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Approved source synthesisEvidence current through August 2026

TB-500 Full Evidence Review

September 01, 2026 · 4 minutes

The strongest direct evidence for TB-500 concerns molecular identity and analytical detection, not completed human outcomes. Esposito et al. identified and synthesized Ac-LKKTETQ from a seized product, while Ho et al. separately detected the acetylated fragment and metabolites after administration in horses. Later metabolism work retained this identity but did not create human efficacy or safety evidence.

Evidence boundary: This review separates chemically verified Ac-LKKTETQ from full-length thymosin beta-4 and every named development product or fragment. Evidence is not transferred across those entities.

Technical conclusion

The strongest direct evidence for TB-500 concerns molecular identity and analytical detection, not completed human outcomes. Esposito et al. identified and synthesized Ac-LKKTETQ from a seized product, while Ho et al. separately detected the acetylated fragment and metabolites after administration in horses. Later metabolism work retained this identity but did not create human efficacy or safety evidence. P001–P004

The parent protein has a much broader mechanistic, animal, and formulation-specific clinical literature. Full-length Tβ4 uses distributed actin contacts, so the presence of LKKTETQ inside the parent sequence does not make the seven-residue fragment functionally interchangeable. P005–P008

Human-evidence boundary

No completed clinical-outcome study of chemically verified Ac-LKKTETQ was identified. TBRIDGE-CV is the first located fragment-specific prospective registry record and had no results at the cutoff. P001, P012

Human records involving full-length Tβ4, RGN-259, RGN-137, RGN-352, recombinant NL005, or Ac-SDKP answer different product and molecular questions. Their findings may explain the surrounding research program, but they cannot establish TB-500 efficacy, pharmacokinetics, safety, or dosing. P009–P010, P014–P019

Musculoskeletal evidence

The 2026 repaired-Achilles rat study explicitly called its commercial test article TB-500 and reported selected biomechanical and histologic differences. It did not report sequence confirmation, molecular mass, purity chromatogram, or other orthogonal identity evidence. Its result is therefore both preclinical and identity-limited. The combination arm did not establish additive benefit with BPC-157. P011

Regulatory and research status

FDA’s 2026 review documented inconsistent naming, product-quality uncertainty, and the absence of an adequate direct human evidence package. WADA separately prohibits thymosin beta-4 and its derivatives, including TB-500. These records establish regulatory and anti-doping context rather than efficacy. P001, P013

Study map

Study records discussed

Exact TB-500 identity and direct-fragment evidenceSee approved evidence mapCompleted

Drug Testing and Analysis

TB5-STUDY-P002

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 Testing an

View study
Exact TB-500 identity and direct-fragment evidenceSee approved evidence mapCompleted

Journal of Chromatography A

TB5-STUDY-P003

Ho ENM, et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin beta-4, in equine urine and plasma by liquid chromatography-mass spectrometry. Journal of Chromatography A. 2012;1265:57–69. DOI: 10.1016/j.chr

View study
Exact TB-500 identity and direct-fragment evidenceSee approved evidence mapCompleted

Journal of Chromatography B

TB5-STUDY-P004

Rahaman MM, 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. Journal of Chromatography B. 2024. DOI: 10

View study
Parent peptide, motif, and related-product attribution controlsSee approved evidence mapCompleted

FASEB Journal

TB5-STUDY-P007

Philp D, et al. The actin binding site on thymosin beta-4 promotes angiogenesis. FASEB Journal. 2003. PMID: 14500546. https://pubmed.ncbi.nlm.nih.gov/14500546/

View study
Parent peptide, motif, and related-product attribution controlsSee approved evidence mapCompleted

Wound Repair and Regeneration

TB5-STUDY-P008

Philp D, et al. Thymosin beta-4 and LKKTETQ in aged-mouse wound research. Wound Repair and Regeneration. 2003. PMID: 12581423. https://pubmed.ncbi.nlm.nih.gov/12581423/

View study
Exact TB-500 identity and direct-fragment evidenceSee approved evidence mapCompleted

Joint Diseases and Related Surgery

TB5-STUDY-P011

Biçer O, et al. Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: a histopathological and biomechanical study. Joint Diseases and Related Surgery. 2026;37(3):822–837. DOI: 10.52312/jdrs.2026.2951. PMID: 42542926. https://pubmed.n

