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MonographTB-500

TB-500 and thymosin β4: three molecules, one commercial name

TB-500 is a trade name applied to more than one substance: full-length thymosin β4, the N-acetylated 17-23 heptapeptide identified in analysed products, and the separate tetrapeptide Ac-SDKP.

Last reviewed
2026-09-22
Reviewer
editorial review pending
Revision
1
Sources
34

Summary

"TB-500" is a trade name rather than an international non-proprietary name or a USAN, and it is applied in commerce to two chemically different molecules 1. One is full-length thymosin β4, the 43-residue endogenous actin-sequestering peptide encoded by the human gene TMSB4X and given the international non-proprietary name timbetasin 234. The other is a synthetic heptapeptide, N-acetyl-Leu-Lys-Lys-Thr-Glu-Thr-Gln, corresponding to residues 17 to 23 of that protein; this is the substance FDA registers under the name TB-500 51. A third peptide, Ac-SDKP, is the N-terminal tetrapeptide of thymosin β4 and a separate substance with its own identifiers and its own international non-proprietary name 62.

The distinction is not academic. Anti-doping laboratories that analysed material sold under the TB-500 name identified the acetylated 17-23 fragment as the ingredient 78, while a 2025 equine doping-control study reports that products offered online claim to contain either the synthetic acetylated fragment or thymosin β4 itself 9. FDA states that websites use "thymosin beta-4" and "TB-500" interchangeably although they are not the same substance 1.

Both molecules are investigational. Full-length thymosin β4 has been through phase 2 and phase 3 trials in ophthalmic and dermal formulations, and no marketing authorisation was found in the United Kingdom, the European Union or the United States on 2026-09-22 10111213. For the heptapeptide, FDA's 2026 evaluation found no clinical studies and no human exposure data, and a single phase 1/2 trial was registered in 2026 114. Both fall within section S2.3 of the WADA Prohibited List in force and are prohibited at all times 15.

The identity panel below is rendered from the database. Because it has not been confirmed which of the two molecules the supplied material corresponds to, the panel shows identity as not yet verified.

Identity · TB-500verified 2026-09-22
Synonyms
—
CAS
Not yet verified
UNII
Not yet verified
PubChem CID
Not yet verified
Formula
Not yet verified
Mol. weight
Not yet verified
Class
Not yet verified
Targets
None identified in retrieved sources

Identity and structure

Full-length thymosin β4

Thymosin β4 is a 43-residue, roughly 5 kDa, acidic and heat-stable peptide, annotated in UniProt as P62328 and described there as organising the cytoskeleton by binding and sequestering monomeric actin 2. The mature chain is the precursor residues 2 to 44, formed by removal of the initiator methionine, with the resulting N-terminal serine acetylated; its sequence is SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES 23. UniProt additionally annotates phosphorylation and lysine N6-acetylation of the native protein that the synthetic substance does not carry: the FDA substance registry describes timbetasin by a chemical name that explicitly removes five lysine acetyl groups and four phosphono groups from thymosin β4 23. In solution the peptide is intrinsically disordered, adopting two α-helices, residues 5 to 16 and 31 to 39, in trifluoroethanol; helix I and the LKKTET segment at residues 17 to 22 are the two principal actin-contact elements 16.

The N-acetylated 17-23 heptapeptide

The fragment is residues 17 to 23 of thymosin β4 carrying an artificial N-terminal acetyl group on Leu17, a leucine that is internal and unacetylated in the parent protein, and a free C-terminal acid 71. Esposito and colleagues prepared the reference peptide by Fmoc solid-phase synthesis on Wang resin, with acetylation of the N-terminal leucine as the final on-resin step 7. FDA notes that N-acetylation irreversibly alters charge, hydrophobicity and size, so the pharmacology of the non-acetylated LKKTETQ used in most published experiments cannot be directly extrapolated to the acetylated substance 1.

Ac-SDKP is a third substance

Ac-SDKP, also known as goralatide and seraspenide, is the N-terminal tetrapeptide of thymosin β4, corresponding to precursor residues 2 to 5, and carries CAS 120081-14-3, UNII H041538E9P, PubChem CID 65938, formula C20H33N5O9 and a molecular weight of 487.5 g/mol 62. It is released from thymosin β4 in vivo by successive hydrolysis involving meprin-α and prolyl oligopeptidase 17. It is neither TB-500 nor thymosin β4, and its literature should not be read across to either.

