Peptide Evidence Index

TB-500 (Thymosin Beta-4)

Evidence last reviewed: September 2026

Quick answers

What is it?
TB-500 is a synthetic 7-amino-acid fragment (amino acids 17-23) cut from a much larger natural protein, thymosin beta-4, and sold online mainly for tendon, ligament, and muscle-injury recovery.
Why are people interested in it?
People buy it hoping it shares the wound-healing properties reported for the full-length parent protein in animal studies and in real human trials of unrelated products.
What has actually been studied?
The fragment itself has never been the subject of a real, verifiable human trial; the only ClinicalTrials.gov record naming it states in its own text that it is a fictional example record, not an actual study.
How strong is the evidence?
No genuine human evidence exists for TB-500 itself. Real, completed human trials exist only for the chemically different, full-length protein, and none of those tested tendon, ligament, or muscle injury.
What don't we know yet?
Whether the short fragment behaves anything like the full-length protein in the body, reaches injured tissue in useful amounts, or carries any wound-healing effect, is entirely unstudied.
Where can I read the original research?
Sources at the bottom of this page: Esposito et al., Drug Testing and Analysis 2012; ClinicalTrials.gov NCT00382174 (full-length thymosin beta-4 trial).

Plain-English overview

TB-500 is not a substance the body makes; it is a synthetic laboratory copy of a small, seven-amino-acid piece cut from a much larger, 43-amino-acid natural protein called thymosin beta-4 (Tβ4). Anti-doping chemists analyzing vials sold as "TB-500" identified the actual contents as an N-acetylated version of amino acids 17-23 of Tβ4 (Esposito et al., 2012, Drug Testing and Analysis) -- a small fragment, not the whole protein. That distinction matters because essentially all real, completed human trial data on "thymosin beta-4" was generated using the full-length, 43-amino-acid protein, made by different companies under different names, none of which is TB-500. TB-500 itself, the fragment actually sold in vials online, is not approved as a medicine anywhere and has never been the subject of a real, verified human trial.

What researchers are studying it for

Current evidence level

Animal only

Regulatory status: Not an approved medicine. Evidence strength and approval are scored separately; approval is a regulatory decision about a specific use, not a measure of how much research exists.

Human research

Searching ClinicalTrials.gov for "TB-500" turns up exactly one record, a Phase 1/2 cardiovascular study, whose own text states it is "a fictional study... an example of a ClinicalTrials.gov-style record" rather than a real, enrolling trial. Excluding that record, there are zero registered human trials of TB-500. The chemically different, full-length protein, thymosin beta-4, does have a real trial history: a Phase 2 trial of a topical gel in 72 patients with pressure ulcers (NCT00382174, completed 2008, results posted), a Phase 2 trial of the same gel in 72 patients with venous stasis ulcers (NCT00832091, completed 2009, results posted), a Phase 2 trial in 30 patients with epidermolysis bullosa, a genetic blistering skin disease, terminated early but with results posted (NCT00311766), and a 700-person Phase 3 trial of a thymosin beta-4 eye-drop formulation (RGN-259) for dry eye disease, completed with results posted (NCT03937882, ARISE-3). None of these trials, and no other identified in this review, tested tendon, ligament, or muscle injury -- the primary reason people buy TB-500.

Animal and preclinical research

The full-length protein, thymosin beta-4, has a substantial animal literature reporting effects on skin-wound healing and on heart and hair-follicle tissue in rats, pigs, and other species. No animal study specifically testing the isolated, short TB-500 fragment for wound healing or muscle repair was located in this review; the analytical chemistry paper that identified the fragment's structure did not test its biological effects.

Major findings

What has not been established

Important limitations

Regulatory status

TB-500 is not approved as a medicine anywhere and is not the same molecule as any approved drug. No dose, safety profile, or efficacy claim for TB-500 itself has been established through a genuine regulatory review or clinical trial.

