# TB-500: The Ac-LKKTETQ Thymosin Beta-4 Fragment, Verified Against the Literature > TB-500 is the synthetic Ac-LKKTETQ fragment of thymosin beta-4, studied for angiogenesis and tissue repair. A sourced readout of what the research shows and what it does not. A verified readout of the record: what the published literature establishes, what is animal-only, and where the fragment ends and the full-length protein begins. Every figure is cited. ## The one fact that organizes everything else TB-500 is the synthetic, N-acetylated heptapeptide Ac-LKKTETQ — seven residues (17-23) lifted from the 43-amino-acid protein thymosin beta-4, where they form the conserved actin-binding motif. That sequence is the whole compound: molecular weight 889.02 Da, formula C38H68N10O14, supplied for laboratory research as a lyophilized powder. Here is the distinction the rest of this site keeps in view. The thing sold and detected as TB-500 is the 7-mer. The overwhelming majority of *efficacy* data — wound healing, cardiac repair, angiogenesis, neuroprotection — comes from full-length thymosin beta-4 (~4963 Da), not the fragment [5][9]. Marketing routinely blurs the two. We do not. Throughout, a finding is tagged for which molecule actually produced it, because whether the isolated heptapeptide reproduces the parent protein's effects at research doses is not established in controlled human trials [13]. What the literature does establish, it establishes well. Structural crystallography showed thymosin beta-4 binds monomeric (G-) actin one-to-one, capping both ends of the monomer to hold it unpolymerized [1]. That actin-buffering mechanism underlies the migration, angiogenesis and anti-scarring biology cataloged across three decades of animal and in-vitro work [5]. The unanswered question is human translation of the fragment — and on that, the honest readout is a row of zeros: no completed controlled clinical trial of the TB-500 heptapeptide exists for any indication [13]. This is the [TB-500 mechanism of action](/research), read as a transcript rather than a sales sheet. ## TB-500 as a Research Peptide: The Ac-LKKTETQ Fragment As a research peptide, the TB-500 peptide is defined by its sequence, not by a therapeutic claim. Ac-LKKTETQ is a WH2-type actin-interacting motif — the short structural element that beta-thymosins use to grab and sequester actin monomers [1]. The full thymosin beta-4 protein is ubiquitous in human cells and is released by platelets and macrophages at sites of injury; the fragment is a synthetic construct, not an endogenous species. That origin matters for reading the literature. When a study reports re-epithelialization figures, cardiac survival signaling, or VEGF induction, it almost always dosed the full-length protein [3][2][8]. The heptapeptide carries the actin-binding core but lacks the rest of the chain — including the N-terminal region that, when cleaved from the parent protein, yields the separately active fragment Ac-SDKP. TB-500 does not generate Ac-SDKP. The compound is therefore best understood as the actin-binding business end of thymosin beta-4, studied on its own merits, with a thin human record of its own. ## What the record genuinely shows In a rat full-thickness wound model, thymosin beta-4 raised re-epithelialization by 42% at four days and up to 61% at seven days versus saline, increased wound contraction by at least 11% by day seven, and lifted collagen deposition and angiogenesis; as little as 10 pg stimulated keratinocyte migration two- to three-fold [3]. In mice, thymosin beta-4 formed a complex with PINCH and integrin-linked kinase, activated the survival kinase Akt, and after coronary artery ligation improved early myocyte survival and cardiac function [2]. A consolidating review ties these threads together: actin binding, cell migration, reduced myofibroblast number, anti-inflammatory and angiogenic signaling [5]. The honest counterweight sits right beside them. Systemic thymosin beta-4 failed to attenuate myocardial ischemia-reperfusion injury in a porcine study, and in dystrophin-deficient mice chronic dosing increased regenerating fibers without improving muscle strength. A 2026 Sports Medicine review places TB-500 and thymosin beta-4 among unapproved peptides with favorable animal outcomes but scarce human safety data and potential for serious harm, operating largely outside regulatory oversight [13]. Both columns are part of the readout. ## The angiogenesis lens This digest reads TB-500 through angiogenesis — the formation of new blood vessels — because that is where the fragment's parent biology is best characterized and where its central safety question lives. Thymosin beta-4 drives endothelial migration and tube formation and induces vascular endothelial growth factor (VEGF) in a HIF-1alpha-dependent manner [7][8]. The same pro-migratory, pro-angiogenic activity that aids repair is the basis of the tumor/angiogenesis concern, because thymosin beta-4 is overexpressed in several cancers and implicated in metastasis [13]. That dual nature — repair-confirmed and caution-flagged from one mechanism — is the reason the [TB-500 angiogenesis research](/angiogenesis-research) gets its own page. For where the substance stands with regulators, see the [TB-500 legal status and FDA 503A category](/legal-status). For the full source list, jump to [references and citations](/references). --- Legit TB-500 runs the thymosin beta-4 literature like a status check: the seven-mer marked present, the full-length protein where the data actually live marked separately, the human-evidence column returning zero, and FDA's standing quoted straight — a console for verifying claims, not a clinic, a pharmacy, or a place anything is sold.