Page data last changed: . Chemistry registry snapshot: . Registry refreshes and identity assessments are separate from scientific content review.
Seven acetylated residues of a 43-residue protein: TB-500's biology is inferred from thymosin β4, and the fragment itself has no published human efficacy data.
Also known as: Ac-LKKTETQ · thymosin β4 (17–23) fragment · TB500 · Tβ4 actin-binding fragment
Part of the Repair & recovery peptides cluster
TB-500 — evidence brief
The defined fragment has laboratory/metabolism evidence; the rat tendon result concerns incompletely characterized TB-500-labelled material. A human eye trial studied full-length thymosin β4, so it cannot validate the fragment or injectable TB-500.
- Version
- 2026-10-05.1
- Snapshot updated
Prepared by Peptides Codex. Independent review by a qualified subject specialist is pending.
Scope of this brief
The selected profile reference is Ac-LKKTETQ, the N-acetylated seven-residue thymosin β4 fragment. Full-length 43-residue thymosin β4 and unspecified TB-500-labelled materials are separate evidence categories. This selected synthesis is not a systematic or independent expert review.
Rahaman et al., 2024 · PMID 38382158
- Material tested
- Defined Ac-LKKTETQ and synthesized metabolite standards.
- Model or population
- Human serum/enzyme systems, rats and cultured fibroblasts.
- Study design
- Analytical/metabolism experiments and an in-vitro wound-closure screen.
- Sample and comparison
- Sample counts not reported in the retrieved abstract.
- Reported finding
- Ac-LKKTE, not parent Ac-LKKTETQ, significantly increased wound closure versus control in the cell assay.
- Limits of this evidence
- A cell assay and metabolism measurements do not establish tendon healing or clinical efficacy. Full methods were not retrieved.
Source access: Primary abstract inspected; full-text methods unavailable during this review.
Biçer et al., 2026 · PMID 42542926
- Material tested
- Authors' TB-500-labelled material; sequence not characterized as Ac-LKKTETQ.
- Model or population
- Rats after Achilles tendon transection and repair.
- Study design
- Randomized four-arm experiment including BPC-157 and a combination; four-week endpoint.
- Sample and comparison
- 32 rats, 8/group; separate endpoint cohorts of 4/group.
- Reported finding
- TB-labelled material improved failure load versus control (adjusted p=0.0406); combination showed no added benefit.
- Limits of this evidence
- Cannot attribute this result to the selected Ac-LKKTETQ fragment. Small animal cohorts do not establish human benefit.
Source access: Primary journal full text and PubMed abstract inspected.
Sosne & Ousler, 2015 · PMID 26056426
- Material tested
- RGN-259 ophthalmic full-length 43-residue thymosin β4, not Ac-LKKTETQ.
- Model or population
- Adults with moderate-to-severe dry eye.
- Study design
- Single-center randomized, double-masked, placebo-controlled phase II trial; 28 days.
- Sample and comparison
- 72 randomized, 36/group; 69 completed.
- Reported finding
- Neither primary endpoint differed significantly; several secondary measures favored treatment.
- Limits of this evidence
- Different molecule, formulation and indication. Secondary findings cannot validate the fragment or injectable TB-500.
Source access: Primary full-text sections retrieved in indexed results; PubMed abstract corroborated.
A finding applies to the material, model and conditions studied. It does not establish safety or effectiveness in other settings.
Overview
TB-500 is the synthetic, N-acetylated heptapeptide Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln (Ac-LKKTETQ), corresponding to residues 17–23 of thymosin β4, the protein's actin-binding motif. It first appeared as a veterinary preparation and is sold as a research chemical; its metabolism has been characterised in rats. A 2026 rat tendon study reported benefits with vendor-labelled TB-500 whose sequence was not characterized, so it does not establish efficacy of Ac-LKKTETQ. The fragment has no published human efficacy data. No product-specific authorization record has been verified in this profile; human trial registration does not establish approval. Its first registered human trial began recruiting in 2026.
