The evidence position
FDA does not state a known mechanism. It offers only that the sequence is “thought to contribute to the wound-healing properties of the full-length thymosin β4 peptide.” (slide 18)
FDA: “No studies were found in the literature in which TB-500 was administered to humans.” (slide 26) And: “FDA did not find any information where TB-500 was administered to patients to treat any disease or condition.” (slide 20)
FDA did not identify “nonclinical toxicity studies to inform safety considerations for potential clinical uses of TB-500.” (slide 21)
WADA lists it under S2.3, growth factors and growth factor modulators — “Thymosin-β4 and its derivatives e.g. TB-500”. Prohibited at all times.
In July 2026 the US Food and Drug Administration reviewed TB-500 for the 503A Bulk Drug Substances list and proposed that it not be included. FDA briefing document, Pharmacy Compounding Advisory Committee, 23–24 July 2026.
The pathways it is reached for
The building of new blood vessels — restorative when it perfuses healthy tissue, pathological when it feeds disease.
Repair as a scheduled sequence — hemostasis, inflammation, proliferation, remodeling. Skipping or prolonging the inflammatory phase is what produces both non-healing wounds and excessive scarring.
TGF-β / Smad signaling — the builder that lays down collagen and directs repair, and the same hand that, overused, drives fibrosis.
When injury keeps repeating, stellate cells lay down collagen where working tissue used to be. Scar does not do any of the jobs a liver does, and past a point it does not come back.
Scar deposition in erectile tissue, replacing compliant smooth muscle with stiff collagen. It is the structural endpoint that makes vascular erectile dysfunction progressively less reversible.
What we carry on those pathways
Shares 2 of these pathways: TGF-β / Smad, Liver Fibrosis.
Immune Surveillance → Wound Healing. “Indeed, the depletion of macrophages is unmistakably detrimental to normal skin healing in adult mammals.” — Macrophages in Healing Wounds: Paradoxes and Paradigms. International Journal of Molecular Sciences, 2021, 22(2):950. doi:10.3390/ijms22020950
What a grade means here
Every ingredient row on our formula pages carries one of these grades, fixed by a standard set before the evidence was gathered. The grades below are reproduced from those pages.
Randomized human trials, or a meta-analysis of them, measuring this pathway's own endpoint — either a clinical outcome or a validated biomarker.
Human data, or animal evidence replicated by an independent laboratory. It opens a pathway only alongside an independent corroborating driver.
Mechanistic, cell or animal evidence. No single preclinical driver opens a pathway on its own.
What this page does not claim
Sharing a pathway is not the same as sharing an effect. Nothing here says a botanical formula does what TB-500 does, and nothing here recommends TB-500. The pathways above are named because that is what the published work on TB-500 points at; the formulas below are listed because our own map records graded, published evidence on those same pathways. Read both columns and judge them yourself — every figure on our side carries its grade and its source.