TB-500 for Research in Canada

TB-500 is a trade name, not a chemical one, and it has been attached to two different molecules. The first is thymosin β4 (Tβ4, INN timbetasin), a 43-amino-acid, N-acetylated peptide that was sequenced from calf thymus in 1981 and later recognised as the main G-actin–sequestering peptide in mammalian cells^{[1, 3]}. The second is Ac-LKKTETQ, the acetylated seven-residue fragment corresponding to Tβ4 residues 17–23; two 2012 analytical papers identified this fragment as the ingredient of commercial “TB-500” preparations^{[9, 10]}. The two molecules differ by more than five-fold in mass (4963 vs 889 g/mol), so a laboratory buying “TB-500” has to read the certificate of analysis to know which one is in the vial. Neither form has an approved product for any use in Canada, the United States or the European Union; the material on this page is sold for laboratory research only.

Key facts

• Two molecules, one name: full-length thymosin β4 (43 aa, C₂₁₂H₃₅₀N₅₆O₇₈S, 4963 g/mol) and the fragment Ac-LKKTETQ (7 aa, C₃₈H₆₈N₁₀O₁₄, 889.0 g/mol).
• Where the fragment sits: residues 17–23 of Tβ4, the actin-binding motif; in vitro this motif alone reproduced the endothelial migration and vessel-sprouting activity of the whole peptide at about 50 nM^[3].
• Evidence base: mostly rat, mouse and cell-culture work on wound closure, angiogenesis and cardiac repair^{[2, 4, 6]}. Human data exist for Tβ4 (not the fragment) as a topical or eye-drop investigational drug and one intravenous phase I study^{[11, 12, 15]}.
• Doping status: TB-500 is described in the analytical literature as a product “suspected to possess doping potential”, and detection methods exist for horses^{[9, 10]}.
• Batch documentation on this site: the 5mg vial has a posted Janoshik report (#219841, result line “TB-500 (TB-4)”, 99.371%). The 10mg vial has no report in the COA library at the time of writing; its page says so.

Discovery and naming

Thymosin β4 was purified from “thymosin fraction 5”, a calf-thymus extract studied as a possible thymic hormone. Low, Hu and Goldstein published its full sequence in 1981: 43 residues, a blocked (acetylated) N-terminus, a calculated mass of 4982 and an isoelectric point of 5.1, with an effect on terminal deoxynucleotidyl transferase in mouse thymocytes^[1]. Over the following two decades it became clear that the peptide is present in most cell types and that its main biochemical job is to bind monomeric (G-) actin, keeping a reserve pool that cells draw on to remodel their cytoskeleton^{[3, 5]}. Wound-repair work began in the late 1990s, when Malinda and colleagues reported that Tβ4 applied to full-thickness rat wounds increased re-epithelialisation and collagen deposition^[2].

The name “TB-500” does not appear in that literature. It entered the scientific record through doping control: in 2012 Esposito and colleagues analysed a formulation sold as TB-500 by high-resolution mass spectrometry and found the N-acetylated 17–23 fragment of human Tβ4 (Ac-LKKTETQ)^[9], and Ho and colleagues at the Hong Kong Jockey Club developed a method to detect the same acetylated heptapeptide and its metabolites in horse urine and plasma, describing TB-500 as a veterinary preparation whose “key ingredient” is LKKTETQ with an artificial N-acetyl group^[10]. Vendors nevertheless also sell full-length Tβ4 under the TB-500 label, which is why the certificate of analysis matters.

Identity

Values were read from PubChem and ChEMBL on 30 September 2026 and the sequence position of the fragment was checked against the UniProt entry (counting from the mature N-terminal serine after removal of the initiator methionine).

What researchers have studied, by model

Cell culture

Philp and colleagues tested natural Tβ4, proteolytic fragments and synthetic peptides in human umbilical-vein endothelial cell migration and chick aortic-arch sprouting assays. The seven-residue actin-binding motif alone was as active as the whole peptide at roughly 50 nM, peptides lacking any part of the motif were inactive, and adding 5–50 nM soluble actin blocked adhesion and sprouting^[3]. In cultured embryonic and postnatal mouse cardiomyocytes, Tβ4 formed a complex with PINCH and integrin-linked kinase (ILK), activating the kinase Akt and improving cell survival^[4]. In high-glucose-treated endothelial cells, it increased migration and proliferation through the VEGF/Akt pathway^[13]; in another endothelial model the effect tracked Notch and NF-κB signalling^[14].

