What it is
TB-500 is a synthetic peptide of seven amino acids: LKKTETQ, with an acetyl group attached to one end, written as Ac-LKKTETQ.
That sequence is not arbitrary. It corresponds to amino acids 17 to 23 of thymosin beta-4, a protein of 43 amino acids that occurs naturally in the body.
So TB-500 is a fragment. Seven links out of forty-three.
The thing almost every page gets wrong
TB-500 and thymosin beta-4 are used interchangeably nearly everywhere the compound is sold or discussed. They are not the same substance, and the difference is not pedantic.
Different regions of the parent protein do different jobs. The LKKTETQ region — the one TB-500 reproduces — is associated in the literature with angiogenesis, wound healing and cell migration. A different fragment of the same protein, the four-amino-acid Ac-SDKP, is produced in the body by an enzyme called prolyl oligopeptidase and acts on inflammation and fibrosis instead. One protein; two fragments; two distinct activities.
The practical consequence is a citation problem. A study on thymosin beta-4 is not automatically a study on TB-500. A study on Ac-SDKP certainly is not. When a page supports a claim about TB-500 with research on the full protein, the citation does not reach the claim it is attached to — and once the two names are treated as synonyms, that substitution becomes invisible.
What it is said to be good for
Healing and recovery: tendon, ligament and muscle injury, and wound repair in general.
The biological reasoning offered is the association of the LKKTETQ region with angiogenesis, wound healing and cell migration. That association is real and is in the literature.
What does not follow from it is that a synthetic acetylated fragment, injected, produces those outcomes in an injured person. That is a separate claim requiring separate evidence, and the evidence for TB-500 specifically in humans is not comparable to the reasoning behind it.
What the research covers
The published work in which TB-500 appears by name is weighted towards analytical chemistry rather than clinical outcomes. A 2012 study synthesised and characterised the N-terminally acetylated 17-23 fragment identified in TB-500, describing it as a product suspected to possess doping potential. Detection methods have been published for equine urine and plasma by liquid chromatography-mass spectrometry.
That is a meaningful body of work, and it says something useful — the compound has been studied carefully enough that it can be reliably identified in a sample. It is not evidence that it heals anything in people.
Where it stands
Approved as a medicine: nowhere.
FDA compounding status: thymosin beta-4 appears on the FDA's compounding page under nominations that were withdrawn, not on the current Category 2 list (page content current as of 2026-04-22). TB-500 as such is not listed under that name.
Sold as: a research chemical, not for human use — frequently under the thymosin beta-4 name, which, as above, describes a different molecule.
In sport: it has been treated as a doping-control target in published analytical work. Current status in any particular sport should be checked against that sport's governing body.
Last checked
2026-09-06. The FDA compounding page was read on that date.