TB-500: what the research shows

What TB-500 is

TB-500 is a catalogue name, not a name from the literature. It refers to a synthetic peptide derived from thymosin beta-4, a 43-residue protein present at high concentration in nearly every mammalian cell type. Thymosin beta-4 is best known as the principal actin-sequestering protein of the cytoplasm: it binds monomeric G-actin and holds it in reserve, which is one of the ways a cell regulates how quickly it can assemble actin filaments and change shape.

The actin-binding activity maps to a short internal stretch, residues 17 to 23 (sequence LKKTETQ). Most material sold as TB-500 corresponds to this seven-residue fragment, sometimes with an N-terminal acetyl group. Some catalogues use the same name for full-length thymosin beta-4, which is about 4.9 kDa. The two are not interchangeable in an experiment, and the product name on the certificate is what tells you which one a lot is; if the distinction matters to your work, ask before ordering.

A separate fragment, the N-terminal tetrapeptide Ac-SDKP, is released from thymosin beta-4 in vivo and has its own literature, mostly on fibrosis. It is a different molecule from the 17-23 fragment and is not what TB-500 usually means.

In cell-based assays the 17-23 region is studied for its effect on cell migration. The working hypothesis is that by handling actin, the fragment influences how readily cells such as keratinocytes, endothelial cells and fibroblasts move across a surface. That is the mechanism the rest of the literature builds on.

What the wound-healing literature actually studied

The largest body of preclinical work on thymosin beta-4 is dermal wound healing, and the study types are consistent: full-thickness excisional wounds in rats and mice, including diabetic (db/db) and aged animals in which healing is impaired, with wound closure, re-epithelialisation, collagen deposition and angiogenesis in the wound bed as the endpoints. The in-vitro companions to those studies are keratinocyte and fibroblast scratch assays, where the measured outcome is how far cells migrate into a cleared strip of a culture dish over a set number of hours.

Endothelial work sits alongside it. Tube-formation assays, chick chorioallantoic membrane assays and endothelial migration assays are the usual formats, and they are the basis for the angiogenesis language that appears in reviews.

Two things are worth holding onto. Almost all of this used full-length thymosin beta-4 rather than the 17-23 fragment, with a smaller number of studies showing that the fragment alone reproduces the migration effect in culture. And every study described is an animal or cell-culture study. Those designs answer questions about mechanism and about rodents. They do not establish what the molecule does in a person, and no thymosin beta-4 product is approved for wound healing in Canada or anywhere else.

Cardiac, corneal, muscle and tendon models

Cardiac studies are the second-largest group. In mouse coronary-artery-ligation models of myocardial infarction, thymosin beta-4 has been examined for effects on cardiomyocyte survival, scar size and left-ventricular function, and in developmental work for its role in coronary vessel formation and in mobilising epicardial progenitor cells. Some of those results proved harder to reproduce across laboratories, which is a normal feature of a young field and a reason to read the primary papers rather than the reviews.

Corneal work uses alkali-burn and epithelial-debridement injury models in mice and rabbits, with corneal epithelial migration assays in culture; endpoints are re-epithelialisation rate and markers of inflammation. This is the line that progressed furthest. An ophthalmic formulation of full-length thymosin beta-4 has been through late-stage human trials in dry eye and neurotrophic keratopathy, and as of this writing it has no marketing approval.

Skeletal-muscle studies use cardiotoxin or crush injury in mice and the mdx mouse model of muscular dystrophy, measuring regeneration markers in tissue and myoblast migration in culture. Tendon and ligament work is smaller and mostly in vitro (tenocyte migration and proliferation), with a few small-animal injury models. The veterinary interest in TB-500, particularly in racehorses, ran well ahead of the published tendon evidence, which is a useful thing to know when reading forum claims about it.

Why it is studied alongside BPC-157

BPC-157 and TB-500 are frequently paired in preclinical protocols and in supplier catalogues, and the reason is mechanistic rather than clinical. Both appear in the same kinds of injury model (dermal, tendon and muscle, plus gastrointestinal in the case of BPC-157) and both are discussed in terms of cell migration and angiogenesis, but they are proposed to act through different routes. BPC-157 is usually discussed in terms of growth-factor and nitric-oxide signalling; thymosin beta-4 in terms of the actin cytoskeleton. An investigator interested in whether two distinct pathways add or interact has an obvious reason to run them in the same model.

That is the whole of the rationale. Being studied side by side does not imply anything about combined use, and there is no controlled human evidence on the pair. Our combined overview at /library/bpc-157-tb-500-research-overview/ covers the BPC-157 literature in the same terms as this page covers TB-500.

