# TB-500 FAQ: Cardiac, Mechanism, Safety, Dosage, and Legal Status > TB-500 questions answered from the source: does it affect the heart, how it works, the tumor signal, the half-life, whether it is FDA-approved or WADA-banned, and the 503A compounding status. Twenty-five questions across cardiac, mechanism, safety, dosage and regulatory standing — each answer cited, each one honest about whether the data came from the 7-mer or the full-length protein. ## Cardiac ### Does TB-500 affect the heart? In mice, thymosin beta-4 activated PINCH-ILK-Akt survival signaling and, after coronary ligation, improved early cardiomyocyte survival and cardiac function [2]. These effects are shown for full-length thymosin beta-4, not confirmed for the 7-mer in humans. The cardiac mechanism is the strongest leg of the record; the human translation is the weakest. ### Is TB-500 cardioprotective after a heart attack? Animal models report cardioprotection — systemic thymosin beta-4 after ischemia [8] and prevention of cardiac rupture after MI in mice [10]. Human data are limited to a completed acute-MI trial of thymosin beta-4 (NCT05984134) [12], and a porcine study used engineered cell delivery [13]. The fragment's human cardioprotective effect is not established. ### Did thymosin beta-4 improve outcomes in cardiac clinical trials? A human acute-myocardial-infarction trial of thymosin beta-4 (NCT05984134) is recorded as completed [12]. Published peer-reviewed efficacy outcomes for the TB-500 fragment in humans are not established [12]. A registry completion is a milestone, not a demonstrated outcome. ## Identity and uses ### What is TB-500? TB-500 is the synthetic, N-acetylated heptapeptide Ac-LKKTETQ corresponding to residues 17-23 — the actin-binding motif — of the 43-amino-acid protein thymosin beta-4 [1]. It is a research and veterinary-context substance with no approved human indication [12]. ### What does TB-500 stand for? `TB` refers to thymosin beta; TB-500 is a research and veterinary designation for the Ac-LKKTETQ active fragment of thymosin beta-4 [5]. The name marks the fragment, while most published efficacy data come from the full-length protein. ### What is TB-500 studied for? In animal and in-vitro models, thymosin beta-4 and its actin-binding region have been studied for wound and corneal healing, muscle and ligament repair, cardiac and neurological recovery, angiogenesis, and hair-follicle activation [5]. These are research contexts, not approved uses. ## Mechanism ### How does TB-500 work? TB-500 carries thymosin beta-4's actin-binding motif; the parent protein sequesters monomeric G-actin one-to-one, regulating cytoskeletal dynamics and cell migration [1], and is associated with angiogenesis and anti-inflammatory, anti-scarring signaling in injury models [5]. Whether the isolated 7-mer reproduces all of this is not established in controlled human trials. ### Does TB-500 promote angiogenesis? Thymosin beta-4 promotes endothelial migration and new-vessel formation, with reported VEGF and HIF-1alpha signaling [5]. This aids repair but is also the basis of the tumor-angiogenesis safety concern — the same property reads as benefit in a wound and risk near a tumor. ### Does TB-500 reduce inflammation? In vitro, thymosin beta-4 suppressed TNF-alpha-induced NF-kappaB activation and IL-8, and recent animal work links it to pro-resolving and anti-fibrotic pathways, including amelioration of liver fibrosis via MAPK/NF-kappaB modulation [9]. This is mechanistic, not a clinical anti-inflammatory indication. ## Repair, recovery, and timeline ### Does TB-500 work for muscle recovery? Thymosin beta-4 acts as a myoblast chemoattractant and aided ligament healing in rats [5], but in dystrophin-deficient (mdx) mice chronic thymosin beta-4 increased regenerating fibers without improving muscle strength — a notable null functional result [5]. ### Can TB-500 help tendon and ligament repair? Thymosin beta-4 enhanced healing of medial collateral ligament injury in rats — one of the few direct connective-tissue findings [5]. This is preclinical and uses the full-length protein, so it informs rationale rather than confirming a human effect. ### Does TB-500 help wound healing? Thymosin beta-4 accelerated re-epithelialization, contraction, collagen deposition and angiogenesis in animal dermal and corneal wound models — up to +61% re-epithelialization at 7 days in rats [3]. A synthetic actin-binding-domain peptide reproduced aspects of that activity [5]. ### How long does TB-500 take to work? No human timeline is established. In