Is TB-500 the same as thymosin beta 4?

No. Thymosin β4 is a 43-amino-acid protein; TB-500 is a short synthetic peptide corresponding to its actin-binding region. Nearly all the published research used the full-length protein, so a study result attributed to TB-500 has usually been transferred from the parent by whoever wrote the summary.

What does the research on thymosin beta 4 report?

Faster wound re-epithelialisation in rats, cardiomyocyte survival and migration after induced ischaemia in mice, and improvement in dry eye signs and symptoms in two phase 2 human trials of an ophthalmic solution. The mechanism proposed throughout is actin sequestration and its effect on cell migration.

Have there been human trials of TB-500?

Not of the fragment. Two published phase 2 randomised trials studied full-length thymosin β4 as an eye drop for dry eye. That is a specific preparation for a specific indication and does not generalise.

Are there known side effects of TB-500?

No dedicated safety study of the fragment has been published, which is a different statement from no side effects being found. The ophthalmic trials report tolerability for a topical eye preparation and say nothing about any other context.

Why do sources disagree about TB-500 research?

Mostly because of the fragment-versus-parent substitution. A source that reports thymosin β4 findings under the TB-500 heading will list far more evidence than one that distinguishes them, without either being factually wrong about the underlying papers.

Research guides

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

The fragment sold as TB-500 is not the molecule most of the literature studied. What the thymosin β4 research reported, including two human eye trials.

Available in the catalogue

Supplied as research material. Sizes and pricing are on the product page. Availability is not a statement about what a compound does.

TB-500 (TB4)
Healing & Repair

This compound requires a distinction before anything else, because almost every summary of it elsewhere skips the distinction and the summaries are wrong as a result.

Fragment and parent are not the same molecule

Thymosin β4 is a 43-amino-acid protein found naturally in human cells. TB-500 is a short synthetic peptide corresponding to its actin-binding region — commonly written as Tβ4 (43–50). The great majority of the published research, including every study cited below, used full-length thymosin β4 rather than the fragment.

That is not a technicality. The fragment retains the actin-binding motif, which is why it exists and why it is reasonable to expect overlapping activity. But a protein does more than one thing, and the parent's reported effects on cell survival, inflammation and vessel formation are not automatically properties of an eight-residue section of it. Where a source attributes a thymosin β4 result to TB-500 without saying so, the attribution has been made by the writer rather than by the study.

Everything in the findings below names the molecule actually used in its model field. Read that field first.

What the parent protein does

Thymosin β4 binds and sequesters actin, the protein cells use to build and remodel their internal scaffolding. Sequestering monomeric actin regulates how readily a cell can reorganise that scaffolding, which is the proposed basis for the reported effects on cell migration — cells moving into damaged tissue — and it is why the protein appears across wound healing, corneal and cardiac repair literature rather than in one field.

Unusually for this catalogue, there are human trials

Two randomised trials of thymosin β4 as an ophthalmic solution for dry eye have been published, both phase 2. They are worth noting precisely because human data is rare across the compounds described on this site — and worth reading carefully, because an eye drop applied to the ocular surface is a specific preparation studied for a specific indication, and reports nothing about the molecule used any other way.

What studies reported

Each entry states what a study examined and the model it used. Nothing below describes an outcome for a person.

Everything below is drawn from published research, and each entry names the model the study used. Approval status varies by compound and by country, and nothing described here is supplied as a medicine or for use in a person.

