What Is TB-500?
TB-500 is a synthetic, N-terminally acetylated heptapeptide corresponding to residues 17–23 of human thymosin beta-4. Its sequence is Ac-LKKTETQ.
It is chemically classified as a thymosin beta-4 peptide fragment. The published identification of TB-500 specifically refers to this acetylated seven-amino-acid sequence.
Research Overview Table
Chemical and Molecular Characteristics
Certificates:
Mechanism of Action Under Investigation
TB-500 is the N-terminally acetylated Ac-LKKTETQ fragment of thymosin β4. The LKKTETQ sequence corresponds to the actin-binding region. Studies of thymosin β4 show binding to monomeric G-actin, forming a 1:1 complex and limiting incorporation of G-actin into filaments.
The interaction changes actin conformation and dynamics and is associated with reduced actin polymerization and nucleotide exchange. However, these findings come primarily from thymosin β4 studies. A TB-500-specific study reported that the biological effects of the parent acetylated peptide had not been documented and found that metabolites may account for activity previously attributed to TB-500. Therefore, the mechanism of the intact TB-500 molecule remains uncertain.
Scientific Research Context
Research on TB-500 includes studies of its chemical identity, metabolism, and biological activity. Published laboratory work has examined the peptide in biochemical and enzyme systems, cell-based experiments, and animal studies. Research has also examined its metabolites after experimental exposure. The available evidence comes mainly from in vitro experiments and preclinical animal research. Studies involving the parent thymosin β4 protein form a much larger literature and should be distinguished from research conducted specifically with TB-500.
TB-500 Biology and Biological Pathways
Primary Biological Function
TB-500 contains the LKKTETQ sequence from the actin-binding region of thymosin β4. Research on this sequence has examined its relationship with actin organization, cell migration and vascular cell behavior. However, the biological function of the intact acetylated TB-500 molecule remains less established than that of thymosin β4.
Relevant Metabolic or Signalling Pathways
Research on the LKKTETQ 17–23 peptide has examined PDGF-BB/Akt signaling, including Akt phosphorylation at T308 and S473 and downstream PRAS40 phosphorylation. Studies of thymosin β4 have also investigated PI3K/Akt/eNOS signaling and ERK1/2 signaling in endothelial progenitor cells.
Tissue-Specific Biology
Studies of thymosin β4 have identified the peptide in the brain, thymus, spleen, lung, kidney, liver, adrenal gland, stomach, and intestine. Thymosin β4 has also been localized in microglia and macrophages. A comparable tissue-distribution profile has not been established for TB-500.
Experimental Biomarkers
Published research has measured PDGFβ receptor, α-SMA, collagen I and Akt phosphorylation in cells exposed to the LKKTETQ sequence. TB-500-specific research has also assessed cell viability and wound-closure activity for TB-500 and its metabolites.
Laboratory Investigation Methods
Research has used biochemical actin assays, cell culture experiments, immunofluorescence, migration assays, Western blotting, RT-PCR, and animal models. TB-500-specific investigations have additionally used UHPLC-Q-Exactive Orbitrap mass spectrometry to examine the parent peptide and its metabolites.
Experimental Models Used in Published Research
The TB-500-specific literature includes in-vitro fibroblast models, rat models and equine models. These systems differ in their biological complexity and species-specific characteristics. The available studies do not establish that findings from these models directly represent human biology.
Fibroblast Cell Models
Cultured fibroblasts provide an isolated cellular model. Their main limitation is the absence of whole-organism metabolism, tissue architecture, circulation, and interactions between different cell types.
Rat Models
Rats provide an intact mammalian model. Their limitation is species-specific peptide metabolism and metabolite formation, which may differ from the corresponding processes in humans.
Equine Models
Thoroughbred horses provide an intact equine model. The limitation is that peptide metabolism and disposition in horses may not correspond directly to those in humans.
Published Research
Peptide Metabolism
Research has investigated the biotransformation of TB-500 and the formation of four metabolites: Ac-LK, Ac-LKK, Ac-LKKT and Ac-LKKTE. Ac-LK was the predominant metabolite during the early sampling period, while Ac-LKK was detected for up to 72 hours.