Source & context
Biological / chemical source: Synthetic fragment related to thymosin β4 research
Primary research or clinical context: Veterinary-origin research chemical; no product-specific authorization record verified in this profile. One registered human trial (phase 1/2, recruiting 2026) does not establish approval
What TB-500 is — and what it is not
TB-500 is a synthetic seven-residue peptide, acetyl-Leu-Lys-Lys-Thr-Glu-Thr-Gln, copied from positions 17 to 23 of thymosin β4 (Tβ4), a 43-residue protein present in nearly every cell that sequesters actin monomers and is involved in cell migration and tissue repair. That seven-residue stretch is Tβ4's actin-binding motif. TB-500 is not thymosin β4: it is one-sixth of it, with an added N-terminal acetyl group, and the assumption that it reproduces the parent protein's biology has not been tested in humans. The name entered the literature as a veterinary preparation marketed for racehorses, which is why the earliest analytical papers come from equine doping control.
Sequence and chemistry
In one-letter code the sequence is LKKTETQ with an N-acetyl cap (formula C38H68N10O14, average mass about 889 Da, CAS 885340-08-9). Two lysines make it basic; the glutamate and threonines make it soluble. There are no cysteines, no cyclisation and no non-canonical residues, so it is a straightforward linear peptide. Rahaman et al. (Journal of Chromatography B 2024) synthesised authentic standards of TB-500 and its metabolites and developed a UHPLC-Orbitrap method to quantify them, noting that the biological effects of TB-500 itself had not previously been documented and that its metabolites had never been structurally identified.
Metabolism: what happens to the fragment
The 2024 metabolism study followed TB-500 in human serum, in enzyme systems and in rats. The primary metabolite was Ac-Leu-Lys (Ac-LK), highest in the first six hours; Ac-Leu-Lys-Lys (Ac-LKK) was a long-lived metabolite still detectable at 72 hours. In fibroblast assays neither the parent nor its metabolites were cytotoxic, and only one fragment, Ac-LKKTE, showed significant wound-healing activity compared with control — the parent TB-500 did not. That last finding matters: the sequence that is sold is not the one that was active in the dish.
| Species | Observation |
|---|---|
| Ac-LKKTETQ (parent) | No cytotoxicity; no significant wound-healing activity in fibroblasts |
| Ac-LKKTE | Only species with significant wound-healing activity |
| Ac-LKK | Long-term metabolite, detectable to 72 h |
| Ac-LK | Primary metabolite, peak at 0–6 h |
Animal evidence
A 2026 rat Achilles-tendon experiment (Biçer et al., Joint Diseases and Related Surgery 2026) used vendor-labelled TB-500 whose sequence was not characterized. It therefore does not establish efficacy of the selected Ac-LKKTETQ reference. In that experiment, 32 rats with transected and repaired tendons received control, BPC-157 (10 µg/kg/day), the authors' TB-500 material (60 µg/kg/day) or both intraperitoneally for four weeks. Maximum load to failure was higher in both peptide groups and reached statistical significance for the TB-500-labelled material; that material also produced significantly lower Bonar histology scores. This is one study of eight animals per group. A 2026 scoping review of six peptides in musculoskeletal medicine (Tewari et al., American Journal of Sports Medicine) found that 67% of all identified publications used animal models, mostly rats, with promising but variable effects and — for the fragment — no human efficacy data.
Human evidence
There is none for TB-500 as such. Full-length thymosin β4 has been studied in small human trials for other indications, but those data belong to the parent protein, not the fragment. Sports-medicine reviews published in 2026 (Mayfield et al.; Mendias and Awan; Rahman et al.) all describe TB-500 as part of a grey market of unapproved compounds marketed on animal data. As of September 2026 a single human trial is registered: NCT07487363, a phase 1/2 study of TB-500 (thymosin β4 17–23 fragment) on cardiovascular biomarkers, listed as recruiting. Until it reports, every human claim for TB-500 rests on extrapolation.
Doping control and regulatory status
Because TB-500 emerged as a veterinary product for racehorses, the Hong Kong Jockey Club laboratory published a liquid chromatography–mass spectrometry method in 2012 to detect the acetylated peptide and its metabolites in equine urine and plasma (Ho et al., Journal of Chromatography A), specifically to control its misuse in equine sport. Human anti-doping laboratories use the same logic. No product-specific authorization record has been verified in this profile. Human trial registration does not establish approval. Authorization and supply restrictions depend on the product, intended use and jurisdiction; consult current regulator records.
