What is TB-500?

TB-500 is a synthetic N-acetylated heptapeptide whose sequence, LKKTETQ, matches positions 17 to 23 of thymosin beta-4, a protein found in most human cells. The Hong Kong Jockey Club's racing laboratory describes it as a veterinary preparation built around that segment, with "artificial acetylation of the N-terminus". ^[2]

The name causes most of the confusion. Many pages call TB-500 "synthetic thymosin beta-4". Chemically, TB-500 is a short synthetic fragment of thymosin beta-4. The parent protein has 43 residues and a molecular weight of 4982, per its 1981 sequencing paper. ^[9] TB-500 has 7 residues and weighs 889.0 g/mol. ^[1] That difference matters for every claim that follows, because most of the literature quoted about TB-500 was done on the whole protein.

How the fragment entered the literature is also specific. In 2012 the Ghent University doping control laboratory analysed a product sold as TB-500, identified Ac-LKKTETQ in it by high-resolution mass spectrometry, and synthesised the peptide itself for reference. ^[3] TB-500 in 10mg vials is in stock with a batch certificate.

TB-500 carries the sequence that thymosin beta-4 uses to bind actin, and its proposed mechanism is borrowed from that parent protein. Thymosin beta-4 is the main actin-sequestering molecule in cells: a 1991 study showed it forms a 1:1 complex with actin monomers and blocks their polymerisation. ^[10] A 2010 review of its active sites places the central actin-binding domain at amino acids 17 to 23, LKKTETQ, and links a short sequence containing it to angiogenesis, cell migration and wound repair in experimental models. ^[11]

Three lines of work test that segment directly:

1. Mouse wound models (2003). A seven-amino-acid synthetic peptide, LKKTETQ, promoted dermal repair in aged mice to a degree the authors called comparable to the parent protein. ^[12]
2. Human liver cells (2018). In cultured human hepatic stellate cells, the 17-23 peptide blocked PDGF-BB-driven increases in PDGF beta receptor, alpha-SMA and collagen 1, and reduced Akt phosphorylation. The 1-15 fragment did not. ^[13]
3. TB-500 and its metabolites (2024). A Korean anti-doping group tested the acetylated fragment and its breakdown products in fibroblasts. They found no cytotoxicity, and only the metabolite Ac-LKKTE showed significant activity in the wound-closure assay. The authors suggested earlier activity reported for TB-500 may come from that metabolite. ^[5]

Two of those studies used unacetylated LKKTETQ, and one tested the product form. The full protein also signals through routes the fragment may not share: in mice, full-length thymosin beta-4 formed a complex with PINCH and integrin-linked kinase and activated Akt in heart cells. ^[14] No study in our set shows the seven-residue fragment reproduces that.

TB-500 is a linear seven-residue peptide, Leu-Lys-Lys-Thr-Glu-Thr-Gln, with an acetyl cap on the N-terminal leucine and a free acid at the C-terminal glutamine. ^[1]

We checked each identifier against PubChem on 29 September 2026. ^[1] The position comes from the human thymosin beta-4 record, which lists 44 residues including the starting methionine. Remove that methionine and LKKTETQ sits at 17 to 23 of the mature 43-residue chain. ^[15]

One structural detail catches people out. Native thymosin beta-4 is acetylated at its own N-terminus, on the serine at position 1. ^[9] The leucine at position 17 is an internal residue with no acetyl group in the protein. The acetyl cap on TB-500 is a synthetic addition, which is why the Hong Kong group calls it artificial. ^[2] When you read a certificate, the mass spectrum should match the acetylated peptide at about 889 g/mol, and a result near 847 would point to the uncapped sequence.

Research on TB-500 has examined how to detect it, how it breaks down and what it does in cells and rodents, and no controlled human trial of the fragment has been published. Our PubMed search on 29 September 2026 for TB-500, TB500 or LKKTETQ in titles and abstracts returned 38 records. Eight were unrelated uses of the same letters. Of the other 30, 14 were doping-control and analytical chemistry papers and 8 were reviews. Filtering the same search for clinical trials returned one record, a tuberculosis study. ^[4]

The table separates three molecules, because sources often blur them: TB-500 (acetylated), the unacetylated LKKTETQ segment, and full-length thymosin beta-4.

The 2026 Istanbul study is the only rodent tendon experiment in our set that names TB-500. The TB-500 group reached statistical significance on load to failure and total Bonar score, BPC-157 did not, and the combination added nothing over either peptide alone. The authors call it exploratory and preliminary. ^[18] Every row above describes what one study reported for its own model. None of it is a claim about a research vial.

The TB-500 evidence does not show any effect in people, because no human trial of the fragment has been published. Four limits matter most.

1. Human trials used a different molecule. The phase I intravenous study, the venous ulcer trial and the dry eye trial all used full-length thymosin beta-4. ^[6][19][20] The dry eye trial missed both primary endpoints. ^[20]
2. The fragment's own activity is thin. The 2024 study states that the biological effects of TB-500 had not been documented, and in its fibroblast test the parent fragment was inactive while one metabolite was active. ^[5]
3. Replication is sparse. One rat tendon study with 8 animals per group is the whole in vivo musculoskeletal record for the named product. ^[18] A 2026 orthopaedic review concluded that thymosin beta-4 and TB-500 showed effects in preclinical models, but "human orthopaedic data are lacking". ^[21]
4. Products vary. French racing chemists who analysed internet products found that TB500 and TB1000 contents were not systematically consistent with their descriptions. ^[17]

A 2026 scoping review of six popular peptides, TB-500 included, found that 67% of publications used animal models and that claimed benefits "remain unsubstantiated by current human trials". ^[22]

No published study reports adverse events for the TB-500 fragment in humans, because no human study of it exists in PubMed. The human data below come from trials of full-length thymosin beta-4, a different molecule given by different routes.

