Compounds / TB-500

TB-500

Also known as: TB500, Ac-LKKTETQ (thymosin beta-4 fragment 17-23)

No human data Not FDA-approved · PCAC review July 2026 Category: Tissue Repair and Regeneration

The compounds described in this library are research-use-labeled chemicals and are not FDA-approved for human use. This content is factual scientific reference drawn from published literature. It is not medical, dosing, or purchasing advice. VialReport does not sell, supply, or distribute any compound.

Short summary

A short synthetic peptide corresponding to a fragment of thymosin beta-4, a much larger naturally occurring protein. It is not the same molecule as thymosin beta-4, and almost all of the published research people associate with it was performed on the full-length protein rather than on this fragment.

Dive deeper

Origin and Development

Thymosin beta-4 (Tβ4) is a naturally occurring 43-amino-acid peptide encoded by the TMSB4X gene, first isolated from the thymus in the 1960s and later found to be expressed in nearly all nucleated cell types. TB-500 was developed as a shorter synthetic sequence corresponding to the actin-binding region of that protein, roughly residues 17 to 23.

Mechanism as Understood in the Literature

The LKKTETQ sequence shared by TB-500 and full-length Tβ4 binds G-actin monomers, influencing the equilibrium between free actin and assembled filaments. In preclinical models that actin-sequestering activity has downstream effects on cell migration and cytoskeletal reorganization. Full-length Tβ4 carries additional active regions that the fragment does not, including the N-terminal Ac-SDKP sequence, which has its own separate documented activity.

Research Status

This is the section that matters most for this compound. Much of the clinical evidence invoked in this market, including the Phase 1 safety work and the RGN-259 ophthalmic program, was generated using pharmaceutical-grade full-length recombinant thymosin beta-4, not the TB-500 fragment sold in research markets. Searching the peer-reviewed literature for thymosin beta-4 returns a large body of work; searching for TB-500 specifically returns very little. Where a study used full-length Tβ4, substituting the fragment changes the molecule being tested.

Regulatory status

Not FDA-approved for any indication. Placed on the FDA's Category 2 bulk drug substances list, then removed from Category 2 in April 2026 following withdrawal of the nomination, without being moved to Category 1 and without a recognized USP/NF monograph. Scheduled for Pharmacy Compounding Advisory Committee review on July 23, 2026. Prohibited in competitive sport under World Anti-Doping Agency rules.

Commonly Confused With

Routinely and incorrectly sold as, or labeled interchangeably with, "Thymosin Beta-4" or "TB4." They are not the same molecule: Tβ4 is 43 amino acids and roughly 4963 Da, while TB-500 is a short fragment of roughly 889 Da. Separately, TB-500 is sometimes confused with Ac-SDKP (goralatide), which is the N-terminal fragment of Tβ4 (residues 1 to 4) and a distinct compound with its own activity. TB-500 does not contain the Ac-SDKP sequence.

How This Compound Is Marketed

Vendors in this market commonly market this compound for soft-tissue repair, recovery from injury, flexibility, and reduced inflammation, frequently paired with BPC-157 in vendor bundles. These are vendors’ marketing claims, not VialReport’s. VialReport does not verify, evaluate, or endorse them, and nothing on this page is medical, dosing, or purchasing advice or a recommendation to use any compound. See “Research status” above for what the published literature actually establishes.

It is frequently paired with BPC-157 in vendor bundles.

Analytical Profile

Fragment of approximately 7 amino acids (Ac-LKKTETQ), molecular weight roughly 889 Da, versus approximately 4963 Da for full-length thymosin beta-4. That mass difference is large and unambiguous, which makes mass spectrometry a reliable way to distinguish the fragment from the full-length protein. Retention-time comparison alone is weaker for this compound precisely because of the substitution question.

Stability and Handling

Supplied lyophilized. Stability depends on molecular form, formulation, moisture, container closure, temperature, and reconstitution conditions, and published data may not apply to research-channel material.

Key Literature

  1. 01 Xing Y, et al. Progress on the function and application of thymosin β4. Front Endocrinol. 2021;12:767785.
  2. 02 Malinda KM, et al. Thymosin beta-4 accelerates wound healing. J Invest Dermatol. 1999. PMID 10233762.
  3. 03 Bock-Marquette I, et al. Thymosin beta-4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature. 2004. PMID 15295105.
  4. 04 Philp D, et al. Thymosin beta-4 and a synthetic peptide containing its actin-binding domain promote dermal wound repair. FASEB J. 2004. PMID 15155564.

VialReport publishes factual reference information and independent test data. Nothing here is medical, dosing, or purchasing advice.

Published reports

Reports for TB-500

No reports for this compound yet.

Want a vendor’s version of this compound tested? Request it and we’ll notify you when a report publishes.

Request a test

Stay current

Get notified when new reports publish.

Free. We email when results are in, and nothing else.

Powered by MailerLite. No spam. Unsubscribe anytime.