# TB-500 Research: Actin Sequestration, Repair, and the Limits of the Evidence > The TB-500 and thymosin beta-4 research, tagged by state: the 1:1 actin-sequestration structure, the wound and cardiac data, the null results, and the absence of controlled human trials of the 7-mer. Mechanism, the strongest repair findings, the null results that temper the narrative, and the human clinical status — every datum tagged with its source molecule. ## How TB-500 works: actin sequestration TB-500 carries the `LKKTETQ` actin-binding motif of thymosin beta-4, the body's principal G-actin-sequestering peptide [1][5]. The mechanism is structural and precise. Crystallography of a gelsolin-domain-1–thymosin beta-4 hybrid bound to actin, resolved to `2 Å`, showed that thymosin beta-4 forms a 1:1 complex with monomeric actin and sequesters it by capping both ends, preventing polymerization; the WH2 actin-interacting motif underlies the binding [1]. By holding a buffered pool of unpolymerized actin, thymosin beta-4 regulates cytoskeletal dynamics and cell motility [5]. A consolidating review frames the downstream biology: thymosin beta-4 binds actin and promotes cell mobilization and migration, decreases myofibroblast number (lowering scar formation), is released by platelets and macrophages after injury to limit apoptosis and inflammation, and promotes angiogenesis [5]. Whether the isolated 7-mer reproduces these effects at research doses is not established in humans [5]. ## TB-500 Benefits: What TB-500 Is Studied For (Reported Research Outcomes) The reported research outcomes — the closest thing to "TB-500 benefits" the literature supports — are repair-associated and almost entirely preclinical. **Wound healing** is the strongest: rat full-thickness wounds treated topically or intraperitoneally with thymosin beta-4 showed `+42%` re-epithelialization at 4 days and `+61%` at 7 days versus saline, with more contraction, collagen, and angiogenesis [3]. **Cardiac** signaling is mechanistically rich: in mice, thymosin beta-4 formed a complex with PINCH and integrin-linked kinase, activated the survival kinase Akt, promoted cardiac and endothelial cell migration, and after coronary artery ligation enhanced early myocyte survival and improved cardiac function [2]. **Angiogenesis** has a molecular route — thymosin beta-4 induces VEGF in a HIF-1α-dependent manner [10] — and **matrix remodeling** is supported by increased matrix metalloproteinase expression during wound repair [11]. Every one of these outcomes was produced with full-length thymosin beta-4, not the TB-500 fragment, and none has been demonstrated for the 7-mer in a controlled human trial [5]. ## The neurological dose-response Neurological repair produced one of the most instructive datasets in this literature, precisely because it is not monotonic. In male Wistar rats with embolic middle cerebral artery occlusion, intraperitoneal thymosin beta-4 — `2`, `12`, or `18 mg/kg`, started 24 hours after stroke and repeated every 3 days for four more doses — improved neurological function at `2` and `12 mg/kg` (significant from day 14 through day 56), while `18 mg/kg` gave no significant benefit; the authors modeled an optimal dose near `3.75 mg/kg` [4]. The shape of that result matters more than any single point on it. Higher was not better — the top dose underperformed the middle doses — which directly undercuts the "loading" rationale that circulates in peptide-research communities [4]. It is also, again, a full-length thymosin beta-4 result in rodents, not a human result for the fragment. ## The null and negative results An honest research page foregrounds the counter-evidence. In dystrophin-deficient `mdx` mice, `150 µg` thymosin beta-4 twice weekly for 6 months raised regenerating-fiber counts but produced no significant improvement in muscle strength, systolic cardiac function, or fibrosis [9]. In a porcine model, systemic thymosin beta-4 given before and after ischemia did not attenuate global myocardial ischemia-reperfusion injury [14] — a negative cardiac result that sits directly against the mouse cardioprotection findings, where systemic thymosin beta-4 after ischemic injury was cardioprotective [13]. The cardiac picture, in short, is mixed. A 2026 narrative review of approved and unapproved peptide therapies for musculoskeletal injuries and athletic performance — which lists TB-500 / thymosin beta-4 and BPC-157 among the unapproved peptides — concludes that many such peptides show favorable tissue-repair outcomes in animal models but that rigorous human safety data are scarce, with potential for serious harm, and that these compounds operate largely outside regulatory oversight [15]. ## Are there any human clinical trials on TB-500? There are no completed controlled trials of the TB-500 heptapeptide [5]. Human data exist only for full-length synthetic thymosin beta-4: a randomized placebo-controlled Phase 1 intravenous safety and pharmacokinetics study, well tolerated to `1260 mg` in 40 healthy volunteers [6], and topical/ophthalmic thymosin beta-4 (RGN-259) dry-eye trials [5]. Injectable thymosin beta-4 stroke and acute-MI studies were registered; the injectable acute-MI study completed and an early injectable trial was withdrawn [5]. Efficacy of the 7-mer in humans is unproven [5]. This is the [human clinical status of TB-500](/research) in one paragraph. ## Does TB-500 affect the heart? In mice, thymosin beta-4 activated the PINCH–ILK–Akt survival pathway, mobilized epicardial progenitors, and improved cardiac function after coronary ligation [2], and systemic thymosin beta-4 after ischemic injury was cardioprotective in a rodent model [13]. But a porcine study found systemic thymosin beta-4 did not attenuate ischemia-reperfusion injury [14], so the cardiac picture is mixed. These are animal findings for the full-length protein. ## Does TB-500 have neuroprotective effects on the brain? In a rat embolic-stroke dose-response study, intraperitoneal thymosin beta-4 improved neurological function at `2` and `12 mg/kg` but not at `18 mg/kg`, with a modeled optimal near `3.75 mg/kg` [4]. These are rodent findings for the full-length protein, not human data for the 7-mer. ## Does TB-500 increase hair growth? Nanomolar thymosin beta-4 stimulated hair growth in rats and mice by activating hair-follicle bulge stem-cell migration and differentiation and increasing matrix metalloproteinase-2 [5][11]. Human hair-growth data for TB-500 are not established [5]. ## Does TB-500 reduce inflammation? Full-length thymosin beta-4 suppressed corneal NF-κB as a potential anti-inflammatory pathway [12], and the consolidating review describes anti-inflammatory and anti-apoptotic signaling among its injury-site activities [5]. These are mechanistic and in-vitro/animal findings, not human anti-inflammatory efficacy. ## Does TB-500 help wound healing? In a rat full-thickness wound model, topical or intraperitoneal thymosin beta-4 increased re-epithelialization by `42%` at 4 days and up to `61%` at 7 days versus saline, with greater contraction, collagen, and angiogenesis; as little as `10 pg` stimulated keratinocyte migration [3]. These are animal results for the full-length protein. ## Does TB-500 work for muscle tears and recovery from exercise? Animal work shows thymosin beta-4 acts as a myoblast chemoattractant and supports tissue repair [5], but the 6-month `mdx`-mouse study found more regenerating fibers without strength gains [9]. Controlled human recovery trials of the 7-mer do not exist [5]. Thymosin beta-4 has been characterized as an exerkine, which is part of why TB-500 draws recovery interest — but interest is not evidence of efficacy in humans. --- A forest-console reading of the TB-500 record — the Ac-LKKTETQ fragment held against thymosin beta-4 study by study, every confirmed finding logged green and every full-length-protein substitution flagged, with no clinic behind the console and nothing here dispensed or sold.