Rat

In the 1999 full-thickness wound study, topical or intraperitoneal Tβ4 increased re-epithelialisation by 42% at day 4 and up to 61% at day 7 versus saline, with more contraction, collagen and new vessels, and stimulated keratinocyte migration in a Boyden chamber at picogram amounts^[2]. A 2015 study embedded Tβ4 in a collagen–chitosan sponge to obtain 12 days of controlled release in diabetic rats with hind-limb ischaemia, reporting faster re-epithelialisation, more CD31-positive vessels and a shift in inflammatory and angiogenic gene expression^[13]. In 2026, a 32-rat Achilles-transection study compared BPC-157, “synthetic thymosin beta-4 (TB-500)” and their combination for four weeks: the TB-500 group had significantly higher load to failure and better Bonar and Movin histology scores than controls, and the combination added nothing over either agent alone^[16]. Rat vibrissa-follicle keratinocytes migrated and differentiated more in the presence of nanomolar Tβ4, and hair growth increased in normal rats and mice^[7].

Mouse

Bock-Marquette and colleagues reported in 2004 that after coronary-artery ligation, Tβ4 treatment raised ILK and Akt activity in the heart, improved early myocyte survival and improved cardiac function^[4]. Smart and colleagues showed in 2007 that Tβ4 is required for coronary vessel development in the embryo and that it drives quiescent adult epicardial explants to produce fibroblasts, smooth-muscle and endothelial cells; knocking it down reduced the pro-angiogenic cleavage product Ac-SDKP^[6]. In dystrophin-deficient mdx mice given Tβ4 repeatedly over six months, regenerating skeletal-muscle fibres increased, but grip strength, systolic function and fibrosis did not improve^[8]. In a critical-limb-ischaemia model, lentiviral Tβ4 over-expression increased CD31, α-SMA, Ang2, Tie2 and VEGFA in muscle^[14].

Horse

The only in-vivo work on the fragment itself that we could locate is the equine doping-control study: after horses received a single dose of a TB-500 product, N-acetylated LKKTETQ and its metabolites were confirmed in plasma and urine at 0.02 and 0.01 ng/mL respectively^[10]. It is a detection paper, not an efficacy study.

Human (thymosin β4 only)

Full-length Tβ4 has been an investigational drug in several indications. A European dose-escalation study of topical Tβ4 in venous leg ulcers was designed for 72 patients across ten sites in Italy and Poland; the 2007 report describes the protocol and enrolment of the first 21 patients, not outcomes^[11]. A small phase 2 trial of Tβ4 eye drops (RGN-259) in nine patients with severe dry eye reported reductions in ocular discomfort and corneal staining versus vehicle at day 56^[12]. A first-in-human phase I study of recombinant human Tβ4 (NL005) in 84 healthy Chinese volunteers, given intravenously as single and repeated doses across the range tested, recorded only mild-to-moderate adverse events and no dose-limiting toxicity^[15]. None of these has led to an approved medicine, and none of them studied the Ac-LKKTETQ fragment.

Study summary

What the evidence does not show

• No study establishes that TB-500 or thymosin β4 heals, repairs or improves anything in healthy people. The human trials were small, indication-specific investigational studies of Tβ4, and one of them reports a protocol rather than results^{[11, 12, 15]}.
• Almost nothing is published on the Ac-LKKTETQ fragment in animals beyond its detection in horses^[10]; its equivalence to whole Tβ4 rests on in-vitro assays^[3].
• Results are not uniformly positive: in the mdx mouse, six months of treatment increased regenerating fibres without improving strength, heart function or fibrosis^[8].
• The single rat study that compared TB-500 with BPC-157 found no additive benefit from combining them and called its own findings exploratory and preliminary^[16].
• Both forms are on doping-control radars, and the fragment is described in the literature as suspected of misuse in sport^{[9, 10]}. Shop Peptides Online supplies the material for laboratory research only and provides no dosing or administration information.

