Sourcing Guide

TB-500 in the US: Synthetic Thymosin β4, Tested by Batch

What is actually in a TB-500 vial, why the naming confusion matters commercially, and how to verify a lot

July 30, 2026·By Adam Reeves · Research Editor, Eppix Labs

TB-500 has a naming problem that is worth resolving before anything else, because it changes what you are comparing when you compare prices. The research literature is about thymosin β4, a 43-residue protein. On the US research market "TB-500" is used both for synthetic full-length thymosin β4 and for the seven-residue fragment Ac-LKKTETQ (residues 17 to 23). They are not the same molecule, and a vial priced against one is not comparable to a vial containing the other.

The Eppix Labs TB-500 is synthetic full-length thymosin β4; the fragment is listed separately as TB-500 Fragment 17-23. This article covers what the thymosin β4 literature supports, what a TB-500 certificate should tell you, and the regulatory position in the US as of August 2026. TB-500 is supplied for in-vitro laboratory research only.

Chemical Identity

Name: TB-500 (synthetic thymosin β4)
Also known as: TB-500, Thymosin beta-4, Tβ4, Timbetasin
Molecular formula: C₂₁₂H₃₅₀N₅₆O₇₈S
Molecular weight: 4963 g/mol
CAS number: 77591-33-4
Sequence (1-letter): SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES
Salt forms: Acetate

What TB-500 is, and what it is not

Thymosin β4 is a 43-amino-acid, 4.9 kDa actin-sequestering protein present in most mammalian cells, first characterized as a thymic peptide and later shown to be a major intracellular G-actin binding protein.[1] Its actin-binding activity localizes substantially to the heptapeptide motif LKKTETQ.

That motif, acetylated, is the product sold as "TB-500 fragment". It weighs 889 g/mol against roughly 4,963 g/mol for the full protein, which is why the label alone settles nothing and the certificate settles everything: an MS identity result near 4.96 kDa is the full protein, one near 0.89 kDa is the fragment.

General Image — TB-500 lyophilized research material as supplied by Eppix Labs. Labeled strength and measured content appear on the certificate below.

Sequence and structure

Forty-three residues, N-terminally acetylated in the native form, with the LKKTETQ actin-binding motif near the start of the chain. The length makes it a harder synthesis than any fragment, which makes substitution with a short, cheap peptide the most tempting adulteration for this product, and one a purity assay alone cannot catch. That is what the MS identity line on the certificate is for.

Amino Acid Sequence diagram — Amino-acid sequence of TB-500.

Chemical Structure diagram — Chemical structure of TB-500.

What the published research shows

The substantive literature is on thymosin β4 itself, which is what this vial contains:

·Actin sequestration. Thymosin β4 is the principal G-actin sequestering protein in mammalian cells, and the actin-binding function is the mechanistic anchor for everything downstream.[1]
·Dermal wound models. Malinda et al. (1999) reported accelerated wound healing and increased keratinocyte migration in full-thickness rat and mouse models.[2]
·Corneal models. Sosne et al. (2002) reported promotion of corneal epithelial wound healing and reduction of inflammation in an experimental model.[3]
·Cardiac models. Bock-Marquette et al. (2004) reported activation of integrin-linked kinase and improved cardiac cell migration and survival after coronary artery ligation in mice.[4]
·Breadth of animal work. Philp and Kleinman (2010) survey the animal literature across dermal, corneal and cardiac repair models.[5]

The limit of the evidence

Thymosin β4 reached human clinical investigation in dermal and corneal indications and has no approved indication. There is no established human dose and no FDA approval for any use.

The seven-residue fragment has almost no literature of its own. Reading full-length thymosin β4 results as if they described the fragment is the most common error in TB-500 marketing copy, and it runs both ways: the full protein should not be sold on fragment claims either.

Regulatory status: the July 2026 advisory vote

On 23 and 24 July 2026 the FDA's Pharmacy Compounding Advisory Committee reviewed TB-500 for inclusion on the Section 503A Bulk Drug Substances List, alongside BPC-157, KPV, TB-500, MOTS-c, Epitalon and Semax. FDA staff had recommended against inclusion for every substance under review, citing insufficient characterization, little or no human effectiveness evidence, and inadequate human safety data. The committee voted in favor anyway. The vote was 8 in favor, 6 against, 1 abstention.

What the vote does not do:

·It is non-binding. The committee advises, it does not decide. No final FDA determination has been issued and none of the six peptides appears in 21 CFR 216.23.
·It requires a further step. Addition to the 503A Bulks List requires formal action by the Secretary of Health and Human Services, which had not occurred as of publication.
·It does not make the compound an FDA-approved drug, and it establishes nothing about efficacy.
·It does not legitimize research-chemical retail. A compounding-list decision concerns licensed pharmacists preparing patient-specific prescriptions under Section 503A, which is a different channel entirely from research material sold in vials.