• Phase I, healthy volunteers (2010). Four cohorts of 10 people received intravenous thymosin beta-4 or placebo, first once and then daily for 14 days. Adverse events were infrequent and mild or moderate, and no serious adverse events were reported. ^[6]
• Dry eye, phase II (2015). 72 adults used 0.1% thymosin beta-4 eye drops or placebo for 28 days. No adverse events were observed. ^[20]
• Venous ulcers, phase II (2010). 73 patients at eight European sites used topical thymosin beta-4. The authors rated its adverse event profile as comparable to placebo. ^[19]

For the fragment itself, the only data are laboratory findings. The 2024 study found no cytotoxicity of TB-500 or its metabolites in fibroblasts. ^[5] The TGA names TB-500 among unapproved peptide products it has not evaluated for safety, quality or effectiveness, and it reports receiving severe allergic reactions and systemic inflammatory response syndrome for unapproved peptide products as a group. ^[23] A 2026 review lists contamination, manufacturing impurities, pathological angiogenesis and carcinogenesis among potential risks of unregulated peptides including TB-500. It describes those as potential risks. ^[24]

On the questions people ask most, liver and heart: no study in our set reports liver or heart measurements for TB-500 in people. The heart research concerns full-length thymosin beta-4 in mice, ^[14] and the liver research concerns the unacetylated segment in cultured human stellate cells. ^[13]

TB-500 is listed in Schedule 4 of the Poisons Standard (prescription only) and in Appendix D clause 5, which makes possession without authority an offence. Thymosin beta-4 has its own separate Schedule 4 entry and its own clause 5 listing. Both sit in the June 2026 Poisons Standard instrument (F2026L00633), which commenced on 1 June 2026, where TB-500 is item 35 and thymosin beta-4 item 36 in the clause 5 table. ^[7]

No TB-500 product is registered as a medicine in Australia. The TGA names TB-500 among examples of unapproved peptide products, ^[23] and Sport Integrity Australia states that thymosin beta-4, also known as TB-500, is not approved by the TGA. ^[8]

For sport, WADA's 2026 Prohibited List, effective 1 January 2026, indexes both TB-500 and thymosin-beta4 in class S2, whose substances are prohibited at all times, in and out of competition. ^[25] Sport Integrity Australia places thymosin beta-4 under S2.3, growth factors and growth factor modulators. ^[8] WADA revises the List every year, so check the current edition. Our guide to Australian peptide law and the Poisons Standard explains what Schedule 4 and Appendix D mean.

TB-500 and BPC-157 are both short synthetic peptides studied in rodent tendon and soft-tissue models, and they differ in origin, size and evidence. TB-500 is a 7-residue fragment of thymosin beta-4. BPC-157 is a 15-residue fragment of a gastric juice protein.

The only head-to-head data are the 2026 rat Achilles study described above. ^[18] The full breakdown is in BPC-157 vs TB-500. Both sit in our recovery research peptides range, and TB-500 is also a component of our Wolverine Stack and KLOW vials.

No published stability study covers lyophilised TB-500, so storage follows general peptide practice: sealed, cold, dry and dark until use. Two published findings are relevant to handling. Human kidney and liver enzyme preparations broke TB-500 down by cleaving all of its peptide bonds, ^[16] so enzyme contamination of a solution is a risk. And a Ghent study found TB-500 adsorbs to lab surfaces, with recovery depending on the glassware or plastic chosen. ^[26] At low concentrations, the vial and tube material can change how much peptide you recover.

Once reconstituted, a peptide solution is far more exposed than the powder. Keep it refrigerated, protect it from light, avoid repeated freezing and thawing, and label the vial with the date, solvent and concentration in mg per mL. Our peptide storage guide covers each of those steps.

On solvents, the 2003 mouse study dissolved thymosin beta-4 in phosphate-buffered saline. ^[12] We stock BAC Water (sterile water with 0.9% benzyl alcohol) in 3ml vials for A$8 for laboratory reconstitution, and the peptide reconstitution guide covers solvent choice and concentration arithmetic.

Peptides Collective sells TB-500 for laboratory research use only, in 10mg vials from A$98. Stock ships from Western Australia with tracking.

Every batch is tested by an independent lab before it goes on sale. The certificate reports purity by HPLC and identity by mass spectrometry, and it is published under the batch number printed on the vial. You can search the certificate of analysis library by that batch number and match the report to the vial in your hand.

Given the 2023 finding that TB500 products sold online did not consistently contain what their descriptions said, ^[17] the certificate is the part of the purchase that carries the evidence. Check that the identity result matches Ac-LKKTETQ at about 889 g/mol. Our guide on how to read a peptide certificate of analysis explains the HPLC trace, the mass spectrum and net peptide content, and the TB-500 product page links the certificate for the current batch.

TB-500 is Ac-LKKTETQ, a seven-residue synthetic copy of the actin-binding segment of thymosin beta-4 with an added acetyl cap. Its own literature is anti-doping chemistry, cell work and one rat tendon study, and the human trials people cite used the full 43-residue protein. In Australia it is a Schedule 4 substance listed in Appendix D clause 5, and WADA prohibits it at all times. For a research vial, the batch certificate is the evidence that settles what is inside.