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TB-500: What the Evidence Actually Shows

Also called Thymosin beta-4 fragment, N-acetylated LKKTETQ, Tβ4 17-23, TB500

TB-500 is sold for tendon, muscle and soft-tissue repair on the strength of research into thymosin beta-4. The first thing to know is that those are two different molecules: TB-500 is N-acetylated LKKTETQ, the seven-residue actin-binding segment at positions 17 to 23 of thymosin beta-4, while the protein itself is 43 residues long. The second is where the human trials went. A ClinicalTrials.gov search for thymosin beta 4 returned 18 studies in August 2026, and the conditions listed across them are dry eye, neurotrophic keratopathy, myocardial infarction, pressure and venous ulcers, epidermolysis bullosa, corneal wounds and endothelial dysfunction. Not one lists a tendon, ligament or muscle injury. The published phase 3 result that does exist is an eye drop, in eighteen patients, whose primary healing comparison did not reach conventional significance.

By Grant Delaney, Research Editor
What is sold

7residues (Tβ4 17-23)

What was studied

43residues (full Tβ4)

Registered trials in musculoskeletal injury

0of 18 studies

FDA approval

Noneany indication

Compound

What it is

TB-500 is a synthetic peptide consisting of the sequence LKKTETQ with an artificial acetyl group on the N-terminus. That sequence is positions 17 to 23 of thymosin beta-4, the segment identified as the actin-binding site responsible for cell migration and wound healing within the larger protein. A 2026 review of peptide therapies marketed direct to patients lists the two separately for exactly this reason — thymosin beta-4 as one entry and TB-500 as the thymosin beta-4 fragment as another. The preparation the sequence first appeared in was a veterinary one.1,2

Mechanism

How it works

The claims made for TB-500 are the claims made for its parent protein's actin-binding region: promotion of endothelial cell differentiation, angiogenesis in dermal tissue, keratinocyte migration, collagen deposition and reduced inflammation. In preclinical work the mechanism does appear to do something — a 2026 orthopaedic review of injectable peptides concluded that thymosin beta-4 and its derivative TB-500 promoted angiogenesis and tissue repair in preclinical models. What the review found next to that is the gap this page is about: human orthopaedic data are lacking, and both are banned substances in sport.1,2,3

Evidence

What the trials found

Animal only

Evidence strength: Animal only. Rodent or cell studies. Nothing published in humans.

The human trial record belongs to full-length thymosin beta-4, and largely to the eye. The published phase 3 result is a randomized, placebo-controlled, double-masked trial of a 0.1% thymosin beta-4 ophthalmic solution in patients with stage 2 and 3 neurotrophic keratopathy: complete healing after four weeks occurred in 6 of 10 treated patients against 1 of 8 on placebo, a difference the authors reported as a strong efficacy trend at p = 0.0656 rather than as a significant result, alongside significant improvements in ocular discomfort, foreign body sensation and dryness. Two 2026 reviews summarise where the rest stands: an orthopaedic review of injectable peptide therapy found human orthopaedic data lacking for both thymosin beta-4 and TB-500, and a sports medicine review groups TB-500 with unapproved compounds that show favourable tissue-repair outcomes in animal models while rigorous human safety data remain scarce. The pharmacokinetic work that exists for TB-500 itself is not human: a doping-control study administered a single dose containing 10 mg of N-acetylated LKKTETQ to horses and characterised the parent peptide and its metabolites in equine urine and plasma.1,2,3,4

18

Registered thymosin beta-4 studies

ClinicalTrials.gov, August 2026. Conditions are ocular, cardiac, dermal and vascular.

18

Patients in the published phase 3

10 on 0.1% thymosin beta-4 eye drops, 8 on placebo, in neurotrophic keratopathy.

—

Human trial of TB-500 for tendon or muscle repair

None appears among the 18 ClinicalTrials.gov records returned for thymosin beta 4 in August 2026.

—

Human dose-ranging study of TB-500

The one administration study with a stated quantity was in horses, for doping-control detection.

Complete corneal healing at 4 weeks, published phase 3 (%)

0.1% Tβ4 eye drops (6 of 10)
60 %
Placebo (1 of 8)
12.5 %

Registered studies by condition area

Ocular surface
7 studies
Cardiac / vascular
6 studies
Skin and wound
3 studies
Healthy volunteers
2 studies
Tendon, ligament or muscle
0 studies
How to read the evidence meter

How to read the evidence meter

Four steps, weakest to strongest. Most peptides sold for a goal light up one. We show the step the published human evidence actually reaches — not the step the seller implies.