Identifiers as the dossier resolves them

FieldHeptapeptide fragment (TB-500)Full-length thymosin β4
Registered nameN-acetyl thymosin β4(17-23), Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH 51Thymosin β4; INN timbetasin, WHO Proposed List 118, USAN GH-159 34
CAS885340-08-9 for the free base; none available for the acetate 518177591-33-4 for timbetasin; a second registry record carries 77642-24-1 319
UNIIQHK6Z47GTG; none for the acetate 512D5MRE3SSY (timbetasin), 549LM7U24W (thymosin β4), 945CRJ0XZ0 (timbetasin acetate) 319
PubChem CID62707662 1845382195 by name lookup; the registry links timbetasin to CID 16132341 203
Molecular formulaC38H68N10O14 free base; acetate C38H68N10O14·CH3COOH 181C212H350N56O78S 20
Molecular weight (g/mol)889.0 free base, exact mass 888.4916; 949.1 for the acetate 1814963 (PubChem) and 4963.0 Da (registry, sequence-calculated) 203
Residues7 1843 221

Four conflicts in the public record bear on reading any certificate. First, the name TB-500 is a common name and not a USAN, several suppliers apply the free-base CAS number to the acetate, and the withdrawn 503A nomination quoted a CAS number, 476014-70-7, and a formula, C38H66N10O14, matching neither form 1. Second, FDA treats TB-500 free base and TB-500 acetate as different bulk drug substances sharing one active moiety 1. Third, CAS 77591-33-4 is assigned to full-length timbetasin in the FDA substance registry but is cited in FDA's 2026 briefing document from a supplier page describing "TB-500 acetate" 31. Fourth, the registry's calculated mass for the TB-500 record, 846.981 Da, corresponds to the non-acetylated heptapeptide and is inconsistent with the record's own N-acetyl name, while its thymosin β4 record gives 4920 Da against 4963 elsewhere 51920. UniProt's 5053 Da is the unprocessed 44-residue precursor including Met1 and is not the mature peptide 2.

Mechanism and pharmacology

Thymosin β4 is the principal monomeric-actin-sequestering peptide of mammalian cells: it forms a 1:1 complex with actin monomers and inhibits salt-induced polymerisation, and the platelet peptide "Fx" was shown to be indistinguishable from it 22. UniProt summarises the function in the same terms 2. In endothelial migration and chick aortic-arch sprouting assays, thymosin β4 and its seven-residue actin-binding motif showed near-identical activity at about 50 nM, peptides lacking any part of the motif were inactive, and soluble actin at 5 to 50 nM inhibited adhesion and sprouting; the motif was identified as the major cell-binding site 21. No membrane receptor has been established for either molecule, and thymosin β4 also acts indirectly through Ac-SDKP released by meprin-α and prolyl oligopeptidase 2117.

For the acetylated fragment the position is weaker. FDA's evaluation identified no in vivo pharmacology studies of TB-500 itself; it reports an in vitro fibroblast scratch assay in which TB-500 at 50 µg/mL did not induce closure, and nonclinical pharmacokinetic data showing that the substance reaches the circulation and is hydrolysed to smaller peptides, while the wound-healing data in aged mice concern non-acetylated LKKTETQ applied topically 1. Rahaman and colleagues attribute the activity seen in fibroblast assays to the metabolite Ac-LKKTE rather than to the parent substance 23.

Clinical and preclinical evidence

All completed and terminated trials retrieved concern full-length thymosin β4 in the RegeneRx formulations: RGN-259, a 0.1% preservative-free ophthalmic solution; RGN-137, a dermal gel; and RGN-352, an injectable formulation described by the developer as phase 2-ready, for which no registry record with results was retrieved 4. The developer reports United States orphan-drug designation for RGN-259 and RGN-137 4. None of the three has been approved in any jurisdiction retrieved 11122413.