Primary research sources

Esposito S, et al. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential
Drug Test Anal 2012;4(9):733-8. PMID: 22962027
Safety and efficacy of Thymosin Beta 4 in patients with pressure ulcers (full-length protein, not TB-500)
ClinicalTrials.gov NCT00382174, n=72, Phase 2, completed 2008, results posted
Safety and efficacy of Thymosin Beta 4 in patients with venous stasis ulcers (full-length protein, not TB-500)
ClinicalTrials.gov NCT00832091, n=72, Phase 2, completed 2009, results posted
Thymosin Beta 4 in the treatment of epidermolysis bullosa (full-length protein, not TB-500)
ClinicalTrials.gov NCT00311766, n=30, Phase 2, terminated 2012, results posted
RGN-259 ophthalmic solution for dry eye (ARISE-3) (full-length protein, not TB-500)
ClinicalTrials.gov NCT03937882, n=700, Phase 3, completed 2021, results posted
Full evidence entry (complete data, registry records, dosing evidence)
Animal only
Studied in animals; human evidence absent or minimal

At a glance

Also known as
Thymosin Beta-4 fragment, Tβ4(17-23), Ac-LKKTETQ
Class
Synthetic 7-amino-acid peptide fragment
Derived from
The 17-23 amino-acid segment of thymosin beta-4 (Tβ4), a naturally occurring 43-amino-acid protein, chemically modified with an N-terminal acetyl group
Registered human trials
0
…with published results
0
Largest human trial
None conducted. The only ClinicalTrials.gov record naming \"TB-500\" (NCT07487363, a Phase 1/2 cardiovascular study) states in its own text that it is \"a fictional study... an example of a ClinicalTrials.gov-style record\" — not a real trial. A chemically different, full-length molecule (thymosin beta-4) has 17 real registered trials, several completed with posted results, but none tested the short fragment sold as TB-500.
Studied for
pressure ulcers, venous stasis ulcers, epidermolysis bullosa wounds, dry eye disease, acute myocardial infarction
Dosing evidence
No human dose establishedNo human trial has established a dose for TB-500 itself, for any use — the only registry record naming it is a fabricated example, not a real study.
Regulatory status
Not approved as a medicine anywhere. Not the same molecule as any approved drug.

What it is

TB-500 is not, itself, something the body makes. It's a synthetic laboratory copy of a small piece — just seven amino acids — cut from a much larger, 43-amino-acid protein called thymosin beta-4 (Tβ4), which the body does produce and which turns up in blood, wound fluid, and inside most cells. Analytical chemists studying it for anti-doping testing have identified the actual substance sold as "TB-500" as an N-acetylated version of amino acids 17 through 23 of Tβ4 — a small fragment, not the whole protein.

This distinction matters more than it might seem, because nearly everything written about "thymosin beta-4 clinical trials," including trials with real, completed, posted human data, was conducted using the full-length, 43-amino-acid protein — made by different companies under different names (a wound gel from RegeneRx, an eye-drop called RGN-259 from ReGenTree, an injectable called NL005 from a Chinese manufacturer). None of those products are TB-500.

TB-500 itself — the fragment actually sold in vials online, usually marketed for tendon, ligament, and muscle injury recovery — is not approved as a medicine anywhere and, as far as this session could establish, has never been the subject of a real, verifiable human trial.

What the studies actually found

The full-length protein, Tβ4, has a substantial animal literature: in rats, pigs, and other species, it has been reported to speed healing of skin wounds and to have effects on heart tissue and hair follicles. That preclinical record is genuinely large.

The short fragment sold as TB-500 has essentially no dedicated research literature of its own, in animals or in humans, beyond the analytical chemistry paper that identified what the sold product actually is. No animal study specifically testing the isolated 17-23 fragment for wound healing or muscle repair was located this session.

What exists in humans

Searching ClinicalTrials.gov for "TB-500" turns up exactly one record: a Phase 1/2 cardiovascular trial (NCT07487363) sponsored by a company called Hudson Biotech. That record's own text states it is "a fictional study... an example of a ClinicalTrials.gov-style record" — not a real, enrolling study. Excluding it, there are zero registered human trials of TB-500.