TB-500 vs BPC-157 and the blend names
TB-500 is paired with BPC-157 in the grey market's default “healing stack”, and appears in the Wolverine, GLOW and KLOW blends. The two peptides come from different biology — an actin-binding motif versus a gastric-juice-derived sequence — and have never been tested together in humans. The 2026 rat tendon study used vendor-labelled TB-500 whose sequence was not characterized. It tested that material with BPC-157 and found the two-peptide group did not outperform the TB-500-labelled material alone on the significant endpoints. These results do not establish the effects of combining Ac-LKKTETQ with BPC-157. The comparison guide and the blend guides go through what is and is not known.
Quality of commercial material
Vendors label material as TB-500, thymosin β4 or TB4 interchangeably; these are different molecules of very different size (889 Da versus about 4,963 Da). A certificate of analysis must state the sequence and observed mass, and an acetylated heptapeptide is easy to distinguish from the 43-residue protein by mass spectrometry. Independent testing of grey-market peptide vials has repeatedly found content that does not match the label. This profile is educational; it does not describe how to obtain or use anything.
Sequence
One-letter sequence commonly cited for TB-500 (educational; isoforms and modifications may differ):
LKKTETQ
Residues plotted ~100° apart around an α-helix — clustering of one color reveals an amphipathic face.
Structure & chemistry
Molecular identity & reference confidence
Source-supported reference
Reference values are taken from the cited molecular record or curated profile. A database match is not independent laboratory verification; modifications, counter-ions, and formulations can change the measured mass.
- Molecular form
- Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln — residues 17–23 of thymosin β4 (43 aa), the segment responsible for actin binding, with an N-terminal acetyl group
- Species
- Not established by this molecular identity audit
- Termini (N / C)
- Not specified / Free acid
Average reference mass
Reference policy updated: 2026-10-05
- PubChem molecular record · 2026-10-01
- Molecular formula
- C38H68N10O14
- Average reference mass
- ≈ 889
- Plasma half-life
- Not established in humans. In rats the primary metabolite Ac-LK peaked at 0–6 h and Ac-LKK persisted to 72 h
- Receptors
- None. The parent motif binds monomeric (G-) actin; the fragment's own biological effects were described in 2024 as undocumented, and only the metabolite Ac-LKKTE showed wound-healing activity in fibroblasts
- Backbone
- Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln — residues 17–23 of thymosin β4 (43 aa), the segment responsible for actin binding, with an N-terminal acetyl group
- C-terminus
- Free acid
- Status
- No product-specific authorization record verified in this profile; registration of the phase 1/2 trial NCT07487363 does not establish approval
N-terminal acetylation is the only modification and distinguishes the commercial product from the native LKKTETQ segment; it also serves as the analytical marker in doping-control methods.
- PubChem CID: 62707662
- CAS RN: 885340-08-9
- UNII: QHK6Z47GTG
Chemistry values: curated profile, PubChem · fetched 2026-10-01.
Clinical development snapshot
ClinicalTrials.gov lists 1 registered study with “TB-500” as an intervention (snapshot 2026-09-06). A registry footprint is not evidence of efficacy or approval.
| NCT | Title | Phase | Status | Updated |
|---|---|---|---|---|
| NCT07487363 | TB-500 (Thymosin Beta 4 17-23 Fragment) for Cardiovascular Biomarkers in Stable ASCVD | Phase 2 | recruiting | 2026-03-23 |
TB-500 — reconstitution calculator
Enter how much peptide is in the vial and how much diluent (e.g. bacteriostatic water) is added. The tool returns the resulting solution concentration — and, for any amount you type, the volume it corresponds to. This is educational arithmetic, not a dosing recommendation.
Reference form: Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln — residues 17–23 of thymosin β4 (43 aa), the segment responsible for actin binding, with an N-terminal acetyl groupAverage reference mass: 889 Da
Enter an amount to see the volume it corresponds to.
