated from studies of the parent protein. The distinction matters: a seven-residue acetylated fragment and a 43-residue protein have different pharmacokinetics and cannot be assumed to share a safety or efficacy profile.

Human observational evidence

Studies observing people without assigning an intervention.

There is no substantial published human observational work on the fragment. Documented human exposure comes largely from anti-doping casework rather than from any clinical follow-up.

Clinical-trial evidence

Studies assigning an intervention to human participants.

There are no published clinical trials of this fragment. A genuine clinical programme does exist, but it used full-length synthetic thymosin beta-4: phase 2 trials in dry eye, a dose-response trial in pressure ulcers, and a small phase 3 in neurotrophic keratopathy that terminated early. Results have been mixed, with the larger dry eye trial missing its primary endpoints. None of that evidence transfers to the fragment sold under this name.

Study limitations

  • The dominant error in the surrounding literature is treating this fragment and full-length thymosin beta-4 as interchangeable. They are different molecules with different pharmacokinetics and different regulatory histories.
  • There are no published human trials of the fragment for any indication.
  • The thymosin beta-4 trials that do exist are small, predominantly ophthalmic and topically administered, and have produced mixed endpoint results.
  • Material supplied outside a regulated supply chain is not manufactured to pharmacopoeial standards, so identity and purity of a given vial are unverified.

UK regulatory context

Experimental — not authorised for human use in the UK

A compound appearing in research literature that holds no UK authorisation for human use in any indication.

Source: The Human Medicines Regulations 2012, regulation 2 — definition of a medicinal product (opens legislation.gov.uk in a new tab) (legislation.gov.uk)

Regulatory classification is jurisdiction-specific. A compound authorised elsewhere is not thereby authorised in the UK, and a supplier’s description of a substance does not determine how it is classified in law. See safety and regulation for the framework and the authoritative sources.

Safety and interpretation

For the fragment, human safety data are essentially absent: there is no published trial, no pharmacokinetic characterisation and no systematic adverse-event reporting. Limited safety information exists for full-length thymosin beta-4 from small ophthalmic trials, in which topical administration was reported as well tolerated, but that cannot be extended to a different molecule given by a different route.

References