RESEARCH DIGEST -- ISSUE No.2
TB-500 is the Ac-LKKTETQ fragment of thymosin beta-4 studied for tissue repair and neurological recovery.
A panel-by-panel reading of what the published research measured, where the evidence is genuinely strong, and the one caveat the whole field turns on: most of the data are for the full-length protein, not the heptapeptide.
TB-500 in one panel
TB-500 is the synthetic N-acetylated heptapeptide Ac-LKKTETQ — residues 17 to 23 of the 43-amino-acid protein thymosin beta-4, and the conserved actin-binding motif of that protein [1]. At roughly 889 Da it is a fraction of the full-length protein's ~4963 Da. It is supplied for laboratory and veterinary contexts and has no approved human therapeutic indication.
That single sentence carries the tension this whole site documents. The name TB-500 is what commerce and the anti-doping literature put on the seven-residue fragment, but the overwhelming majority of the efficacy research — the wound-healing numbers, the stroke models, the cardiac data — was run on full-length thymosin beta-4, not the 7-mer [5]. Whether the isolated fragment reproduces the parent protein's effects at the doses used in peptide research has not been established in controlled human trials [10]. Where a finding below comes from the full-length protein, this digest says so.
TB-500 Peptide: The Ac-LKKTETQ Fragment of Thymosin Beta-4
The TB-500 peptide is one short stretch of a much larger story. Thymosin beta-4 is the body's principal G-actin-sequestering peptide — present in nearly every human cell and released by platelets and macrophages at sites of injury [5]. Its job is to bind monomeric (globular) actin one-to-one and cap both ends of the monomer, holding a buffered reserve of unpolymerized actin that the cell can draw on to remodel its cytoskeleton, migrate, and repair [1].
The LKKTETQ segment that TB-500 reproduces is the actin-binding core of that protein — a WH2-type motif. So the fragment carries the parent protein's docking site for actin without the rest of the molecule. That structural fact is the reason TB-500 is studied for repair at all, and the reason its evidence base has to be read carefully: a docking motif is not the whole protein. The corpus flags this fragment-versus-full-length distinction on every page where it matters.
What the research has actually shown
In a rat full-thickness wound model, thymosin beta-4 increased re-epithelialization by 42% at four days and up to 61% at seven days versus saline, raised wound contraction, and increased collagen deposition and new-vessel formation; as little as ~10 pg stimulated keratinocyte migration two- to three-fold [3]. In male Wistar rats with embolic stroke, intraperitoneal thymosin beta-4 at 2 and 12 mg/kg improved neurological function while 18 mg/kg did not — a non-monotonic result that quietly undercuts the "more is better" loading logic [4]. In mice, thymosin beta-4 activated the PINCH-ILK-Akt survival pathway and improved cardiac function after coronary artery ligation [2].
Those are the kinds of discrete, quotable findings this site is built around — each one a panel you can check against its source. The deep dives live on TB-500 benefits observed in research models and the dedicated TB-500 neuroprotection and neurological recovery research page. The recurring editor's note, in plain print: items [2], [3] and [4] all used full-length thymosin beta-4, not the TB-500 heptapeptide.
Where the human data stop
No completed controlled clinical trial of the TB-500 heptapeptide exists for any indication [10]. The only controlled human exposure to thymosin beta-4 in this digest is a randomized, placebo-controlled Phase 1 study in which the full-length synthetic protein was given intravenously to 40 healthy volunteers at 42, 140, 420 or 1260 mg, well tolerated to the top dose with no serious adverse events [6]. Topical ophthalmic thymosin beta-4 (RGN-259) has been studied for corneal healing and dry eye [9].
That is the honest shape of the evidence: large, reproducible effects in animal models; a clean Phase 1 safety read on the full-length protein in humans; and essentially no human efficacy data on the fragment itself. For how that lands on access, see TB-500 legal status and FDA 503A category. A pro-angiogenic, pro-migratory signal that aids repair also underlies a flagged tumor-biology concern, covered in TB-500 side effects and safety signals.
What is TB-500?
TB-500 is the synthetic N-acetylated heptapeptide Ac-LKKTETQ, corresponding to residues 17 to 23 — the actin-binding motif — of the 43-amino-acid protein thymosin beta-4 [1]. It is supplied for research and veterinary contexts and has no approved human therapeutic indication. The parent protein is abbreviated Tβ4; "TB" in TB-500 refers to thymosin beta.