View study

Permanent sources

Reference ledger

  1. P001Exact TB-500 identity and direct-fragment evidence

    TB-500-Related Bulk Drug Substances: Pharmacy Compounding Advisory Committee Scientific Review

    U.S. Food and Drug Administration. U.S. Food and Drug Administration. TB-500-Related Bulk Drug Substances: Pharmacy Compounding Advisory Committee Scientific Review. 2026. https://www.fda.gov/media/193349/download(2026)

  2. P002Exact TB-500 identity and direct-fragment evidence

    Drug Testing and Analysis

    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. 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 Testing and Analysis. 2012;4(9):733–738. DOI: 10.1002/dta.1402. PMID: 22962027. https://pubmed.ncbi.nlm.nih.gov/22962027/(2012). DOI: 10.1002/dta.1402

  3. P003Exact TB-500 identity and direct-fragment evidence

    Journal of Chromatography A

    Ho ENM, et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin beta-4, in equine urine and plasma by liquid chromatography-mass spectrometry. Ho ENM, et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin beta-4, in equine urine and plasma by liquid chromatography-mass spectrometry. Journal of Chromatography A. 2012;1265:57–69. DOI: 10.1016/j.chroma.2012.09.043. PMID: 23084823. https://pubmed.ncbi.nlm.nih.gov/23084823/(2012). DOI: 10.1016/j.chroma.2012.09.043

  4. P004Exact TB-500 identity and direct-fragment evidence

    Journal of Chromatography B

    Rahaman MM, 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. Rahaman MM, 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. Journal of Chromatography B. 2024. DOI: 10.1016/j.jchromb.2024.124033. PMID: 38382158. https://pubmed.ncbi.nlm.nih.gov/38382158/(2024). DOI: 10.1016/j.jchromb.2024.124033

  5. P005Parent peptide, motif, and related-product attribution controls

    UniProt. Thymosin beta-4, TMSB4X, P62328. Full-length 43-residue parent identity. https://www.uniprot.org/uniprotkb/P62328/entry

    UniProt. Thymosin beta-4, TMSB4X, P62328. Full-length 43-residue parent identity. https://www.uniprot.org/uniprotkb/P62328/entry

  6. P006Parent peptide, motif, and related-product attribution controls

    EMBO Journal

    Van Troys M, et al. The actin binding site of thymosin beta-4 mapped by mutational analysis. Van Troys M, et al. The actin binding site of thymosin beta-4 mapped by mutational analysis. EMBO Journal. 1996. PMID: 8617195. https://pmc.ncbi.nlm.nih.gov/articles/PMC449934/(1996)

  7. P007Parent peptide, motif, and related-product attribution controls

    FASEB Journal

    Philp D, et al. The actin binding site on thymosin beta-4 promotes angiogenesis. Philp D, et al. The actin binding site on thymosin beta-4 promotes angiogenesis. FASEB Journal. 2003. PMID: 14500546. https://pubmed.ncbi.nlm.nih.gov/14500546/(2003)

  8. P008Parent peptide, motif, and related-product attribution controls

    Wound Repair and Regeneration

    Philp D, et al. Thymosin beta-4 and LKKTETQ in aged-mouse wound research. Philp D, et al. Thymosin beta-4 and LKKTETQ in aged-mouse wound research. Wound Repair and Regeneration. 2003. PMID: 12581423. https://pubmed.ncbi.nlm.nih.gov/12581423/(2003)

  9. P009Parent peptide, motif, and related-product attribution controls

    Ruff D, et al. Randomized placebo-controlled study of full-length thymosin beta-4 in healthy volunteers. 2010. PMID: 20536472. https://pubmed.ncbi.nlm.nih.gov/20536472/

    Ruff D, et al. Randomized placebo-controlled study of full-length thymosin beta-4 in healthy volunteers. 2010. PMID: 20536472. https://pubmed.ncbi.nlm.nih.gov/20536472/(2010)

  10. P010Parent peptide, motif, and related-product attribution controls

    Wang X, et al. Phase I study of recombinant human thymosin beta-4, NL005. 2021. PMID: 34346165. https://pmc.ncbi.nlm.nih.gov/articles/PMC8419156/

