Thymosin Beta-4

Thymosin Beta-4 (Tβ4) is a ubiquitous, naturally occurring 43-amino-acid peptide — the body's principal G-actin-sequestering molecule, concentrated in platelets, wound fluid, and many tissues. Thymosin β4 was first isolated and characterized from thymic tissue by Allan Goldstein and colleagues, who named the thymosin peptide family. It is the full-length parent of the widely sold TB-500, and the molecule used in most published tissue-repair, wound-healing, and cardiac research. It is not approved and is supplied for research use only.

What is Thymosin Beta-4, and how does it differ from TB-500?

This is the single most important framing for the compound: TB-4 is the complete 43-amino-acid peptide (mature, N-terminally acetylated form ≈ 4,963 Da) with several functional domains, while "TB-500" most rigorously refers to a shorter synthetic fragment (the Ac-LKKTETQ actin-binding motif, residues 17–23) — they are related but not necessarily the same molecule, and much of the efficacy literature was generated with full-length TB-4. Vendors often use the two names loosely, which is a real source of confusion; if a study you're relying on used full-length TB-4, a fragment labeled "TB-500" may not reproduce it. Note that some suppliers also sell full-length 43-aa material under the "TB-500" name — another reason identity testing matters.

Source: Thymosin beta-4 (human), TMSB4X — sequence/mass identity, UniProt Consortium, UniProt, 2026

How does Thymosin Beta-4 work?

By binding and sequestering monomeric G-actin, TB-4 maintains a reservoir that cells draw on to rapidly build the actin filaments needed for migration — the basis for its roles in wound healing, angiogenesis, and tissue repair. Full-length TB-4 also carries signaling sequences the isolated fragment lacks, and can be cleaved at its N-terminus to the separately active peptide Ac-SDKP.

What does the research on Thymosin Beta-4 show?

Preclinical studies show TB-4 promotes dermal wound healing and activates cardioprotective (Akt) survival signaling after simulated myocardial infarction, with additional work in corneal and neural repair; human clinical work has reached early phase: the first-in-human Phase 1 study in this family tested recombinant human thymosin β4 (the full-length protein, not the TB-500 fragment) in healthy volunteers, and there are no large approved outcomes trials.

Source: A first-in-human… phase I study of recombinant human thymosin β4 in healthy Chinese volunteers, Wang X. et al., J Cell Mol Med, 2021 · Evidence level: extensive preclinical + early-phase human; not approved

What are the safety concerns and regulatory status?

Thymosin Beta-4 is not approved for human use, its long-term human safety is not established, and it is prohibited in sport under S2.3 (Growth Factors and Growth Factor Modulators), at all times. See the legal status guide.

Source: WADA Prohibited List (current year)

Why does vendor verification matter, and how does Peptigrity verify?

Because "TB-4" and "TB-500" are used interchangeably in the market despite referring to different molecules, mass-spec identity (full-length peptide vs the ~889 Da fragment) and HPLC purity are exactly the checks a buyer needs. Peptigrity collects independent third-party Certificates of Analysis from shops' official channels and verifies each for authenticity before publishing; because shops choose which COAs to publish, results reflect the batches shops make public rather than every batch — a selection bias we state openly, and a community-funded Testing Grant to buy and test vials anonymously is in development. The trust score weights lab purity and reviews equally (50/50). See how to read lab results.

Educational information only; not medical advice. Thymosin Beta-4 is not approved for human use. Consult a qualified healthcare provider. Peptigrity does not sell, endorse, or recommend products or vendors.

Frequently asked questions