  1. AnecdotalUser reports and forum consensus. No controlled data.
  2. Animal onlyRodent or cell studies. Nothing published in humans.
  3. Early humanSmall, open-label, or phase 1/2 trials. Promising, unproven.
  4. Randomized trialsRandomized controlled trials in humans, at scale.

Timeline

Development pipeline

  1. 1 — Current step

    Preclinical

    Where TB-500's evidence sits — angiogenesis and tissue repair in animal models

  2. 2 — Not reached

    Phase 1

    For TB-500 in a musculoskeletal indication

  3. 3 — Not reached

    Phase 2

  4. 4 — Not reached

    Phase 3

  5. 5 — Not reached

    FDA review & approval

    No approved TB-500 product, any indication

Summary

What the evidence does — and doesn't — support

Studied, but not for this

A ClinicalTrials.gov search for thymosin beta 4 returned 18 studies in August 2026. The conditions listed across that set are dry eye, neurotrophic keratopathy, acute myocardial infarction, pressure and venous stasis ulcers, epidermolysis bullosa, corneal wounds in diabetes, atherosclerotic cardiovascular disease with endothelial dysfunction, and healthy volunteers. None of the 18 lists a tendon, ligament, joint or muscle injury.
What the evidence supports
  • Angiogenesis and tissue repair by thymosin beta-4 and TB-500 in preclinical models
  • A defined actin-binding sequence — LKKTETQ, positions 17 to 23 — with a plausible wound-healing rationale
  • Improved corneal healing measures and symptoms with a thymosin beta-4 eye drop in an 18-patient phase 3 trial
What it does not support
  • Tendon, ligament or muscle repair in a human being — no registered trial lists such a condition
  • Transfer of full-length thymosin beta-4 results to the seven-residue TB-500 fragment
  • Transfer of eye-drop and topical results to subcutaneous injection
  • Any human dose — the one administration study with a stated quantity was in horses
  • Identity or purity of what is sold — a 2023 analysis found internet-sold TB500 products inconsistent with their descriptions

Reality check

The catch

Three separate gaps sit between the marketing and the evidence, and each one alone would be enough. The molecule is not the one in the research: TB-500 is a seven-residue acetylated fragment, and the protein studied in the human trials is 43 residues long. The route is not the one being sold: the phase 3 evidence is an ophthalmic solution instilled in an eye, and the phase 2 wound trials were topical, while TB-500 is marketed as a subcutaneous injection. And the indication is not the one being claimed: a ClinicalTrials.gov search for thymosin beta 4 returned 18 studies in August 2026, with conditions listed as dry eye, neurotrophic keratopathy, acute myocardial infarction, pressure ulcers, venous stasis ulcers, epidermolysis bullosa, corneal wounds in diabetes, atherosclerotic cardiovascular disease with endothelial dysfunction, and healthy volunteers — none of the 18 lists a tendon, ligament or muscle injury. Two phase 3 dry-eye trials in that set completed in March 2018 (601 participants) and October 2021 (700 participants); as of August 2026 the 700-participant record shows no posted results on ClinicalTrials.gov. Separately, what is actually in the vial is a live question rather than a rhetorical one: a 2023 analysis of products sold over the internet under the names TB500 and TB1000 reported that their content is not systematically consistent with the products' own former descriptions. On top of all of that, a drugsFDA search returns no match for TB-500 and none for thymosin, so there is no approved label, no approved manufacturer, and no regulator that has verified the identity or purity of anything sold under the name.

Dosing

Dosing evidence

There is no human dose-ranging or pharmacokinetic study of TB-500 to derive a dose from. The one administration study with a stated quantity is veterinary: a single dose containing 10 mg of N-acetylated LKKTETQ given to horses for the purpose of developing a doping-control detection method, which reports detection limits in equine urine and plasma rather than an effect on any outcome. Reviews of the peptides marketed direct to patients make the same point from the clinical side — a 2026 orthopaedic review states that information regarding indications, dosing, frequency and duration of treatment remains unknown for the injectable peptides it examined. Any milligram figure circulating for human use is therefore not derived from a human study, and nothing on this page is a dose for a reader to take.1,2

Already have a dose in mind? Our reconstitution calculator converts it to syringe units. It does not suggest one.