Educational concentration mathematics only. This tool does not recommend a dose, amount, or protocol, and nothing here is medical advice. Many peptides are not authorized by Health Canada for human use — see our reconstitution and bacteriostatic-water guides for context.
Change log
Dated observations from the data pipeline (registry flags, trial footprints, identifiers) and editorial reviews of this profile.
- EditorialProfile content reviewed and updated by the editorial team.
FAQ about TB-500
What is TB-500?+
TB-500 is the synthetic, N-acetylated heptapeptide Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln (Ac-LKKTETQ), corresponding to residues 17–23 of thymosin β4, the protein's actin-binding motif. It first appeared as a veterinary preparation and is sold as a research chemical; its metabolism has been characterised in rats. A 2026 rat tendon study reported benefits with vendor-labelled TB-500 whose sequence was not characterized, so it does not establish efficacy of Ac-LKKTETQ. The fragment has no published human efficacy data. No product-specific authorization record has been verified in this profile; human trial registration does not establish approval. Its first registered human trial began recruiting in 2026.
What Canadian product status is recorded for TB-500?+
Canadian product status for TB-500 has not been verified in this profile. No verified record here does not mean no authorization exists. Status depends on the product, formulation and use; consult Health Canada's product records.
What is the typical length of TB-500?+
TB-500 is commonly described as approximately 7 amino acids (Synthetic thymosin β4 fragment (research peptide)).
What is TB-500?+
A synthetic, N-acetylated 7-residue peptide (Ac-LKKTETQ) copied from the actin-binding motif of thymosin β4. It is a fragment of the protein, not the protein itself.
Is TB-500 the same as thymosin beta-4?+
No. Thymosin β4 is a 43-residue protein (~4,963 Da); TB-500 is residues 17–23 with an acetyl cap (~889 Da). Human data for the protein do not transfer to the fragment.
Is there human evidence for TB-500?+
No published efficacy data. The first registered human trial (phase 1/2, cardiovascular biomarkers, NCT07487363) began recruiting in 2026.
What did the rat tendon study show?+
In 32 rats, the authors' vendor-labelled TB-500 material significantly increased Achilles tendon load to failure and improved histology scores over four weeks; BPC-157 trended the same way without reaching significance. The material's sequence was not characterized, so these results do not establish efficacy of Ac-LKKTETQ.
Is TB-500 approved or legal?+
No product-specific authorization record has been verified in this profile. Human trial registration does not establish approval. Authorization and supply restrictions depend on the product, intended use and jurisdiction; consult current regulator records. Doping-control methods exist to detect the acetylated peptide and its metabolites.
What is the sequence of TB-500?+
Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln (LKKTETQ, N-acetylated). Formula C38H68N10O14, mass about 889 Da.
Further reading
- ComparisonBPC-157 vs TB-500: Differences, Research Context & ComparisonSide-by-side educational comparison of BPC-157 and TB-500—sequences, research themes, stacking discussions, and evidence limits.
- Blends explainedWhat Is the “Wolverine” Peptide? BPC-157 + TB-500, and What the Evidence Actually Shows“Wolverine peptide” (or “Wolverine stack”) is a vendor nickname for BPC-157 combined with TB-500. This guide explains what each component is, what has actually been studied in humans (very little), what a rat combination study found and what remains untested in humans, and where it stands legally.
- Blends explainedWhat Is the “GLOW” Peptide? GHK-Cu + BPC-157 + TB-500, Explained From the Evidence“GLOW peptide” is a vendor blend name for GHK-Cu, BPC-157 and TB-500 in one vial. This guide explains each component, the linked cellular and animal evidence, the gaps for a three-way injectable blend, and product-specific authorization.
- Blends explainedWhat Is the “KLOW” Peptide? KPV + GHK-Cu + BPC-157 + TB-500, Component by Component“KLOW peptide” is a four-peptide vendor blend: KPV, GHK-Cu, BPC-157 and TB-500. This guide explains what each is, what has been studied in humans (very little beyond topical GHK-Cu), why a four-way mix is untested, and where it stands legally.