Metabolite Biological Activity
Researchers have examined whether the metabolites retain biological activity associated with the parent sequence. Comparative experiments assessed cytotoxicity and wound-closure activity for TB-500 and its metabolites. The reported activity was associated with Ac-LKKTE, rather than the parent peptide, in the wound-closure experiments.
Post-Administration Detection
Research has investigated the presence of N-acetylated LKKTETQ and its metabolites after administration. The parent peptide and metabolites were detected in post administration plasma and urine samples, including N-acetylated LK.
Corneal Injury Research
The study examined TB500 in an alkaline-phosphatase-triggered peptide hydrogel, focusing on corneal epithelial migration, proliferation and tight junction recovery, as well as stromal fibroblast differentiation and cytoskeletal reorganization. It also examined epithelial regeneration, inflammation, and corneal barrier function following corneal injury.
Limitations of Current Research
Evidence Is Predominantly Preclinical
The TB-500 literature remains limited mainly to experimental research. Published evidence has focused on metabolism, metabolite activity, analytical detection and selected biological investigations. A broad clinical evidence base has not been established, leaving the overall evidence base predominantly preclinical.
Human Clinical Evidence
No completed, controlled clinical study of TB-500 itself has established human clinical evidence. Published human studies involving full length thymosin β4 are not equivalent because that molecule differs from the Ac-LKKTETQ fragment. This leaves a major gap in direct human evidence for TB-500.
Species Differences
Species differences are a limitation because TB-500 metabolism has been examined in both equine and rodent systems, with metabolite profiles identified in each. The available studies do not establish that peptide metabolism or metabolite persistence is equivalent across species.
Study Design Limitations
The TB-500 literature uses different experimental designs, analytical endpoints and research conditions. Some studies assess detection or metabolism, while others examine cellular activity. Because the studies address different questions and use different endpoints, their findings cannot be directly compared as a single body of evidence.
Independent Replication
Independent replication remains limited within the TB-500 literature. Several research areas are represented by individual or relatively few publications. Repeated findings from independent research groups would be needed to determine how consistently the reported observations can be reproduced.
Long-Term Evidence
Long-term evidence for TB-500 is limited. The published studies identified here focus on relatively short observation periods, including metabolite detection through 72 hours. They do not provide sufficient longitudinal data to determine whether biological changes persist over longer periods.
Analytical Documentation
HPLC separates the components of a sample and produces a chromatographic profile. It can support the assessment of purity and help distinguish the principal component from related substances.
LC-MS combines chromatographic separation with mass spectrometry. The resulting mass-to-charge data can support compound identification and help distinguish related molecular species.
NMR provides structural information based on the magnetic properties of atomic nuclei. Its use depends on the material and the analytical purpose. A Certificate of Analysis records batch-specific test results against defined quality specifications.
These records provide analytical information about a laboratory material and support assessment of its measured characteristics. Analytical documentation verifies product identity and quality, not biological performance.
Storage and Laboratory Handling
Keep the material refrigerated at 2–8°C and protect it from heat, moisture, and direct light. Keep the container closed except when the material is being handled.
Handling should be carried out by qualified laboratory personnel using appropriate clean-handling practices. Avoid unnecessary exposure to the surrounding environment to reduce the risk of contamination.
Why Researchers Choose Direct SARMs?
Direct SARMs is an established supplier of research peptides. We are committed to product quality, reliable service, and helpful customer support.
Our European-made products undergo rigorous purity testing, with clear product information provided for each research material. We also aim to provide dependable shipping and a smooth ordering experience.
Our support team is available to assist with orders, shipping, payments, and general questions. At Direct SARMs, we aim to make the research supply process simple, clear, and reliable.
Frequently asked questions
Why choose us?
Direct SARMs is an established supplier of research peptides. We are committed to product quality, reliable service, and helpful customer support.
Our European-made products undergo rigorous purity testing, with clear product information provided for each research material. We also aim to provide dependable shipping and a smooth ordering experience.
Our support team is available to assist with orders, shipping, payments, and general questions. At Direct SARMs, we aim to make the research supply process simple, clear, and reliable.