Safety

Safety and side effects

Human safety data for TB-500 specifically is essentially absent, and what exists belongs to the parent protein by other routes. The phase 3 ophthalmic trial of 0.1% thymosin beta-4 reported no significant adverse effects in its 18 patients — a real finding at a sample size that cannot detect an uncommon one, and for an eye drop rather than an injection. A 2026 sports medicine review of approved and unapproved peptide therapies states that rigorous human safety data are scarce across the unapproved group it examined, which includes TB-500, and that there is potential for serious harm to patients. The product-identity problem compounds this: a 2023 analysis found the content of internet-sold TB500 and TB1000 products not systematically consistent with their former descriptions, which means a safety profile cannot be attached to material whose composition is not established.3,4,5

Sold for laboratory use. Not a legal medicine for people.

The sequence, precisely

Thymosin beta-4 is a 43-residue protein. Within it, the segment at positions 17 to 23 — leucine, lysine, lysine, threonine, glutamate, threonine, glutamine, written LKKTETQ — is the actin-binding site to which the protein's effects on cell migration and wound healing are attributed 1. TB-500 is that seven-residue segment, synthesised and acetylated at the N-terminus 1. A fragment carrying a protein's active site is a reasonable thing to build, and it is not the same object as the protein. When a marketing page cites "over 40 years of thymosin beta-4 research", it is citing research on the larger molecule.

Where the human trials actually went

As of August 2026 a ClinicalTrials.gov search for thymosin beta 4 returns 18 studies. Sorted by what they were for, the picture is unambiguous: five in dry eye, one in neurotrophic keratopathy, four in acute myocardial infarction, one in pressure ulcers, one in venous stasis ulcers, one in epidermolysis bullosa, one in corneal wounds in diabetes, one in atherosclerotic cardiovascular disease with endothelial dysfunction, two in healthy volunteers, and one withdrawn myocardial ischaemia study. Three are designated phase 3 and a fourth phase 2/3; all four are ophthalmic. None of the 18 lists a tendon, ligament, joint or muscle injury as a condition studied.

The one registry entry that names TB-500 itself rather than thymosin beta-4 is a phase 1/2 study of cardiovascular biomarkers in stable atherosclerotic disease, listed as recruiting in August 2026 with an estimated completion in February 2028. It has not reported, and its subject is endothelial function rather than musculoskeletal repair.

The phase 3 that exists, read carefully

"Phase 3" sounds like the end of the road. This one enrolled eighteen patients. In the published trial of 0.1% thymosin beta-4 ophthalmic solution in stage 2 and 3 neurotrophic keratopathy, complete healing at four weeks occurred in 6 of 10 treated patients and 1 of 8 on placebo — 60% against 12.5% — which the authors reported at p = 0.0656 and described as a strong efficacy trend rather than a significant difference 2. Other measures did reach significance: healing assessed at day 43 at p = 0.0359, disease-stage improvement at day 43 at p = 0.0467, and symptom scores at several timepoints 2. This is a real, carefully reported small trial in a difficult condition. It is also an eye drop, at a sample size of eighteen, for a corneal defect. Nothing in it speaks to a torn hamstring.

Two larger phase 3 dry-eye trials sit in the registry rather than the literature: one with 601 participants completed in March 2018, and one with 700 completed in October 2021, whose ClinicalTrials.gov record showed no posted results as of August 2026.

What is in the vial

There is a step before "does it work", which is "is it the thing". A 2023 analysis of misbranded and adulterated products sold over the internet examined material sold as TB500 and TB1000 and reported that the content is not systematically consistent with the products' own former descriptions 5. That is a finding about the supply, not about the peptide, and it is the reason this page treats any claimed dose or anecdote about TB-500 as being about a substance whose composition has not been established. Our BPC-157 page covers the same structural problem in the compound TB-500 is most often stacked with.

What would change this page

A registered, randomized trial of TB-500 — the fragment, injected, in people with a tendon, ligament or muscle injury, with a healing or function endpoint. As of August 2026 no such record appears among the 18 ClinicalTrials.gov studies returned for thymosin beta 4. A 2026 orthopaedic review of injectable peptide therapy reports human orthopaedic data for this compound as lacking 2, and a 2026 sports medicine review reaches the same conclusion about rigorous human data across the unapproved group it examined 3. Until that changes, the animal work is the whole of the case, and animal work is where this compound's evidence tier sits.

Questions

Frequently asked questions

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

No. Thymosin beta-4 is a 43-residue protein. TB-500 is the seven-residue segment at positions 17 to 23 of that protein — LKKTETQ — synthesised with an acetyl group on the N-terminus. A 2026 review of peptide therapies lists them as separate entries for that reason. Research on the full protein is not automatically research on the fragment.