Studies as reported · design and results from the cited publication or registry record
StudyDesignnInterventionComparatorDurationPrimary endpointResult
SEER-1: 0.1% RGN-259 in neurotrophic keratopathyNCT02600429Phase 3, multicentre, randomised, double-masked, placebo-controlled; terminated early on a business decision; adults with stage 2 or 3 neurotrophic keratopathy with a persistent epithelial defect180.1% RGN-259 preservative-free eye drops, five times daily for 4 weeks (n = 10)vehicle placebo with identical excipients (n = 8)4 weeks of treatment, follow-up to day 43Complete healing of the epithelial defect at day 296 of 10 versus 1 of 8 healed at day 29 (p = 0.0656, Fisher's exact, not significant); at day 43, 5 of 10 versus 0 of 8 (p = 0.0359); 16 adverse events in 7 subjects, one treatment-related, mostly mild ocular events. [sosne-2023-ijms]
ARISE-2: RGN-259 in dry eye syndromeNCT02974907Phase 3, multicentre, randomised, quadruple-masked, placebo-controlled, in adults with dry eye syndrome601RGN-259 eye drops four times daily for 28 daysvehicle placebo28 daysOcular discomfort and corneal fluorescein staining at day 29Registry-posted mean change at day 29: ocular discomfort 0.07 versus −0.04; corneal staining 0.07 versus −0.01. No p-values posted and no peer-reviewed primary publication retrieved. [ctgov-nct02974907]
ARISE-3: RGN-259 in dry eye, controlled adverse environmentNCT03937882Phase 3, multicentre, randomised, quadruple-masked, placebo-controlled, in adults with dry eye700RGN-259 eye drops four times daily for 14 daysvehicle placebo14 daysChange from baseline in inferior corneal staining and in pre-exposure ocular discomfort at day 15Registry-posted means: inferior corneal staining change −0.41 versus −0.46; ocular discomfort change −0.4 versus −0.4. No p-values posted and no peer-reviewed publication retrieved. [ctgov-nct03937882]
Phase 2 thymosin β4 ophthalmic solution in moderate-to-severe dry eyeNCT01387347Phase 2, single-centre, randomised 1:1, double-masked, placebo-controlled, controlled adverse environment model720.1% thymosin β4 (RGN-259) eye drops for 28 daysplacebo28 days, visits over 32 daysOcular discomfort score and inferior corneal staining at day 29Neither primary endpoint differed significantly at day 29; secondary controlled-adverse-environment discomfort reduced 27% versus placebo on day 28 (p = 0.0244); central and superior corneal staining improved (p = 0.0075 and 0.0210); no adverse events reported. [sosne-2015-clinophthalmol]
Topical thymosin β4 gel in venous stasis ulcersNCT00832091Phase 2, randomised, double-blind, placebo-controlled dose-escalation at eight European sites72topical thymosin β4 gel at 0.01%, 0.03% and 0.1% (18 active per cohort)placebo gel (6 per cohort)up to 84 daysSafety and tolerability: number of adverse and serious adverse events over 84 daysSafety comparable to placebo; the registry records 104 adverse and serious adverse events across the three active groups versus 24 with placebo. The 0.03% concentration was reported as possibly accelerating healing, with complete healing within 3 months in about 25% of patients. [guarnera-2010-annnyas]
CELEB: RGN-137 topical gel in junctional and dystrophic epidermolysis bullosaNCT03578029Phase 2, randomised, single-blind, placebo-controlled, self-matched pairing; terminated on a business decision4RGN-137 gel applied once daily to index wounds for up to 84 daysplacebo gelup to 84 daysTime to 50% reduction in index-wound area up to day 84No results posted; terminated after 4 participants. [ctgov-nct03578029]

For the acetylated heptapeptide, one registered human trial was retrieved, and it post-dates FDA's finding that no human exposure data existed 1.

Studies as reported · design and results from the cited publication or registry record
StudyDesignnInterventionComparatorDurationPrimary endpointResult
TB-500 (thymosin β4 17-23 fragment) in stable atherosclerotic cardiovascular diseaseNCT07487363Phase 1/2, randomised, double-blind, placebo-controlled, sequential dose-escalation; recruiting, start 2026-02-05, estimated completion 2028-02-1780TB-500 (thymosin β4 17-23 fragment)matching vehicle placebo12 weeks, the primary safety windowIncidence of treatment-emergent adverse events over 12 weeks and serious adverse events over 28 daysNo results. Enrolment of 80 is an estimate; this is the only human trial of the fragment retrieved. [ctgov-nct07487363]
Evidence level

Full-length thymosin β4: phase 2 and phase 3 trials in ophthalmic and dermal formulations, two of them terminated early, with no authorisation in any jurisdiction retrieved 102513. Acetylated 17-23 fragment: no published human exposure data, one phase 1/2 trial registered in 2026, and in vitro evidence that the substance itself may be inactive 11423.

