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

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.

TB-500 in commercial research supply is that motif, acetylated at the N-terminus and usually amidated at the C-terminus. It is around a quarter the mass of the parent protein and is synthesized rather than expressed. Suppliers that describe their TB-500 vial using thymosin β4 clinical or preclinical data are, strictly, describing a different molecule; a certificate resolves which one you are actually being sold, because the measured mass is unambiguous.

Research Material

Seven residues, all standard, with terminal modifications. The synthesis is simple and the mass is distinctive, which is exactly why an MS identity line on the certificate is worth insisting on: substitution with a cheaper short peptide is the most economically attractive form of adulteration for a product this small, and it is invisible to a purity assay alone.

Amino Acid Sequence

Chemical Structure

Nearly all of the substantive literature is on thymosin β4 itself rather than on the seven-residue fragment. That distinction is worth carrying through the reading:

• ·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]

Thymosin β4 reached human clinical investigation in dermal and corneal indications and has no approved indication. The seven-residue TB-500 fragment sold on the research market has no human trial literature of its own at all. There is no established human dose, no human safety record for the fragment, and no jurisdiction in which it is authorized.

Reading parent-protein data as if it were fragment data is the single most common error in TB-500 marketing copy. The fragment carries the actin-binding motif; whether it reproduces the parent protein's behaviour in any given model is a question the published work has largely not asked.

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.

Three numbers, and they are not interchangeable. Identity by mass spectrometry establishes that the material is the LKKTETQ fragment and not a cheaper substitute of similar appearance. 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 Janoshik Analytical, with the certificate published before the lot is sold and verifiable on the laboratory's own database. The current lot is below.

Published Certificate

Batch

TB-CA-26A-01

Purity (HPLC)

99.182%

Measured content

11.52 mglabeled 10 mg

Laboratory

Janoshik

Verify on the lab’s own databaseAll published certificates

Domestic fulfillment is by FedEx, typically one to two days nationwide, free over $200, with an additional discount for card or PayPal checkout and mix-and-match pricing at 5 and 10 vials.

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