# TB-500: research overview — Carolina Peptide > A literature summary of TB-500, a synthetic actin-binding fragment of thymosin beta-4. Covers the mechanism, cited animal and human Phase 1 findings, the fragment-versus-full-protein distinction, and safety cautions. The lead compound on this desk — an actin-binding fragment of thymosin beta-4, with the deepest and most varied evidence base of the three peptides, and one important asterisk: most of that evidence was measured on the full-length protein, not the fragment sold as TB-500. ## The short version TB-500 is a synthetic, 7-amino-acid fragment (Ac-LKKTETQ) of a naturally occurring 43-amino-acid protein, thymosin beta-4. That parent protein's job in the body is to bind and buffer actin, the building block of the cell's internal skeleton, which lets cells move, repair wounds, and grow new blood vessels. Animal studies of the full-length protein — and, less often, the fragment itself — report faster wound closure, improved outcomes after simulated stroke and heart injury, and reduced scarring. A single completed human trial exists: a Phase 1 safety study of the full-length protein, given intravenously to 40 healthy volunteers, that found it well tolerated up to a 1260 mg dose. **No comparable human trial of the 7-residue fragment has been published.** TB-500 has no FDA-approved use, is prohibited in tested sport, and nothing on this page is a recommended dose or a suggestion for human use. ## What it is TB-500 is the N-acetylated heptapeptide Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH, corresponding to residues 17-23 of thymosin beta-4 (gene TMSB4X) — the conserved actin-binding motif shared across the beta-thymosin family. The fragment (approximately 889 Da) is a small piece of a much larger protein (approximately 4963 Da), and this size difference matters: **the overwhelming majority of published efficacy studies used the full-length protein, not the fragment sold commercially as TB-500.** Whether the isolated 7-mer reproduces the parent protein's effects at research-community doses has not been established in a controlled trial — a distinction this page flags every time a cited finding used the full protein rather than the fragment. "TB-500" and "TB1000" are also used as veterinary designations, and the compound has drawn analytical attention from anti-doping laboratories, which have developed detection methods for it and its breakdown products in both human and equine samples. ## How it works Thymosin beta-4's core biochemical job is to bind monomeric (G-)actin in a 1:1 complex, capping both ends of the actin monomer to hold a buffered reserve of unpolymerized actin — a 2004 crystal structure resolved this dual-end-capping mechanism at 2 angstrom resolution [14]. That buffering role gives the protein outsized influence over cytoskeletal dynamics: cell migration, wound-edge closure, and the mobilization of repair and progenitor cells all depend on actin polymerization being available on demand. In injury models, the protein — and its LKKTETQ region specifically — is associated with faster cell migration, new blood-vessel formation, anti-inflammatory and anti-apoptotic signaling, reduced myofibroblast/scar formation, and recruitment of progenitor cells to the injury site. In the heart specifically, it forms a complex with PINCH and integrin-linked kinase (ILK) that activates the pro-survival kinase Akt, a pathway shown to improve cardiomyocyte survival after simulated coronary injury [15]. ## What the research shows A 2026 Sports Medicine review naming TB-500 (and BPC-157) among unapproved musculoskeletal peptides concludes that this class shows favorable tissue-repair outcomes in animal models but that rigorous human safety data remain scarce, with real potential for harm outside regulatory oversight [1]. *Wound healing (1999).* In a rat full-thickness wound model, thymosin beta-4 (given topically or intraperitoneally) increased re-epithelialization by 42% at 4 days and 61% at 7 days versus saline, increased wound contraction by at least 11% by day 7, and raised collagen deposition and angiogenesis; as little as 10 picograms stimulated a 2-3-fold increase in keratinocyte migration [16]. *Cardiac repair (2004).* In mice, thymosin beta-4 formed a functional complex with PINCH and integrin-linked kinase, activating Akt; it promoted cardiac and endothelial cell migration and, after coronary artery ligation, enhanced early myocyte survival and improved cardiac function [15]. *Actin-binding structure (2004).