Stability, storage and reconstitution

TB-500 ships as a lyophilised powder in a sealed vial. In that form it tolerates the temperatures of a domestic parcel for the days it takes to arrive, but it should not be stored that way. Keep unopened vials refrigerated, or frozen for storage beyond a few months, in the dark and away from moisture. Lyophilised peptide is hygroscopic, so let a cold vial reach room temperature before opening it; opening it cold pulls condensation onto the powder.

Reconstitution uses bacteriostatic water, which is sterile water containing 0.9% benzyl alcohol as a preservative. Add the diluent slowly down the inside wall of the vial rather than onto the powder, then swirl or roll gently until the solution is clear. Do not shake; peptides in solution are sensitive to shear and foaming. Once reconstituted, store at 2 to 8 C and do not freeze and thaw repeatedly. Reconstituted solution is generally used within weeks rather than months, and a solution that has turned cloudy or shows particulates should be discarded.

Diluent volume, the resulting concentration and everything downstream of that is protocol, and it is deliberately not on this page. The reported protocol for TB-500, including a concentration table computed from the vial mass we actually ship, is at /protocols/tb-500/.

Reading the certificate for a TB-500 lot

Pure North commissioned Canada Peptide Testing, as a paying client. Published reports for this product: 10 mg vial, CPT-TB500-10-091226 (98.84% area purity; 10.41 mg measured content). Read the original documents at /lab-results/.

The published Canada Peptide Testing reports measure RP-HPLC-UV area purity and content. They do not include mass-spectrometry identity, endotoxin, water content or a related-substances breakdown. These results do not establish clinical safety or regulatory approval.

Match the compound, vial size and printed lot to the report before relying on it. An assigned reference is not automatically the batch code on a vial. If they differ, email purenorthpeptides@proton.me with the vial details and report number to confirm the connection. Do not extend a report to another size or lot.

Regulatory status in Canada

TB-500 is supplied in Canada as a research-use-only laboratory reference standard. It is not approved by Health Canada for any use in people, it carries no Drug Identification Number or Natural Product Number, and no thymosin beta-4 product is an authorised therapeutic anywhere. That is the category the material sits in, and it constrains what we can say: no health claims and no outcomes. The schedules that do appear on the protocol pages are a summary of what the literature reports, not a recommendation, and they carry the same research-use framing as this page.

Every order requires a research-use declaration at checkout confirming that the material is for laboratory research. That is the buyer's side of the same category.

Two further points people searching for this compound often need. TB-500 and thymosin beta-4 are on the World Anti-Doping Agency prohibited list, and racing authorities prohibit them in horses; anyone subject to those rules is subject to them regardless of how the material is labelled. And this page is general information, not legal advice. Classification is compound-specific and can change, Health Canada is the authority, and our overview of the research-use framework is at /library/are-research-peptides-legal-in-canada/.

Frequently asked

What is TB-500?

TB-500 is a catalogue name for a synthetic peptide derived from thymosin beta-4, a 43-residue actin-binding protein found in most mammalian cells. The name usually refers to the seven-residue actin-binding fragment (residues 17 to 23), though some suppliers use it for the full-length protein. It is supplied as a research-use-only laboratory reference standard.

What are the benefits of TB-500 in research?

In preclinical research the question is what the molecule does in a given model, not what it does for a person. Thymosin beta-4 and its 17-23 fragment have been studied in rodent dermal wound models, mouse coronary-ligation models of heart injury, corneal injury models, skeletal-muscle injury and the mdx mouse, and in cell-culture migration and tube-formation assays. Those studies report effects on cell migration, re-epithelialisation and angiogenesis in those systems. None of that is human evidence, and no TB-500 product has approval for any indication.

Is TB-500 the same as thymosin beta-4?

No. Thymosin beta-4 is the full 43-residue protein. TB-500 usually denotes a synthetic seven-residue fragment corresponding to its actin-binding region, residues 17 to 23. Some catalogues use TB-500 for full-length material, so check the product name on the certificate for the lot you receive.

How is TB-500 stored?

Lyophilised vials are kept refrigerated, or frozen for longer storage, dry and out of light. After reconstitution with bacteriostatic water the solution is kept at 2 to 8 C, not repeatedly frozen and thawed, and used within weeks. Let a cold vial reach room temperature before opening it so condensation stays off the powder.

Is TB-500 legal in Canada?

It is sold as a research-use-only laboratory reference standard, a category distinct from products approved for human use. It is not approved by Health Canada and carries no DIN or NPN, and buyers sign a research-use declaration at checkout. It is separately prohibited in sport under the WADA list. Classification can change; confirm your own position with Health Canada rather than with a supplier's website.

Referenced in our catalog

Related library entries