What Is TB-500? The Thymosin Beta-4 Peptide Explained

By DoseGauge Editorial · Updated 2026-06-14 · 5 min read

TB-500 is a synthetic heptapeptide fragment, the sequence Ac-LKKTETQ, derived from thymosin beta-4 (TB4), a naturally occurring 43-amino-acid protein found in many mammalian tissues. It has been studied in the context of tissue repair, wound healing, and angiogenesis, mostly through the research on its parent protein. It is a research peptide, not approved by the FDA for any use, and it is prohibited at all times in sport by the World Anti-Doping Agency. The evidence base is largely preclinical: most of what is known comes from cell-culture and animal studies of thymosin beta-4, with very limited human data. This page explains what TB-500 is and how it is reported to work. It is informational and educational only, not medical advice, and it does not recommend TB-500 or any dose.

What TB-500 is

TB-500 is a short synthetic peptide. Its sequence, written Ac-LKKTETQ, is a seven-amino-acid (heptapeptide) fragment that corresponds to a part of thymosin beta-4, a larger protein the body makes on its own. The "Ac" marks an acetylated N-terminus on the synthetic peptide.

Thymosin beta-4 itself is a naturally occurring 43-amino-acid peptide found in many mammalian tissues. The cited reviews describe it as a small secreted peptide built around a central actin-binding domain (Maar et al., 2021). TB-500 reproduces only a portion of that full sequence, so it is best understood as a fragment of thymosin beta-4 rather than the whole protein. That distinction matters for reading the science: the peer-reviewed literature cited here studies thymosin beta-4, the parent protein, and findings about the full protein do not automatically transfer to the shorter synthetic fragment.

TB-500 versus thymosin beta-4

These two names get used interchangeably, but they are not the same thing. Thymosin beta-4 is the full, naturally occurring protein: 43 amino acids long, with a central actin-binding domain flanked by helical regions (Maar et al., 2021). It is produced endogenously in many tissues and is the molecule the published reviews actually study.

TB-500 is a synthetic peptide that reproduces a short fragment of that protein, the sequence Ac-LKKTETQ. It is manufactured rather than naturally produced, and it represents only part of the parent sequence. So when a study reports a property of thymosin beta-4, that is a finding about the full protein. It is reasonable context for TB-500 because TB-500 is derived from that sequence, but it is not the same as a result demonstrated for the fragment itself. Keeping the fragment-versus-parent distinction in view is the accurate way to read claims about TB-500.

How TB-500 is thought to work

The proposed mechanisms come from research on thymosin beta-4, the parent protein, and they are largely preclinical (cell and animal). A central one is actin binding. The reviews describe thymosin beta-4 as an actin-sequestering peptide that helps regulate actin filament assembly, which in turn supports cell migration (Maar et al., 2021; Xing et al., 2021). One review notes that the peptide links actin polymerization to cell migration through a profilin-dependent step (Xing et al., 2021).

From that base, the reviews describe roles in angiogenesis, the formation of new blood vessels, with thymosin beta-4 reported to upregulate VEGF expression and act through signaling pathways such as PI3K/Akt/eNOS (Xing et al., 2021). The same literature ties the peptide to wound healing and tissue repair, describing effects on cell migration, cytokine regulation, and reduced inflammation in injury models (Xing et al., 2021; Maar et al., 2021). It is worth being precise: these are mechanisms reported for thymosin beta-4 in preclinical research, not established outcomes for TB-500 in people.

Regulatory and sport status

TB-500 is a research peptide. It is not approved by the FDA for any indication, and there is no established clinical dose or approved human use. Human pharmacokinetic data are extremely limited, and no validated human elimination half-life for TB-500 has been published in the peer-reviewed literature.

It is also banned in sport. The World Anti-Doping Agency prohibits TB-500 and thymosin beta-4 at all times under the Prohibited List, category S2.3 (Growth Factors and Related Substances), so a competitive athlete who tests positive is subject to sanction regardless of intent. None of that amounts to regulatory approval or an established safety and efficacy profile in humans. This page describes what TB-500 is and how it is reported to work; it does not claim it is safe, effective, or appropriate for any purpose, and it does not recommend using it. Whether any research peptide is appropriate is a decision for a licensed clinician. For what the research has examined, see tb-500 benefits, and for how it compares with a commonly paired peptide, see tb-500 vs bpc-157.

Frequently asked questions

What is TB-500 used for?

TB-500 is a research peptide studied in the context of tissue repair, wound healing, and angiogenesis, largely through preclinical work on its parent protein, thymosin beta-4 (Xing et al., 2021; Maar et al., 2021). Those mechanisms come from cell and animal studies, not from controlled human trials. It is not FDA-approved for any use, and this page does not recommend it for any purpose.

Is TB-500 the same as thymosin beta-4?

No. TB-500 is a synthetic heptapeptide fragment (Ac-LKKTETQ) derived from thymosin beta-4, while thymosin beta-4 is the full, naturally occurring 43-amino-acid protein (Maar et al., 2021). TB-500 reproduces only part of that sequence, so it is a fragment of the larger protein, not identical to it. The peer-reviewed reviews cited here study the parent protein.

Is TB-500 FDA-approved?

No. TB-500 is not approved by the FDA for any indication. It is a research peptide, human pharmacokinetic data are extremely limited, and no validated human half-life has been published. Consult a licensed clinician before using any research peptide.

Is TB-500 banned in sport?

Yes. The World Anti-Doping Agency prohibits TB-500 and thymosin beta-4 at all times under the Prohibited List, category S2.3 (Growth Factors and Related Substances). A competitive athlete who tests positive is subject to sanction regardless of intent.

Informational and educational only. Not medical advice. DoseGauge computes from the values you enter and does not recommend a dose. Talk to a licensed clinician before using any peptide or GLP-1 medication.