a rat wound model, thymosin beta-4 increased re-epithelialization by 42% at 4 days and up to 61% at 7 days versus saline [3] — an animal timescale on the full-length protein, not a human dosing schedule. ### Does TB-500 have neuroprotective effects? In rat embolic-stroke models, intraperitoneal thymosin beta-4 improved neurological function at 2 and 12 mg/kg but not at 18 mg/kg, with a modeled optimal dose near 3.75 mg/kg [4]. This is preclinical and used the full-length protein. ### Does TB-500 increase hair growth? Nanomolar thymosin beta-4 activated hair-follicle bulge stem cells and accelerated hair growth in rats and mice [5]. This is animal data for the full-length protein, not a human hair-loss treatment. ## Safety and evidence ### What are the side effects of TB-500? No controlled human safety profile exists for the heptapeptide [12]. Intravenous full-length thymosin beta-4 was well tolerated to 1260 mg in a Phase 1 study [6], but the principal theoretical concern is the tumor and angiogenesis signal [5]; research-grade purity is also a recurring issue. ### Does TB-500 cause cancer or promote tumor growth? Thymosin beta-4 is overexpressed in several cancers and is implicated in metastasis and tumor angiogenesis [5]; the same pro-migratory, pro-angiogenic properties that aid repair could theoretically support tumor progression, and human safety data for the fragment are scarce [12]. ### Is TB-500 safe for long-term use? Long-term human safety of the TB-500 fragment is unknown — no chronic controlled human trials exist [12]. The tumor and angiogenesis signal [5] and unregulated product quality are the main reasons community loading-then-maintenance protocols are not validated [12]. ### Are there human clinical trials on TB-500? There are no completed controlled trials of the TB-500 heptapeptide [12]. Human data exist only for full-length thymosin beta-4: a randomized placebo-controlled Phase 1 intravenous safety study [6] and topical ophthalmic trials; a completed acute-MI trial and a withdrawn early stroke trial are also on record [12]. ### What is the difference between TB-500 and BPC-157? Both appear among unapproved peptides studied for musculoskeletal repair in the 2026 Sports Med review [7]. TB-500 is the actin-binding thymosin beta-4 fragment, a distinct molecule with its own largely full-length-protein preclinical literature [5]. Neither is FDA-approved [12]. ## Legal status and access ### Is TB-500 banned by WADA? Yes. TB-500 and thymosin beta-4 fall under WADA prohibited peptide, growth-factor and tissue-repair categories, banned in and out of competition for the relevant classes, and are detected by LC-MS anti-doping assays in equine and human matrices [12]. ### Is TB-500 FDA approved? No. TB-500 has no FDA-approved therapeutic indication; it is a research chemical and veterinary-context substance [12]. FDA reviewed `Thymosin beta-4, fragment (LKKTETQ), also known as TB-500` and placed it in 503A Category 2 over safety concerns [14]. ### Is TB-500 legal? TB-500 is not an FDA-approved drug and is handled as a research / veterinary-context substance; it is WADA-prohibited and a prescription medicine in some jurisdictions [12]. For compounding, FDA placed it in 503A Category 2 effective September 29, 2023, so it is not within FDA's enforcement-discretion policy for routine 503A compounding [14]. General regulatory information, not legal advice. ### Can you get TB-500 from a compounding pharmacy? Legally compounded access requires a licensed-prescriber evaluation and a valid patient-specific prescription filled by a 503A pharmacy or 503B outsourcing facility [16]. But a Category 2 substance like TB-500 is not eligible for routine 503A compounding while that status stands [14][16]. This site names no pharmacy or provider. ### What is the FDA 503A status of TB-500? FDA placed `Thymosin beta-4, fragment (LKKTETQ), also known as TB-500` in 503A Category 2 — a bulk substance identified as possibly presenting significant safety risks — effective September 29, 2023 [14]. `TB-500 (free base)` and `TB-500 acetate` are on the July 23-24, 2026 PCAC agenda as candidates being considered for the 503A Bulks List, which is a scheduled discussion, not a decision [14]. --- A pure-black analytics console querying the TB-500 and thymosin beta-4 record — the established findings held live in volt, the full-length-protein substitutions and the empty human-trial channel logged plainly, and the FDA 503A standing read before anything else; no clinic runs this console and nothing here is dispensed or sold.