A reference work, not a recommendation to use: this profile describes mechanism and evidence and does not replace medical advice. The claims come from marketing and forums and are tested here, not endorsed.

Claims checked

  • Injuries of tendons, muscles and skin heal faster

    Not studied

    Recovery & healing · Patients: sports and soft tissue injuries · Animal study

    The fragment LKKTETQ promoted skin wound healing in old mice [4]; for acetylated TB-500, only a breakdown product showed a significant effect in fibroblasts [7]. There are no studies in humans with TB-500; no data were found on tendon or muscle injuries.

  • Chronic wounds heal faster (full-length thymosin β4)

    Single unconfirmed finding

    Recovery & healing · Patients: venous leg ulcers, pressure ulcers · Human, randomised

    In two phase II studies, faster healing only in the people whose wounds healed; presented by the developer group, primary data not checked as full text [8]. Applies to the 43-amino-acid protein, not to TB-500.

  • Protects the heart after infarction (full-length thymosin β4)

    Mixed results

    Heart & blood vessels · Patients: ST-elevation myocardial infarction after catheter treatment · Human, randomised small studiesEvery study behind this level and result had fewer than 100 participants. Small studies report larger effects on average than large ones, so the result is less certain.

    In a randomized study with 96 people, infarct size was not significantly smaller overall, only in the subgroup with early administration; study with involvement of the manufacturer [12].

small studies: Every study behind this level and result had fewer than 100 participants. Small studies report larger effects on average than large ones, so the result is less certain.

Mechanism of action

Evidence map: TB-500

Each line stands for a published finding; line style and color show where it comes from. The filter hides weaker evidence levels. Sources: see references.

Thymosin β4 is a protein of 43 amino acids that occurs in almost all cells, where it binds free actin. Different segments have different functions: the central actin-binding domain (amino acids 17–23, LKKTETQ) is associated with new blood vessel formation, wound healing and cell migration, the start of the protein (Ac-SDKP) with anti-inflammatory effects and less fibrosis [1]. In cell experiments, a peptide with this seven-amino-acid motif promoted endothelial cell migration and vessel sprouting about as strongly as the whole protein (at about 50 nM); peptides without the motif were ineffective [2]. In rats, full-length thymosin β4 accelerated wound healing, and re-formation of the epidermis was up to 61% above control after 7 days [3]. In old mice, the synthetic fragment LKKTETQ also promoted skin wound healing similarly to the parent protein [4].

TB-500 appeared as a veterinary product for racehorses; its main component is LKKTETQ with an artificially acetylated start (Ac-LKKTETQ) [5]. A Belgian doping laboratory confirmed this fragment in a TB-500 product [6]. A Korean analytical study notes that the biological activity of TB-500 itself is not documented; in its experiments, it was rapidly broken down in the rat body into short pieces such as Ac-LK and Ac-LKK, and in fibroblasts only the breakdown product Ac-LKKTE showed a significant effect in the wound healing assay [7]. Online claims about TB-500 therefore rest largely on data for a different, larger molecule.

With the full-length protein, there are clinical studies. In two phase II studies in venous leg ulcers and pressure ulcers, wounds healed almost a month faster according to the developer group, but only in the people whose wounds healed at all [8]. Eye drops with thymosin β4 missed both primary endpoints in dry eye in a randomized study with 72 people, but improved some secondary endpoints [9]; a very small study with 9 people found clearer effects [10]. As an infusion, recombinant thymosin β4 was well tolerated in a phase I study [11]; after myocardial infarction, infarct size was not significantly smaller in the overall group, only in a subgroup with early administration [12]. In mice, increased thymosin β4 production in melanoma cells promoted tumor vessels and metastases [13]. TB-500 products sold over the internet did not consistently match their description in one analysis [14]. TB-500 is prohibited in sport [15].

Targets

TargetTypeActionKey dataEvidence
G-actin (monomer)OtherBinding Laboratory[1][2]
Endothelial cells: migration and vessel sprouting (actin motif)Signaling pathwayActivator≈ 50 nM, similar to thymosin β4 (cell experiment) Laboratory[2]
ErbB2-Raf1 pathway (full-length thymosin β4, cardiomyocytes)Signaling pathwayActivator Animal study[12]

Effect profile

Which signaling systems the compound affects according to current data. ↑ enhanced, ↓ dampened, ≈ modulated, ○ no effect; dots = evidence level.