- SafetyPeptide Safety and Risks: A Balanced Educational OverviewAn objective, balanced overview of what research does and does not establish about peptide risks—unknowns, purity and contamination concerns, and why unapproved compounds carry uncertainty. Not reassurance and not medical advice.
- FoundationsWhat Are Research Peptides? A Clear Educational GuideLearn what “research peptides” means, how they differ from approved peptide drugs, quality markers (COA, purity), and how to study them responsibly.
Related peptides
References & further reading
- 1.Safer et al. (1997). Thymosin beta 4 binds actin in an extended conformation and contacts both the barbed and pointed ends. Biochemistry
- 2.Hannappel et al. (1993). Actin-sequestering ability of thymosin beta 4, thymosin beta 4 fragments, and thymosin beta 4-like peptides as assessed by the DNase I inhibition assay. Biol Chem Hoppe Seyler
- 3.Yarmola et al. (2007). Thymosin beta4: actin regulation and more. Ann N Y Acad Sci
- 4.Goldstein et al. (2005). Thymosin beta4: actin-sequestering protein moonlights to repair injured tissues. Trends Mol Med
- 5.Malinda et al. (1999). Thymosin beta4 accelerates wound healing. J Invest Dermatol
- 6.Philp et al. (2006). Thymosin beta4 promotes matrix metalloproteinase expression during wound repair. J Cell Physiol
- 7.Philp et al. (2004). Thymosin beta4 promotes angiogenesis, wound healing, and hair follicle development. Mech Ageing Dev
- 8.Kleinman et al. (2016). Thymosin β4 Promotes Dermal Healing. Vitam Horm
- 9.Philp et al. (2003). The actin binding site on thymosin beta4 promotes angiogenesis. FASEB J
- 10.Smart et al. (2007). Thymosin beta4 and angiogenesis: modes of action and therapeutic potential. Angiogenesis
- 11.Dubé et al. (2018). Thymosin β4 and the vasculature: multiple roles in development, repair and protection against disease. Expert Opin Biol Ther
- 12.Bock-Marquette et al. (2004). Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature
- 13.Srivastava et al. (2007). Thymosin beta4 is cardioprotective after myocardial infarction. Ann N Y Acad Sci
- 14.Smart et al. (2007). Thymosin beta-4 is essential for coronary vessel development and promotes neovascularization via adult epicardium. Ann N Y Acad Sci
- 15.Srivastava et al. (2012). Cardiac repair with thymosin β4 and cardiac reprogramming factors. Ann N Y Acad Sci
- 16.Hao et al. (2018). A dimeric thymosin beta 4 with novel bio-activity protects post-ischemic cardiac function by accelerating vascular endothelial cell proliferation. Int J Cardiol
- 17.Sosne et al. (2007). Thymosin beta 4: A novel corneal wound healing and anti-inflammatory agent. Clin Ophthalmol
- 18.Sosne et al. (2015). Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea
- 19.Sosne 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. Int J Mol Sci
- 20.Sosne et al. (2016). Thymosin Beta 4: A Potential Novel Therapy for Neurotrophic Keratopathy, Dry Eye, and Ocular Surface Diseases. Vitam Horm
- 21.Sosne (2018). Thymosin beta 4 and the eye: the journey from bench to bedside. Expert Opin Biol Ther
- 22.Nguyen et al. (2025). Engineered Tandem Thymosin Peptide Promotes Corneal Wound Healing. Invest Ophthalmol Vis Sci
- 23.Rahaman et al. (2024). Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro. Journal of Chromatography B
- 24.Biçer et al. (2026). Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: A histopathological and biomechanical study. Joint Diseases and Related Surgery
- 25.Ho 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
- 26.Tewari et al. (2026). Peptide Supplements and Their Therapeutic Applications in Sports Medicine. American Journal of Sports Medicine
- 27.Mendias & Awan (2026). Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance. Sports Medicine
- 28.Mayfield et al. (2026). Injectable Peptide Therapy: A Primer for Orthopaedic and Sports Medicine Physicians. American Journal of Sports Medicine
- 29.PubChem — TB-500 (CID 62707662)