Has TB-500 been tested in humans for tendon or muscle injury?

A ClinicalTrials.gov search for thymosin beta 4 returned 18 studies in August 2026, and none lists a tendon, ligament, joint or muscle injury as a condition studied. The one registry entry naming TB-500 itself is a phase 1/2 cardiovascular-biomarker study in stable atherosclerotic disease, recruiting as of August 2026 with an estimated completion in February 2028. Two 2026 reviews that examined injectable peptides for musculoskeletal use both describe human orthopaedic data for this compound as lacking.

What did the thymosin beta-4 phase 3 trial find?

The published phase 3 tested a 0.1% thymosin beta-4 ophthalmic solution in 18 patients with stage 2 and 3 neurotrophic keratopathy. Complete healing at four weeks occurred in 6 of 10 treated patients against 1 of 8 on placebo, reported at p = 0.0656 — described by the authors as a strong efficacy trend rather than a significant difference. Healing assessed at day 43 and disease-stage improvement did reach significance, as did several symptom measures. It is an eye drop trial in 18 people.

What dose of TB-500 is effective?

There is no human dose-ranging or pharmacokinetic study to answer that from. The one administration study with a stated quantity gave horses a single dose containing 10 mg of N-acetylated LKKTETQ, and its purpose was to develop a doping-control detection method rather than to measure an effect. A 2026 orthopaedic review states that indications, dosing, frequency and duration remain unknown for the injectable peptides it examined.

Is TB-500 legal, and is it safe?

A drugsFDA search returns no match for TB-500 and none for thymosin, so there is no approved product for any indication. A 2026 orthopaedic review notes that thymosin beta-4 and TB-500 are banned substances in sport, and a 2026 sports medicine review states that rigorous human safety data are scarce across the unapproved peptides it examined, with potential for serious harm. A 2023 analysis of internet-sold TB500 and TB1000 products found their content not systematically consistent with the products' own former descriptions — so a safety profile cannot reliably be attached to what is actually being sold.

Glossary

Key terms

Peptide fragment
A short piece cut from a larger protein's sequence. TB-500 is residues 17 to 23 of thymosin beta-4, seven of its 43.
N-acetylation
An acetyl group added to a peptide's leading end, usually to slow degradation. TB-500 carries an artificial one.
Ophthalmic solution
A drug formulated as eye drops. The route of the phase 3 thymosin beta-4 evidence — not a subcutaneous injection.
Neurotrophic keratopathy
A corneal disease in which reduced nerve supply leaves persistent surface defects. The indication of the published phase 3 trial.
Misbranded product
Material sold under a name or description its contents do not match — the finding of a 2023 analysis of internet-sold TB500 and TB1000.
Preclinical
Animal or laboratory research conducted before human trials. It is where this compound's evidence for tissue repair currently stops.

Sources

References

  1. Ho EN, Kwok WH, Lau MY, et al. (2012). Doping control analysis of TB-500, a synthetic version of an active region of thymosin β4, in equine urine and plasma by liquid chromatography-mass spectrometry. Journal of Chromatography A. https://pubmed.ncbi.nlm.nih.gov/23084823/
  2. Mayfield CK, Bolia IK, Feingold CL, et al. (2026). Injectable Peptide Therapy: A Primer for Orthopaedic and Sports Medicine Physicians. American Journal of Sports Medicine. https://pubmed.ncbi.nlm.nih.gov/41476424/
  3. Mendias CL, Awan TM (2026). Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance. Sports Medicine. https://pubmed.ncbi.nlm.nih.gov/41966639/
  4. Sosne G, Kleinman HK, Springs C, et al. (2022). 0.1% RGN-259 (Thymosin ß4) Ophthalmic Solution Promotes Healing and Improves Comfort in Neurotrophic Keratopathy Patients in a Randomized, Placebo-Controlled, Double-Masked Phase III Clinical Trial. International Journal of Molecular Sciences. https://pubmed.ncbi.nlm.nih.gov/36613994/
  5. Delcourt V, Garcia P, Chabot B, et al. (2023). TB500/TB1000 and SGF1000: A scientific approach for a better understanding of misbranded and adulterated drugs. Drug Testing and Analysis. https://pubmed.ncbi.nlm.nih.gov/36482504/

Medical disclaimer: This content is for general educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a licensed healthcare professional before starting, stopping, or changing any treatment.