Analytical characterisation

What products sold under the name contain has been established twice in the doping-control literature. Esposito and colleagues analysed a TB-500 formulation by high-resolution Orbitrap mass spectrometry, identified the N-terminally acetylated 17-23 fragment of human thymosin β4, synthesised the reference peptide and proposed a liquid chromatography triple-quadrupole method for plasma and urine 7. Ho and colleagues describe a veterinary preparation "known as TB-500" whose key ingredient is LKKTETQ with artificial N-terminal acetylation, and detected the parent and its metabolites in equine urine and plasma after a single administration of material containing 10 mg of the acetylated peptide, with confirmation limits of 0.02 ng/mL in plasma and 0.01 ng/mL in urine after ion-exchange solid-phase extraction 8. Delcourt and colleagues report that intelligence and doping-control laboratories have encountered numerous online products claiming to contain either the synthetic acetylated fragment or thymosin β4 itself, established an endogenous equine plasma range for thymosin β4 that did not depend on sex, age or breed, and detected a non-natural synthesis impurity after a single administration of a thymosin β4-containing product 9.

Metabolite work supports both identifications. In rats and in vitro systems the fragment's principal early metabolite is Ac-LK, with Ac-LKK persisting to 72 hours, quantified by ultra-high-performance liquid chromatography Orbitrap tandem mass spectrometry against synthesised standards 23. For the full-length peptide, thirteen in vitro metabolites were identified and Ac-Tβ1-14, absent from blank human urine, was proposed as a urinary marker of exogenous administration, with a limit of detection of 0.19 ng/mL 26.

Quality data are thin. No United States Pharmacopeia, National Formulary or European Pharmacopoeia monograph exists for TB-500 1. A public-domain certificate of analysis for the free base covered only appearance and chromatographic and mass-spectrometric identity and purity, while a nominator-supplied certificate for the acetate set a largest single impurity of 1.0% or less and total impurities of 2.0% or less without reporting identification, assay, aggregates or bacterial endotoxin; FDA therefore considers both forms not well characterised and flags peptide-related impurities, aggregation and immunogenicity for injectable routes 1.

Analytical data

Certificates of analysis, identity data and lot verification for the research material characterised on this page.

View analytical data · BPC-157 / TB-500 blend →

Stability and handling

Laboratory handling data only. Every figure for the fragment is supplier data reproduced in FDA's evaluation rather than an independent or pharmacopoeial determination 1.

  • Fragment, free base: a white to off-white solid, water solubility 50 mg/mL, the powder held at −80 °C for 2 years or −20 °C for 1 year, and solutions at −80 °C for 6 months or −20 °C for 1 month, sealed, dry, dark and under nitrogen 1.
  • Fragment, acetate: the certificate of analysis gives 2 to 8 °C, and a public safety data sheet below −15 °C protected from light 1.
  • FDA notes that peptides of this type are sensitive to pH, temperature, concentration and impurities, which can drive aggregation and loss of activity, and that size-exclusion chromatography or field-flow fractionation may be needed to detect aggregates 1.
  • Full-length thymosin β4: no solubility or storage figure was found in an allowed source. The SEER-1 investigators state that the 0.1% RGN-259 ophthalmic solution is used at room temperature, in contrast to a cold-chain comparator 10. In equine work, plasma thymosin β4 rises at 4 °C when blood is not separated from cells, a pre-analytical artefact relevant to biomarker studies 9.

Regulatory status

The dated per-jurisdiction rows below are rendered from the database and cover the United Kingdom, the European Union, the United States and the WADA Prohibited List 1112115.

Regulatory status · TB-500Investigational or unlicensed compound

No medicine containing this compound is authorised in any jurisdiction checked. It has no established safety profile in humans outside registered clinical research. It is supplied for laboratory research only.

The rows below record the absence of authorisation and any compounding, evaluation or anti-doping status found on the date checked.