  • Dopamineno data
  • Noradrenalineno data
  • Serotoninno data
  • Acetylcholineno data
  • Glutamate · AMPAno data
  • Glutamate · NMDAno data
  • GABAno data
  • Histamineno data
  • Orexinno data
  • Adenosineno data
  • Opioidsno data
  • Melatoninno data
  • Neurotrophinsno data
  • Blood flow↑ · Actin motif promotes vessel sprouting (cell experiment); more vessels in wounds with full-length thymosin β4 (rat)[2][3]
  • Nitric oxideno data
  • Energy metabolismno data
  • Insulin · glucoseno data
  • Inflammation · oxidative↓ · Anti-inflammatory effect attributed mainly to the Ac-SDKP segment of the full-length protein, not to the TB-500 fragment[1]
  • Stress axisno data
  • Testosterone axisno data
  • Endocannabinoidsno data
  • Autophagy · senescenceno data
  • Immune systemno data
  • Lipid metabolismno data
  • Coagulation · fibrinolysisno data
  • Methylationno data

Routes of administration and bioavailability

How much of a compound reaches the blood or target tissue depends on the route into the body and on the dosage form. All routes of administration explained

  • Subcutaneous (under the skin) · Solution (TB-500)

    Common online; pharmacokinetics of TB-500 in humans not studied. In rats, rapid breakdown to Ac-LK; the fragment Ac-LKK was detectable in urine for up to 72 hours [7].

    No data

  • Intravenous · recombinant full-length thymosin β4

    100% (by definition)

    In a phase I study, peak levels and area under the curve rose with the amount; no accumulation with repeated administration [11].

    Human, randomised

Human studies

  • Thymosin β4 eye drops in dry eye

    randomized, double-masked, placebo-controlled (phase II) · Patients: moderate to severe dry eye · n = 72 · 28 days

    Measured: Ocular discomfort and inferior corneal staining

    Result: Both primary endpoints missed; some secondary endpoints (discomfort in the controlled adverse environment chamber, central corneal staining) better; no side effects. Full-length protein, not TB-500.[9]

    Human, randomised

  • Thymosin β4 eye drops in severe dry eye

    randomized, double-masked, placebo-controlled (phase II) · Patients: severe dry eye · n = 9 · 28 days of treatment, 28 days of follow-up

    Measured: Ocular discomfort (OSDI), corneal staining

    Result: On day 56, discomfort 35.1% and corneal staining 59.1% lower than under vehicle; very small study. Full-length protein.[10]

    Human, randomised

  • First-in-human use of recombinant thymosin β4 as an infusion

    randomized, double-blind, placebo-controlled (phase I) · healthy · n = 84 · Single dose or 10 days, 28 days of observation each

    Measured: Safety, tolerability, pharmacokinetics, antibodies

    Result: Mild to moderate side effects, no serious ones; 54 people in the single-dose and 30 in the multiple-dose phase. Three authors employed by the manufacturer.[11]

    Human, randomised

  • Recombinant thymosin β4 after myocardial infarction

    randomized, double-blind, placebo-controlled · Patients: ST-elevation myocardial infarction after catheter treatment · n = 96 · 90 days

    Measured: Infarct size

    Result: No significant difference overall; smaller infarct size only in the subgroup with first dose within 8 hours (n = 43). Authors employed by the manufacturer.[12]

    Human, randomised

Risks and warnings

  • No safety data on the fragment

    According to an analytical study, the biological activity of TB-500 is not documented [7]; studies in humans were not found. Tolerability data exist only for the full-length protein (infusion, eye drops) [9][11].

    No data

  • Mislabeled products

    TB500 and TB1000 products sold over the internet did not consistently match their description in a laboratory analysis [14].

    No data

  • Theoretical: tumor growth and metastases

    In mice, melanoma cells with increased thymosin β4 production formed larger tumors, more tumor vessels and more lung metastases [13]. Whether externally administered TB-500 acts similarly has not been studied; the risk is theoretical.

    Animal study

  • Doping

    Thymosin β4 and derivatives such as TB-500 are on the WADA Prohibited List [15]; detection methods for Ac-LKKTETQ and its breakdown products exist [5][6][7].

    No data

Fact check: common claims

  • refuted

    “TB-500 is thymosin β4”

    Thymosin β4 has 43 amino acids [1]; TB-500 contains as its main component an acetylated fragment of seven amino acids [5][6].

