Thymosin Beta-4 and TB-500: The Actin Mechanism and the Models Built on It
Most research peptides come with a scattered literature. TB-500 is different, because the protein it is based on, thymosin beta-4 (Tβ4), is abundant in the human body and its mode of action has been mapped closely. In the research market the name TB-500 covers synthetic Tβ4 as well as its active fragments. Below, the study models come first, then the mechanism that ties them together.
Four groups of study models
Cardiac injury
Mice given a coronary ligation showed better cardiomyocyte survival and activation of epicardial progenitor cells when Tβ4 was given. Work on the heart is still going on, and it is still preclinical.
Fibrosis and inflammation
In several models of organ injury, researchers have described smaller scars and less inflammatory infiltration.
Eye surface
After corneal injury, Tβ4 helped the epithelium grow back. That finding led to human trials of Tβ4 eye drops, coded RGN-259, in dry eye and in neurotrophic keratopathy. Few thymosin programs have reached the clinic; this is one of them.
Skin wounds
The foundational experiments were dermal. Rodents, among them diabetic and aged animals, healed wounds faster with topical or systemic Tβ4; keratinocytes and endothelial cells migrated more, and collagen deposition improved.
One mechanism underneath
What links those models is actin. Tβ4, a chain of 43 amino acids, is the body’s chief G-actin sequestering molecule: it holds on to free actin monomers and so regulates how quickly they polymerize into filaments. Cells rely on actin dynamics to change shape, divide and move, which puts Tβ4 directly upstream of migration. Much of that activity is reproduced by a short fragment from the middle of the chain containing the LKKTETQ actin-binding motif, and several research versions are built on that fragment.
Where the evidence stops
Only the eye-drop work has gone beyond the preclinical stage. Sports anti-doping agencies explicitly ban TB-500, and no injectable form is approved for human or veterinary use. Consistent animal results, however many there are, cannot establish that something is effective or safe in people.
Bench handling
TB-500 dissolves cleanly in bacteriostatic water. After that, standard storage practice applies: refrigerate, keep it dark, and finish within the 30-day window. Because it is a bigger molecule than the short peptides, mix it with extra care. Swirl the vial; never shake it.
TB-500 at LiliPeptide
The single-compound listing is TB-500 (Thymosin Beta-4) in 5mg and 10mg. TB-500 is also part of the BPC-157 + TB-500 Blend (10mg, 20mg), GLOW (GHK-Cu + TB-500 + BPC-157) at 70mg and KLOW (GHK-Cu + TB-500 + BPC-157 + KPV) at 80mg. Since the name covers both full-length Tβ4 and fragments, check the listing and its paperwork for which form you are getting.
On our COAs page there is one Freedom Diagnostics Testing report for this compound: TB-500 10mg, tested 31 Aug 2026, report lili2608270163. Its batch column reads “Clear Pink Cap” rather than a lot code, so open the PDF and see how the report identifies the sample before matching it to a vial. The report applies only to that sample; the page has no report for the 5mg option or for the blends.
For a mechanism-level comparison with BPC-157, see the side-by-side guide. For research use only. Not for human or veterinary use.