United Kingdom
No UK marketing authorisation: the MHRA products index returns no document for 'thymosin' or 'timbetasin' (searched 2026-09-22), and no UK orphan designation or MHRA notice specific to thymosin β4 or TB-500 was found.Checked 2026-09-22 · Medicines and Healthcare products Regulatory Agency
European Union
No centrally authorised medicine and no orphan designation: the Union Register of medicinal products for human use (1,544 entries) and the Community Register of orphan medicinal products (2,194 designations), both last updated 21/09/2026, contain no entry for thymosin, timbetasin, RGN-259 or RGN-137.Checked 2026-09-22 · European Commission, DG Health and Food Safety
United States
Not approved (Drugs@FDA has no record for thymosin, timbetasin or TB-500 on 2026-09-22); FDA's May 2026 evaluation concludes the criteria weigh against placing TB-500 (free base) and TB-500 acetate on the 503A bulks list, the substance is listed on FDA's page of nominated substances that may present significant safety risks, and FDA has told a manufacturer that marketed Thymosin Beta-4 is an unapproved new drug and an unlicensed biological product.Checked 2026-09-22 · U.S. Food and Drug Administration
WADA Prohibited List
Prohibited at all times (in- and out-of-competition) under S2.3 'Growth factors and growth factor modulators' as 'Thymosin-β4 and its derivatives e.g. TB-500'; S2 substances are non-Specified.Checked 2026-09-22 · World Anti-Doping Agency

United States: compounding and enforcement

FDA's Pharmacy Compounding Advisory Committee discussed TB-500-related bulk drug substances on 23 July 2026 under docket FDA-2025-N-6895 1. The briefing document dated 15 May 2026 concludes that the balance of criteria weighs against listing TB-500 free base and TB-500 acetate under section 503A, citing inconsistent naming, the absence of impurity, aggregate and endotoxin data, the absence of any human exposure data or adverse-event reports through 26 March 2025, immunogenicity risk for subcutaneous and intramuscular routes, and the existence of approved wound therapies; the nomination had been withdrawn 1. FDA's presentation states that it is proposing that both substances not be included on the 503A bulks list, and no final determination was retrieved 27. FDA's page of bulk substances that may present significant safety risks, current to 22 April 2026, lists "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" among nominated-but-withdrawn substances, and the 503A bulks page current to 14 May 2026 does not list thymosin in any category 2829. A warning letter of 20 January 2026 states that Thymosin Beta-4 products are unapproved new drugs under section 505 of the Federal Food, Drug, and Cosmetic Act and biological products under section 351 of the Public Health Service Act with no approved biologics licence application 30.

Anti-doping

Under the list in force, section S2 covers peptide hormones, growth factors, related substances and mimetics, is prohibited at all times and is non-Specified; item S2.3, growth factors and growth factor modulators, names "Thymosin-β4 and its derivatives e.g. TB-500" alongside fibroblast, hepatocyte, insulin-like, mechano, platelet-derived and vascular endothelial growth factors, and closes with a class catch-all reaching any further growth factor or growth factor modulator with comparable effects on connective-tissue protein turnover, vascularisation, energy use, regenerative capacity or fibre type switching 15. The wording covers both the full-length peptide and the fragment, and FDA's briefing document independently records TB-500 under section S2.3 151.

Open questions

  1. Which molecule a given material is remains undetermined for the supplied product: the analytical literature identifies Ac-LKKTETQ as the ingredient of TB-500 products, but products claiming full-length thymosin β4 also circulate, and a certificate carrying mass-spectrometric identity is required before either set of identifiers can be used 79.
  2. Free base or acetate is likewise undetermined; FDA treats them as different bulk drug substances and reports suppliers applying the free-base CAS number to the salt 1.
  3. Only one identity database yielded a CAS number for the full-length peptide, so the two-source rule is not met for that field 3.
  4. Registry molecular-weight fields are internally inconsistent for both molecules 51920.
  5. The committee vote and any final FDA determination after the July 2026 meeting were not retrieved 27.
  6. The ARISE-2 and ARISE-3 primary results are registry-posted without p-values and without a retrieved publication, and the ARISE-3 means show no separation from placebo 3132.
  7. Whether the acetylated fragment has any pharmacological effect in vivo is unestablished, and in vitro data suggest that activity may reside in a metabolite rather than in the substance itself 123.
  8. No solubility or storage data from an allowed source exist for full-length thymosin β4, and the fragment's figures are supplier data reproduced by FDA rather than pharmacopoeial determinations 1.