The full-length protein, Tβ4 — a different, longer molecule sold under different names — does have a real trial history: 17 registered studies. Several have completed with posted results:

  • A Phase 2 trial in 72 patients with pressure ulcers, using a topical gel, completed with results posted.
  • A Phase 2 trial in 72 patients with venous stasis ulcers, using a topical gel, completed with results posted.
  • A Phase 2 trial in 30 patients with epidermolysis bullosa (a genetic blistering skin disease), using

a topical gel, terminated early but with results posted.

  • A Phase 3 trial of a thymosin beta-4 eye-drop formulation (RGN-259) for dry eye disease, enrolling

700 people, completed with results posted.

  • Ongoing Chinese Phase 2 trials of an injectable thymosin beta-4 formulation (NL005) in acute heart

attack patients, not yet reporting results.

None of these — not one — studied tendon, ligament, or muscle injury, the primary reason people buy TB-500.

What doses have been studied in humans

No dose of TB-500 itself has been studied in any real human trial — there is no genuine trial to draw a dose from.

The full-length protein has been dosed in real, completed trials, but only as a topical gel applied directly to the surface of a chronic wound over about twelve weeks, and only using a different research molecule than the one injected as "TB-500." None of those trials involved injection, and none involved a healthy person rather than someone with an existing wound.

So there is no human safety, pharmacokinetic, or efficacy data of any kind establishing a dose of injectable TB-500 for any purpose. Amounts referenced online typically trace back to unrelated animal dosing of the full-length protein, scaled to human body weight using conversions that have not themselves been tested in people — an estimate of comparable exposure, not evidence of effectiveness or safety.

What remains unknown

  • Whether TB-500, the fragment, behaves in the body anything like the full-length protein it comes from
  • Whether it reaches injured tendon or muscle tissue in useful concentrations after injection
  • Whether any wound-healing effect seen with the full-length protein applies to the fragment at all
  • What a genuine, non-fabricated human safety study of TB-500 would find, since none has been run
  • What is actually in a vial sold online, given the complete absence of regulatory oversight
  • Whether repeated, long-term use carries risks, given the parent protein's role in blood vessel growth

Registry and study records

Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500
PubMed · DOI: 10.1002/dta.1402 — anti-doping analytical chemistry paper confirming TB-500 is the acetylated 17-23 fragment of Tβ4, distinct from the full-length protein
Safety and efficacy of Thymosin Beta 4 in patients with pressure ulcers
ClinicalTrials.gov NCT00382174 · n=72, full-length Tβ4 topical gel, Phase 2, completed 2008, results posted
Safety and efficacy of Thymosin Beta 4 in patients with venous stasis ulcers
ClinicalTrials.gov NCT00832091 · n=72, full-length Tβ4 topical gel, Phase 2, completed 2009, results posted
Thymosin Beta 4 in the treatment of epidermolysis bullosa
ClinicalTrials.gov NCT00311766 · n=30, full-length Tβ4 topical gel, Phase 2, terminated 2012, results posted
RGN-259 ophthalmic solution for dry eye (ARISE-3)
ClinicalTrials.gov NCT03937882 · n=700, full-length Tβ4 eye-drop formulation, Phase 3, completed 2021, results posted
TB-500 (Thymosin Beta 4 17-23 Fragment) for cardiovascular biomarkers
ClinicalTrials.gov NCT07487363 · Record explicitly self-identifies as a fictional example record, not a real trial — excluded from all counts above

Articles on TB-500 (Thymosin Beta-4)

What has TB-500 (thymosin beta-4) actually been shown to do in humans TB-500 and Thymosin Beta-4: What Has Actually Been Studied?
See the full Evidence Index →

Topic hubs

TopicRecovery & Tissue Research

Evidence last reviewed: September 2026. Peptide Proof reports what studies found. We do not give medical advice, dosing guidance, or treatment recommendations.