Evidence current through August 2026

TB-500

N-terminally acetylated thymosin beta-4 residues 17–23, Ac-LKKTETQ-OH

The best-supported product-specific definition of TB-500 is an N-terminally acetylated seven-amino-acid peptide: Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH, abbreviated Ac-LKKTETQ. It corresponds to residues 17–23 within the much larger endogenous protein thymosin beta-4.

Full-length mature human thymosin beta-4—also called Tβ4 or timbetasin—is a 43-amino-acid peptide encoded by the TMSB4X gene. It contains the LKKTETQ sequence, but also includes substantial N-terminal and C-terminal regions absent from TB-500.

Research areas

TB-500 identity
Relationship to Tβ4
Fragment migration and sprouting
Direct TB-500 human outcomes
Direct human PK and safety
Full-length Tβ4 wound and ocular research
Full-length Tβ4 animal research
TB-500 musculoskeletal research
Combination with BPC-157
Regulatory status

Evidence at a glance

What the current record supports

TB-500 identity: Analytical and regulatory sources converge on Ac-LKKTETQ

Relationship to Tβ4: TB-500 contains the 17–23 motif but lacks most of the full-length peptide

Fragment migration and sprouting: LKKTETQ produced activity similar to full-length Tβ4 in a narrow endothelial/aortic-sprouting study

Direct TB-500 human outcomes: No completed clinical-outcome study of verified Ac-LKKTETQ was identified

Qualification

Limitations and evidence gaps

Limitations and contradictory findings

Ac-LKKTETQ is the best-supported identity for TB-500, but marketed naming and product identity remain inconsistent. No completed human outcome, pharmacokinetic, or controlled safety study was identified for chemically verified Ac-LKKTETQ. Evidence involving full-length thymosin beta-4, RGN-259, RGN-137, RGN-352, recombinant NL005, or other fragments cannot be transferred to the seven-residue fragment.

Direct musculoskeletal evidence is limited to small, identity-weak animal reports, while several full-length thymosin beta-4 clinical programs missed primary endpoints or remain incompletely published. Mechanistic, histologic, and biomarker findings do not establish human healing outcomes.

Safety and evidence gaps

No interpretable human safety dataset or adequate toxicology, safety-pharmacology, reproductive, carcinogenicity, or immunogenicity package exists for verified Ac-LKKTETQ. Short-term tolerability data for full-length or recombinant thymosin beta-4 products do not establish safety of the fragment, unknown salts, impurities, aggregates, or nonsterile material.

Product content, sterility, impurities, aggregation, and route-specific exposure remain poorly characterized. Angiogenesis and tumor-related mechanisms are plausible and context-dependent in model systems, but their relevance to the short fragment is unknown and no human TB-500 cancer-risk estimate exists.

Research path

Connected research articles

Overview

TB-500 Research Overview

Read overview

Full review

TB-500 Full Evidence Review

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...

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Study map

Connected study records

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

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

TBRIDGE-CV (NCT07487363): TB-500 17–23 Fragment Registry Study

TB5-STUDY-P012

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

View study

Source ledger

References

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)
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
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
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
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
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)
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)
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)
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)
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)
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
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
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)
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)
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)
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)
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)
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)
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)