Questions this page answers

Are TB-500 and thymosin β4 the same substance?
No. Thymosin β4 is a 43-residue endogenous peptide (UniProt P62328). The substance registered by FDA as TB-500 is a synthetic seven-residue fragment, N-acetyl-Leu-Lys-Lys-Thr-Glu-Thr-Gln, corresponding to residues 17 to 23 of that protein. FDA states that websites use the two names interchangeably although they are not the same substance, and each has its own CAS number, UNII, formula and molecular weight.
What did analytical laboratories find in products sold as TB-500?
Esposito and colleagues analysed a TB-500 formulation by high-resolution mass spectrometry and identified the N-terminally acetylated 17-23 fragment of human thymosin β4. Ho and colleagues describe a veterinary preparation known as TB-500 whose key ingredient is LKKTETQ with artificial N-terminal acetylation. A 2025 equine doping-control study reports that products offered online claim to contain either the acetylated fragment or thymosin β4 itself.
Is TB-500 or thymosin β4 an authorised medicine?
No authorisation was found in the United Kingdom, the European Union or the United States on 22 September 2026. FDA has told a manufacturer that marketed Thymosin Beta-4 products are unapproved new drugs and unlicensed biological products, and in 2026 proposed that TB-500 free base and TB-500 acetate not be included on the 503A bulk drug substances list.
Is TB-500 on the WADA Prohibited List?
Yes. Section S2.3 of the list in force, covering growth factors and growth factor modulators, names "Thymosin-β4 and its derivatives e.g. TB-500". Class S2 is prohibited at all times, in and out of competition, and is non-Specified.
How is Ac-SDKP related to TB-500?
Ac-SDKP (goralatide; CAS 120081-14-3, UNII H041538E9P, PubChem CID 65938) is the N-terminal tetrapeptide of thymosin β4, released in vivo by successive hydrolysis involving meprin-α and prolyl oligopeptidase. It is a distinct substance with its own identifiers and is neither TB-500 nor thymosin β4.