  • not supported

    “Clinical studies prove the healing effect of TB-500”

    The clinical studies were done with the full-length protein [8][9][11][12]; for TB-500 itself, the biological activity is not documented [7].

  • not supported

    “TB-500 accelerates the healing of sports injuries”

    Only skin wounds in rodents with the non-acetylated fragment [4]; no study on tendon or muscle injuries in humans.

  • refuted

    “TB-500 is undetectable in sport”

    Validated detection methods for the fragment and its breakdown products have been published [5][6][7]; the substance is prohibited [15].

Pharmacokinetics

Absorption
No data for TB-500 in humans; for full-length thymosin β4, only infusion studied [11].
Half-life
Not verified for TB-500.
Metabolism
Breakdown in serum and in rats to Ac-LK (main product), Ac-LKK (up to 72 hours in urine) and Ac-LKKTE [7]; detection of Ac-LKKTETQ and breakdown products also in horse urine and plasma [5].
Entry into the brain
Not studied.

Legal status

Germany
No marketing authorization known; not checked in medicines registers.
EU
No marketing authorization known; not verified. Originally appeared as a veterinary product for horses [5].
USA
No FDA approval known; not verified. According to the sources checked, even full-length thymosin β4 is not approved anywhere.
Other countries
Sport: thymosin β4 and its derivatives (expressly TB-500) are on the 2025 WADA Prohibited List under S2 (growth factors) [15].

Related compounds

BPC-157same class

Open questions

  • Does the acetylated fragment Ac-LKKTETQ act at all in the living organism, or only its breakdown products?
  • Is there a controlled study with TB-500 in people with tendon or muscle injuries?
  • Does externally administered thymosin β4 or its fragment increase the risk of tumor growth?

References

  1. Sosne G, Qiu P, Goldstein AL, Wheater M. Biological activities of thymosin beta4 defined by active sites in short peptide sequences. FASEB J. 2010;24(7):2144–51. doi:10.1096/fj.09-142307 · PubMed
  2. Philp D, Huff T, Gho YS, Hannappel E, Kleinman HK. The actin binding site on thymosin beta4 promotes angiogenesis. FASEB J. 2003;17(14):2103–5. doi:10.1096/fj.03-0121fje · PubMed
  3. Malinda KM, Sidhu GS, Mani H, Banaudha K, Maheshwari RK, Goldstein AL, et al. Thymosin beta4 accelerates wound healing. J Invest Dermatol. 1999;113(3):364–8. doi:10.1046/j.1523-1747.1999.00708.x · PubMed
  4. Philp D, Badamchian M, Scheremeta B, Nguyen M, Goldstein AL, Kleinman HK. Thymosin beta 4 and a synthetic peptide containing its actin-binding domain promote dermal wound repair in db/db diabetic mice and in aged mice. Wound Repair Regen. 2003;11(1):19–24. doi:10.1046/j.1524-475x.2003.11105.x · PubMed
  5. Ho EN, Kwok WH, Lau MY, Wong AS, Wan TS, Lam KK, et al. 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. J Chromatogr A. 2012;1265:57–69. doi:10.1016/j.chroma.2012.09.043 · PubMed
  6. Esposito S, Deventer K, Goeman J, Van der Eycken J, Van Eenoo P. 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. doi:10.1002/dta.1402 · PubMed
  7. Rahaman KA, Muresan AR, Min H, Son J, Han HS, Kang MJ, et al. 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. J Chromatogr B Analyt Technol Biomed Life Sci. 2024;1235:124033. doi:10.1016/j.jchromb.2024.124033 · PubMed
  8. Treadwell T, Kleinman HK, Crockford D, Hardy MA, Guarnera GT, Goldstein AL. The regenerative peptide thymosin β4 accelerates the rate of dermal healing in preclinical animal models and in patients. Ann N Y Acad Sci. 2012;1270:37–44. doi:10.1111/j.1749-6632.2012.06717.x · PubMed
  9. Sosne G, Ousler GW. Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, phase II clinical trial conducted using the controlled adverse environment (CAE) model. Clin Ophthalmol. 2015;9:877–84. doi:10.2147/OPTH.S80954 · PubMed
  10. Sosne G, Dunn SP, Kim C. Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea. 2015;34(5):491–6. doi:10.1097/ICO.0000000000000379 · PubMed
  11. Wang X, Liu L, Qi L, Lei C, Li P, Wang Y, et al. A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers. J Cell Mol Med. 2021;25(17):8222–8. doi:10.1111/jcmm.16693 · PubMed
  12. Zhang Y, Dong Q, Bian X, Qiao Z, Cui C, Yang N, et al. Recombinant human thymosin beta 4 improves ischemic cardiac dysfunction in mice and patients with acute ST-segment elevation myocardial infarction after reperfusion. Cardiovasc Res. 2025;121(17):2747–58. doi:10.1093/cvr/cvaf223 · PubMed
  13. Cha HJ, Jeong MJ, Kleinman HK. Role of thymosin beta4 in tumor metastasis and angiogenesis. J Natl Cancer Inst. 2003;95(22):1674–80. doi:10.1093/jnci/djg100 · PubMed
  14. Delcourt V, Garcia P, Chabot B, Barnabé A, Bouscarel M, Loup B, et al. TB500/TB1000 and SGF1000: a scientific approach for a better understanding of misbranded and adulterated drugs. Drug Test Anal. 2023;15(4):458–64. doi:10.1002/dta.3421 · PubMed
  15. Thevis M, Kuuranne T, Geyer H. Annual banned-substance review 18th edition – analytical approaches in human sports drug testing 2024/2025. Drug Test Anal. 2026;18(4):458–82. doi:10.1002/dta.70033 · PubMed
How this profile was checked