Verifying a TB-500 lot

Three numbers, and they are not interchangeable. Identity by mass spectrometry establishes that the material is full-length thymosin β4 and not the fragment or a cheaper substitute. Purity by HPLC establishes what fraction of the vial contents is that compound. Measured content establishes how much is in the vial against the labeled amount. Underfilling is the failure mode that a purity-only certificate cannot detect, and it is the one a buyer pays for directly.

Every Eppix TB-500 lot is tested by an independent laboratory, with the certificate published and verifiable on the laboratory's own database. The current lot is below.

Certificate of analysis for TB-500 10mg, batch TB5-CA-26F-10, 99.182% purity, 11.52 mg measured content — Published certificate of analysis for the current TB-500 lot, with batch, HPLC purity and measured content read live from the batch record.

Sourcing in the United States

Domestic fulfillment is by FedEx, typically one to three business days, free over $200, with mix-and-match volume discounts applied automatically in the cart.

TB-500 and BPC-157 are the two compounds most often run alongside each other in tissue-repair work. The mechanistic and evidential differences are set out in BPC-157 vs TB-500, and the BPC-157 sourcing guide is at buy BPC-157 in the US.

Available at Eppix Labs

TB-500

10mg

Every batch tested by an independent laboratory, with the certificate published before sale.

From $59.99 USDIn stock

Frequently Asked

Ours is. The Eppix Labs TB-500 is synthetic full-length thymosin β4, the 43-residue, 4.9 kDa protein. Vials sold as "TB-500 fragment" contain the acetylated seven-residue Ac-LKKTETQ instead, under a fifth of the mass, and this store lists that separately. The MS identity result on a certificate tells you which you have.

It may be sold and held as a laboratory research material. It is not approved by the FDA for human or veterinary use. This is not legal advice.

No. An FDA advisory committee voted 8-6 in July 2026 to recommend it for the Section 503A compounding bulks list, against FDA staff's own recommendation. The vote is non-binding, addition to the list still requires action by the Secretary of Health and Human Services, and no final determination has been issued.

Batch number matching the vial, the named testing laboratory with an independent verification path, MS identity confirmation against the thymosin β4 mass near 4,963 Da, HPLC purity, and measured vial content against the labeled amount.

TB-500 and thymosin β4 appear on the World Anti-Doping Agency Prohibited List under growth factors affecting muscle, tendon or ligament. That is a competition matter and is separate from its status as a research material; it is noted here because researchers working with athletes ask.

Lyophilized: cool, dry, dark, at -20 °C for long-term storage. Reconstituted: refrigerated, used within the window your protocol defines. See the peptide storage guide.

References

Goldstein, A.L., Hannappel, E., Kleinman, H.K. (2005). Thymosin β4: actin-sequestering protein moonlights to repair injured tissues. Trends Mol Med 11(9):421-429. PMID 16099219
Malinda, K.M. et al. (1999). Thymosin beta4 accelerates wound healing. J Invest Dermatol 113(3):364-368. PMID 10469335
Sosne, G. et al. (2002). Thymosin beta 4 promotes corneal wound healing and decreases inflammation in vivo following alkali injury. Exp Eye Res 74(2):293-299. PMID 11950239
Bock-Marquette, I. et al. (2004). Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature 432(7016):466-472. PMID 15565145
Philp, D., Kleinman, H.K. (2010). Animal studies with thymosin beta 4, a multifunctional tissue repair and regeneration peptide. Ann N Y Acad Sci 1194:81-86. PMID 20536453
US Food and Drug Administration (2026). Pharmacy Compounding Advisory Committee meeting, 23-24 July 2026: bulk drug substances nominated for inclusion on the Section 503A Bulks List. FDA Advisory Committee Calendar. Source
US Food and Drug Administration (2026). FDA briefing document, Pharmacy Compounding Advisory Committee: BPC-157, KPV, TB-500, MOTS-c, Emideltide, Semax and Epitalon. Agency review recommended against inclusion for each substance. FDA. Source
Office of the Federal Register (2026). 21 CFR 216.23: bulk drug substances that can be used to compound drug products under section 503A. None of the six peptides appear on the list as of publication. eCFR. Source

BPC-157

From $49.99 USD · Janoshik-verified COA

TB-500

From $59.99 USD · Janoshik-verified COA

Research Use Only

This article summarizes published preclinical research literature. Compounds referenced are supplied by Eppix Labs strictly as research materials for laboratory investigation within the United States. They are not approved by the FDA for human or veterinary use, and nothing on this page should be interpreted as medical advice or guidance on human or animal administration.