References

  1. 1.Mathew B, Mattingly A, Rupp T, Albuquerque E, Benedict A, Kneeream E, Kasim S (FDA CDER). FDA Briefing Document, Pharmacy Compounding Advisory Committee Meeting July 23-24, 2026: Evaluation of TB-500-related Bulk Drug Substances (TB-500 (Free Base) and TB-500 acetate) for Inclusion on the 503A Bulk Drug Substances List. U.S. Food and Drug Administration (2026). https://www.fda.gov/media/193349/download · accessed 2026-09-22
  2. 2.UniProtKB P62328 (TYB4_HUMAN) Thymosin beta-4, gene TMSB4X. UniProt Consortium (2026). https://rest.uniprot.org/uniprotkb/P62328.json · accessed 2026-09-22
  3. 3.FDA Global Substance Registration System: TIMBETASIN (UNII 2D5MRE3SSY). FDA / NCATS GSRS (2026). https://gsrs.ncats.nih.gov/api/v1/substances(2D5MRE3SSY)?view=full · accessed 2026-09-22
  4. 4.World Health Organization Recommends INN for Thymosin Beta 4 as "timbetasin". RegeneRx Biopharmaceuticals, Inc. (2018). https://www.regenerx.com/2018-09-06-World-Health-Organization-Recommends-INN-for-Thymosin-Beta-4-as-timbetasin · accessed 2026-09-22
  5. 5.FDA Global Substance Registration System: TB-500 (UNII QHK6Z47GTG). FDA / NCATS GSRS (2026). https://gsrs.ncats.nih.gov/api/v1/substances(QHK6Z47GTG)?view=full · accessed 2026-09-22
  6. 6.PubChem Compound 65938: Goralatide (Ac-Ser-Asp-Lys-Pro, Ac-SDKP). National Center for Biotechnology Information (2026). https://pubchem.ncbi.nlm.nih.gov/compound/65938 · accessed 2026-09-22
  7. 7.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). doi:10.1002/dta.1402 PMID 22962027 · accessed 2026-09-22
  8. 8.Ho ENM, Kwok WH, Lau MY, Wong ASY, Wan TSM, Lam KKH, Schiff PJ, Stewart BD. 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 (2012). doi:10.1016/j.chroma.2012.09.043 PMID 23084823 · accessed 2026-09-22
  9. 9.Delcourt V, Garcia P, Chabot B, Aber N, Pescher M, Cacault M, Scholtes P, Loup B, Barnabé A, Popot M-A, Bailly-Chouriberry L. Equine Doping Controls of Thymosin β4: A Population Study and Strategy for Misuse Detection. Drug Testing and Analysis (2025). doi:10.1002/dta.3806 PMID 39314109 · accessed 2026-09-22
  10. 10.Sosne G, Kleinman HK, Springs C, Gross RH, Sung J, Kang S. 0.1% RGN-259 (Thymosin ß4) Ophthalmic Solution Promotes Healing and Improves Comfort in Neurotrophic Keratopathy Patients in a Randomized, Placebo-Controlled, Double-Masked Phase III Clinical Trial. International Journal of Molecular Sciences (2023). doi:10.3390/ijms24010554 PMID 36613994 · accessed 2026-09-22
  11. 11.MHRA Products: search results for 'thymosin'. Medicines and Healthcare products Regulatory Agency (2026). https://products.mhra.gov.uk/search/?search=thymosin&page=1 · accessed 2026-09-22
  12. 12.Union Register of medicinal products for human use (alphabetical listing). European Commission, DG Health and Food Safety (2026). https://ec.europa.eu/health/documents/community-register/html/alfregister.htm · accessed 2026-09-22
  13. 13.Drugs@FDA (openFDA drugsfda endpoint) search for thymosin / timbetasin / TB-500. U.S. Food and Drug Administration (2026). https://api.fda.gov/drug/drugsfda.json?search=openfda.substance_name:%22thymosin%22+OR+openfda.brand_name:%22thymosin%22+OR+products.active_ingredients.name:%22thymosin%22&limit=5 · accessed 2026-09-22
  14. 14.A Phase 1/2, Randomized, Double-Blind, Placebo-Controlled, Sequential Dose-Escalation Study of TB-500 (Thymosin Beta 4 17-23 Fragment) in Adults With Stable Atherosclerotic Cardiovascular Disease. ClinicalTrials.gov (Hudson Biotech) (2026). https://clinicaltrials.gov/study/NCT07487363 · accessed 2026-09-22
  15. 15.The Prohibited List (List of Prohibited Substances and Methods in force). World Anti-Doping Agency (2026). https://www.wada-ama.org/en/prohibited-list · accessed 2026-09-21
  16. 16.Simenel C, Van Troys M, Vandekerckhove J, Ampe C, Delepierre M. Structural requirements for thymosin beta4 in its contact with actin. An NMR-analysis of thymosin beta4 mutants in solution and correlation with their biological activity. European Journal of Biochemistry (2000). doi:10.1046/j.1432-1327.2000.01380.x PMID 10848969 · accessed 2026-09-22
  17. 17.Kumar N, Nakagawa P, Janic B, Romero CA, Worou ME, Monu SR, Peterson EL, Shaw J, Valeriote F, Ongeri EM, Niyitegeka J-MV, Rhaleb N-E, Carretero OA. The anti-inflammatory peptide Ac-SDKP is released from thymosin-β4 by renal meprin-α and prolyl oligopeptidase. American Journal of Physiology - Renal Physiology (2016). doi:10.1152/ajprenal.00562.2015 PMID 26962108 · accessed 2026-09-22
  18. 18.PubChem Compound 62707662: TB500 (Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH). National Center for Biotechnology Information (2026). https://pubchem.ncbi.nlm.nih.gov/compound/62707662 · accessed 2026-09-22
  19. 19.FDA Global Substance Registration System: THYMOSIN .BETA.-4 (UNII 549LM7U24W). FDA / NCATS GSRS (2026). https://gsrs.ncats.nih.gov/api/v1/substances(549LM7U24W)?view=full · accessed 2026-09-22
  20. 20.PubChem Compound 45382195: Thymosin Beta 4. National Center for Biotechnology Information (2026). https://pubchem.ncbi.nlm.nih.gov/compound/45382195 · accessed 2026-09-22
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For laboratory research use only. This article summarises published literature and regulatory records; it does not describe or recommend any use of a material in or on humans or animals.
Cite this page
Harvard
HelixEVO Labs (2026) TB-500 and thymosin β4: three molecules, one commercial name. Available at: https://helixevo.net/knowledge-base/compounds/tb-500 (Accessed: 2026-09-25).
APA
HelixEVO Labs. (2026). TB-500 and thymosin β4: three molecules, one commercial name. https://helixevo.net/knowledge-base/compounds/tb-500
BibTeX
@misc{helixevo-2026-tb-500-and-thymosin-4-three-molecules-on,
  title = {TB-500 and thymosin β4: three molecules, one commercial name},
  author = {{HelixEVO Labs}},
  year = {2026},
  howpublished = {\url{https://helixevo.net/knowledge-base/compounds/tb-500}},
  note = {Reviewed 2026-09-22; accessed 2026-09-25}
}
Revision history
  1. r1 · 2026-09-25 · Initial import