Last reviewed: 2026-10-23. All sources with a DOI or PMID were resolved automatically via Crossref or doi.org and PubMed.

Translated from the German profile (version of 2026-10-23); translation checked on 2026-10-26.

Checked

  • All 15 DOIs via Crossref, PMIDs via PubMed.
  • Key figures checked against abstracts: 43 amino acids, LKKTETQ = amino acids 17–23 [1]; ≈ 50 nM, peptides without the motif inactive [2]; re-epithelialization +42% (day 4), +61% (day 7) [3]; LKKTETQ in old mice [4]; Ac-LKKTETQ as main component of TB-500, veterinary product [5]; fragment confirmed in TB-500 [6]; activity of TB-500 not documented, Ac-LK, Ac-LKK up to 72 h, only Ac-LKKTE active [7]; phase II ulcer studies [8]; n = 72, primary endpoints missed [9]; n = 9, −35.1% and −59.1% [10]; 54 + 30 people, manufacturer employees [11]; n = 96, subgroup n = 43, manufacturer employees [12]; melanoma mouse model [13]; mislabeled TB500/TB1000 [14].
  • In the full text [15], Table 1: “thymosin-β4 and its derivatives (TB-500)” under S2.3 of the 2025 WADA Prohibited List.
  • ClinicalTrials.gov (October 23, 2026): 18 entries for thymosin β4 (eye drops RGN-259 including the phase III studies ARISE-1 to -3 and neurotrophic keratopathy, skin ulcers, epidermolysis bullosa, myocardial infarction); no credible entry for TB-500.
  • October 26, 2026, precision flags (m004; rules in the guideline under “Number rule and precision flags”, implementation by Claude pending confirmation by Tilman): “Protects the heart after infarction (full-length thymosin β4)”: “kleine_studien” – [12] 96 patients (abstract). Set to not manufacturer-funded: three authors at Beijing Northland Biotech; whether the company made the study drug or funded the study is not documented in the abstract.

Not verified

  • Registry entry NCT07487363 (Hudson Biotech, “TB-500 for Cardiovascular Biomarkers”) describes itself in the brief summary as a fictitious example; not used.
  • Results of the phase III studies ARISE-2 and ARISE-3 (eye drops) are deposited at ClinicalTrials.gov but were not evaluated; no PubMed publication found.
  • Primary data of the phase II ulcer studies only via the review [8]; possible conflicts of interest of the authors (developer company) cannot be checked from the abstract.
  • How Delcourt et al. [14] quantified the deviations of the TB500 products precisely is known only from the abstract.
  • Authorization status of thymosin β4 and TB-500 in Germany, the EU and the US not checked in registers.
  • Funding of [12] not documented: according to the conflict-of-interest statement, three authors are employees of Beijing Northland Biotechnology; the funding information in PubMed names only public funders; whether the company made the study drug is not evident from the abstract. Therefore no manufacturer-funded flag for “Protects the heart after infarction” (October 26, 2026).

No dosages, no sources of supply. This information does not replace medical advice.

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