TB-500 FRAG

Technical data

INN name

TB-500 Fragment 17-23 (Ac-LKKTETQ)

CAS

885340-08-9

Molecular formula

C38H68N10O14

Molecular weight

889.02 g/mol

Identity and composition

TB-500 FRAG is a short synthetic peptide that corresponds to fragment 17-23 of human thymosin β4, in its N-terminally acetylated form. It is studied as the functional actin-binding motif of that protein, in contexts of cell migration and angiogenesis at the preclinical level.

As for its chemical identity, the amino acid sequence is LKKTETQ (N-acetylated form Ac-LKKTETQ), corresponding to residues 17-23 of human thymosin β4. It is also known by the synonyms TB-500, TB-500 fragment, Thymosin β4 17-23 fragment, Ac-LKKTETQ y peptide of the actin-binding motif of thymosin beta-4.

For this compound there is no verified CAS number, molecular weight or molecular formula in the reference sources, so such data are omitted rather than estimated.

Product for research use.

Mechanism of action

The peptide reproduces the central actin-binding motif of thymosin β4 (LKKTET, residues 17-22, plus a Q at position 23). Thymosin β4 is an actin-sequestering protein, and this seven-residue motif constitutes the molecule's main binding site for actin and for cells.

In preclinical studies using endothelial migration and vascular sprouting assays (chicken aorta and aortic arch), thymosin β4 and the isolated motif peptide have been observed to show nearly identical activity at low, nanomolar-range concentrations, whereas peptides lacking some part of the motif are inactive. The addition of soluble G-actin competitively inhibits adhesion and vascular sprouting, indicating that these effects are mediated by binding to actin. Thus, the motif drives the endothelial migration, cell adhesion and vascular sprouting (angiogenesis) (FASEB J 2003; PMID 14500546).

The acetylated fragment Ac-LKKTETQ has been chemically identified as a component of the product marketed as TB-500 (Drug Test Anal 2012; PMID 22962027).

Pharmacokinetics

Reliable human pharmacokinetic data (half-life, clearance) were not confirmed for the isolated Ac-LKKTETQ fragment from the reviewed sources. In the anti-doping field, HPLC-MS/MS methods were developed to detect the acetylated fragment in plasma and urine, but no validated pharmacokinetic parameters were reported (PMID 22962027). Therefore, any half-life or dynamics figure is deliberately omitted, as no supported data exist.

Scientific evidence

The available evidence is largely preclinical and in vitro, and it should be read as hypothesis-generating, not as established clinical benefit. The studies include endothelial cell (HUVEC) migration and adhesion assays and vascular sprouting assays in aortic arch and aortic ring, which suggest angiogenic and cell migration activity of the actin-binding motif (FASEB J 2003; PMID 14500546). It has been studied mainly in the context of angiogenesis, wound healing, and tissue repair, as the active fragment of thymosin β4. No controlled, completed clinical trials establishing the efficacy of the isolated 17-23 fragment were confirmed. Interest in TB-500 has arisen largely in sports and anti-doping contexts, where it is flagged as a substance suspected of doping rather than as an approved therapeutic (Drug Test Anal 2012; PMID 22962027).

Research applications

Ideal for (in research):

• Preclinical in vitro studies on migration and adhesion of endothelial cells.
• Models of vascular sprouting and angiogenesis as the active fragment of the actin-binding motif.
• Research on the structure-function relationship between the LKKTET motif and full-length thymosin β4.
• Development and validation of analytical methods (for example, HPLC-MS/MS detection in anti-doping contexts).

Not applicable for:

• Any form of human consumption or administration.
• Clinical, diagnostic, or therapeutic use: it is not an approved drug.
• Sporting use: in the anti-doping literature it is characterized as a substance suspected of misuse in sport.

Product for research use.

Research protocols

The available data come from in vitro preclinical trials, not of dosing protocols in humans. In studies of endothelial migration and vascular sprouting, activity of the actin-binding motif has been observed at low concentrations on the order of nanomolar (approximately 50 nM), with competitive inhibition upon adding soluble G-actin in the range of 5 to 50 nM (FASEB J 2003; PMID 14500546).

No doses in milligrams, administration schedules or validated guidelines are available for the isolated fragment in human subjects; therefore, any clinical dosing protocol is omitted as there is no support in the consulted literature. The cited concentrations correspond solely to experimental laboratory conditions.