Malinda et al. (1999)Journal of Investigative Dermatology · 113(3):364–8
Reported accelerated re-epithelialisation of dermal wounds relative to saline controls.
rat full-thickness wound model, full-length thymosin β4 Source
Bock-Marquette et al. (2004)Nature · 432:466–72
Reported that thymosin β4 activated integrin-linked kinase and Akt, promoting cardiomyocyte survival and migration after ischaemic injury.
mouse coronary artery ligation, full-length thymosin β4 Source
Sosne et al. (2015)Cornea · 34(5):491–6
Reported improvement in signs and symptoms of severe dry eye against vehicle control in a randomised trial.
human, phase 2 randomised, ophthalmic solution of full-length thymosin β4 Source
Sosne & Ousler (2015)Clinical Ophthalmology · 9:877–84
Evaluated an ophthalmic solution of thymosin β4 for dry eye using a controlled adverse environment exposure model, reporting improvement in ocular discomfort against placebo.
human, phase 2 randomised placebo-controlled, controlled adverse environment model Source

Adverse and null findings reported

No dedicated safety study has been published for this compound. That is not a finding that none exists — it means the question has not been asked in print, and the gaps below say so.

What the research does not establish

An absence cannot be cited, so these are stated plainly. They are the part of the picture that silence would otherwise hide.

No published trial has studied the TB-500 fragment itself in humans. The human data that exists is for full-length thymosin β4, as an ophthalmic solution, for dry eye.
No systemic human trial has been published for either the fragment or the parent protein. Extrapolating from an eye drop to any other context is not supported by the cited work.
The adverse-findings list above is empty, and that means nobody has published a dedicated safety assessment of the fragment rather than that one found nothing. The ophthalmic trials report tolerability for a topical ocular preparation only.
Thymosin β4 promotes cell migration and vessel formation, and the implications of that in the presence of existing pathology have not been characterised in the published literature.
Comparative potency between the fragment and the full-length protein has not been established, so it is not known whether findings for one transfer to the other quantitatively even where they transfer qualitatively.

Common questions

Is TB-500 the same as thymosin beta 4?: No. Thymosin β4 is a 43-amino-acid protein; TB-500 is a short synthetic peptide corresponding to its actin-binding region. Nearly all the published research used the full-length protein, so a study result attributed to TB-500 has usually been transferred from the parent by whoever wrote the summary.
What does the research on thymosin beta 4 report?: Faster wound re-epithelialisation in rats, cardiomyocyte survival and migration after induced ischaemia in mice, and improvement in dry eye signs and symptoms in two phase 2 human trials of an ophthalmic solution. The mechanism proposed throughout is actin sequestration and its effect on cell migration.
Have there been human trials of TB-500?: Not of the fragment. Two published phase 2 randomised trials studied full-length thymosin β4 as an eye drop for dry eye. That is a specific preparation for a specific indication and does not generalise.
Are there known side effects of TB-500?: No dedicated safety study of the fragment has been published, which is a different statement from no side effects being found. The ophthalmic trials report tolerability for a topical eye preparation and say nothing about any other context.
Why do sources disagree about TB-500 research?: Mostly because of the fragment-versus-parent substitution. A source that reports thymosin β4 findings under the TB-500 heading will list far more evidence than one that distinguishes them, without either being factually wrong about the underlying papers.

Compounds covered

The reference page for each compound this article discusses.

TB-500

BPC-157: what the research says
Body Protection Compound 157 has a large rodent literature and almost no human data. What the studies measured, in which models, and the caveat behind them.
GHK-Cu copper peptide: what the research says
The copper tripeptide GHK-Cu has the strongest published evidence of any repair peptide here, spanning wound models, gene expression and cosmetic dermatology.
How to store research peptides
Lyophilised peptides at -20°C, reconstituted at 2–8°C, ambient in transit. Why the dry cake tolerates shipping, and what actually degrades a vial.

About this article

Everything reported here comes from published research, and each finding names the model the study used — cell culture, rat, or human. Findings in one model do not transfer to another, most of the work described is preclinical, and none of it is a claim that a compound is safe or effective for any purpose. Nothing on this page describes doses, routes of administration, or use in a person.

Approval status varies by compound and by country. A few of the substances described are the active ingredient of medicines authorised in the EU; most have no marketing authorisation anywhere and have never been assessed by a regulator. Neither is supplied as a medicine here. All material supplied by ASSAY is sold for in-vitro laboratory research only, and is not a drug, food, cosmetic or medical device, and not for human or veterinary use.

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