Compound monograph
TB-500
Analytical studies have identified an N-terminally acetylated heptapeptide with the residue sequence LKKTETQ in material labeled TB-500. The designation alone does not establish the complete molecular identity of another preparation.
01
Identity & nomenclature
Analytical studies have identified an N-terminally acetylated heptapeptide with the residue sequence LKKTETQ in material labeled TB-500. The designation alone does not establish the complete molecular identity of another preparation.
TB-500 is a product designation whose use does not uniquely specify a molecular structure. This dossier concerns the acetylated LKKTETQ referent identified in analytical literature. PubChem CID 62707662 and GSRS UNII QHK6Z47GTG, which lists CAS 885340-08-9, identify Ac-LKKTETQ-OH; these identifiers describe the defined fragment and do not establish the composition of another preparation labeled TB-500. It does not establish the identity or composition of a commercial preparation.
Declared aliases and development codes: N-acetyl-thymosin beta-4 (17-23).
02
Molecular properties
| CAS Registry Number | 885340-08-9 |
|---|---|
| PubChem CID | 62707662 |
| UNII | QHK6Z47GTG |
| One-letter sequence | LKKTETQ |
| Three-letter sequence | Leu–Lys–Lys–Thr–Glu–Thr–Gln |
| Terminal groups | N-terminal acetylation at Leu1; Free C-terminal carboxyl |
The residue sequence LKKTETQ corresponds to positions 17-23 of mature human thymosin beta-4 and positions 18-24 of UniProt P62328, whose initiator methionine is removed. The fragment's N-terminal acetyl modification is attached to leucine, rather than to the serine that begins the mature parent.
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Structural characteristics
Terminal features: N-terminal acetylation at Leu1, Free C-terminal carboxyl.
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Molecular targets & mechanisms
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Analytical considerations
The retrieved registry representations disagree on molecular formula and molecular weight. Their reported properties are retained as conflicting observations; no settled formula or average molecular weight is assigned here. A calculation for a specified terminal structure characterizes that structure and does not resolve the source disagreement. PubChem CID 62707662 explicitly represents the acetylated seven-residue fragment with a free Gln7 carboxyl, so that end can be declared for this structure without settling the retained inter-registry formula disagreement. PubChem CID 62707662 reports C38H68N10O14, whereas GSRS UNII QHK6Z47GTG reports C36H66N10O13 despite specifying N-acetylation, leaving the registry property disagreement explicit.
Disagreements and mix-ups
Points where sources disagree about this compound's identity, or where a name or form is easily confused with another, as noted in this record. The discrepancy register quotes the passage for each one.
Sources disagree · unresolved · Formula or mass
Molecular formula and weight across registry recordsOften mixed up · Name or substance
"TB-500" does not name one structure
What the studies reported
Each finding describes one cited study in its stated model. These observations are specific to that study and do not establish effects in other settings.
Animal studies
Plasma and urine from horses
Ho et al. detected N-acetylated LKKTETQ and its metabolites by liquid chromatography–mass spectrometry in plasma and urine from horses following TB-500 administration.
Reference [2]
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Verified bibliography
Cited studies by type
The 3 papers this record cites, counted by the kind of work each reports. A count is the size of this record's selection, not of the research that exists, and says nothing about results, safety, effectiveness or approval.
A paper can report more than one kind of work. Each count opens those papers in the bibliography. Compare every record on the Evidence Map.
Reference 1
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
Drug testing and analysis · 2012-09-07 · Journal Article
currentReference 2
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.Ho EN, Kwok WH, Lau MY, Wong AS, Wan TS, Lam KK, Schiff PJ, Stewart BD
Journal of chromatography. A · 2012-09-23 · Journal Article
currentReference 3
TB500/TB1000 and SGF1000: A scientific approach for a better understanding of misbranded and adulterated drugs.Delcourt V, Garcia P, Chabot B, Barnabé A, Bouscarel M, Loup B, Popot MA, Bailly-Chouriberry L
Drug testing and analysis · 2022-12-23 · Journal Article
current
Study models of these references
What kind of experiment each cited paper reports, taken from its abstract unless marked. Not a summary of results.
| Reference | Study models |
|---|---|
| Esposito S et al. 2012 | Chemical, structural or analytical study; no biological model reported |
| Ho EN et al. 2012 | Study models reported: in vitro; animal (horse) · from the abstract |
| Delcourt V et al. 2022 | Chemical, structural or analytical study; no biological model reported |
Compare
Record history
Published 2026-09-28.
- : Sequence and structure
- : Sequence and structure, Analytical notes
- : Identity and nomenclature, Analytical notes
Each entry names the parts of this record that changed on that date. Changes to links between records and to catalogue links are not listed. This history covers the tracked record fields; study findings are not listed here.
Cite this record: Purely Peptides Research Library. TB-500. Published 2026-09-28; updated 2026-10-15. https://purelypeptides.org/research/compounds/tb-500/
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Methodology & citation verification
Reference identity is checked against official PubMed metadata. Local deterministic receipts bind each normalized title and canonical metadata record to its verification date. Scientific values remain absent when an authoritative source has not been verified.
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