Reconstitution

As a general standard laboratory handling guide, lyophilized peptides are usually reconstituted with bacteriostatic water (water with approximately 0.9% benzyl alcohol), added slowly along the vial wall to avoid abrupt agitation of the peptide.

• Let the solvent run down the inner wall of the vial instead of directing it directly onto the powder.
• Do not shake; swirl the vial gently until a clear solution is achieved.
• Calculate the reconstitution volume according to the working concentration desired for your assay, considering the nominal content of 10 mg per vial.

This information is for guidance on laboratory handling and does not constitute a preparation guideline for administration to people.

Stability and storage

As standard laboratory handling practice for peptides:

• Lyophilized (powder): it is best stored in cool, dry conditions, protected from light and moisture; refrigeration or freezing prolongs its stability for long-term storage.
• Reconstituted (in solution): must be kept refrigerated and used within a relatively short period, avoiding repeated freeze-thaw cycles that can degrade the peptide.

Always handle under adequate laboratory conditions. These indications are of a general nature and do not replace the specifications of the batch or of the analytical supplier.

Safety profile

No confirmed formal safety or clinical toxicology profile for the isolated fragment in the reviewed literature. The compound is not an approved drug and, in the anti-doping literature, it is characterized as a substance suspected of misuse in sport (Drug Test Anal 2012; PMID 22962027).

It has been reported that the sequence LKKTETQ also appears as a natural degradation product of thymosin β4 in wound fluid, which suggests possible endogenous relevance; however, this does not establish the safety of exogenous dosing. There are no documented contraindications or verified adverse event rates for the isolated fragment, so such data are omitted. Handle only as research material, with the usual laboratory precautions.

Comparative context

TB-500 FRAG is a short synthetic peptide of 7 residues, versus the full-length thymosin β4, of 43 residues.

In preclinical assays of endothelial migration and sprouting, the isolated actin-binding motif reproduces much of the angiogenic activity of the full protein at comparable concentrations on the order of low nanomolar, which suggests that the motif is the key functional determinant (FASEB J 2003; PMID 14500546).

However, the full protein contains additional domains (for example, its N-terminal and C-terminal regions) involved in other activities that the heptapeptide does not reproduce. In summary, the fragment concentrates the functional actin-binding site, but does not encompass the entire repertoire of the original molecule.

History and development

TB-500 FRAG derives from the study of thymosin β4, an actin-sequestering protein. Preclinical research identified that its central actin-binding motif (LKKTET, residues 17-22) is the main site responsible for its activity on endothelial migration and vascular sprouting, laying the groundwork for interest in the isolated fragment (FASEB J 2003; PMID 14500546).

Subsequently, the N-acetylated fragment of residues 17-23 (Ac-LKKTETQ) was synthesized and chemically characterized by HPLC-HRMS, identifying it as a component of the product marketed as TB-500, in work framed within the anti-doping field that flagged it as a substance with potential for misuse in sport (Drug Test Anal 2012; PMID 22962027).

FAQ

Certificate of analysis per batch

TB-500 FRAG batch with certificate of analysis published in the COA catalog:

• Lot EXO010626035A — 10 mg, issued 2026-05-29

Scientific references (5)

Peer-reviewed literature on TB-500 FRAG, with its PubMed identifier where available:

• Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applications (Goldstein AL, et al. · Expert Opinion on Biological Therapy · 2012) — Review of thymosin beta-4 (TB-500) in tissue repair and regenerative medicine. PMID 22074294.
• Thymosin β4 activates ILK and promotes cardiac migration, survival, and repair (Bock-Marquette I, Saxena A, White MD, et al. · Nature · 2004) — Study in murine infarction models demonstrating that Tβ4 activates integrin-linked kinase and promotes cardiomyocyte survival. PMID 15565145.
• Thymosin β4 accelerates wound healing (Malinda KM, Sidhu GS, Mani H, et al. · Journal of Investigative Dermatology · 1999) — Study in rat dermal wound-healing models, evaluating topical and systemic application of Tβ4. PMID 10469335.
• 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, et al. · Drug Testing and Analysis · 2012) PMID 22962027.
• Solid-phase extraction of small biologically active peptides on cartridges and microelution 96-well plates from human urine (Semenistaya, et al. · Drug Testing and Analysis · 2016) PMID 26472487.

Otras presentaciones de TB-500 FRAG

• TB-500

Other related research peptides

• ACE-031
• ARA-290
• BPC-157
• BPC-157 + TB-500
• BPC-157 + TB-500 + KPV
• KPV
• PTD-DBM
• TB-500