    Wang X, et al. Phase I study of recombinant human thymosin beta-4, NL005. 2021. PMID: 34346165. https://pmc.ncbi.nlm.nih.gov/articles/PMC8419156/(2021)

  11. P011Exact TB-500 identity and direct-fragment evidence

    Joint Diseases and Related Surgery

    Biçer O, et al. Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: a histopathological and biomechanical study. Biçer O, et al. Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: a histopathological and biomechanical study. Joint Diseases and Related Surgery. 2026;37(3):822–837. DOI: 10.52312/jdrs.2026.2951. PMID: 42542926. https://pubmed.ncbi.nlm.nih.gov/42542926/(2026). DOI: 10.52312/jdrs.2026.2951

  12. P012Exact TB-500 identity and direct-fragment evidence

    ClinicalTrials.gov. NCT07487363, TBRIDGE-CV. Registry record; no results at the evidence cutoff. https://clinicaltrials.gov/study/NCT07487363

    ClinicalTrials.gov. NCT07487363, TBRIDGE-CV. Registry record; no results at the evidence cutoff. https://clinicaltrials.gov/study/NCT07487363

  13. P013Regulatory and anti-doping context

    2026 Prohibited List

    World Anti-Doping Agency. World Anti-Doping Agency. 2026 Prohibited List. Thymosin beta-4 and derivatives including TB-500. https://www.wada-ama.org/sites/default/files/2025-09/2026listenfinalcleanseptember2025.pdf(2026)

  14. P014Parent peptide, motif, and related-product attribution controls

    Sosne G, Ousler GW. Clinical development records for full-length Tβ4 ophthalmic RGN-259. 2015. PMID: 26056426. https://pmc.ncbi.nlm.nih.gov/articles/PMC4445951/

    Sosne G, Ousler GW. Clinical development records for full-length Tβ4 ophthalmic RGN-259. 2015. PMID: 26056426. https://pmc.ncbi.nlm.nih.gov/articles/PMC4445951/(2015)

  15. P015Parent peptide, motif, and related-product attribution controls

    Sosne G, et al. Full-length Tβ4 ophthalmic controlled study. 2015. PMID: 25826322. https://pubmed.ncbi.nlm.nih.gov/25826322/

    Sosne G, et al. Full-length Tβ4 ophthalmic controlled study. 2015. PMID: 25826322. https://pubmed.ncbi.nlm.nih.gov/25826322/(2015)

  16. P016Parent peptide, motif, and related-product attribution controls

    SEER-1 investigators. RGN-259 in neurotrophic keratopathy. 2023. PMID: 36613994. https://pmc.ncbi.nlm.nih.gov/articles/PMC9820614/

    SEER-1 investigators. RGN-259 in neurotrophic keratopathy. 2023. PMID: 36613994. https://pmc.ncbi.nlm.nih.gov/articles/PMC9820614/(2023)

  17. P017Parent peptide, motif, and related-product attribution controls

    Guarnera G, et al. Full-length Tβ4/RGN-137 dermal wound research. 2007. PMID: 17495250. https://pubmed.ncbi.nlm.nih.gov/17495250/

    Guarnera G, et al. Full-length Tβ4/RGN-137 dermal wound research. 2007. PMID: 17495250. https://pubmed.ncbi.nlm.nih.gov/17495250/(2007)

  18. P018Parent peptide, motif, and related-product attribution controls

    Zhang Y, et al. Recombinant thymosin beta-4/NL005 myocardial-infarction study. 2025. PMID: 41229390. https://pubmed.ncbi.nlm.nih.gov/41229390/

    Zhang Y, et al. Recombinant thymosin beta-4/NL005 myocardial-infarction study. 2025. PMID: 41229390. https://pubmed.ncbi.nlm.nih.gov/41229390/(2025)

  19. P019Parent peptide, motif, and related-product attribution controls

    Ezan E, et al. Human pharmacokinetic research involving Ac-SDKP/seraspenide, a different Tβ4 fragment. 1994. PMID: 7895600. https://pubmed.ncbi.nlm.nih.gov/7895600/

    Ezan E, et al. Human pharmacokinetic research involving Ac-SDKP/seraspenide, a different Tβ4 fragment. 1994. PMID: 7895600. https://pubmed.ncbi.nlm.nih.gov/7895600/(1994)

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