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For research use only.

TB-500

Thymosin beta-4 fragment · 7 amino acids
What it is

TB-500 is a short, lab-made piece of thymosin beta-4: the 7-amino-acid stretch LKKTETQ, from a 43-amino-acid peptide that platelets and other cells release after an injury.[1][2]

Origin: Its parent, thymosin beta-4, was first sequenced from calf thymus in 1981 by Low, Hu, and Goldstein.[3] TB-500 appears to have first been made in 2003, after Philp, Kleinman, and colleagues at the National Institutes of Health in Bethesda, Maryland, found this actin-binding stretch is key to thymosin beta-4’s effect on blood vessel growth in lab tests.[1][4]

TB-500 is amino acids 17 to 23 of thymosin beta-4A strip of the 43 amino acids of thymosin beta-4, in order. Amino acids 17 to 23, L K K T E T Q, are highlighted: this 7-amino-acid stretch is the TB-500 fragment.THYMOSIN BETA-4 · 43 AMINO ACIDS124SDKPDMAEIEKFDKSKLKKTETQETB-500 · amino acids 17–23 · 7 amino acids2543KNPLPSKETIEQEKQAGES
TB-500 is amino acids 17 to 23 of thymosin beta-4A strip of the 43 amino acids of thymosin beta-4, in order. Amino acids 17 to 23, L K K T E T Q, are highlighted: this 7-amino-acid stretch is the TB-500 fragment.THYMOSIN BETA-4 · 43 AMINO ACIDS115SDKPDMAEIEKFDKS1630KLKKTETQEKNPLPSTB-500 · amino acids 17–23 · 7 amino acids3143KETIEQEKQAGES
What researchers study it for

Research areas

Most of this research is on full-length thymosin beta-4, not the TB-500 fragment, and all of it is in cells and animals.

  • Helping repair cells move toward damaged tissue[2]
  • Heart repair in mice after a blocked heart artery[5]
  • Lower inflammation and less scarring[2]
  • Hair growth in rats and mice[6]
  • Healing of skin wounds, eye injuries, and brain injury[2]

Evidence level

Level 1 of 4: Lab and animal onlyFDA found no published studies in which TB-500 was given to people.[1]

Why so few human trials?

Cautions

Studies and regulators point to several reasons for care.

  • FDA says thymosin beta-4 and TB-500 are not the same substance, even though many websites use the names as if they were[1]
  • FDA has not found any human exposure data, so it lacks the information to know whether TB-500 would harm people[7]
  • FDA found no animal toxicity studies and no animal studies showing TB-500 helps wounds heal[1]
  • The World Anti-Doping Agency bans thymosin beta-4 and its derivatives, such as TB-500, in tested sports at all times[8]

TB-500 is not FDA approved.[1]

Also called

TB-500 goes by several names.

  • Thymosin beta-4 fragment (LKKTETQ)[7]
  • Ac-LKKTETQ, the acetylated 17 to 23 fragment of thymosin beta-4[9]
  • TB-500 acetate, its salt form[1]

Often paired with

BPC-157. Together they’re known as the Wolverine blend, also nicknamed the Wolverine stack.[10]

BPC-157Together:BlendWolverine blend →

Good to know

In animals, injected TB-500 reaches the bloodstream and is broken down into smaller peptides.[1] In one lab study FDA reviewed, TB-500 did not help scratch wounds close in cultured connective tissue cells, though one of those smaller pieces appeared to.[1]

Handling

Storage basics General

These general basics apply to most freeze-dried research peptides.

Most research peptides come as a freeze-dried powder in a sealed vial
Unmixed vials are generally kept cold, dry, and away from light
Mixed solutions are generally refrigerated, since they are less stable than the dry powder
Peptides 101For mixing basicsNPL Dose CalculatorTo work out concentration after mixing
Go deeper

Sources and studies

These studies and official pages are the research behind this profile.

  1. 1July 23-24, 2026, Meeting of the Pharmacy Compounding Advisory Committee: FDA Briefing Document for TB-500-Related Bulk Drug Substances (TB-500 (Free Base) and TB-500 Acetate)U.S. Food and Drug Administration (2026)
  2. 2Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applicationsGoldstein AL, et al. (2012) · Expert Opinion on Biological Therapy
  3. 3Complete amino acid sequence of bovine thymosin beta 4: a thymic hormone that induces terminal deoxynucleotidyl transferase activity in thymocyte populationsLow TL, et al. (1981) · Proceedings of the National Academy of Sciences of the United States of America
  4. 4The actin binding site on thymosin beta4 promotes angiogenesisPhilp D, et al. (2003) · The FASEB Journal
  5. 5Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repairBock-Marquette I, et al. (2004) · Nature
  6. 6Thymosin beta4 increases hair growth by activation of hair follicle stem cellsPhilp D, et al. (2004) · The FASEB Journal
  7. 7Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety RisksU.S. Food and Drug Administration (2026)
  8. 8The Prohibited ListWorld Anti-Doping Agency (2026)
  9. 9Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potentialEsposito S, et al. (2012) · Drug Testing and Analysis
  10. 10Will the FDA Allow Compounding Pharmacies to Produce the "Wolverine Stack" and Other Peptides?Gussow L (2026) · Emergency Medicine News