Handling and storage for laboratory use

• Supplied as lyophilized powder in a sealed vial. Keep sealed vials cool, dry and dark; store long-term at −20 °C as the site’s storage guidance states.
• The peptides are water-soluble; published animal work dissolved Tβ4 in saline or PBS^{[2, 16]}. Laboratories also use sterile or bacteriostatic water. Reconstituted solutions are less stable than dry powder; avoid repeated freeze–thaw.
• Identity: Tβ4 (about 4963 Da) and the fragment (889 Da) separate cleanly by mass spectrometry, which is how the analytical papers told them apart^[9]. Read the mass-spec line on the certificate of analysis, not just the purity percentage; our HPLC vs. mass-spec guide explains the difference.

References

1. Low TL, Hu SK, Goldstein AL (1981). Complete amino acid sequence of bovine thymosin beta 4: a thymic hormone that induces terminal deoxynucleotidyl transferase activity in thymocyte populations. Proceedings of the National Academy of Sciences of the United States of America 78(2):1162-6. doi:10.1073/pnas.78.2.1162. PMID 6940133
2. Malinda KM, Sidhu GS, Mani H et al. (1999). Thymosin beta4 accelerates wound healing. The Journal of investigative dermatology 113(3):364-8. doi:10.1046/j.1523-1747.1999.00708.x. PMID 10469335
3. Philp D, Huff T, Gho YS et al. (2003). The actin binding site on thymosin beta4 promotes angiogenesis. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 17(14):2103-5. doi:10.1096/fj.03-0121fje. PMID 14500546
4. Bock-Marquette I, Saxena A, White MD et al. (2004). Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature 432(7016):466-72. doi:10.1038/nature03000. PMID 15565145
5. Goldstein AL, Hannappel E, Kleinman HK (2005). Thymosin beta4: actin-sequestering protein moonlights to repair injured tissues. Trends in molecular medicine 11(9):421-9. doi:10.1016/j.molmed.2005.07.004. PMID 16099219
6. Smart N, Risebro CA, Melville AA et al. (2007). Thymosin beta4 induces adult epicardial progenitor mobilization and neovascularization. Nature 445(7124):177-82. doi:10.1038/nature05383. PMID 17108969
7. Philp D, Nguyen M, Scheremeta B et al. (2004). Thymosin beta4 increases hair growth by activation of hair follicle stem cells. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 18(2):385-7. doi:10.1096/fj.03-0244fje. PMID 14657002
8. Spurney CF, Cha HJ, Sali A et al. (2010). Evaluation of skeletal and cardiac muscle function after chronic administration of thymosin beta-4 in the dystrophin deficient mouse. PloS one 5(1):e8976. doi:10.1371/journal.pone.0008976. PMID 20126456
9. Esposito S, Deventer K, Goeman J et al. (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):733-8. doi:10.1002/dta.1402. PMID 22962027
10. Ho EN, Kwok WH, Lau MY 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
11. Guarnera G, DE Rosa A, Camerini R (2007). Thymosin beta-4 and venous ulcers: clinical remarks on a European prospective, randomized study on safety, tolerability, and enhancement on healing. Annals of the New York Academy of Sciences 1112:407-12. doi:10.1196/annals.1415.003. PMID 17495250
12. Sosne G, Dunn SP, Kim C (2015). Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea 34(5):491-6. doi:10.1097/ICO.0000000000000379. PMID 25826322
13. Ti D, Hao H, Xia L et al. (2015). Controlled release of thymosin beta 4 using a collagen-chitosan sponge scaffold augments cutaneous wound healing and increases angiogenesis in diabetic rats with hindlimb ischemia. Tissue engineering. Part A 21(3-4):541-9. doi:10.1089/ten.TEA.2013.0750. PMID 25204972
14. Lv S, Cai H, Xu Y et al. (2020). Thymosin‑β 4 induces angiogenesis in critical limb ischemia mice via regulating Notch/NF‑κB pathway. International journal of molecular medicine 46(4):1347-1358. doi:10.3892/ijmm.2020.4701. PMID 32945357
15. Wang X, Liu L, Qi L et al. (2021). A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers. Journal of cellular and molecular medicine 25(17):8222-8228. doi:10.1111/jcmm.16693. PMID 34346165
16. Biçer O, Adanir O, Güleryüz Y 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 37(3):822-837. doi:10.52312/jdrs.2026.2951. PMID 42542926