TB-500

TB-500
The structure of TB-500.
Identifiers
  • (2S)-2-[[(2S,3R)-2-[[(2S)-2-[[(2S,3R)-2-[[(2S)-2-[[(2S)-2-[[(2S)-2-acetamido-4-methylpentanoyl]amino]-6-aminohexanoyl]amino]-6-aminohexanoyl]amino]-3-hydroxybutanoyl]amino]-4-carboxybutanoyl]amino]-3-hydroxybutanoyl]amino]-5-amino-5-oxopentanoic acid
CAS Number
PubChem CID
ChemSpider
UNII
Chemical and physical data
FormulaC38H68N10O14
Molar mass889.018 g·mol−1
3D model (JSmol)
  • C[C@H]([C@@H](C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H]([C@@H](C)O)C(=O)N[C@@H](CCC(=O)N)C(=O)O)NC(=O)[C@H](CCCCN)NC(=O)[C@H](CCCCN)NC(=O)[C@H](CC(C)C)NC(=O)C)O
  • InChI=1S/C38H68N10O14/c1-19(2)18-27(42-22(5)51)35(58)44-23(10-6-8-16-39)32(55)43-24(11-7-9-17-40)33(56)47-30(20(3)49)36(59)45-25(13-15-29(53)54)34(57)48-31(21(4)50)37(60)46-26(38(61)62)12-14-28(41)52/h19-21,23-27,30-31,49-50H,6-18,39-40H2,1-5H3,(H2,41,52)(H,42,51)(H,43,55)(H,44,58)(H,45,59)(H,46,60)(H,47,56)(H,48,57)(H,53,54)(H,61,62)/t20-,21-,23+,24+,25+,26+,27+,30+,31+/m1/s1
  • Key:ADKDNDYYIZUVCZ-ZQNQAVPYSA-N

TB-500 (Ac-LKKTETQ) is a synthetic heptapeptide that corresponds to the N-acetylated active fragment (amino acids 17–23)[1] of the endogenous signaling factor thymosin beta-4.[2] It is claimed to increase muscle growth and accelerate wound healing and tissue repair,[3] reduce inflammation, and improve flexibility.[4][5] There is concern it could be used in sports doping.[4] It gained attention during the 2020's uptick in off-label peptide use.[6] It has not undergone any human trials and high levels of it are associated with tumor development.[7][8]

It has been encountered as a designer drug mainly in racehorses,[9] but is also prohibited for use by athletes in competition by the World Anti-Doping Agency, and is classified as a prescription medicine in some jurisdictions such as Australia and New Zealand.[10]

N-acetylated LKKTETQ (Ac-LKKTETQ) and several of its metabolites can be detected in equine urine and plasma following administration of TB-500 using liquid chromatography–mass spectrometry, with metabolite profiling enabling identification of peptide-derived products in biological samples.[11]

See also

References

  1. ↑ Esposito S, Deventer K, Goeman J, Van der Eycken J, Van Eenoo P (September 2012). "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. 4 (9): 733–738. doi:10.1002/dta.1402. PMID 22962027.
  2. ↑ Van Troys M, Dewitte D, Goethals M, Carlier MF, Vandekerckhove J, Ampe C (January 1996). "The actin binding site of thymosin beta 4 mapped by mutational analysis". The EMBO Journal. 15 (2): 201–210. doi:10.1002/j.1460-2075.1996.tb00350.x. PMC 449934. PMID 8617195.
  3. ↑ Rahaman KA, Muresan AR, Min H, Son J, Han HS, Kang MJ, et al. (March 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, Analytical Technologies in the Biomedical and Life Sciences. 1235 124033. doi:10.1016/j.jchromb.2024.124033. PMID 38382158.
  4. 1 2 Davison G, Brown S (2013). "The potential use and abuse of thymosin β-4 in sport and exercise science". Journal of Sports Sciences. 31 (9): 917–918. doi:10.1080/02640414.2013.771958. PMID 23421910.
  5. ↑ Ying Y, Lin C, Tao N, Hoffman RD, Shi D, Chen Z, et al. (2023). "Thymosin β4 and Actin: Binding Modes, Biological Functions and Clinical Applications". Current Protein & Peptide Science. 24 (1): 78–88. doi:10.2174/1389203724666221201093500. PMID 36464872.
  6. ↑ Prisk DV. "TB-500 Exposed: The Risks Outweigh the Benefits". www.orthoandwellness.com. Prisk Orthopaedics and Wellness. Retrieved 2026-08-15.
  7. ↑ Dodge D (2025-11-18). "The Internet Loves Peptide Therapy. Is It Really a Miracle Cure?". The New York Times. ISSN 0362-4331. Retrieved 2026-08-15.
  8. ↑ Chi LH, Chang WM, Chang YC, Chan YC, Tai CC, Leung KW, et al. (August 2017). "Global Proteomics-based Identification and Validation of Thymosin Beta-4 X-Linked as a Prognostic Marker for Head and Neck Squamous Cell Carcinoma". Scientific Reports. 7 (1) 9031. doi:10.1038/s41598-017-09539-w. PMC 5567379. PMID 28831179.
  9. ↑ Kwok WH, Ho EN, Lau MY, Leung GN, Wong AS, Wan TS (March 2013). "Doping control analysis of seven bioactive peptides in horse plasma by liquid chromatography-mass spectrometry". Analytical and Bioanalytical Chemistry. 405 (8): 2595–2606. doi:10.1007/s00216-012-6697-9. PMID 23318763.
  10. ↑ "Classification of Unscheduled Peptides. Submission to the Medicines Classification Committee" (PDF). Medsafe. New Zealand Medicines and Medical Devices Safety Authority. June 2025.
  11. ↑ Ho EN, Kwok WH, Lau MY, Wong AS, Wan TS, Lam KK, 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. 1265: 57–69. doi:10.1016/j.chroma.2012.09.043. PMID 23084823.
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