* X-ray crystallography at 2 angstrom resolution established that thymosin beta-4 sequesters G-actin in a 1:1 complex via dual-end capping, providing the structural basis for its actin-buffering role [14]. *Stroke dose-response (2014).* In rats with embolic middle cerebral artery occlusion, intraperitoneal thymosin beta-4 at 2 and 12 mg/kg improved neurological function significantly from day 14 through day 56, while a higher 18 mg/kg dose gave no significant benefit — a non-monotonic dose-response, with a modeled optimal dose near 3.75 mg/kg [11]. *Human Phase 1 safety (2010).* In a randomized, placebo-controlled trial, 40 healthy volunteers received the full-length protein intravenously — a single dose, then daily for 14 days, across four dose cohorts (42, 140, 420, or 1260 mg). It was well tolerated, with only infrequent mild-to-moderate adverse events, no dose-limiting toxicities, and dose-proportional pharmacokinetics [13]. *Consolidated mechanism review (2012).* A review summarizes the actin-binding, migration, anti-scarring, anti-inflammatory, and angiogenic mechanisms that provided the rationale for clinical trials in dermal wounds, corneal injury, and heart/CNS repair [12]. ## Reported effects, cautions & safety Reports from research-use communities about TB-500 are **anecdotal, not clinical evidence** — none of them come from a controlled human trial of the fragment, and none specify a verified dose. The most frequently described benefit, by a wide margin, is faster-feeling recovery from a nagging tendon, ligament, or muscle injury, alongside less joint pain, better range of motion, and improved overall flexibility. Smaller numbers of accounts mention faster-looking wound or skin healing, and, least often, hair regrowth. On the adverse side, mild injection-site redness, swelling, or aching is reported most consistently (typical of injected peptides generally, not unique to TB-500), followed by temporary tiredness or lethargy in the first day or two. Less frequent reports mention a brief head rush or headache, a flu-like feeling, nausea, a sense that an existing injury feels more "active," or short-lived mood changes. The cited cautions carry more weight than the anecdotes. **Human safety in people is essentially unstudied**: there is no completed controlled human trial of the fragment itself, and the one relevant human safety trial used the full-length protein [1][13]. **TB-500 is banned in tested sport** under WADA's peptide/growth-factor categories, detectable by anti-doping laboratories in both human and equine samples [1]. **TB-500 is a fragment, not the full protein** — nearly all of the encouraging efficacy data above comes from the 43-residue parent, and applying those results to the 7-residue fragment is an extrapolation that has not been confirmed [12]. A cautionary counter-example exists in the literature too: in dystrophin-deficient mice, long-term thymosin beta-4 increased the number of regenerating muscle fibers but did not improve muscle strength, cardiac function, or fibrosis — a reminder that more regeneration on paper does not automatically mean better function. Theoretical concerns round out the caution list and have not been measured directly for the fragment in people: a tumor/angiogenesis signal tied to the parent protein's role in some cancers, unverified research-grade product purity, and unstudied risk in bleeding disorders, surgery, pregnancy, or growing bodies. ## Where it fits in soft-tissue and connective-tissue repair research TB-500 is the lead compound on this desk because its evidence base — spanning wound healing, cardiac repair, stroke, and one human safety trial — is the largest and most varied of the three, even accounting for the fragment-versus-full-protein caveat that runs through every finding above. Its actin-binding mechanism is also the one [GLOW](/glow) borrows directly, pairing it with BPC-157's vascular signal and GHK-Cu's matrix signal on the theory that migration, vessels, and matrix are complementary legs of repair. Where [KPV](/kpv) targets a single organ system (the gut) through inflammation control, TB-500's mechanism — actin availability for cell movement — is generic enough to show up in tendon, skin, cornea, and heart studies alike. See the [comparison page](/compare) for the three side by side. ![TB-500 research illustration — abstract cell-migration and actin motifs in teal](/images/tb-500.webp) --- A data-first ledger of tissue-repair peptide research — effect sizes and citations, not a clinic or a shop.